I have to say I thoroughly enjoy your videos, Informative and entertaining. My middle son just joined the USAF Reserves as a jet engine mechanic. I spent 13 years in the USAF as a crew chief on A-10's and F-111's so I can now share some information, augmented with the information from your channel, with someone else who has a grasp of the unimaginable power and intricacies of turbine engines. On a slightly off topic comment, sitting in the cockpit of an F-111 doing a maintenance engine run is an experience you can"t explain unless you've been there, great fun! Zone 5 afterburner shakes the entire earth, or it sometimes feels as if it does.
I also cracked up when he said that. And I almost believed there was such a measurement due to the mater of fact and non-pulsed way AgentJayZ used it. Canadian humor rocks, lol.
The billimeter is a slang term, coined by some mathematical illiterate, to probably mean the next big jump down from millimeter, so it may have been meant to refer to the micron. I have appropriated the term to refer to the nominal diameter of the heatilon*, so it's more along the lines of the nanometer. So, an easy way to remember is the billimeter is one billionth of a meter... sort of. * Heatilon - the imaginary particle of heat, discovered in 1992 by AgentJayZ during the North Van period. According to the RUclips page, and Wikipedia.
I work in a production facility that makes blades. I assume that the pin grooves I grind in some are so the blades can slide over the locking tabs. One other thing we do, is after the fir tree is cut on some blades, we grind down the root to create a tab. I assume this is to lock it in on one side and a locking ring is used on the other side. I believe that part is a stage 4 blade for the PW F100. I love watching your videos and since I started working at the plant, I am totally amazed how my parts are integrated into the whole package.
I love watching the amazing technology that makes these marvels of the jet age, as thankyou agent jay, as i use stainless steel wire to lock my v8 rebuild, as found it holds the bolts from getting free
Hi Jay, Many thanks as always for devoting all your time to present these amazingly informative videos :). I have almost never asked any questions as anything I ever wanted to know about turbojets & fan-jets has been thoroughly covered in one of them. I was wondering however if you guys were able to locate any more parts for the Iroquois and if any progress had been made on it. Thanks again.
Wow, what an incredibly interesting channel. I'm in no way a mechanic but you have taught me an incredible amount about something of which I had absolutely no knowledge. You manage to translate highly technical information into language a complete noob can understand. Thank you. I have a question which you have probably answered in the past. I've seen that you weigh each turbine blade before installing them. Clearly this is part of the balancing process so I wonder, do you try to place similarly weighted blades exactly opposite each other on the turbine wheel? On one video (from 2014) you appeared to be alternating lower weighted blades with higher weight blades as you install them. Clearly you have a strategy and I was hoping you could describe it in a bit more detail. Again, if you've answered this question already I'll understand if you don't wish to repeat yourself.
The weighing, sorting, and arranging the blades gets you to the starting point. From there the balancing process begins using a sensitive machine that spins the assembly, measures vibration and angle, then recommends changes. Sometimes it takes minutes, sometimes hours.
Nice video. Does the mass flow rate of air into compressor section (inlet) for a turbine remains constant all the time or could be changed by some special arrangement (like changing angle of compressor guide blades).....consider steady flow for simplicity. I am interested to know..!!
Also, when the engine is getting hot the metal will expand a bit and it will fit even tighter. At least that's what I expect. Quite amazing that most of it is all machined without CNC machinery, yet it is done with the highest level of precision.
The disc expands thermally and it also dilates as a result of C/F (note the difference in terminology). The blade and its fir tree root expand thermally, with the blade root running hotter than the disc, and the blade material may also have a coefficient of thermal expansion higher than that of the disc. The clever part of the design process is to ensure that the bottom serration loads up first and that the combination of thermal expansion and C/F allows the serrations to load up progressively and uniformly. That is where the incorporation of 'differential pitch' comes in during the design process. Typically. as manufactured, the flank-to-flank dimensions of the blade serration will be slightly less than those of the disc slot. PS The design of a fir tree root should be such that it never becomes 'solid': there should always be a clearance between all the features of the fir tree form, except for the loaded flanks.
Well, CNC just makes precision machining faster and more affordable because you don't need a human to constantly control things. Computers just make things cheaper.
Hey Jay, I machine aerospace parts and the "fur tree" is called a root. And they are ground onto the blades with big sand wheels "conventional wheels" and at the place I work we most likely manufactured those blades.
Yes, the fir tree form is typically ground onto the blade root with a grinding wheel, which, in the latest manufacturing cells, is continuously redressed. The fir tree form in the disc slot is typically produced by a progressive broaching process. The tolerances have to be within 'tenths' (of a thousandth of an inch), to ensure reasonably uniform sharing of the loads on the loaded flanks of the fir tree form. And there is something called 'differential pitch', to complicate the design process still further.
So are you based at Wixom or Harbor Springs? I took early retirement from Rolls-Royce in 2003, after 41 years service and returned for another three years part-time, as a consultant. Following my apprenticeship, my whole career was in gas turbine design. From 1967 to 1982, I was in the design office at R-R's Industrial and Marine Division. In 1982, I transferred to R-R Bristol, where I was involved in the design of military engines.
11:59. could/would you run water/smoke through the blade. 12:03 Based on what appeared as leading edge holes, does it create a cool air buffer similar to that of a rocket engine nozzle or do they serve another purpose such as some kind of stall prevention? Thanks for another great inside scope of a jet turbine.
glenn tanner they're simply for cooling and they work exactly how you thought. They are fed air that has already been through the compressor but has not been through the combustors and turned into "working air", as Jay calls it
Hey Jay, if the fir trees/blade roots are designed to lock under the centifugal force of the rotation of the turbine, then why are the wider sections of the fir trees placed further away from the centre of the rotor? It seems to me that the locking mechanism would afford a more secure lock if the wider section of the fur tree were placed at the 'bottom' of the turbine blade, closer to the centre of the rotor disc. Unless the turbine wheel is better able to efficiently distribute the force of the blades when the wider sections of the fir trees are placed closer to the outside edge... Anyway, love your videos, many thanks from the UK!
That's a good answer and I can say that as a former Chief Designer - Turbines. I don't think that I've given away any secrets in saying that (see my answer to Darren Duncan).
In simple terms, if the geometry of a fir tree root was reversed, then this would place the thinnest section of the root form of both the disc and the blade at the position of the highest load in both parts. PS The term "lock" is not really appropriate for the radial retention of the blades in the disc. While the centripetal force applied by the disc to the blade root is equivalent to several (even tens of) thousand times the weight of the blade, there will still be some small movements in the root, as a result of differential growths between the blade and the disc. And let me throw in something that I was told as a first-year engineering undergrad: "there is no such thing as centrifugal force."
As this video is showing us an engine that originated in the 1940s, can I share the nostalgia trip I've just had as a Jet Provost flew low over my home? Its Armstrong Siddeley Viper engine is of a similar vintage and the Viper was the second engine type that I laid a spanner* on as a Bristol Siddeley Coventry apprentice in 1963. *For you people in N America, spanner = wrench.
grahamj9101 I got to see the "AFTERSHOCK" twin engine 1940 Ford Fire Truck at a local air show here in Mississippi this past June 2018 powered by a pair of Rolls Royce Viper engines. They allowed me to look the truck and engines over well and answered lots of questions. June of 2017 they had their pair of single engine "Flash Fire" jet trucks at the air show and I got to check them out closely as well. Afterburners/Reheaters Rock on Jet Trucks! Here is a video from a diff air show this year of the Fire Truck. ruclips.net/video/EO98zY2S9SQ/видео.html
Most likely it's the decimal fraction of the weight in ounces. We only use one digit after the decimal point when we weigh in grams. It's lazy and bad practice to not record the whole number.
Ok, then I get it. The weight is some whole number of ounces + .098 But if it was written on there during the previous overhaul, that would mean that the writing survived the engine running for a long time? Is that possible?
Nice demo of the firtree - simple but effective idea. What's up with the numbers? At first I thought you've numbered each blade so they go back in the same order. Then I noticed that quite a few of the blades around where you're working are all called 098, so even though I haven't had my coffee, I blew that theory out... is that a dot? A dimension?
Chris Comley pretty sure they are weight.. just the decimal part as they all should be extremely close, they weigh each one and mark weight to help balance the turbine wheel.
You'll notice I'm removing the blades... The numbers were put there the last time the turbine was balanced... by somebody too lazy to write down the entire number. They have since been cleaned up, inspected, and had their weight recorded on them in full, in grams.
As it's your shop, then it's your responsibility to ensure that the blades are marked in a manner that is understandable and acceptable to you. Having said that, provided the process and the marking is in accordance with approved build instructions, it may not be necessary to mark the weight in full. I have an Olympus 593 LP turbine blade in my possession: it is marked, '+51-56' and '5' (circled). The marking must have survived some thousands of hours in service. Having left the Olympus 593 in-service engineering team in 1996, with the passing of the years, I now have no idea what the '+51-56' refers to, in relation to a blade that weighs 910 grams on my kitchen scales.
What do you use to remove the oxidation? a chemical? Rubbing it with a brush would give you odd tolerances and imbalances I'm guessing, that a human can't possibly determine this by any faculty we have. Yet doing it by hand and checking by instruments would present a very high failure rate.
Just re-watched your lock wire vid and I have a question...Have you ever taken apart an engine and found a fastener that was loosened against the lock wire persay? Also do you know when they started using lockwire and if there was a situation that caused the manufacturer to have to? Also this is Gary Ferguson...I changed my google name...thanks Sir
I've seen a combustor locator pin that had come loose and was held in place by lockwire, and continued to perform its function. That the only case in about 15 years I can think of. I think lockwire was used by the builders of the very first aircraft, as they realized that problems could not be dealt with while flying. I've seen wire locked turnbuckles on the bracing cables between the wings of WW1 biplanes.
do you do any kind of dimensional checking of the tree on the blade or the groves in the disks? Isn´t there any wear during startup and before stopping?
There are measurements to be taken if any wear is visible. These blade roots do not show any wear and fit very snugly, so they don't need to be measured. Their inspection findings would read "no visible signs of wear".
In my experience, the terms 'wheels' and 'buckets' are commonly used in relation to steam turbines. Their use for those components in a 'heavyweight' industrial gas turbine, such as a GE Frame 5, is, therefore, quite understandable. That there might be a difference in terminology between products from GE Schenectady and GE Evendale is also quite understandable, considering the differences in terminology that still exist between, for example, R-R Bristol and R-R Derby.
AgentJayZ - Hi, I'm an Engineer and Mechanic/Aviation Geek and I am having trouble trying to find a GE T58? How much does one really cost? I am at the beginning stage of building a plane and want to learn how to build and fix a T58 and/or all turbines in general. Is a T58 reliable for a replica P51 Mustang that i am beginning to build? Is there another engine that would be a better fit? From what i have found the the T58 weight/thrust is right in-line for what i am looking for. Love your channel by the way and watch them pretty much all day at work. Keep up the great work! Would love to hear back from you. Thanks Andrew
Learning how to fix or build turbine engines is a step or two before actually putting one in a Mustang. It's easy to start that process inexpensively by reading a few of the books I recommend. As for powering your Mustang, instead of a helicopter turboshaft like the T58, a turboprop in the 1,200 to 2,000 Hp range might be a better choice. I would suggest a P&W PT6. Keep in mind that this project would be much more than bolting in an engine... The aircraft would need to be integrated with all the control systems of an engine it was not designed for. ... Then, you would have a very reliable and responsive engine that makes all the wrong sounds for warbird enthusiasts. It might be difficult to find anyone who sees any value in your creation if you ever wanted to sell it. I think it's a cool idea, but then it would also be a monumental job to make it work. I wish you luck, and would love to see the result.
Hi I was just wondering I noticed on the ge90 b788 when the jet engine is coming up from idle to higher rev there is like a gear like sound quite loud is it the turbines
Could you explain something about the Avro Arrow Engine That was developed specially for that aircraft and what the difference is between that engine and the ones that you show now? Or was that just Hollywood?
@@syx3s thank you for that information it was very interesting reading. The movie got me interested in that aircraft and engine. I live in the USA and I saw the movie years ago on TV here and tried to buy the video but was not available in the United States only in Canada. So I did take advantage of buying that and some books also. Must have been a great time to work there.
@@ronaldshepard4625 I was looking around nobel (on google maps) where many of the factories were.... now it's just a bunch of foundations covered with wilderness. even the gates onto the main road are hardly noticeable. really sad. ( ) = edit
It is something, the wide variety of comments & questions you get regarding one topic. I get this one though, dependable, secure & fairly simple design that works, thanks to lots of gramj9101's out there doin' the designin'! Of course the 'simple' design requires a complex manufacturing process, including 'how do those cooling air holes get there'? Some kind of electro-boring process done under water (electrolytic solution) using very fine wire; what's that process called Graham? It's something I'd seen somewhere but it's obviously outside of my wheel house. Thanks Jay for the video. DD
Thanks, that sounds familiar. I am not sure if that is the way GE did/does it but those holes are small; maybe 0.010 - 0.015", and numerous. I think the EDM method can make some pretty small holes so sounds possible. Maybe Graham knows the method used.
I was going to mention both EDM (aka spark erosion) and laser drilling, but I've been out of the industry for twelve years now. However, I do keep in regular contact with a former colleague who is still involved in turbine design at R-R Bristol. I will have a discussion with him when we next have a liquid lunch. - but I must be careful. A long-retired former Head of Combustion at R-R Derby was arrested recently for allegedly giving away secrets of the F-35 engine, the P&W F135. His experience was mostly with civil engines at R-R Derby and he had never worked on the F135 engine's combustion system, so he couldn't be privy to any secret features of the engine. Since retirement he has lectured on combustion systems as a visiting professor, including during visits to China. Apparently, he discussed thermal barrier coatings and mentioned the F135, which has got him into trouble with the US military, who got the British authorities to arrest him. I think I must avoid saying too much about the Pegasus engine in future. I don't want to be arrested on a 'trumped-up' charge.
Thanks for the reply & information. I went to the link listed below in Richard's comment RE. RR's ABCF plant in Sheffield & found it informative. Check it out if you havn't already... Cheers!
I used to see and read 'The Engineer' regularly when I was still at R-R: perhaps I should get back on the circulation list. As usual, however, there's some journalistic hype in the piece: apart from the information that the wax assembly and investment process is now increasingly automated, there's nothing particularly new in the article. I was very familiar with the Precision Casting Facility (PCF) at Derby, where the wax room had a large number of female operatives assembling the waxes by hand, albeit with some of the investment already being done by robots. The manufacture of Single Crystal (SX) and Directionally Solidified (DS) blades was already common practice in the 1990s, well before I took early retirement in 2003. My first experience with ceramic cores for cooled turbine blades was in 1971, when R-R's Industrial and Marine Division designed an uprated version of the Industrial Olympus. We knew it as the Olympus 'C' (aka the 2020 series) and it's the version that AgentJayZ has shown us on occasions. While I (a designer of less than five years' experience) was designing the LP turbine blade, my senior colleague, Alan C***, was designing a brand-new cooled HP turbine blade. It had multi-pass internal cooling passages, using a ceramic core: I recall joining him on a visit to the prospective manufacturer of the cores in Staffordshire, a part of England with a long history of ceramic manufacture. We were probably in advance of R-R Derby at the time in utilising the technology, as they were still working on an improved version of a cooled forged blade for the RB211.
Yes and the corrosion is why I asked. But I guess if that was the case you might have a bigger problem to deal with. I learned a lot in school but not everything. Just like the tool you had made to pull the collar that was stuck.
Wouldn't it be easier if the entire ring came off or had secondary ring to hold them all in place...take it off, dump all the blades out at once to be refubished, install new ones.
AgentJayZ If you can produce parts that meet standard specifications all of those variables should be met. Seems overly complex to service when every blade needs to be numbered or has unique variables.
AgentJayZ said no and I too say no, having been responsible for the design of turbines and turbine blades. It is quite impracticable, even with the degree of precision used in their manufacture, to produce blades that are totally interchangeable in a disc. When the engine is running at maximum rpm, each of those blades is exerting a reaction force on the disc equivalent to, say, the weight of a truck - and individually producing as much power as the engine of that truck. The slightest variation in mass and/or CofG is, therefore, effectively magnified tens of thousands of times. The blades have to be weighed, numbered and distributed in an alternating light-heavy-light pattern around the disc and then the bladed disc has to be balanced. I'm not quite sure what you mean by a "secondary ring". If you are suggesting that the blades could be restrained radially by a ring instead of of a disc, then that's not possible with current materials and technology: the ring would simply fly apart. In turbine (and compressor) disc design, there is something known as the 'free ring radius' or 'free hoop diameter': in simple terms, this means that, at a given speed of rotation, all the material inside that diameter is effectively holding on to all the material outside that diameter. If you are suggesting the equivalent of a giant circlip to hold the blades in place, then it has been done. However, because that ring would be well outside the free ring radius, it would be restrained from flying apart by the blades themselves and would be exerting a significant additional load on the blades. And, because the blades (and the disc slots) can never be made absolutely identical, the load can never be distributed uniformly between the blades: a few will take no load, while some will take most of the load. I've been there, done that, in terms of trying to address an intractable problem.
grahamj9101 did I read in the comments long ago that if a turbine disc failed from over speed that it would burst into 3 approx same size pieces failing about 120 degrees apart around the circumference of the disc? I may have dreamed that up but i think either you or someone else explained it in the comments. I have not been able to find the topic again in the comments but if I didn't dream it up, could you explain the how and why of it failing in 3 equal parts? (Hopefully I didn't dream it up. ) Thanks!
No, you didn't dream it up, Mr Good: I made that statement in a previous comment. When I saw the photo of a segment of the burst IP turbine disc from the QF32 uncontained engine failure over Indonesia in 2010, I immediately recognised it as an overspeed failure. The distortion of the sheared disc drive arm also suggested that it had been softened by severe overheating. Three days after the event, I wrote a hypothesis of the failure sequence, which was essentially correct. However, I digress. In my time at R-R, I saw several photos of discs that had been intentionally taken to overspeed failure in a spin pit: the three-segment failure is classic. So why is this the case? I won't pretend that I'm up to speed with the theory after all these years and you really need a stress engineer to explain it in detail. However, from what I recall, it essentially begins with the first failure initiating at a position somewhere on the periphery (I think) of the disc where it is very slightly weaker. The first crack propagates at that position and it is down to curved beam theory that the consequent failures are at the highest stress positions, which are 120deg apart.
I'd like to know the profit margin on turbine engines.. They just seem to be somewhat of a Monopoly and way overpriced? I think I saw that like One A380 engine is $10 million USD? so times 4 for engines? I mean how can one engine cost $10 million? Just doesn't seem right... I'd bet it costs 1 million and 9 million is profit per engine is my guess..
Wrong! The big engine manufacturers typically sell their engines at a loss initially, to get them installed on an aircraft type. The profit comes, in the longer term, from the sale of spares and through repair and overhaul contracts, and in-service support arrangements. Mr Morin has got it about right.
I'm only responding to this comment to say it's not worth responding to any comment that complains : "it just doesn't seem right" C'mon, man... It just doesn't seem right that I have to pay so much for my house... or my food... or my taxes... It is what it is, and it's nobody's responsibility but yours to make you understand it.
I have to say I thoroughly enjoy your videos, Informative and entertaining. My middle son just joined the USAF Reserves as a jet engine mechanic. I spent 13 years in the USAF as a crew chief on A-10's and F-111's so I can now share some information, augmented with the information from your channel, with someone else who has a grasp of the unimaginable power and intricacies of turbine engines. On a slightly off topic comment, sitting in the cockpit of an F-111 doing a maintenance engine run is an experience you can"t explain unless you've been there, great fun! Zone 5 afterburner shakes the entire earth, or it sometimes feels as if it does.
As a machinist, those double blades makes me drool of joy!
Awesome definition of centrifugal and centripetal force!
The method to hold the turbine blade in place is quite clever. Great video!
I can't stop thinking about "billimeter"; first time I've heard that dimensional unit.
I also cracked up when he said that. And I almost believed there was such a measurement due to the mater of fact and non-pulsed way AgentJayZ used it. Canadian humor rocks, lol.
The billimeter is a slang term, coined by some mathematical illiterate, to probably mean the next big jump down from millimeter, so it may have been meant to refer to the micron.
I have appropriated the term to refer to the nominal diameter of the heatilon*, so it's more along the lines of the nanometer.
So, an easy way to remember is the billimeter is one billionth of a meter... sort of.
* Heatilon - the imaginary particle of heat, discovered in 1992 by AgentJayZ during the North Van period. According to the RUclips page, and Wikipedia.
Fabulous video as usual
I work in a production facility that makes blades. I assume that the pin grooves I grind in some are so the blades can slide over the locking tabs. One other thing we do, is after the fir tree is cut on some blades, we grind down the root to create a tab. I assume this is to lock it in on one side and a locking ring is used on the other side. I believe that part is a stage 4 blade for the PW F100. I love watching your videos and since I started working at the plant, I am totally amazed how my parts are integrated into the whole package.
Great to hear the perspective of someone who makes these amazing parts!
Simply Amazing. All that power and majesty held in by a large paperclip looking device. Thank you again Sir Special AgentJayZed.
Yeah... in this video I kind of explain that that is exactly what is not happening.
I love watching the amazing technology that makes these marvels of the jet age, as thankyou agent jay, as i use stainless steel wire to lock my v8 rebuild, as found it holds the bolts from getting free
Awesome video Jay, as always.
Great video.
Good explanation. Keep up the good work.
Good job.
Those "baffles" might also be providing an element of damping for the blades.
So nice these are... Thankfully
Holy crap the tolerances in these engines are almost pornographic
Hi Jay, Many thanks as always for devoting all your time to present these amazingly informative videos :). I have almost never asked any questions as anything I ever wanted to know about turbojets & fan-jets has been thoroughly covered in one of them. I was wondering however if you guys were able to locate any more parts for the Iroquois and if any progress had been made on it. Thanks again.
Thanks for the lesson.
Hi, I have a question
like a compressor of a turbshaft compressed the air
does that sound the same as the sound of a propeller ???
Wow, what an incredibly interesting channel. I'm in no way a mechanic but you have taught me an incredible amount about something of which I had absolutely no knowledge. You manage to translate highly technical information into language a complete noob can understand. Thank you.
I have a question which you have probably answered in the past. I've seen that you weigh each turbine blade before installing them. Clearly this is part of the balancing process so I wonder, do you try to place similarly weighted blades exactly opposite each other on the turbine wheel? On one video (from 2014) you appeared to be alternating lower weighted blades with higher weight blades as you install them. Clearly you have a strategy and I was hoping you could describe it in a bit more detail.
Again, if you've answered this question already I'll understand if you don't wish to repeat yourself.
The weighing, sorting, and arranging the blades gets you to the starting point.
From there the balancing process begins using a sensitive machine that spins the assembly, measures vibration and angle, then recommends changes.
Sometimes it takes minutes, sometimes hours.
Thanks, I couldn't imagine that it would be a simple process.
Nice video. Does the mass flow rate of air into compressor section (inlet) for a turbine remains constant all the time or could be changed by some special arrangement (like changing angle of compressor guide blades).....consider steady flow for simplicity.
I am interested to know..!!
Are the locking tabs "single use"? You said you discarding them, Are they still manufactured or do you have to have them made somewhere?
I'm guessing they are single use since unbending metal weakens it.
Single use.
They are available NOS, and we also can make them out of modern superior materials.
Also, when the engine is getting hot the metal will expand a bit and it will fit even tighter. At least that's what I expect. Quite amazing that most of it is all machined without CNC machinery, yet it is done with the highest level of precision.
The disk expands more than the blade root, so the fit becomes looser at high temps.
The disc expands thermally and it also dilates as a result of C/F (note the difference in terminology). The blade and its fir tree root expand thermally, with the blade root running hotter than the disc, and the blade material may also have a coefficient of thermal expansion higher than that of the disc. The clever part of the design process is to ensure that the bottom serration loads up first and that the combination of thermal expansion and C/F allows the serrations to load up progressively and uniformly. That is where the incorporation of 'differential pitch' comes in during the design process. Typically. as manufactured, the flank-to-flank dimensions of the blade serration will be slightly less than those of the disc slot.
PS The design of a fir tree root should be such that it never becomes 'solid': there should always be a clearance between all the features of the fir tree form, except for the loaded flanks.
thank you for the detailed explanation.
OK, didn't expect that, thanks for clearing that up :-)
Well, CNC just makes precision machining faster and more affordable because you don't need a human to constantly control things. Computers just make things cheaper.
so.. the turbine blade retainers of an engine designed in the late 40's are STILL being made?? Thanks for the vids.. always, always interesting
There's progress. Some engines now use a "blisk". But, why re-invent something that works so well, especially something pretty simple.
Awesome
Hey Jay, I machine aerospace parts and the "fur tree" is called a root. And they are ground onto the blades with big sand wheels "conventional wheels" and at the place I work we most likely manufactured those blades.
Yes, the fir tree form is typically ground onto the blade root with a grinding wheel, which, in the latest manufacturing cells, is continuously redressed. The fir tree form in the disc slot is typically produced by a progressive broaching process. The tolerances have to be within 'tenths' (of a thousandth of an inch), to ensure reasonably uniform sharing of the loads on the loaded flanks of the fir tree form. And there is something called 'differential pitch', to complicate the design process still further.
grahamj9101 where do you work at if you don't mind me asking? I work for Moeller aerospace manufacturing.
So are you based at Wixom or Harbor Springs?
I took early retirement from Rolls-Royce in 2003, after 41 years service and returned for another three years part-time, as a consultant. Following my apprenticeship, my whole career was in gas turbine design. From 1967 to 1982, I was in the design office at R-R's Industrial and Marine Division. In 1982, I transferred to R-R Bristol, where I was involved in the design of military engines.
grahamj9101 harbor springs. And that's really cool, I'd love to do something like that. I do 5 axis grinding and milling.
"Turbine Blades: What Hold!?" would be funniest. :D
I was thinking "purgatory" and then you go and say it lol.
11:59. could/would you run water/smoke through the blade. 12:03 Based on what appeared as leading edge holes, does it create a cool air buffer similar to that of a rocket engine nozzle or do they serve another purpose such as some kind of stall prevention? Thanks for another great inside scope of a jet turbine.
Have a look at a video called air cooled blades...
glenn tanner they're simply for cooling and they work exactly how you thought. They are fed air that has already been through the compressor but has not been through the combustors and turned into "working air", as Jay calls it
Thanks guys. Still wouldn't mind "seeing" the flow if you ever get the chance.
Air Cooled Blades: ruclips.net/video/7upnkrhqRWQ/видео.html
Hey Jay, if the fir trees/blade roots are designed to lock under the centifugal force of the rotation of the turbine, then why are the wider sections of the fir trees placed further away from the centre of the rotor? It seems to me that the locking mechanism would afford a more secure lock if the wider section of the fur tree were placed at the 'bottom' of the turbine blade, closer to the centre of the rotor disc.
Unless the turbine wheel is better able to efficiently distribute the force of the blades when the wider sections of the fir trees are placed closer to the outside edge...
Anyway, love your videos, many thanks from the UK!
Yes! I understand now, and that's a brilliant design actually. Thank you for teaching me that! :)
That's a good answer and I can say that as a former Chief Designer - Turbines. I don't think that I've given away any secrets in saying that (see my answer to Darren Duncan).
In simple terms, if the geometry of a fir tree root was reversed, then this would place the thinnest section of the root form of both the disc and the blade at the position of the highest load in both parts.
PS The term "lock" is not really appropriate for the radial retention of the blades in the disc. While the centripetal force applied by the disc to the blade root is equivalent to several (even tens of) thousand times the weight of the blade, there will still be some small movements in the root, as a result of differential growths between the blade and the disc.
And let me throw in something that I was told as a first-year engineering undergrad: "there is no such thing as centrifugal force."
As this video is showing us an engine that originated in the 1940s, can I share the nostalgia trip I've just had as a Jet Provost flew low over my home? Its Armstrong Siddeley Viper engine is of a similar vintage and the Viper was the second engine type that I laid a spanner* on as a Bristol Siddeley Coventry apprentice in 1963.
*For you people in N America, spanner = wrench.
grahamj9101 I got to see the "AFTERSHOCK" twin engine 1940 Ford Fire Truck at a local air show here in Mississippi this past June 2018 powered by a pair of Rolls Royce Viper engines. They allowed me to look the truck and engines over well and answered lots of questions. June of 2017 they had their pair of single engine "Flash Fire" jet trucks at the air show and I got to check them out closely as well. Afterburners/Reheaters Rock on Jet Trucks! Here is a video from a diff air show this year of the Fire Truck. ruclips.net/video/EO98zY2S9SQ/видео.html
Are the numbers on the blades (ex .098) their weight in pounds? Kg?
Most likely it's the decimal fraction of the weight in ounces. We only use one digit after the decimal point when we weigh in grams.
It's lazy and bad practice to not record the whole number.
Ok, then I get it. The weight is some whole number of ounces + .098
But if it was written on there during the previous overhaul, that would mean that the writing survived the engine running for a long time? Is that possible?
Nice demo of the firtree - simple but effective idea. What's up with the numbers? At first I thought you've numbered each blade so they go back in the same order. Then I noticed that quite a few of the blades around where you're working are all called 098, so even though I haven't had my coffee, I blew that theory out... is that a dot? A dimension?
Chris Comley pretty sure they are weight.. just the decimal part as they all should be extremely close, they weigh each one and mark weight to help balance the turbine wheel.
You'll notice I'm removing the blades... The numbers were put there the last time the turbine was balanced... by somebody too lazy to write down the entire number.
They have since been cleaned up, inspected, and had their weight recorded on them in full, in grams.
As it's your shop, then it's your responsibility to ensure that the blades are marked in a manner that is understandable and acceptable to you. Having said that, provided the process and the marking is in accordance with approved build instructions, it may not be necessary to mark the weight in full. I have an Olympus 593 LP turbine blade in my possession: it is marked, '+51-56' and '5' (circled). The marking must have survived some thousands of hours in service. Having left the Olympus 593 in-service engineering team in 1996, with the passing of the years, I now have no idea what the '+51-56' refers to, in relation to a blade that weighs 910 grams on my kitchen scales.
What do you use to remove the oxidation? a chemical? Rubbing it with a brush would give you odd tolerances and imbalances I'm guessing, that a human can't possibly determine this by any faculty we have. Yet doing it by hand and checking by instruments would present a very high failure rate.
After everything is cleaned and inspected... then we balance the assembly
Just re-watched your lock wire vid and I have a question...Have you ever taken apart an engine and found a fastener that was loosened against the lock wire persay? Also do you know when they started using lockwire and if there was a situation that caused the manufacturer to have to? Also this is Gary Ferguson...I changed my google name...thanks Sir
I've seen a combustor locator pin that had come loose and was held in place by lockwire, and continued to perform its function.
That the only case in about 15 years I can think of.
I think lockwire was used by the builders of the very first aircraft, as they realized that problems could not be dealt with while flying. I've seen wire locked turnbuckles on the bracing cables between the wings of WW1 biplanes.
do you do any kind of dimensional checking of the tree on the blade or the groves in the disks? Isn´t there any wear during startup and before stopping?
There are measurements to be taken if any wear is visible. These blade roots do not show any wear and fit very snugly, so they don't need to be measured. Their inspection findings would read "no visible signs of wear".
In my experience, the terms 'wheels' and 'buckets' are commonly used in relation to steam turbines. Their use for those components in a 'heavyweight' industrial gas turbine, such as a GE Frame 5, is, therefore, quite understandable. That there might be a difference in terminology between products from GE Schenectady and GE Evendale is also quite understandable, considering the differences in terminology that still exist between, for example, R-R Bristol and R-R Derby.
Yes, the Frankenstein warehouse of magical engineering fun. love the show. everything you explain makes me purr, and I'm not a girl.
its gorgeous! :)
Any reason why you don't use some light oil to lower the friction of removing the blades?
Oil seems to mix with the dust to make a sort of paste that does not help removal, and slows down the cleaning of the blades once removed.
AgentJayZ -
Hi, I'm an Engineer and Mechanic/Aviation Geek and I am having trouble trying to find a GE T58? How much does one really cost? I am at the beginning stage of building a plane and want to learn how to build and fix a T58 and/or all turbines in general. Is a T58 reliable for a replica P51 Mustang that i am beginning to build? Is there another engine that would be a better fit? From what i have found the the T58 weight/thrust is right in-line for what i am looking for. Love your channel by the way and watch them pretty much all day at work. Keep up the great work! Would love to hear back from you.
Thanks Andrew
Learning how to fix or build turbine engines is a step or two before actually putting one in a Mustang.
It's easy to start that process inexpensively by reading a few of the books I recommend.
As for powering your Mustang, instead of a helicopter turboshaft like the T58, a turboprop in the 1,200 to 2,000 Hp range might be a better choice.
I would suggest a P&W PT6.
Keep in mind that this project would be much more than bolting in an engine...
The aircraft would need to be integrated with all the control systems of an engine it was not designed for.
...
Then, you would have a very reliable and responsive engine that makes all the wrong sounds for warbird enthusiasts.
It might be difficult to find anyone who sees any value in your creation if you ever wanted to sell it.
I think it's a cool idea, but then it would also be a monumental job to make it work.
I wish you luck, and would love to see the result.
If you use a T55 engine, you can build a replica Piper PA-48 Enforcer...
I see measurements on each blade, are you looking for wear ?
Keith Lewis I believe that it's for balancing purpouses🤔
Hi I was just wondering I noticed on the ge90 b788 when the jet engine is coming up from idle to higher rev there is like a gear like sound quite loud is it the turbines
Darren Ormond that is the turbine blades breaking the sound barrier.
So you bend both sides of the lockpin on for example the J79?
Yes, they are supplied as a flat piece of metal.
Could you explain something about the Avro Arrow Engine That was developed specially for that aircraft and what the difference is between that engine and the ones that you show now? Or was that just Hollywood?
that was the Orenda Iroquois engine. pretty decent information on it in Wikipedia. en.wikipedia.org/wiki/Orenda_Iroquois
@@syx3s thank you for that information it was very interesting reading. The movie got me interested in that aircraft and engine. I live in the USA and I saw the movie years ago on TV here and tried to buy the video but was not available in the United States only in Canada. So I did take advantage of buying that and some books also. Must have been a great time to work there.
@@ronaldshepard4625 I was looking around nobel (on google maps) where many of the factories were.... now it's just a bunch of foundations covered with wilderness. even the gates onto the main road are hardly noticeable. really sad. ( ) = edit
It is something, the wide variety of comments & questions you get regarding one topic. I get this one though, dependable, secure & fairly simple design that works, thanks to lots of gramj9101's out there doin' the designin'! Of course the 'simple' design requires a complex manufacturing process, including 'how do those cooling air holes get there'? Some kind of electro-boring process done under water (electrolytic solution) using very fine wire; what's that process called Graham? It's something I'd seen somewhere but it's obviously outside of my wheel house. Thanks Jay for the video.
DD
Thanks, that sounds familiar. I am not sure if that is the way GE did/does it but those holes are small; maybe 0.010 - 0.015", and numerous. I think the EDM method can make some pretty small holes so sounds possible. Maybe Graham knows the method used.
I was going to mention both EDM (aka spark erosion) and laser drilling, but I've been out of the industry for twelve years now. However, I do keep in regular contact with a former colleague who is still involved in turbine design at R-R Bristol. I will have a discussion with him when we next have a liquid lunch. - but I must be careful.
A long-retired former Head of Combustion at R-R Derby was arrested recently for allegedly giving away secrets of the F-35 engine, the P&W F135. His experience was mostly with civil engines at R-R Derby and he had never worked on the F135 engine's combustion system, so he couldn't be privy to any secret features of the engine. Since retirement he has lectured on combustion systems as a visiting professor, including during visits to China. Apparently, he discussed thermal barrier coatings and mentioned the F135, which has got him into trouble with the US military, who got the British authorities to arrest him.
I think I must avoid saying too much about the Pegasus engine in future. I don't want to be arrested on a 'trumped-up' charge.
That is a great link there Richard! Graham will also enjoy reading it if he hasn't yet, so thanks again for the education.
Thanks for the reply & information. I went to the link listed below in Richard's comment RE. RR's ABCF plant in Sheffield & found it informative. Check it out if you havn't already... Cheers!
I used to see and read 'The Engineer' regularly when I was still at R-R: perhaps I should get back on the circulation list. As usual, however, there's some journalistic hype in the piece: apart from the information that the wax assembly and investment process is now increasingly automated, there's nothing particularly new in the article. I was very familiar with the Precision Casting Facility (PCF) at Derby, where the wax room had a large number of female operatives assembling the waxes by hand, albeit with some of the investment already being done by robots. The manufacture of Single Crystal (SX) and Directionally Solidified (DS) blades was already common practice in the 1990s, well before I took early retirement in 2003.
My first experience with ceramic cores for cooled turbine blades was in 1971, when R-R's Industrial and Marine Division designed an uprated version of the Industrial Olympus. We knew it as the Olympus 'C' (aka the 2020 series) and it's the version that AgentJayZ has shown us on occasions. While I (a designer of less than five years' experience) was designing the LP turbine blade, my senior colleague, Alan C***, was designing a brand-new cooled HP turbine blade. It had multi-pass internal cooling passages, using a ceramic core: I recall joining him on a visit to the prospective manufacturer of the cores in Staffordshire, a part of England with a long history of ceramic manufacture. We were probably in advance of R-R Derby at the time in utilising the technology, as they were still working on an improved version of a cooled forged blade for the RB211.
cool
Nice
If you have a blade that is stuck and normal pulling won't remove it what do you use or do to get it out?
That has never happened. Have you watched this video?
Yes and the corrosion is why I asked. But I guess if that was the case you might have a bigger problem to deal with.
I learned a lot in school but not everything. Just like the tool you had made to pull the collar that was stuck.
one doesn't "play" with manual focus.
Sir I have been searching for a topic "pressure recovery" but I found it nowhere so please can u explain it to me
You've put two words together, and they could mean anything.
You need to be far more specific.
Sir it's also termed as shock recompression
See previous comment.
Shock recompression?
Is that what happens when my motorcycle hits two bumps in a row?
Maybe try searching "supersonic inlet" instead...
Wouldn't it be easier if the entire ring came off or had secondary ring to hold them all in place...take it off, dump all the blades out at once to be refubished, install new ones.
Weight...
Unsprung weight...
Rotating weight...
...Dump?...
Yeah... no.
AgentJayZ If you can produce parts that meet standard specifications all of those variables should be met. Seems overly complex to service when every blade needs to be numbered or has unique variables.
AgentJayZ said no and I too say no, having been responsible for the design of turbines and turbine blades. It is quite impracticable, even with the degree of precision used in their manufacture, to produce blades that are totally interchangeable in a disc. When the engine is running at maximum rpm, each of those blades is exerting a reaction force on the disc equivalent to, say, the weight of a truck - and individually producing as much power as the engine of that truck. The slightest variation in mass and/or CofG is, therefore, effectively magnified tens of thousands of times. The blades have to be weighed, numbered and distributed in an alternating light-heavy-light pattern around the disc and then the bladed disc has to be balanced.
I'm not quite sure what you mean by a "secondary ring". If you are suggesting that the blades could be restrained radially by a ring instead of of a disc, then that's not possible with current materials and technology: the ring would simply fly apart. In turbine (and compressor) disc design, there is something known as the 'free ring radius' or 'free hoop diameter': in simple terms, this means that, at a given speed of rotation, all the material inside that diameter is effectively holding on to all the material outside that diameter.
If you are suggesting the equivalent of a giant circlip to hold the blades in place, then it has been done. However, because that ring would be well outside the free ring radius, it would be restrained from flying apart by the blades themselves and would be exerting a significant additional load on the blades. And, because the blades (and the disc slots) can never be made absolutely identical, the load can never be distributed uniformly between the blades: a few will take no load, while some will take most of the load. I've been there, done that, in terms of trying to address an intractable problem.
grahamj9101 did I read in the comments long ago that if a turbine disc failed from over speed that it would burst into 3 approx same size pieces failing about 120 degrees apart around the circumference of the disc? I may have dreamed that up but i think either you or someone else explained it in the comments. I have not been able to find the topic again in the comments but if I didn't dream it up, could you explain the how and why of it failing in 3 equal parts? (Hopefully I didn't dream it up. ) Thanks!
No, you didn't dream it up, Mr Good: I made that statement in a previous comment. When I saw the photo of a segment of the burst IP turbine disc from the QF32 uncontained engine failure over Indonesia in 2010, I immediately recognised it as an overspeed failure. The distortion of the sheared disc drive arm also suggested that it had been softened by severe overheating. Three days after the event, I wrote a hypothesis of the failure sequence, which was essentially correct. However, I digress.
In my time at R-R, I saw several photos of discs that had been intentionally taken to overspeed failure in a spin pit: the three-segment failure is classic. So why is this the case? I won't pretend that I'm up to speed with the theory after all these years and you really need a stress engineer to explain it in detail. However, from what I recall, it essentially begins with the first failure initiating at a position somewhere on the periphery (I think) of the disc where it is very slightly weaker. The first crack propagates at that position and it is down to curved beam theory that the consequent failures are at the highest stress positions, which are 120deg apart.
It's not a graveyard its a turbine gallery or turbine's get together
I'd like to know the profit margin on turbine engines.. They just seem to be somewhat of a Monopoly and way overpriced? I think I saw that like One A380 engine is $10 million USD? so times 4 for engines? I mean how can one engine cost $10 million? Just doesn't seem right... I'd bet it costs 1 million and 9 million is profit per engine is my guess..
Wrong!
The big engine manufacturers typically sell their engines at a loss initially, to get them installed on an aircraft type. The profit comes, in the longer term, from the sale of spares and through repair and overhaul contracts, and in-service support arrangements.
Mr Morin has got it about right.
I'm only responding to this comment to say it's not worth responding to any comment that complains : "it just doesn't seem right"
C'mon, man... It just doesn't seem right that I have to pay so much for my house... or my food... or my taxes...
It is what it is, and it's nobody's responsibility but yours to make you understand it.