Grey coating is an insulator, to prevent circulating currents through the bearings from any slight imbalance in magnetic field in the motor. there is a single bearing that is grounded ( the shiny one) to prevent charge build up on the rotor and a flash over to the frame, but the rest have to be insulated so they do not have a shorted turn through the frame that can cause a high circulating current through the bearings that rapidly erodes them through arcing. There are current paths for this current via things like the output shafts and the selector forks, but they probably assumed that, being long thin wall section steel assemblies, this long path would both keep the current low enough not to cause any major extra wear, and also the long output shaft would be mostly self cancelling field wise as well. A lot of larger electric motors handle this with one end having coated bearings, or they make them with ceramic bearing balls inside, or just make both sides with insulated bearing mounting frames, and provide a grounding carbon brush assembly to handle shaft grounding. Drawback of the coated bearing is that you have to ensure that there is absolutely no damage to the coating on the outside and the side facing the frame, so that there is no metal to metal path. However, depending on the exact coating applied, this coat can be both insulating and tougher than the steel of the bearing itself. grey would point to a spray on ceramic coating, probably vacuum deposited before final bearing assembly or applied as a plasma coating.
SeanBZA - Those early Tesla Model S drive failures everyone was talking about a few years ago? That was the far end bearing being eroded by current leakage. There was already a brush grounding the shaft to the case, but it was insufficient. Apparently, the Model S induction rotor pumps out a lot stay voltage compared to a permanent magnet motor.
WeberAuto - the Tesla motor issue would seem to have been addressed more recently than would have occurred during the design phase of the Bolt EV powertrain, although we don’t know when Tesla knew of the issue/solution with their motors, and started working on a solution. Unless there was some information sharing between OEMs and suppliers that occurred, I’d think a similar outcome from this issue affecting 2 or perhaps multiple OEMs would be unlikely. This is where information sharing as EV powertrains evolve would benefit us all in the long run. There’s no sense in having ALL OEMs encounter - and learn from - the same failures.
@@dennislyon5412 Thanks for your feedback, I it makes sense to share that type of information if we want to promote the success and reliability of this powertrain type.
I'm a mechanic of internal combustion engines and you just introduced me to the future of automobiles. I'll remember you to my grand kids years from now when they start to learn to fix their own EVs. Thank you, Sir.
I had been an auto mechanic for many years. I developed multiple sclerosis which is slowly leaving me dependent on my wheelchair more and more. Watching this video, was amazingly awesome. It gives me hope that even though I'm more dependent on my wheelchair, it doesn't leave me nearly as helpless as I had once thought. Thank you.
The fact that you can do what you do, by yourself, in a wheelchair, while being both patient and professional, is absolutely amazing. Keep up the good work professor. I'm just a curious viewer but wholesomely impressed by what I see.
Congratulations. After all these years on You Tube, at last a professional quality video. A no nonsense, no childish attempted humour. a clean workshop and no dropping tools or bits. From 00:00 seconds to 58:42 seconds it looks to have been well prepared and delivered in a beautiful clearly spoken voice. This is a first class video.
Yes, totally agree about the 'no childish attempted humor'. I am SO tired of seemingly endless video makers who seem to feel that to get information across they need to 'spice it up' with lame humor, or obnoxious rock music or absolutely unnecessary computer graphic intros. It's exasperating. Just clean and clear, understandable, accurate, in-depth information goes SO much farther.
I had very little idea of what was going on under the hood of my 2023 Bolt 2LT until I stumbled upon your videos. Thanks for all the time and effort you've invested in this brilliant series. We owners are your beneficiaries!
I will never disassemble one of these motor units, but found the whole thing riveting. I cannot begin to understand how engineers design and manufacture this and other precision machinery, it is all beyond my feeble brain. Thank you Professor.
What can i say that hasn't been said already. Absolutely the best presentation on the Bolt inner workings period! Professor, you sir, know how to teach and illuminate the minds of the curious. Thank you!
Weber Auto is an absolute gift. One can gleam some mighty useful information in these clear, concise, and very educational videos. Thank you for the dedication to teaching us!
"There are no instructions on disassembling this, so I assume we're not supposed to disassemble it, but that's exactly what I like to do, take things apart i'm not supposed to, as long as I can get them back together and work again" the best quote in the video :) You are one of my hero's professor Kelly, and you inspire me to keep living, even in the darkest hours of life, thank buddy, your content helped to save my life!
"...but that's exactly what I like to do, take things apart I'm not supposed to.." Right on! I was going to quote him on the same LOL. That's a great T-shirt quote
What a treat to see the electric motor in my 2017 Bolt! Thanks! I've had it about a year. It feels like it could go a million miles. No pistons and valves thrashing about. No transmission. No gas station. No maintenance.
Would love to see how this compares functionally to the Model 3, also can't wait to hear your opinions on reliability between the two. Thanks again for the hard work!
@@belvedere351 Million mile Model 3 mule is in good condition: twitter.com/elonmusk/status/1051917544301285376?ref_src=twsrc%5Etfw%7Ctwcamp%5Etweetembed%7Ctwterm%5E1051917544301285376&ref_url=https%3A%2F%2Felectrek.co%2F2018%2F10%2F15%2Ftesla-drive-after-million-miles-test%2F
@@ravismaximus7972 Unlike the Nissan Leaf battery disaster, the liquid cooled Chevrolet Volt batteries made by LG are holding up very well after 8 years now. The liquid cooled Bolt EV batteries are also made by LG. Only time will tell, but I suspect they will last just as long.
Did this all my life before I retired, and this is an extremely well made video with plenty of tips for 'Flat Rate' Techs that need to gain an edge in knowledge. Congratulations Sir, well done!
Your videos bring be back 30 years to being a kid in the garage with dad, being taught how to rebuild chevy small blocks. I have no business in ever servicing an EV, but I still can't stop watching your video's due to the "dad factor" here. Thank you!
This was really cool. I'm not even a car guy, but that hour went by really quickly. I love deep dives into the nitty gritty of different technology and you did it while explaining things really well. Cheers!
When I disassembled my dad's rotary engine, I was impressed by its simplicity. However, I didn't know that engine was plagued by problematic high maintenance seal issues. This looks truly high tech and low maintenance. Excellent video.
Just beautiful! The beauty is indeed in its simplicity! The passthrough drive shaft is just brilliant. Amazing to conclude that this 4x shoebox produces 360NM and 201 HP.
I agree with that part being simple and elegant. The rest of it, though, I am not so convinced. The transmission fluid cooling of the motor, for instance, seems to me to be a bit difficult to service. Does the level of the transmission fluid not reach the rotor also? Otherwise there would fluid friction losses there.
Mechanical Engineering student from India. I wish we had such a well equipped machine shop at our college, but you have been a tremendously helpful source for me to understand EV technology and this is perhaps the best online resource for EV enthusiasts and students looking to develop their skills. Thank you so much Professor Kelly, I hope I can meet you in person.
Just stumbled upon this vid. As a former mechanic with little knowledge of EV's I have to say this was beyond interesting and would add that this is probably the best instructional review I've ever seen. I was particularly impressed about the differential fluid baffle, something most people wouldn't give any thought to. I'll definitely be checking out more from you.
Spectacularly well done video, sir! You are super great at explaining the design and design intent, and, as you say, the motor is a masterpiece. It's also really great to see a differently abled person doing this sort of work. You extend the range of being for all of us. Thank you very very much.
The most clear and concise instructional video I have ever seen.Thank you for a highly professional presentation of technology that many of us are still struggling to comes to terms with. I feel so much more enlightened now.
As a Belgian collegue, 'welded to a wheelchair', I see knowledge combined with persistence, and a very very clear and teachfull explanation. I just pulled my eyes when you hoisted (which you had never done, and never should do again that way: a hoist eye with an M20 threaded hole on the rod @10 USD would have been safer) But: overall big respect, and many thanks for this (un)remarkable explanation! Thanks! The heat for an electric motor like that is regulated at 110° C or 230° F. (Class F means 150¨C or 302°F max) So special coolant indeed needed. VERY HOT!
You Are one of the best, most thorough, detailed instructors i have ever had a chance to watch, you are probably better at explaining the concept then the people who designed it!! thanks- Virian Bouze'.
Watching this, I’m reminded of the gynaecologist, who, trying to broaden his interest, went to a Community College for a course on Auto Mechanics. The final exam involved disassembling and reassembling a car’s engine. He was surprised that his mark was 150 out of 100. When he questioned the instructor, the response was. . . “50 for disassembly, 50 for reassembly, and 50 for doing the whole job through the tailpipe. I am in awe!
I've been watching these videos to start learning about EV's and how they work since my background is piston engines ☺️. fascinating. that bolt drive unit is really thought out!
After seeing your professional work/explanation even with your difficulty from sitting in wheelchair, it is so amazing and inspiring. From now on I need to improve how I work and change my attitude towards problems that lie in front. Thank you sir.
"You can't be a mechanic because you're handicapped" "Oh, wait a minute... You can?" Very well explained, the video has a pleasant structure and an insight into the additional difficulties you have in a wheelchair. And everything without a helper. I am impressed and hope that I can learn something from it when something is a bit more difficult than I would like it to be!
Just wanted to thank you for the wonderful information you and Weber State share with the world. I'm the kind of guy who almost never buys a new car, but rather buys something that I feel confident I can service. Your videos have saved me from being lulled into buying something that was never intended to be serviced. The oil level check, draining, and filling procedures were enough to scare me off of this platform permanently.
I know your primary intent is to learn, and teach in these. Sometimes you mention something about the design or an improvement (like the incorrectly sized shaft tool), but with all of your experience I'd love to hear about what you think are potential failure points, and weaknesses. Your videos are amazing. Thank you so much for want you're doing.
My first reaction was that the electric oil pump was a weak point. Thankfully its external and relatively easy to get to. I hope they have multiple sensors to catch a failure in the pump or motor or loss of oil pressure. GM in the past hasn't been the greatest at making their small electric motors very durable (fuel pumps etc) and letting the economy cost reduction engineers reduce thickness and length of wires, i.e. Not making the wires going to that little motor thick enough and using high enough quality of relays.
Thank you Chevy designers! I love my 2019 BoltEV. As an efficiency nut, I'm continually amazed by this technology. Keep up the good work - I'm ready to buy a work van version.
My wife and I are buying our first EV vehicle, and I'm the guy that generally has to know first hand with my own eyes, all the inner workings of my vehicles. I was, until now... accepting that I have no idea how these things work. Now I do! Awesome.
Appreciating the precise to the point crystal clear language, and its application to bring to the audience a piece of new automotive technology we are all going to be using, the sooner the better.
Excellent video, very well explained and very clear spoken commentary. Thank you for that. That motor is a master piece of engineering. The coating on the roller bearing is some kind of insulation medium to reduce circulating currents in the armature, which can cause pitting of the races of the roller bearings. Similar bearing coatings are used in large traction motors of railway locomotives and large industrial motors subjected to heavy loads.
@@WeberAuto C A U T I O N (?--lol)----i see now a possible reason to not re-use those shims...that coating... not that it matters much,how can ANY mechanic successfully rebuild that contraption after a major (or even minor) failure!!! it's a mother ... of all complications; i thought it was simple,just an electric motor; silly me!
Jose Peixoto: What mechanic rebuilds engines or transmissions? The amount of specialty equipment needed means we have shops that specialize in doing just one thing. Engine rebuilds, transmission shops, radiator shops, muffler shops, tire stores, diesel fuel injection pump rebuilders, etc. When was the last time a mechanic removed a motor, disassembled it, machined the head, honed the cylinders, ground the crank bearings and cam lobes, etc and reassembled everything himself. The economics make that untenable. Early repairs will be warranty replacements from the manufacturer, then salvaged units and then 3rd party rebuilders. The days of simple electric motors and boat batteries meant a range of 20-50 miles and replacing batteries every year. Hi-tech electric motors do work a lot better. People wreck cars faster then they wear them out so there is a surplus of engines that cost far less than rebuiding. By the time the Bolt warranty expires, there will be plenty of salvaged units available.
Thank you Professor. Very instructive, very lucid explanations! One comment. Someone was asking if this motor is a "BLDC" and you responded in the affirmative. Although these motors still seem to be classified as BrushLess DC, it seems a shame because the term can be misleading. The elimination of physical "brushes" that commutated (or made a pathway for) an electric current to be fed to the rotor was made possible by electronically bridging current to the rotor. However, the Bolt EV and most if not all similar EV motors do NOT conduct a current to the rotor. Therefore I favor the designation "SPM" (Switched Permanent Magnet) motor, because it is in fact the natural rare earth magnets buried in the rotor that supply the opposing magnetic field that interacts with the switched (switched on and off) electromagnets in the stator coils. Another designator that may apply to this motor is "IPM" or Interior Permanent Magnet motor. As noted in your video and a relevant SAE paper I just located (and linked below) The magnets are buried in a "V" patterns in the interior of the rotor. The Tesla Model 3, and many EVs, have gone to the IPM design (although the exact layout of the magnets inside the rotor may be radically different). Finally, and not to be too confusing, another attribute of many of these EV motors is that they use "reluctance forces" that augment the permanent magnets. A Reluctance machine is simply one with embedded ferrous material (but not magnets) in the rotor that react to the electromagnetism produced by the stator. I have head it said that the Bolt EV motor is a IPM / reluctance hybrid design (as is the Model 3 rear motor). The SAE paper does not explicitly state this, however, even Nikola Tesla described reluctance forces at work in his AC induction motor. (Another reason I hate to see the term BLDC used is that it gives the impression the motor is primarily a DC (Direct Current) motor, when in fact, as I best understand it, the Bolt EV motor (again, like the Model 3 rear motor) is a 3-phase AC motor. An inverter in both cars converts battery DC to Alternating Current, which is switched On/off in order to produce spurts of electromagnetism in the stator windings... which of course interact with the permanent magnets and reluctance forces in the rotor... causing it to spin. ;> So here's a request: Please take that Bolt EV rotor APART so that we can see exactly what's goin' on in there! www.sae.org/publications/technical-papers/content/2016-01-1228/
Thanks for your great feedback. I understand there are several names for this type of motor. An additional one is "Synchronous AC motor". There is SAE terminology, manufacturer terminology, service industry terminology, and the general public's various descriptions of the motor as well. I have even seen two different names in the same document. It can be confusing for everyone involved. I try to use the manufacturer's own terminology in my videos and fall back on the SAE terminology when necessary. One clarification: An inverter does not create AC current. It simply pulses DC current through the wye wound three phase windings in sequential order over and over again (giving the illusion of AC current) to drive the rotor. Thanks again!
@@WeberAuto "An inverter does not create AC current. It simply pulses DC current through the wye wound three phase windings in sequential order over and over again (giving the illusion of AC current) to drive the rotor" Ha ha. Well there may be more to say about that, in another venue, but alas, I am a mere student of this science anyway. :> I guess you may be loathe to take apart that Bolt rotor, because who knows what special tools might be needed to pry that can off. But it seems to me the arrangement of the interior magnets is where the real nuance is, where motor engineers are coaxing out the last possible bit of power. I'd love to see a side-by-side view of the Bolt and Model 3 disassembled rotors, because Tesla has been at it in Greece cooking up their own brand of secret sauce. Still, that was very enlightening what you passed on about the Bolt's stator. Clearly GM is pushing the envelope there. Again, thank you for this long awaited Bolt video!
I have no doubt I could disassemble the rotor, but I need to use it again in the car. The SAE document clearly shows a cross section of the magnet arrangement in the rotor along with a few other surprises to decrease torque ripple and increase efficiency. I would love to get my hands on a model 3 and do a comparison. That may be a while ;) have a good evening.
You are right about the terminology being a bit off. A BLDC really means what you might call a synchronous AC packaged with a controller so you can supply DC to it, and it runs, without having brushes. To the end user, it is a brushless motor they can supply DC to. As others mentioned, the motor itself isn't exactly running on AC anymore, either, since it is just getting well timed pulses of DC, instead, in the vast majority of cases. Some controllers do attempt to ramp the current up and down to more closely mimic what we think of as AC, but others just bang it with all the volts switching on and off and let reactive power try to smooth it out.
If I was 20 I would move to whereever this school is and attend. Hybrid training is offered in person boot camp style for less than $2,500 or online for even less. People truly certified in electric cars will be gold plated. Absolutely the best value in education possible.
At last, somebody knows how to speak clearly! This man John D Kelly knows how to speak clearly and exacting. Thank you so very much! I am anxious to sit down and watch more of you speak to me as a professional teacher should in every sense of the word. I will be watching and listening to every word you say when it comes down to learning about these amazing new engine technologies
Mrs. Kelly: John, for crying out loud have you seen my boxes of Ziplock bags ?!? Fascinating engineering! Thanks again, Professor Kelly for this amazing content.
Welcome to the future, where you use power to go, instead of tricking million year old algae into mixing with the right amount of air, exploding it, and trying to catch as much of that explosion as possible while firing the bulk of it out the back and into the surrounding environment as waste gasses and heat,.
It really is. I was blown away by how thin the stator was. The stator field on just a 3/4 hp fan squirrel cage motor is far thicker. This engineering is the future
21:17 Anytime you have to shim pack for play adjustment... there will usually be 2 or 3 different size shims: 1- "face" or "thrust" shims... these will be on either end of the pack, and may be 2 different sizes. They are usually differentiated by surface laminates or composition materials. 2- "fill shims" or "packing shims" are usually made of cheaper materials, as they don't require as much friction/deformation resistance.
Professor Kelly, You are such a gifted teacher and right to the point including detailed nuances. Thank you for this fabulous vide. Happy New Year to you Thank you so much! Armin
Prof., I am your latest new fun from Nairobi Kenya. I love your videos very much. Am currently working as a mechanic for a British army engineering contractor here in Kenya and your videos are very helpful in my work. Thank You.
In the first 3 minutes, you perfectly illustrate why we calculate power:) Please understand I really enjoyed the video. My issue was only with a 30 second segment. I mean this constructively. I just hope this helps a few people to begin to understand something very important and elementary about engineering in these subjects... Here's the issue: The statement at 3:30 that the Bolt EV's drive is "more efficient" and a "better design electric motor" could be true, but actually nothing you'd said so far suggests it. The crux of my point is that in order to draw conclusions about performance (how much oomph does the vehicle have) we need to *either* deal with metrics that have those dimensions (power), or know something about *all* major factors that contribute to it. In the case of a vehicle, voltage, current, and torque and speed are all just factors. For example, if we're going to compare lower-dimension metrics like torque (anywhere) between two drives and use that to conclude anything about higher dimension metrics like power, we need to first establish that all the other lower dimension metrics are unchanged or known (which they aren't in this case). Operating voltages or motor speeds between the two cars were never mentioned. So we can't conclude anything about power or efficiency. In more specific terms: In order to know the efficiency of a motor you must compare power-in and useful power-out. Power-in is electrical (voltage x current), and the two forms of power out; mechanical (rotational speed x torque) and thermal (Joules/s, etc...). You have only compared the current of the two motors. We don't know how the operating voltages compare, so we can't know how power-in compares. And on the output side you have only really given torque. We don't know how rotational speeds compare, so we don't know mechanical power-out either. Now it must be said that since we are comparing two small passenger vehicles, we could expect the axle speed to be similar... but I digress. What I'm really getting at is that by just citing the rated power of the Spark EV, we would have had a good sense of how the two drive units compare performance-wise. You had already stated the rated power of the Bolt EV. Then with additional clarification of power in vs out we could then calculate efficiency and even the heat remainder we have to dissipate. It may seem like nit-picking to some, but to the many who pursue and invest in mechanical ideas without understanding what dimensions are, these often becomes toxic misconceptions that seem to last way too long. They are also tragically reinforced by oblivious marketing and other things. Since electric propulsion is still finding new applications, and since in many ways it has fewer design constraints than combustion engines, we often see a lot of variation between the propulsion units of otherwise similar electric vehicles. This makes is easy to show (as you did) that peak motor/engine torque alone tells you nothing about vehicle performance... As you pointed out, It's really all about the "thrust" - torque at the wheels (divided by wheel diameter of course), and to know that you have to know the total gear ratio at the moment in question. But for a given road speed, that ratio (and thus the torque multiplication) is directly related to how fast the motor is turning. So if our goal was to have a sense of how much performance we can expect, we should skip talking about gear ratios and diameters and simply consider the power (torque x rotational speed, or volts x amps x efficiency). Obviously this video focuses on a specific drive system, and so appropriately you dive into that... which was very interesting! I'm just getting at the common dimensional misconception about torque, volts, and amps, and speed vs power. A great example is the cordless tool market. 12V was bested by 18V, 20V, 36V, 60V... and so people begin thinking voltage = power. Nope! The higher voltage HAS usually correlated to higher power, but only because the current is has been held constant the whole time by simple things like standardized battery cell size. Battery packs could have just as easily been made in parallel instead of series and the motor given a different winding, but then we'd see a 3.7 V drill for the same price as a 20V! You would actually have to try it to find that the performance (power) and battery life are identical:) In that market, smaller factors like using lighter gauge wires tipped the scales toward using series packs... If it had gone the other way, we'd be choosing one drill over another "cuz it's got more amps" Lol! This misconception tends to be strongest among groups of people where hardware is the most consistent - where those pesky unknown variables don't change much and using things like torque, volts, or amps, as a performance benchmark is forgiven by the uniformity of the things being compared. Enter the Small Block V8 :) The standardized ways we typically mod combustion engines, increasing the peak torque of a given engine *does* usually increase performance, and so the misunderstanding is reinforced. It is generally true that if you push harder on the pistons, you push backward harder on the pavement as long as it doesn't require you to shift up... it usually doesn't, so folks can continue thinking its all about torque without understanding or caring that they also just increased power. Then there's the very real effect of the shape of the power curve and how this has a measurable effect during takeoff and for discrete-gear transmissions which must spend time off-peak. Aaaand then there's the internet sludge resulting from confusion over units like magic 550 HP-torque "cross over points"... I deeply love piston engines, but I hope as EVs come more into focus, it becomes easier for budding engineers to see how physics works:) Cheers for reading this.
Thanks for your detailed feedback and constructive criticism. The Spark and the Bolt both have 400 V batteries (which I did not mention in the video). Motor rpm of both the Spark and Bolt EV were discussed at 3:25. FYI this is the 7th video in series on the Bolt EV where we totally removed/disassembled/reassembled/reinstalled the 400V Li-Ion battery as well as the other HV components of the vehicle. Have a great day!
Astute observations and I generally agree. It will be interesting to watch how the general conversation transforms as folks begining to grasp and internalize these "new" fundamentals.
"ET" = Extra Terrestrial where I come from! Great video. An amazing piece of engineering. Makes me appreciate my 2017 Bolt even more (34k miles and counting!) But I sure hope my Bolt never needs any service on the 1ET25. Why? Three words, "Chevy dealer mechanics"
Thanks for you feedback. There are good and bad technicians out there, obviously the trouble is finding one you can trust. We are slowly training a new generation of technicians to work on these vehicles.
I actually came here looking for a teardown of the powertrain of a Tesla, but I found pure gold, I'm not a mechanical engineer nor into cars. I'm a Computer Science student and electric engineer, but I was able to catch all the details! 10/10 great video!
Sir, a very Excellent video and disassembly work on this equipment. I enjoyed watching your clear presentation and no nonsense professional attitude. My compliments then. V/r, Steve Ferguson
@52:02 that stator looks like a work of art compared to those with lots of turn of thin wire. Precisely the amount of copper exactly where it’s needed for efficiency....and then someone came along and put that crude gear range selector mechanism and actuator on it.
@@WeberAuto Exactly. Why go all Rube Goldberg with it like this when they could have just had the actuator run only the parking pawl like the NHW20 Prius, unless doing so would have violated a Toyota patent or they initially planned to just have a conventional shift cable. Oh well, it makes it easier to repurpose this unit for things like doing a BEV conversion of an ICE car and just reuse its shift cable.
I enjoyed this video very much, thank you. I especially appreciate the clarity of the presentation. Also, you were wearing your wristwatch while handling the rotor. You didn't get stuck, eh?
Great Tear down! Whilst this eMachine is considered to be decent (if not quite class leading) for mass production EV powertrains, it's miles away from the "ultimate" electric machine! I worked on the FormulaE motors, which make 300 bhp from around 20kg, and spin at up to 25,000 rpm! (the magnetics alone cost $$$$$$ they use water cooled rotors (ie water is pumped into the spinning rotor and out again to limit the maximum magnet temperature due to the high speed rotor losses... ;-) The advantage of a 'hairpin' stator winding architecture (its easy build and assembly, that avoid the complex multi-filament winding and packing of a conventional stator) is of course offset by a lower efficiency due to skin effects (high frequency AC) in those large cross section hairpin conductors. Using 6 stacked hairpins is a sort of half-way-house, keeping the relative ease of assembly, but reducing that AC loss. Note, the loss is proportional to switching frequency (and it's harmonics) rather than motor rotational speed. Those losses can be further reduced by running a lower fundamental switching frequency, at the cost of an increase in I2R losses due to the additional ripple current that results. It's also worth noting that, actually, motor efficiency is NOT the be-all-or-end-all of EVs, because even absolutely terrible eMachines are still around 93% efficient, with an F1 spec motor being say 98% efficient, that's 'just' a 5% increase. Worthwhile, but not actually that significant on it's own (Hence most EVs today major on reducing the roadload (low drag) in order to maximise range)
The best power to weight ratio I could find is 16kW/kg from an induction machine for aerospace applications. Your formula E is about 10kW/kg. The power electronics are included in that power to weight ratio, but no gears. The heat rejection (losses) of 98% efficient 200kW is only 4kW - thats brilliant - and makes the cooling system small and effective.
Yeah, compared to a gasoline or diesel, definite advantage, but I am thinking that these could still be simplified quite a bit. One thing that comes to mind is to just put motors or gear-motor combos in each wheel. Then you don't need to have differentials (handled by computer) and cv shafts. You could power 2 or 4 wheels, do traction control all in drive train and skip break disk traction control all together possibly. Also the inverters should be on each wheel with only power lines, break lines, control lines to each wheel. Also the wheels themselves could be designed a lot better at dissipating heat from the motor also. It could be simplified to the point where the wheels and the steering mechanism and a cooling pump are the only moving parts. All of the rest are just in control and support of the wheels.
@@IntenseGrid Yep. Good analysis. When this happens in a modular style the world will change. You'll be picking a Tesla wheel in LA, and a Colorado Solar wheel in the mountains, or some such. The evolution from here to more than four wheels e.g. powered trailers and so forth would allow for greater efficiency. SOVs need to get smaller. Air drag is about all that is left when system efficiency rises to these levels. Hurray for MOSFETs, IGBTs, and whatever is next. Will capitalism allow a modular style like the IBM PC? Musk could make it so.
Yeah. I have been thinking about this design for more than a decade, but don't have the resources to implement it. Then I saw some prototype at some show with what was called a "skateboard" design, which is very similar. The other thing is power generation. With robotics the way it is, if you need longer range, like for a long trip, with open spec power and coolant connections, you could have a gasoline or diesel charging unit sit in your garage, and when you need it, you give it the command, and it robotically climbs into your trunk. Or, you could have extra battery packs install the same way. There is no reason to be hauling around all of the extra weight (like 200+ lbs) for your daily commute. The ICE can be designed for peak efficiency, without the need to rev for acceleration. With open standards, competition can drive more and more efficiency. Also, with open standards, we can stop being churned by the big motor companies, which right now change some things just for the sake of extracting money from you.
@@IntenseGrid I wouldn't skip CV shafts. Even smaller motors fitable to wheels have significant mass. It would be better to accept losses at CV shaft, then put that mass into the wheel. But otherwise I agree.
An amazing video. You are the king of explaining things. Your students are very fortunate to have you as their instructor. I have to tell that I watched all of your Bolt EV videos before I bought my 2021 Bolt. You were a major contributor to me deciding it would be a great car and I really Love. Thank you for being who you are. I’m 74 years old and worked cars all my life and I was surprised on the lack of parts in the drive unit. You explained it very well.
I am only echoing others when I say this is the best technical video I have ever seen. At no time was I bored. Every bit of information was useful. Skillfully edited and well photographed. Superb work. Your students are lucky to have you.
The difference between this dratrain and the Leaf is that the Leaf started out from a Kei design - Nissan simply replaced the 660cc engine and transaxle with an electric motor mated to a single speed transaxle in the first iteration. It was conservative, absolute minimum re-engineering - which was sensible given the gamble the company was taking being essentially first-to-market with a mass-production, mass-sale, reasonably priced EV and the risk that something radical might also have had reliability issues (that whole "not changing too many things at once" philosophy) It also meant that the production line facilities didn't need any tweaking - important if sales didn't do well. Remember the Leaf was essentially an experiment produced to see if there was a mass market for EVs Newer generations will probably follow GM's lead and go to a unified transaxle. WRT the layers of conductors and comments about AC losses - as the motor speeds up, skin effect(*) is going to start playing a big part in the impedance of the windings - this is where most of the heating is coming from. (*) As frequencies rise, currents only travel in the outer surfaces of the conductor rather than the whole body. The depth is more-or-less known for any given frequency and starts becoming an issue above about 20kHz. The other part that becomes problematic is that high frequency currents "don't like sharp corners" (the magnetic fields tend to distort and "fly off the end"), so those hairpin folds will become essentially a pinch point for high frequency current flow. Traditionally the stator winding ends would be smooth arcs. I suspect that GM will modify this design as RF power engineering expertise is brought to bear on increasing AC efficiency and improving motor rotoational top speed.
@@WeberAuto NP. FWIW, it's worth noting that a lot of very high power electric motors have _hollow_ conductors (remember that skin effect) which can have coolant run along their insides. Whether this is tenable in an automotive environment remains to be seen but I'll bet some motor makers are considering it.
Professor John D. Kelly: I'm a Master´s student in UNAM Mexico. Are you going to do a next video about 1ET25. I'm looking for the dimensions and features of the gears, specially the module or the diametral pitch. Thank you very mucho for all those videos
I live in Finland and my English is not very good but I want to say that these videos are so excellent and well done! I have been always interested about all technical things and these videos shows exactly how things works. Also Your English is clear and easy to understand even for me and it makes videos easy to follow. Thank You very much, I hope You will make many more videos in the future! All the best for You sir!
As a tech I would have a .25" wall aluminum cylinder lined with a nylon liner to hold that magnet with aluminum caps. This would keep it safe from metal partials in the air in a shop environment.
I was thinking something similar. That rotor is pretty bad ass... and probably impossible to clean of shavings. But I'm a newbie to this channel and am blown away by the complexity of automotive tech these days.
(edited, somehow the first para of my reply went walkies) You _can_ remove _tiny_ and low ferrous content stuff off superstrong magnets with silly putty/bluetak, but having had to do something like this, you really don't want to have do _do_ it. I second the sleeve idea and would go as far as suggesting that it should somehow be thin enough to slide into rotor before withdrawing it from the motor and/or wrapping a few layers of saran wrap or similar whilst it's still on the hanger after withdrawal. You really _dont_ want any form of magnetic contamination on this surface. As for actually _removing_ it in the car as GM are clearly expecting - "You'd have to be nuts". The engine/motor bay of a car with a few thousand miles on it is simply not clean enough no matter what you might do. I wouldn't even encourage attempts to disassemble this thing/remove the endcaps in the average service workshop, let alone an engine bay. The clearances, in-service voltages and magnetic fields grabbing onto anything nearby effectively require "clean" conditions and an attention to detail that most dealer service bays simply lack (and good luck making it work after the semi-skilled apprentice has been tasked with "the minor jobs"). I foresee a lot of wailing and gnashing of teeth when these things start requiring in-field servicing. That 3-phase connection port is going to require extra special attention to ensure _nothing_ gets into the works during normal servicing if the cables/grommet are disconnected. and similar special attention when reassembled. I spent half the video looking at the cutout and the access pathways it provides for contaminant, shaking my head and saying "they didn't really do that, did they?" to myself. This is likely to prove a weak point in future and GM could have engineered it out from the beginning with some suitably shaped inserts to effectively keep that connection port IP56-rated until they're removed from the _inside_. .
If I may, keeping in mind I'm never going to be working on one....When pulling the rotor I would have continued turning the top nut until I squeezed the top and bottom nut against the plate so that it wouldn't flop around as much. It's a pleasure watching you work. Cheers and prosperity in the New Year.
Grey coating is an insulator, to prevent circulating currents through the bearings from any slight imbalance in magnetic field in the motor. there is a single bearing that is grounded ( the shiny one) to prevent charge build up on the rotor and a flash over to the frame, but the rest have to be insulated so they do not have a shorted turn through the frame that can cause a high circulating current through the bearings that rapidly erodes them through arcing. There are current paths for this current via things like the output shafts and the selector forks, but they probably assumed that, being long thin wall section steel assemblies, this long path would both keep the current low enough not to cause any major extra wear, and also the long output shaft would be mostly self cancelling field wise as well.
A lot of larger electric motors handle this with one end having coated bearings, or they make them with ceramic bearing balls inside, or just make both sides with insulated bearing mounting frames, and provide a grounding carbon brush assembly to handle shaft grounding. Drawback of the coated bearing is that you have to ensure that there is absolutely no damage to the coating on the outside and the side facing the frame, so that there is no metal to metal path. However, depending on the exact coating applied, this coat can be both insulating and tougher than the steel of the bearing itself. grey would point to a spray on ceramic coating, probably vacuum deposited before final bearing assembly or applied as a plasma coating.
Fantastic information! Thank you very much! The Nissan Leaf gear reduced uses brushes for shaft grounding. Have a great day!
SeanBZA - Those early Tesla Model S drive failures everyone was talking about a few years ago? That was the far end bearing being eroded by current leakage. There was already a brush grounding the shaft to the case, but it was insufficient. Apparently, the Model S induction rotor pumps out a lot stay voltage compared to a permanent magnet motor.
I wondered if that was the problem with the Tesla bearing failures. Thank you!
WeberAuto - the Tesla motor issue would seem to have been addressed more recently than would have occurred during the design phase of the Bolt EV powertrain, although we don’t know when Tesla knew of the issue/solution with their motors, and started working on a solution. Unless there was some information sharing between OEMs and suppliers that occurred, I’d think a similar outcome from this issue affecting 2 or perhaps multiple OEMs would be unlikely. This is where information sharing as EV powertrains evolve would benefit us all in the long run. There’s no sense in having ALL OEMs encounter - and learn from - the same failures.
@@dennislyon5412 Thanks for your feedback, I it makes sense to share that type of information if we want to promote the success and reliability of this powertrain type.
My university days are long behind me but I spent 3 hours on 2 videos, without stopping. You give great presentations.
I'm a mechanic of internal combustion engines and you just introduced me to the future of automobiles. I'll remember you to my grand kids years from now when they start to learn to fix their own EVs. Thank you, Sir.
I had been an auto mechanic for many years. I developed multiple sclerosis which is slowly leaving me dependent on my wheelchair more and more. Watching this video, was amazingly awesome. It gives me hope that even though I'm more dependent on my wheelchair, it doesn't leave me nearly as helpless as I had once thought.
Thank you.
Thank you very much! Best wishes
The fact that you can do what you do, by yourself, in a wheelchair, while being both patient and professional, is absolutely amazing. Keep up the good work professor. I'm just a curious viewer but wholesomely impressed by what I see.
Congratulations.
After all these years on You Tube, at last a professional quality video.
A no nonsense, no childish attempted humour. a clean workshop and no dropping tools or bits.
From 00:00 seconds to 58:42 seconds it looks to have been well prepared and delivered in a beautiful clearly spoken voice. This is a first class video.
Thank you very much!
Yes, totally agree about the 'no childish attempted humor'. I am SO tired of seemingly endless video makers who seem to feel that to get information across they need to 'spice it up' with lame humor, or obnoxious rock music or absolutely unnecessary computer graphic intros. It's exasperating. Just clean and clear, understandable, accurate, in-depth information goes SO much farther.
I had very little idea of what was going on under the hood of my 2023 Bolt 2LT until I stumbled upon your videos. Thanks for all the time and effort you've invested in this brilliant series. We owners are your beneficiaries!
I will never disassemble one of these motor units, but found the whole thing riveting. I cannot begin to understand how engineers design and manufacture this and other precision machinery, it is all beyond my feeble brain. Thank you Professor.
Thank you very much
And this is an *incredibly* simple gearbox. You should see what the inside of an automatic transmission looks like; absolute madness.
I'm almost retired but want to take this man's classes and start my career all over again!
What can i say that hasn't been said already. Absolutely the best presentation on the Bolt inner workings period! Professor, you sir, know how to teach and illuminate the minds of the curious. Thank you!
Weber Auto is an absolute gift. One can gleam some mighty useful information in these clear, concise, and very educational videos. Thank you for the dedication to teaching us!
Thank you!
"There are no instructions on disassembling this, so I assume we're not supposed to disassemble it, but that's exactly what I like to do, take things apart i'm not supposed to, as long as I can get them back together and work again" the best quote in the video :)
You are one of my hero's professor Kelly, and you inspire me to keep living, even in the darkest hours of life, thank buddy, your content helped to save my life!
Thank you very much! I love exploring technology
"...but that's exactly what I like to do, take things apart I'm not supposed to.." Right on! I was going to quote him on the same LOL. That's a great T-shirt quote
What a treat to see the electric motor in my 2017 Bolt! Thanks! I've had it about a year. It feels like
it could go a million miles. No pistons and valves thrashing about. No transmission. No gas station.
No maintenance.
Very reliable system!
Would love to see how this compares functionally to the Model 3, also can't wait to hear your opinions on reliability between the two. Thanks again for the hard work!
@@belvedere351 Million mile Model 3 mule is in good condition:
twitter.com/elonmusk/status/1051917544301285376?ref_src=twsrc%5Etfw%7Ctwcamp%5Etweetembed%7Ctwterm%5E1051917544301285376&ref_url=https%3A%2F%2Felectrek.co%2F2018%2F10%2F15%2Ftesla-drive-after-million-miles-test%2F
Battery are the fail point in about 5 more yrs and will be more then the car 10 fold good luck
@@ravismaximus7972 Unlike the Nissan Leaf battery disaster, the liquid cooled Chevrolet Volt batteries made by LG are holding up very well after 8 years now. The liquid cooled Bolt EV batteries are also made by LG. Only time will tell, but I suspect they will last just as long.
Did this all my life before I retired, and this is an extremely well made video with plenty of tips for 'Flat Rate' Techs that need to gain an edge in knowledge. Congratulations Sir, well done!
Thank you very much!
I'm an engineer helping design transmissions. Really appreciate your videos, you do an excellent job of understanding and explaining things.
Your videos bring be back 30 years to being a kid in the garage with dad, being taught how to rebuild chevy small blocks. I have no business in ever servicing an EV, but I still can't stop watching your video's due to the "dad factor" here. Thank you!
"Simplicity is not necessarily easy." Great video. Really shows how much smaller, simpler, and efficient than ICE.
Wow that hour went by fast! Extremely interesting. Thanks for the video!
Thank you!
I really appreciate these videos produced by Professor John. Great job. There are generations of technical minded people who can benefit from this.
Thank you very much!
Thank you doctor. It is refreshing to listen to someone who knows the details of what he speaks. Truly.
Thank you very much!
This was really cool. I'm not even a car guy, but that hour went by really quickly. I love deep dives into the nitty gritty of different technology and you did it while explaining things really well. Cheers!
Thank you!
When I disassembled my dad's rotary engine, I was impressed by its simplicity. However, I didn't know that engine was plagued by problematic high maintenance seal issues. This looks truly high tech and low maintenance. Excellent video.
Thank you!
Just beautiful! The beauty is indeed in its simplicity! The passthrough drive shaft is just brilliant. Amazing to conclude that this 4x shoebox produces 360NM and 201 HP.
Thanks for your feedback!
I agree with that part being simple and elegant. The rest of it, though, I am not so convinced. The transmission fluid cooling of the motor, for instance, seems to me to be a bit difficult to service. Does the level of the transmission fluid not reach the rotor also? Otherwise there would fluid friction losses there.
@@IntenseGrid "seems to me to be a bit difficult to service." Even if this is true, the fluids don't need to be changed until 150k miles!
Mechanical Engineering student from India. I wish we had such a well equipped machine shop at our college, but you have been a tremendously helpful source for me to understand EV technology and this is perhaps the best online resource for EV enthusiasts and students looking to develop their skills. Thank you so much Professor Kelly, I hope I can meet you in person.
I am happy they are helpful for you. Thanks for watching
Just stumbled upon this vid. As a former mechanic with little knowledge of EV's I have to say this was beyond interesting and would add that this is probably the best instructional review I've ever seen. I was particularly impressed about the differential fluid baffle, something most people wouldn't give any thought to. I'll definitely be checking out more from you.
Thank you very much!
Spectacularly well done video, sir! You are super great at explaining the design and design intent, and, as you say, the motor is a masterpiece. It's also really great to see a differently abled person doing this sort of work. You extend the range of being for all of us. Thank you very very much.
Thank you very much!
The most clear and concise instructional video I have ever seen.Thank you for a highly professional presentation of technology that many of us are still struggling to comes to terms with. I feel so much more enlightened now.
Thank you very much!
You get an "A" in communications skills and the spoken English language.
English? What is aluminum and farenheit?
@@fivish _ Well, you can tell he is not talking about a female body part when he pronounces "CAN'T", right?
@@fivish Aluminum is a metal in the boron group, and Fahrenheit is a unit measure of temperature - DUH.....
As a Belgian collegue, 'welded to a wheelchair', I see knowledge combined with persistence, and a very very clear and teachfull explanation. I just pulled my eyes when you hoisted (which you had never done, and never should do again that way: a hoist eye with an M20 threaded hole on the rod @10 USD would have been safer) But: overall big respect, and many thanks for this (un)remarkable explanation! Thanks! The heat for an electric motor like that is regulated at 110° C or 230° F. (Class F means 150¨C or 302°F max) So special coolant indeed needed. VERY HOT!
You Are one of the best, most thorough, detailed instructors i have ever had a chance to watch, you are probably better at explaining the concept then the people who designed it!! thanks- Virian Bouze'.
Thank you very much!
Watching this, I’m reminded of the gynaecologist, who, trying to broaden his interest, went to a Community College for a course on Auto Mechanics.
The final exam involved disassembling and reassembling a car’s engine.
He was surprised that his mark was 150 out of 100.
When he questioned the instructor, the response was. . .
“50 for disassembly, 50 for reassembly, and 50 for doing the whole job through the tailpipe.
I am in awe!
😅😅😅😅😅😅😅😅😅
First time here - I really appreciate how clear and specific you are with everything. Thank you!
Welcome! Thank you very much!
I've been watching these videos to start learning about EV's and how they work since my background is piston engines ☺️. fascinating. that bolt drive unit is really thought out!
thought out to be a typical gm piece of shit
I want to give you one ,like, every minute of those 58 minutes for this video ,great job professor.
Wow, thanks!
After seeing your professional work/explanation even with your difficulty from sitting in wheelchair, it is so amazing and inspiring. From now on I need to improve how I work and change my attitude towards problems that lie in front. Thank you sir.
Thank you very much! Best wishes!
40K miles on my 2017 BoltEV. This is awesome to see. Thank you.
Awesome! 40k miles. Thank you!
This video and motor design was so much better then I expected but, I can't wrap my brain around the need of the complex shifting mechanism.
Thanks for your feedback. It is a strange shifting system
Yeah. That's super weird. My Tesla "shifts" forward and backward electronically and the parking brake just clamps the disc brake rotor.
"You can't be a mechanic because you're handicapped"
"Oh, wait a minute... You can?"
Very well explained, the video has a pleasant structure and an insight into the additional difficulties you have in a wheelchair. And everything without a helper.
I am impressed and hope that I can learn something from it when something is a bit more difficult than I would like it to be!
Lol, yes I can. Thanks for your feedback!
Thank you professor. It's encouraging to see American ingenuity is alive and well. I love your thoroughness.
Just wanted to thank you for the wonderful information you and Weber State share with the world. I'm the kind of guy who almost never buys a new car, but rather buys something that I feel confident I can service. Your videos have saved me from being lulled into buying something that was never intended to be serviced. The oil level check, draining, and filling procedures were enough to scare me off of this platform permanently.
Thanks for your feedback. Those procedures are pretty typical of any newer car or truck.
Thanks to your videos, I've been able to keep our 2005 Prius in tip top shape - thank you!
I know your primary intent is to learn, and teach in these. Sometimes you mention something about the design or an improvement (like the incorrectly sized shaft tool), but with all of your experience I'd love to hear about what you think are potential failure points, and weaknesses. Your videos are amazing. Thank you so much for want you're doing.
Great idea, Thank you for your feedback!
My first reaction was that the electric oil pump was a weak point. Thankfully its external and relatively easy to get to. I hope they have multiple sensors to catch a failure in the pump or motor or loss of oil pressure. GM in the past hasn't been the greatest at making their small electric motors very durable (fuel pumps etc) and letting the economy cost reduction engineers reduce thickness and length of wires, i.e. Not making the wires going to that little motor thick enough and using high enough quality of relays.
That ingenious yet simple design spells longevity in my book . Well done GM 👏👏👏👏
Thank you Chevy designers! I love my 2019 BoltEV. As an efficiency nut, I'm continually amazed by this technology. Keep up the good work - I'm ready to buy a work van version.
My wife and I are buying our first EV vehicle, and I'm the guy that generally has to know first hand with my own eyes, all the inner workings of my vehicles. I was, until now... accepting that I have no idea how these things work. Now I do! Awesome.
Appreciating the precise to the point crystal clear language, and its application to bring to the audience a piece of new automotive technology we are all going to be using, the sooner the better.
Thank you for watching
Wonderful, detailed video. Thanks for all you do Professor! Have a Merry Christmas!
Thank you and Merry Christmas to you!
Thanks as always Professor!
You are welcome, thank you!
@@WeberAuto Oh and I forgot! congratulations on your TST 2018 Tool and Equipment Awards!
Thank you very much!
Just another great video. Nothing new :)
Like joining your academy
The most amazing thing - THREE MOVING PARTS and reliability at 54:56
I agree it's a piece of engineering beauty.
salute to professor despite all difficulty he manages to teach
This is one of most in depth informative channels on youtube. So grateful you're putting this online for everyone to see!!
Excellent video, very well explained and very clear spoken commentary. Thank you for that. That motor is a master piece of engineering. The coating on the roller bearing is some kind of insulation medium to reduce circulating currents in the armature, which can cause pitting of the races of the roller bearings. Similar bearing coatings are used in large traction motors of railway locomotives and large industrial motors subjected to heavy loads.
Thank you and thanks for the information on the grey coating.
@@WeberAuto C A U T I O N (?--lol)----i see now a possible reason to not re-use those shims...that coating...
not that it matters much,how can ANY mechanic successfully rebuild that contraption after a major (or even minor) failure!!! it's a mother ... of all complications; i thought it was simple,just an electric motor; silly me!
Jose Peixoto: What mechanic rebuilds engines or transmissions? The amount of specialty equipment needed means we have shops that specialize in doing just one thing. Engine rebuilds, transmission shops, radiator shops, muffler shops, tire stores, diesel fuel injection pump rebuilders, etc. When was the last time a mechanic removed a motor, disassembled it, machined the head, honed the cylinders, ground the crank bearings and cam lobes, etc and reassembled everything himself. The economics make that untenable. Early repairs will be warranty replacements from the manufacturer, then salvaged units and then 3rd party rebuilders. The days of simple electric motors and boat batteries meant a range of 20-50 miles and replacing batteries every year. Hi-tech electric motors do work a lot better. People wreck cars faster then they wear them out so there is a surplus of engines that cost far less than rebuiding. By the time the Bolt warranty expires, there will be plenty of salvaged units available.
@@josepeixoto3384 Yes, the shims are also coated. Reassembly must be done very carefully to avoid damage to any coatings.
Ball Bearing!
Thank you Professor. Very instructive, very lucid explanations!
One comment. Someone was asking if this motor is a "BLDC" and you responded in the affirmative. Although these motors still seem to be classified as BrushLess DC, it seems a shame because the term can be misleading. The elimination of physical "brushes" that commutated (or made a pathway for) an electric current to be fed to the rotor was made possible by electronically bridging current to the rotor. However, the Bolt EV and most if not all similar EV motors do NOT conduct a current to the rotor. Therefore I favor the designation "SPM" (Switched Permanent Magnet) motor, because it is in fact the natural rare earth magnets buried in the rotor that supply the opposing magnetic field that interacts with the switched (switched on and off) electromagnets in the stator coils.
Another designator that may apply to this motor is "IPM" or Interior Permanent Magnet motor. As noted in your video and a relevant SAE paper I just located (and linked below) The magnets are buried in a "V" patterns in the interior of the rotor. The Tesla Model 3, and many EVs, have gone to the IPM design (although the exact layout of the magnets inside the rotor may be radically different).
Finally, and not to be too confusing, another attribute of many of these EV motors is that they use "reluctance forces" that augment the permanent magnets. A Reluctance machine is simply one with embedded ferrous material (but not magnets) in the rotor that react to the electromagnetism produced by the stator. I have head it said that the Bolt EV motor is a IPM / reluctance hybrid design (as is the Model 3 rear motor). The SAE paper does not explicitly state this, however, even Nikola Tesla described reluctance forces at work in his AC induction motor. (Another reason I hate to see the term BLDC used is that it gives the impression the motor is primarily a DC (Direct Current) motor, when in fact, as I best understand it, the Bolt EV motor (again, like the Model 3 rear motor) is a 3-phase AC motor. An inverter in both cars converts battery DC to Alternating Current, which is switched On/off in order to produce spurts of electromagnetism in the stator windings... which of course interact with the permanent magnets and reluctance forces in the rotor... causing it to spin. ;>
So here's a request: Please take that Bolt EV rotor APART so that we can see exactly what's goin' on in there!
www.sae.org/publications/technical-papers/content/2016-01-1228/
Thanks for your great feedback. I understand there are several names for this type of motor. An additional one is "Synchronous AC motor". There is SAE terminology, manufacturer terminology, service industry terminology, and the general public's various descriptions of the motor as well. I have even seen two different names in the same document. It can be confusing for everyone involved. I try to use the manufacturer's own terminology in my videos and fall back on the SAE terminology when necessary.
One clarification: An inverter does not create AC current. It simply pulses DC current through the wye wound three phase windings in sequential order over and over again (giving the illusion of AC current) to drive the rotor. Thanks again!
@@WeberAuto "An inverter does not create AC current. It simply pulses DC current through the wye wound three phase windings in sequential order over and over again (giving the illusion of AC current) to drive the rotor"
Ha ha. Well there may be more to say about that, in another venue, but alas, I am a mere student of this science anyway. :>
I guess you may be loathe to take apart that Bolt rotor, because who knows what special tools might be needed to pry that can off. But it seems to me the arrangement of the interior magnets is where the real nuance is, where motor engineers are coaxing out the last possible bit of power. I'd love to see a side-by-side view of the Bolt and Model 3 disassembled rotors, because Tesla has been at it in Greece cooking up their own brand of secret sauce. Still, that was very enlightening what you passed on about the Bolt's stator. Clearly GM is pushing the envelope there.
Again, thank you for this long awaited Bolt video!
I have no doubt I could disassemble the rotor, but I need to use it again in the car. The SAE document clearly shows a cross section of the magnet arrangement in the rotor along with a few other surprises to decrease torque ripple and increase efficiency. I would love to get my hands on a model 3 and do a comparison. That may be a while ;) have a good evening.
You are right about the terminology being a bit off. A BLDC really means what you might call a synchronous AC packaged with a controller so you can supply DC to it, and it runs, without having brushes. To the end user, it is a brushless motor they can supply DC to. As others mentioned, the motor itself isn't exactly running on AC anymore, either, since it is just getting well timed pulses of DC, instead, in the vast majority of cases. Some controllers do attempt to ramp the current up and down to more closely mimic what we think of as AC, but others just bang it with all the volts switching on and off and let reactive power try to smooth it out.
There is no such thing as a brushless DC motor they are all AC motors! usually cheap and nasty PM can be very noisy too!
Dang John I’ve never seen someone so fast with a impact!! 😂 great video, keep up the good work!
If I was 20 I would move to whereever this school is and attend. Hybrid training is offered in person boot camp style for less than $2,500 or online for even less. People truly certified in electric cars will be gold plated. Absolutely the best value in education possible.
At last, somebody knows how to speak clearly! This man John D Kelly knows how to speak clearly and exacting. Thank you so very much! I am anxious to sit down and watch more of you speak to me as a professional teacher should in every sense of the word.
I will be watching and listening to every word you say when it comes down to learning about these amazing new engine technologies
Thank you ,professor. I enjoyed the lesson and learned a great deal as well. I look forward to watching your next video.
thanks so much for a detailed breakdown so few moving parts & in detail too! its the next generation of people movers ect thanks very much for the vid
Thank you very much!
Thanks, you're a great teacher and it's nice to see the nuts and bolts of the new ev motor.
Thank you!
Mrs. Kelly: John, for crying out loud have you seen my boxes of Ziplock bags ?!?
Fascinating engineering! Thanks again, Professor Kelly for this amazing content.
Lol. They are great for staying organized!
Incredibly good discussion of the disassembly. As an industry engineer I really enjoyed the video.
Thank you!
Astounding how small the motor is and how much power it puts out for the size.
It is incredible!
Welcome to the future, where you use power to go, instead of tricking million year old algae into mixing with the right amount of air, exploding it, and trying to catch as much of that explosion as possible while firing the bulk of it out the back and into the surrounding environment as waste gasses and heat,.
well said. don't forget the pistons changing direction all of the time, and wasting energy that way... @@samurphy
It really is. I was blown away by how thin the stator was. The stator field on just a 3/4 hp fan squirrel cage motor is far thicker. This engineering is the future
@pete smyth ...from solar PV at my house!
and I though scotty killmer was great ...man you are the father fo all mechanics
21:17
Anytime you have to shim pack for play adjustment... there will usually be 2 or 3 different size shims:
1- "face" or "thrust" shims... these will be on either end of the pack, and may be 2 different sizes. They are usually differentiated by surface laminates or composition materials.
2- "fill shims" or "packing shims" are usually made of cheaper materials, as they don't require as much friction/deformation resistance.
Thanks for your feedback
Best teacher ever , for the mechanically inclined. Thank's
Thank you very much!
Excellent and very clear lesson to us non-mechanically oriented. I hadnn't the slightest idea on such a matter. Thank you.
Thank you!
Professor Kelly,
You are such a gifted teacher and right to the point including detailed nuances.
Thank you for this fabulous vide. Happy New Year to you
Thank you so much!
Armin
Thank you very much!
Amazing! And with such clear & comprehensive explanation. Thank you so much.
Quite easy to see that this is the future.
Thank you for your feedback
Prof., I am your latest new fun from Nairobi Kenya. I love your videos very much. Am currently working as a mechanic for a British army engineering contractor here in Kenya and your videos are very helpful in my work.
Thank You.
Thanks for watching
Even more than by the motor itself, I'm impressed by you, Mr Kelly.
Thank you, I appreciate your kind words
another awesome video, Thanks
I really like to see the same disassembly of Tesla model 3 to compare their design approach vs Bolt
Thank you!
Jack rickard, evtv
I second the idea of the Tesla Model 3 comparison, especially since both are American designed & American made :)
In the first 3 minutes, you perfectly illustrate why we calculate power:)
Please understand I really enjoyed the video. My issue was only with a 30 second segment. I mean this constructively. I just hope this helps a few people to begin to understand something very important and elementary about engineering in these subjects...
Here's the issue: The statement at 3:30 that the Bolt EV's drive is "more efficient" and a "better design electric motor" could be true, but actually nothing you'd said so far suggests it. The crux of my point is that in order to draw conclusions about performance (how much oomph does the vehicle have) we need to *either* deal with metrics that have those dimensions (power), or know something about *all* major factors that contribute to it. In the case of a vehicle, voltage, current, and torque and speed are all just factors. For example, if we're going to compare lower-dimension metrics like torque (anywhere) between two drives and use that to conclude anything about higher dimension metrics like power, we need to first establish that all the other lower dimension metrics are unchanged or known (which they aren't in this case). Operating voltages or motor speeds between the two cars were never mentioned. So we can't conclude anything about power or efficiency.
In more specific terms:
In order to know the efficiency of a motor you must compare power-in and useful power-out. Power-in is electrical (voltage x current), and the two forms of power out; mechanical (rotational speed x torque) and thermal (Joules/s, etc...).
You have only compared the current of the two motors. We don't know how the operating voltages compare, so we can't know how power-in compares. And on the output side you have only really given torque. We don't know how rotational speeds compare, so we don't know mechanical power-out either. Now it must be said that since we are comparing two small passenger vehicles, we could expect the axle speed to be similar... but I digress.
What I'm really getting at is that by just citing the rated power of the Spark EV, we would have had a good sense of how the two drive units compare performance-wise. You had already stated the rated power of the Bolt EV. Then with additional clarification of power in vs out we could then calculate efficiency and even the heat remainder we have to dissipate.
It may seem like nit-picking to some, but to the many who pursue and invest in mechanical ideas without understanding what dimensions are, these often becomes toxic misconceptions that seem to last way too long. They are also tragically reinforced by oblivious marketing and other things.
Since electric propulsion is still finding new applications, and since in many ways it has fewer design constraints than combustion engines, we often see a lot of variation between the propulsion units of otherwise similar electric vehicles. This makes is easy to show (as you did) that peak motor/engine torque alone tells you nothing about vehicle performance... As you pointed out, It's really all about the "thrust" - torque at the wheels (divided by wheel diameter of course), and to know that you have to know the total gear ratio at the moment in question.
But for a given road speed, that ratio (and thus the torque multiplication) is directly related to how fast the motor is turning. So if our goal was to have a sense of how much performance we can expect, we should skip talking about gear ratios and diameters and simply consider the power (torque x rotational speed, or volts x amps x efficiency). Obviously this video focuses on a specific drive system, and so appropriately you dive into that... which was very interesting!
I'm just getting at the common dimensional misconception about torque, volts, and amps, and speed vs power.
A great example is the cordless tool market. 12V was bested by 18V, 20V, 36V, 60V... and so people begin thinking voltage = power. Nope! The higher voltage HAS usually correlated to higher power, but only because the current is has been held constant the whole time by simple things like standardized battery cell size. Battery packs could have just as easily been made in parallel instead of series and the motor given a different winding, but then we'd see a 3.7 V drill for the same price as a 20V! You would actually have to try it to find that the performance (power) and battery life are identical:) In that market, smaller factors like using lighter gauge wires tipped the scales toward using series packs... If it had gone the other way, we'd be choosing one drill over another "cuz it's got more amps" Lol!
This misconception tends to be strongest among groups of people where hardware is the most consistent - where those pesky unknown variables don't change much and using things like torque, volts, or amps, as a performance benchmark is forgiven by the uniformity of the things being compared. Enter the Small Block V8 :) The standardized ways we typically mod combustion engines, increasing the peak torque of a given engine *does* usually increase performance, and so the misunderstanding is reinforced. It is generally true that if you push harder on the pistons, you push backward harder on the pavement as long as it doesn't require you to shift up... it usually doesn't, so folks can continue thinking its all about torque without understanding or caring that they also just increased power.
Then there's the very real effect of the shape of the power curve and how this has a measurable effect during takeoff and for discrete-gear transmissions which must spend time off-peak. Aaaand then there's the internet sludge resulting from confusion over units like magic 550 HP-torque "cross over points"...
I deeply love piston engines, but I hope as EVs come more into focus, it becomes easier for budding engineers to see how physics works:)
Cheers for reading this.
Thanks for your detailed feedback and constructive criticism. The Spark and the Bolt both have 400 V batteries (which I did not mention in the video). Motor rpm of both the Spark and Bolt EV were discussed at 3:25. FYI this is the 7th video in series on the Bolt EV where we totally removed/disassembled/reassembled/reinstalled the 400V Li-Ion battery as well as the other HV components of the vehicle. Have a great day!
Astute observations and I generally agree. It will be interesting to watch how the general conversation transforms as folks begining to grasp and internalize these "new" fundamentals.
"ET" = Extra Terrestrial where I come from! Great video. An amazing piece of engineering. Makes me appreciate my 2017 Bolt even more (34k miles and counting!) But I sure hope my Bolt never needs any service on the 1ET25. Why? Three words, "Chevy dealer mechanics"
Thanks for you feedback. There are good and bad technicians out there, obviously the trouble is finding one you can trust. We are slowly training a new generation of technicians to work on these vehicles.
One of the few Yourube presenters, or any presenter for that fact, that presents facts and not emotions.
Great job, as usual!
I actually came here looking for a teardown of the powertrain of a Tesla, but I found pure gold, I'm not a mechanical engineer nor into cars. I'm a Computer Science student and electric engineer, but I was able to catch all the details! 10/10 great video!
Sir, a very Excellent video and disassembly work on this equipment. I enjoyed watching your clear presentation and no nonsense professional attitude. My compliments then. V/r, Steve Ferguson
Thank you!
Thanks for all your videos. Merry Christmas Prof.
Thank you, Merry Christmas to you as well.
Great video with the right level of detail! I would LOVE to see you get your hands on a Model 3 drive unit to disassemble in the same fashion.
Thank you, I would like that
You are an excellent teacher ...I wish I had a shop/auto instructor like you..
Thank you very much!
I've watched this video two or three times already. It's such a well-delivered explanation. Highly enjoyable.
Glad you enjoyed it!
After wathing a few of his explanations, I am starting to fall in love with ev's (hope my wife won't see this comment).
Awesome!
Your wife doesn't like better power, less maintenance, cheaper fueling, and easier fueling (95% of the time)? She enjoys going to gas stations?
@52:02 that stator looks like a work of art compared to those with lots of turn of thin wire. Precisely the amount of copper exactly where it’s needed for efficiency....and then someone came along and put that crude gear range selector mechanism and actuator on it.
My thoughts as well, thanks for your feedback.
@@WeberAuto Exactly. Why go all Rube Goldberg with it like this when they could have just had the actuator run only the parking pawl like the NHW20 Prius, unless doing so would have violated a Toyota patent or they initially planned to just have a conventional shift cable. Oh well, it makes it easier to repurpose this unit for things like doing a BEV conversion of an ICE car and just reuse its shift cable.
Exactly my thoughts but I wasn't able to articulate it as politely.lol.
I enjoyed this video very much, thank you. I especially appreciate the clarity of the presentation. Also, you were wearing your wristwatch while handling the rotor. You didn't get stuck, eh?
Only once! lol Thank you
Thank professor Kelly, I love your calmness and how you tranfer your knowledge. Learned a lot !!!!
Thank you very much
Your series on the Bolt is phenomenal, I'm gaining a little respect for Chevrolet and a lot for you.
Who says you can't teach an old dog new tricks.
LOL, Thank you!
Thanks for all your videos. Merry Christmas Professor.
Thank you and merry Christmas to you as well!
Great Tear down!
Whilst this eMachine is considered to be decent (if not quite class leading) for mass production EV powertrains, it's miles away from the "ultimate" electric machine! I worked on the FormulaE motors, which make 300 bhp from around 20kg, and spin at up to 25,000 rpm! (the magnetics alone cost $$$$$$ they use water cooled rotors (ie water is pumped into the spinning rotor and out again to limit the maximum magnet temperature due to the high speed rotor losses... ;-)
The advantage of a 'hairpin' stator winding architecture (its easy build and assembly, that avoid the complex multi-filament winding and packing of a conventional stator) is of course offset by a lower efficiency due to skin effects (high frequency AC) in those large cross section hairpin conductors. Using 6 stacked hairpins is a sort of half-way-house, keeping the relative ease of assembly, but reducing that AC loss. Note, the loss is proportional to switching frequency (and it's harmonics) rather than motor rotational speed. Those losses can be further reduced by running a lower fundamental switching frequency, at the cost of an increase in I2R losses due to the additional ripple current that results.
It's also worth noting that, actually, motor efficiency is NOT the be-all-or-end-all of EVs, because even absolutely terrible eMachines are still around 93% efficient, with an F1 spec motor being say 98% efficient, that's 'just' a 5% increase. Worthwhile, but not actually that significant on it's own (Hence most EVs today major on reducing the roadload (low drag) in order to maximise range)
Thank you and thanks for the fantastic feedback; very interesting information about the formulaE motors.
The best power to weight ratio I could find is 16kW/kg from an induction machine for aerospace applications. Your formula E is about 10kW/kg. The power electronics are included in that power to weight ratio, but no gears. The heat rejection (losses) of 98% efficient 200kW is only 4kW - thats brilliant - and makes the cooling system small and effective.
Excellent video. Learned a lot. I just cant see how electric cars CANNOT be the future. 13 moving parts vs thousands? thats a no brainer.
Thank you!
Yeah, compared to a gasoline or diesel, definite advantage, but I am thinking that these could still be simplified quite a bit. One thing that comes to mind is to just put motors or gear-motor combos in each wheel. Then you don't need to have differentials (handled by computer) and cv shafts. You could power 2 or 4 wheels, do traction control all in drive train and skip break disk traction control all together possibly. Also the inverters should be on each wheel with only power lines, break lines, control lines to each wheel. Also the wheels themselves could be designed a lot better at dissipating heat from the motor also. It could be simplified to the point where the wheels and the steering mechanism and a cooling pump are the only moving parts. All of the rest are just in control and support of the wheels.
@@IntenseGrid Yep. Good analysis. When this happens in a modular style the world will change. You'll be picking a Tesla wheel in LA, and a Colorado Solar wheel in the mountains, or some such. The evolution from here to more than four wheels e.g. powered trailers and so forth would allow for greater efficiency. SOVs need to get smaller. Air drag is about all that is left when system efficiency rises to these levels. Hurray for MOSFETs, IGBTs, and whatever is next. Will capitalism allow a modular style like the IBM PC? Musk could make it so.
Yeah. I have been thinking about this design for more than a decade, but don't have the resources to implement it. Then I saw some prototype at some show with what was called a "skateboard" design, which is very similar.
The other thing is power generation. With robotics the way it is, if you need longer range, like for a long trip, with open spec power and coolant connections, you could have a gasoline or diesel charging unit sit in your garage, and when you need it, you give it the command, and it robotically climbs into your trunk. Or, you could have extra battery packs install the same way. There is no reason to be hauling around all of the extra weight (like 200+ lbs) for your daily commute. The ICE can be designed for peak efficiency, without the need to rev for acceleration. With open standards, competition can drive more and more efficiency. Also, with open standards, we can stop being churned by the big motor companies, which right now change some things just for the sake of extracting money from you.
@@IntenseGrid I wouldn't skip CV shafts. Even smaller motors fitable to wheels have significant mass. It would be better to accept losses at CV shaft, then put that mass into the wheel. But otherwise I agree.
An amazing video. You are the king of explaining things. Your students are very fortunate to have you as their instructor. I have to tell that I watched all of your Bolt EV videos before I bought my 2021 Bolt. You were a major contributor to me deciding it would be a great car and I really Love. Thank you for being who you are. I’m 74 years old and worked cars all my life and I was surprised on the lack of parts in the drive unit. You explained it very well.
I am only echoing others when I say this is the best technical video I have ever seen. At no time was I bored. Every bit of information was useful. Skillfully edited and well photographed. Superb work. Your students are lucky to have you.
The difference between this dratrain and the Leaf is that the Leaf started out from a Kei design - Nissan simply replaced the 660cc engine and transaxle with an electric motor mated to a single speed transaxle in the first iteration.
It was conservative, absolute minimum re-engineering - which was sensible given the gamble the company was taking being essentially first-to-market with a mass-production, mass-sale, reasonably priced EV and the risk that something radical might also have had reliability issues (that whole "not changing too many things at once" philosophy)
It also meant that the production line facilities didn't need any tweaking - important if sales didn't do well. Remember the Leaf was essentially an experiment produced to see if there was a mass market for EVs
Newer generations will probably follow GM's lead and go to a unified transaxle.
WRT the layers of conductors and comments about AC losses - as the motor speeds up, skin effect(*) is going to start playing a big part in the impedance of the windings - this is where most of the heating is coming from.
(*) As frequencies rise, currents only travel in the outer surfaces of the conductor rather than the whole body. The depth is more-or-less known for any given frequency and starts becoming an issue above about 20kHz. The other part that becomes problematic is that high frequency currents "don't like sharp corners" (the magnetic fields tend to distort and "fly off the end"), so those hairpin folds will become essentially a pinch point for high frequency current flow. Traditionally the stator winding ends would be smooth arcs. I suspect that GM will modify this design as RF power engineering expertise is brought to bear on increasing AC efficiency and improving motor rotoational top speed.
Thanks for your informative feedback!
@@WeberAuto NP.
FWIW, it's worth noting that a lot of very high power electric motors have _hollow_ conductors (remember that skin effect) which can have coolant run along their insides. Whether this is tenable in an automotive environment remains to be seen but I'll bet some motor makers are considering it.
@@alanbrown397Thanks for the additional information.
Professor John D. Kelly:
I'm a Master´s student in UNAM Mexico. Are you going to do a next video about 1ET25. I'm looking for the dimensions and features of the gears, specially the module or the diametral pitch. Thank you very mucho for all those videos
Too bad the car didn't look as good as the motor drive unit. Great videos!
Thanks for your feedback!
Probably the best lighting and audio of any automotive how to video series I’ve ever seen on RUclips. Content is great, too.
I live in Finland and my English is not very good but I want to say that these videos are so excellent and well done! I have been always interested about all technical things and these videos shows exactly how things works. Also Your English is clear and easy to understand even for me and it makes videos easy to follow. Thank You very much, I hope You will make many more videos in the future! All the best for You sir!
As a tech I would have a .25" wall aluminum cylinder lined with a nylon liner to hold that magnet with aluminum caps. This would keep it safe from metal partials in the air in a shop environment.
Thanks for your feedback.
I was thinking something similar. That rotor is pretty bad ass... and probably impossible to clean of shavings. But I'm a newbie to this channel and am blown away by the complexity of automotive tech these days.
I have received feedback indicating the the rotor can be cleaned of shavings and etc. by using Silly Putty.
I was thinking a couple layers of plastic wrap, but you do you.
(edited, somehow the first para of my reply went walkies)
You _can_ remove _tiny_ and low ferrous content stuff off superstrong magnets with silly putty/bluetak, but having had to do something like this, you really don't want to have do _do_ it.
I second the sleeve idea and would go as far as suggesting that it should somehow be thin enough to slide into rotor before withdrawing it from the motor and/or wrapping a few layers of saran wrap or similar whilst it's still on the hanger after withdrawal. You really _dont_ want any form of magnetic contamination on this surface.
As for actually _removing_ it in the car as GM are clearly expecting - "You'd have to be nuts".
The engine/motor bay of a car with a few thousand miles on it is simply not clean enough no matter what you might do.
I wouldn't even encourage attempts to disassemble this thing/remove the endcaps in the average service workshop, let alone an engine bay. The clearances, in-service voltages and magnetic fields grabbing onto anything nearby effectively require "clean" conditions and an attention to detail that most dealer service bays simply lack (and good luck making it work after the semi-skilled apprentice has been tasked with "the minor jobs").
I foresee a lot of wailing and gnashing of teeth when these things start requiring in-field servicing. That 3-phase connection port is going to require extra special attention to ensure _nothing_ gets into the works during normal servicing if the cables/grommet are disconnected. and similar special attention when reassembled. I spent half the video looking at the cutout and the access pathways it provides for contaminant, shaking my head and saying "they didn't really do that, did they?" to myself.
This is likely to prove a weak point in future and GM could have engineered it out from the beginning with some suitably shaped inserts to effectively keep that connection port IP56-rated until they're removed from the _inside_. .
"Don't turn it on, Take it Apart!" --Favorite Aussie sparky dude
I like it! Thank you for your feedback
Superb and Outstanding Presentation. Thank You Kindly For Sharing. Best Regards.
Probably my favorite channel in RUclips. The knowledge and communication makes it a pleasure to watch. Thank you for what you do sir.
If I may, keeping in mind I'm never going to be working on one....When pulling the rotor I would have continued turning the top nut until I squeezed the top and bottom nut against the plate so that it wouldn't flop around as much.
It's a pleasure watching you work. Cheers and prosperity in the New Year.
Good idea, thanks for your feedback