Great idea of doing videos and really clear explanation about how air moves around different shapes. Could you talk about how the air is effected when it comes in contact with the wheels, what problems you have to solve and what compromises you have to make. Thanks good work!
@Ioan Hill: Thank you for your question. We looked into boundary layer control. Suction is useful if you are going to have boundary layer separation. In my other video I describe why this is not a problem for the ETA. Golf ball dimples solve the problem in a worse way, so we dont need them either, for the same reasons. In an airplane the suction is useful, because you can have boundary layer separation at extreme angles of attack. The only case this might happen with the bike is if we have high side winds, but that would mean the record would be unoficial anyway (the legal limit for wind is very low).
Dear Aero Velo, Seeing as speedbikes need a flow of fresh air for the occupant to breath and keep cool, would there be any case where it is advantageous to use some portion of the pedal power to perform boundary layer suction to supply this airflow? The skin of the speedbike could be porous, through which air could be drawn by an efficient pump. Perhaps the energy required to run the pump would be offset by the power saved through reduced drag. Alternatively to a porous skin, a simple narrow circumferential slot or series of slots in the aerodynamic shell could also be used for boundary layer suction. Any boundary layer suction method would likely be more effective on the rear of the speedbike shell, where laminar flow starts to deteriorate. I notice the tape-seam of Eta is towards the rear, where the airflow-tripping effect of the seam matters less. If the seam was instead a boundary layer suction gap, it would keep flow attached longer rather than tripping it. I would be interested to hear if you have considered this, and if so, what your conclusion was.
Along the lines of loan Hill's question regarding boundary layer control, except I'm wondering about the discomfort of the rider during the speed run and ways to offset this. I saw where you removed the clear windshield because the rider's heat and moisture would fog the window. Perhaps a ducted fan could be used to direct interior air out the back of the vehicle through a slot running vertically along the tail. Properly set up, the exiting air would reduce or eliminate the vortices at the trailing edge and air being drawn into the vehicle through the wheel openings would cool the rider. Is this something you looked into?
Do you have plans for your human power technology to become commercial products, or is it just for breaking records? I'd love to ride one of those bikes to school! :D
I know some very high performance cars have used a high-speed flywheel that stores kinetic energy during braking, then dumps its energy into the drivetrain when accelerating out of the corners (see kinetic energy recovery systems). Perhaps a smaller version could be used to store energy during the two-mile run to the speed trap, then help push the vehicle to a very high speed during the timed trap. Since it's powered entirely by the rider, maybe this would be a legal option. Thoughts?
+Phillip Breske We're working on a mechanical kinetic energy recovery system for our new ASME bike. Electrical systems are not allowed, and the energy scales possible with mechanical storage are not enough to drastically increase the top speed of such a bike. Mostly it saves some time and energy from 0-30 kph.
Hello everyone, I'm Brazilian and I liked the song (Aerovelo) I would like you to do a video explaining how to make an airplane (from its extrusion to the pedal system) I would like to create an equal project in the back of my garage !! thank you
A lot of bikes competing at Battle Mountain use similar designs. There are 2 chains. One transmits the motion from the cranks to the intermediate drive (which you can see in the video. The shiftier is located at this drive. This first chain stage is quite similar to a normal bike. A second chain transmits the motion from the intermediate drive to the wheel. The chain twists as you turn the wheel, but that is not actually a big problem, if you keep the power side of the chain aligned with the steering axis. Let me know if you have any other questions.
there are a lot of issues with that...I will probably have a full episode on it as soon as I finish my thesis and have more time. The biggest points are: 1) crashes would be bad. We race on roads with no cars, obstacles, rails, etc. If you crash, you just skip like a stone on the road until you stop. 2) wind is bad. Even light gusts can throw the bike 1-2 meters laterally. A semi going beside you would make you loose control 3) vision is a problem. Hard to see the bike from the chase vehicle, even if you know it is there. It is hard to see from inside the bike. Long distances on bike-only, well maintained and lit highways would be probably feasible...dutch velomobiles are getting close.
+Sentinalh the main problem on the road is point 2. VRagusila made. even on a TT bike with disc wheels if you only get a slight wind from the side, it starts to be unrideable. that why on Hawaii (Kona Ironman) disc wheels are not allowed since ppl would crash all the time.
I am thinking a typical spoked bicycle wheel spinning at close to 160 Kms/hr. must be approaching it's self destruct load. Can you reveal what tires & diameter wheels are used?
we spun wheels quite fast in testing, and I doubt you will get anywhere close to their self destruct load. Mountain bikers have gone down at 200+ kph and their wheels survived. We used normal aluminum rims mounted on custom carbon disks made by us. Our tires are special Continentals, much thinner than other road tires. They also held up just fine to fast racing. You have to realize that, while our speed is quite high, road racers reach 100+ kph quite often when going down hill. This means most bike components are ok at the speeds we see. If we would go 200+, then I would start to worry about components failing.
+Sam Meyerson I dont remember the exact gears we use, we kept changing them for different days depending on Todd's preferred RPM. He was not spinning much faster than 110rpm for the record, so you can calculate the gear inch from that.
Hey Mark, I am one of the team members this summer, in charge of the gearing. While we haven't had the chance to measure the power output in 1st and 2nd gear, we do know that it is a level where you will not get tired. In fitness terms, we are certainly not exceeding the aerobic threshold (the power output you could sustain for hours), which for Todd is around 350 watts. In the bike shown, which has 4 speeds, second gear puts you around 70 km/h. I have tried riding these bikes on the course, and I can tell you that 70 km/h is effortless to maintain. Without air resistance, we could all be riding around A LOT faster.
Simon WoodburyForget A vehicle like this is would certainly be safe if you could convert all highways to being bikes only. In the real world, this vehicle could not be used around your neighborhood. However, it does not take much modification before something like this (streamlined and high-speed) is completely feasible and able to commercialized - take a look at the vehicles that compete in the ASME Human Powered Vehicle Challenge. The competition is a much more practical version of the speed challenge and includes speed bumps, stop signs, hairpin turns, rumble strips and other obstacles.
I say, old boy, that is old school stuff, so, similarly, one would presume that you should have known better and should have preferred not to use the slang application for "man" as an exclamation of surprise or delight to make and emphasis on the situation. Also, through saying," the grammar in that title", without your own statement containing a verb, it does not explain the detail of what the man-made symbols in that statement are referring to. Perhaps you should consider the following:- "Wow, just observe the terrible English grammar and lack of detail found in that title written on the board. To ensure that the title was referring to the number of gears installed on the record breaking bicycle and not the number of gears in the store or available elsewhere, the written title should have specified that very clearly." In spite of the imperfection in the title, one cannot fault this gentleman on his presentation of the technical substance and he did do better than anyone else, breaking records with it. He seems to care more about how to apply it rather than how to write it or how to utter it. Because of their old philosophies, many old schools missed out on many other types of intelligence of people who made all the modern comforts which are found in every modern home. Through history, all philosophies of written and spoken languages, written religions and writing down good rules of grammar in court rules and other social regulations, never provided any tangible comfort for anyone's home. It was the silent people who did it all like the invention of the clock by George Harrison . No academic person in any British University who could read and write accurately, ever found a method how to navigate the seas using longitudes and latitudes and it was a silent woodworker who did it all , working alone with the silent logic and processes of the universe, and not the scribes that wrote religions, rules and regulations nor the written ethics that are continuously broken by those who write them.
hahaha thanks, but I DID mess up the title big time. Was meant to be "How many Gears do do you need to bike at 145km/hr?", which doesnt really roll of the tongue either...:P
Belts are actually very close to good chains in power loss. We are investigating both for the second version of ETA, due to race in 2015. Belts are not ideal because you cant use them in with dérailleurs, (and internal hubs ARE inefficient). Also, we have a front wheel drive bike, so the belt has to twist as the wheel turns. We are not yet sure if it can do that. I will probably have one more transmission episode (and a few on other topics) as soon as my gradschool thesis is complete, and I have more time.
I like this guy, he's really good at explaining things.
Great idea of doing videos and really clear explanation about how air moves around different shapes. Could you talk about how the air is effected when it comes in contact with the wheels, what problems you have to solve and what compromises you have to make. Thanks good work!
@Ioan Hill: Thank you for your question. We looked into boundary layer control. Suction is useful if you are going to have boundary layer separation. In my other video I describe why this is not a problem for the ETA. Golf ball dimples solve the problem in a worse way, so we dont need them either, for the same reasons.
In an airplane the suction is useful, because you can have boundary layer separation at extreme angles of attack. The only case this might happen with the bike is if we have high side winds, but that would mean the record would be unoficial anyway (the legal limit for wind is very low).
Dear Aero Velo,
Seeing as speedbikes need a flow of fresh air for the occupant to breath and keep cool, would there be any case where it is advantageous to use some portion of the pedal power to perform boundary layer suction to supply this airflow? The skin of the speedbike could be porous, through which air could be drawn by an efficient pump. Perhaps the energy required to run the pump would be offset by the power saved through reduced drag.
Alternatively to a porous skin, a simple narrow circumferential slot or series of slots in the aerodynamic shell could also be used for boundary layer suction. Any boundary layer suction method would likely be more effective on the rear of the speedbike shell, where laminar flow starts to deteriorate. I notice the tape-seam of Eta is towards the rear, where the airflow-tripping effect of the seam matters less. If the seam was instead a boundary layer suction gap, it would keep flow attached longer rather than tripping it.
I would be interested to hear if you have considered this, and if so, what your conclusion was.
Along the lines of loan Hill's question regarding boundary layer control, except I'm wondering about the discomfort of the rider during the speed run and ways to offset this. I saw where you removed the clear windshield because the rider's heat and moisture would fog the window. Perhaps a ducted fan could be used to direct interior air out the back of the vehicle through a slot running vertically along the tail. Properly set up, the exiting air would reduce or eliminate the vortices at the trailing edge and air being drawn into the vehicle through the wheel openings would cool the rider. Is this something you looked into?
Do you have plans for your human power technology to become commercial products, or is it just for breaking records? I'd love to ride one of those bikes to school! :D
I know some very high performance cars have used a high-speed flywheel that stores kinetic energy during braking, then dumps its energy into the drivetrain when accelerating out of the corners (see kinetic energy recovery systems). Perhaps a smaller version could be used to store energy during the two-mile run to the speed trap, then help push the vehicle to a very high speed during the timed trap. Since it's powered entirely by the rider, maybe this would be a legal option. Thoughts?
+Phillip Breske I looked into exactly that. Stored energy is not allowed on events under 1km, whether that energy is chemical, electric, kinetic, etc.
+Phillip Breske
We're working on a mechanical kinetic energy recovery system for our new ASME bike. Electrical systems are not allowed, and the energy scales possible with mechanical storage are not enough to drastically increase the top speed of such a bike. Mostly it saves some time and energy from 0-30 kph.
Great job, thank you.
Hello everyone, I'm Brazilian and I liked the song (Aerovelo) I would like you to do a video explaining how to make an airplane (from its extrusion to the pedal system) I would like to create an equal project in the back of my garage !! thank you
there are a few books on human powered airplanes. Start with www.amazon.com/Gossamer-Odyssey-Triumph-Human-Powered-Flight/dp/0395305314
Could you please share some info about how how you are transmitting power from crank(pedals) to front wheel .
A lot of bikes competing at Battle Mountain use similar designs. There are 2 chains. One transmits the motion from the cranks to the intermediate drive (which you can see in the video. The shiftier is located at this drive. This first chain stage is quite similar to a normal bike.
A second chain transmits the motion from the intermediate drive to the wheel. The chain twists as you turn the wheel, but that is not actually a big problem, if you keep the power side of the chain aligned with the steering axis.
Let me know if you have any other questions.
I have a question. Do you guys foresee highway capable bikes for long distance high speed travel as an eventual possibility?
there are a lot of issues with that...I will probably have a full episode on it as soon as I finish my thesis and have more time. The biggest points are:
1) crashes would be bad. We race on roads with no cars, obstacles, rails, etc. If you crash, you just skip like a stone on the road until you stop.
2) wind is bad. Even light gusts can throw the bike 1-2 meters laterally. A semi going beside you would make you loose control
3) vision is a problem. Hard to see the bike from the chase vehicle, even if you know it is there. It is hard to see from inside the bike.
Long distances on bike-only, well maintained and lit highways would be probably feasible...dutch velomobiles are getting close.
+Sentinalh the main problem on the road is point 2. VRagusila made.
even on a TT bike with disc wheels if you only get a slight wind from the side, it starts to be unrideable. that why on Hawaii (Kona Ironman) disc wheels are not allowed since ppl would crash all the time.
I am thinking a typical spoked bicycle wheel spinning at close to 160 Kms/hr. must be approaching it's self destruct load. Can you reveal what tires & diameter wheels are used?
we spun wheels quite fast in testing, and I doubt you will get anywhere close to their self destruct load. Mountain bikers have gone down at 200+ kph and their wheels survived.
We used normal aluminum rims mounted on custom carbon disks made by us. Our tires are special Continentals, much thinner than other road tires. They also held up just fine to fast racing.
You have to realize that, while our speed is quite high, road racers reach 100+ kph quite often when going down hill. This means most bike components are ok at the speeds we see. If we would go 200+, then I would start to worry about components failing.
Can you disclose the gear inch that you used for your record run? Thank you
+Sam Meyerson I dont remember the exact gears we use, we kept changing them for different days depending on Todd's preferred RPM. He was not spinning much faster than 110rpm for the record, so you can calculate the gear inch from that.
what sort of power are we talking about in gears one, and two?
Hey Mark,
I am one of the team members this summer, in charge of the gearing. While we haven't had the chance to measure the power output in 1st and 2nd gear, we do know that it is a level where you will not get tired. In fitness terms, we are certainly not exceeding the aerobic threshold (the power output you could sustain for hours), which for Todd is around 350 watts. In the bike shown, which has 4 speeds, second gear puts you around 70 km/h. I have tried riding these bikes on the course, and I can tell you that 70 km/h is effortless to maintain. Without air resistance, we could all be riding around A LOT faster.
Simon WoodburyForget A vehicle like this is would certainly be safe if you could convert all highways to being bikes only. In the real world, this vehicle could not be used around your neighborhood. However, it does not take much modification before something like this (streamlined and high-speed) is completely feasible and able to commercialized - take a look at the vehicles that compete in the ASME Human Powered Vehicle Challenge. The competition is a much more practical version of the speed challenge and includes speed bumps, stop signs, hairpin turns, rumble strips and other obstacles.
+Marc Jutras effortless at 70kmh/45 mph!! wow :)
I'd like a lot more detail. I'd watch for an hour if it was that long.
That's one scary helmet ( = = ' )
Now put a 50cc engine in that
Man; the grammar in that title.
I say, old boy, that is old school stuff, so, similarly, one would presume that you should have known better and should have preferred not to use the slang application for "man" as an exclamation of surprise or delight to make and emphasis on the situation. Also, through saying," the grammar in that title", without your own statement containing a verb, it does not explain the detail of what the man-made symbols in that statement are referring to.
Perhaps you should consider the following:-
"Wow, just observe the terrible English grammar and lack of detail found in that title written on the board. To ensure that the title was referring to the number of gears installed on the record breaking bicycle and not the number of gears in the store or available elsewhere, the written title should have specified that very clearly."
In spite of the imperfection in the title, one cannot fault this gentleman on his presentation of the technical substance and he did do better than anyone else, breaking records with it. He seems to care more about how to apply it rather than how to write it or how to utter it.
Because of their old philosophies, many old schools missed out on many other types of intelligence of people who made all the modern comforts which are found in every modern home. Through history, all philosophies of
written and spoken languages, written religions and writing down good rules of grammar in court rules and other social regulations, never provided any tangible comfort for anyone's home. It was the silent people who did it all like the invention of the clock by George Harrison . No academic person in any British University who could read and write accurately, ever found a method how to navigate the seas using longitudes and latitudes and it was a silent woodworker who did it all , working alone with the silent logic and processes of the universe, and not the scribes that wrote religions, rules and regulations nor the written ethics that are continuously broken by those who write them.
hahaha thanks, but I DID mess up the title big time. Was meant to be "How many Gears do do you need to bike at 145km/hr?", which doesnt really roll of the tongue either...:P
wouldnt it be more efficient if instead of conventional bike chains you use belts...somethig like this /watch?v=u6RcwB3XVts
No. Belts continually drain away power as they flex around the drive pulleys. Chains are extremely efficient. Belts are much less so.
Belts are actually very close to good chains in power loss. We are investigating both for the second version of ETA, due to race in 2015. Belts are not ideal because you cant use them in with dérailleurs, (and internal hubs ARE inefficient). Also, we have a front wheel drive bike, so the belt has to twist as the wheel turns. We are not yet sure if it can do that.
I will probably have one more transmission episode (and a few on other topics) as soon as my gradschool thesis is complete, and I have more time.