Flywheel Bike KERS

[Applause] a kinetic energy recovery system stores energy during braking to later assist with acceleration instead of wasting the energy as heat in the brakes this is very similar to regenerative braking in electric and hybrid cars but in some cases the energy can be stored in a flywheel and if you're a subscriber of this channel you'll know that i love flywheels so let's build a bike with a flywheel kinetic energy recovery system the plan is to use the bike that i previously made to be air powered from another video as the frame is a simple tubular design and has lots of space for a flywheel plus i already have a cad model of it so that will save some design time from this i can work out how large of a flywheel i need which seems to be about a 30 centimeter diameter or about 15 centimeter radius speaking of raid raid shadow legends is sponsoring this video raid is a mobile game with console level graphics it's a turn-based battle game where you take turns to control your champions to 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single month and it's never easier to get started so what are you waiting for go to the video description and click on my links to support my channel by downloading raid today so where on earth do i get such a flywheel i have a cnc router to cut parts for a lot of my projects but i've never cut anything heavier than aluminium ideally the flywheel needs to be made from steel as steel is three times denser than aluminium whilst browsing the internet for steel sheets i found a bunch of sellers on ebay selling laser-cut steel discs to the perfect dimensions i need which saves me a ton of work to turn this steel disc into a flywheel i first measured and drilled some holes on a friend's drill press but because i measured the hole positions by hand they probably won't be perfectly aligned so i positioned the flywheel at a distance from my camera and took a photo i can then import this image into my cad software and make a model of the flywheel which shows the center of the drilled holes to only be out by 0.086 of a millimeter which was a pleasant surprise also i can use this template to design some side plates that were correct for this small misalignment and allow the bearings to be mounted either side of the flywheel the purpose of the disc brake will become clear later the next step was to make the brackets that will hold the flywheel inside the bike frame these were cut from six millimeter thick aluminium sheet which should provide plenty of strength to keep the flywheel from breaking loose at high rpm it was then time to check if my measurement and design were correct by attaching everything to the bike and there we have it a flywheel on a bike now we need to figure out how to connect it to the rear wheel to capture the braking energy and assist with acceleration in an ideal world the bike wheel and the flywheel must be coupled together using an infinitely variable transmission this would allow the bike to travel at a certain speed and the flywheel to be stationary then when the bike slows down the flywheel will speed up to a really high rpm the only problem is this is very difficult to do mechanically as you would basically need an infinitely variable gear ratio so the next best solution is to use a clutch system that can engage and disengage the flywheel during braking and acceleration this isn't an original idea and in fact a number of other people have built very similar bikes in the past and you can find their videos here on youtube however i couldn't find much information on how effective their bikes were so what do you do when you can't find any more information on a subject you run the experiment yourself to fit the clutch within the bike frame i need to make this plate on my cnc which took a while to cut and was pretty wasteful of material and memory card space but it can be attached to another plate that has specially designed cutouts for mounting brake pads this can then be positioned on the same shaft as the flywheel and press against the brake disc to act as a clutch so not only are the bike parts cheap and easily available but it's also a really compact clutch mechanism that easily fits within the bike frame at regular cycling speeds bike wheels don't spin much faster than about 300 rpm but i need this flywheel to spin around 2000 rpm to store the energy required to get me going again so there needs to be a large gear ratio between the bike wheel and the flywheel this means the flywheel will spin in the opposite direction to the bike wheels but i'm hoping that won't be an issue so the clutch design kinda works but it also sticks a lot the clutch plate i cut earlier needs to be one piece to allow for this small gear to fit around the small bearings however my cnc router isn't very good at cutting perfectly round holes so these thin wall bearings are slightly squeezed out of being circular which makes him spin terribly and barely slide along the shaft causing the clutch to get stuck the solution to this was to increase the size of the gear and use a larger bearing but this reduces the gear ratio to the rear wheel so i had to make a larger rear sprocket to maintain the same ratio between the wheels to engage the clutch i 3d printed two discs with thread-like slopes which when twisted push each other apart these needed to be really compact as there's only about six millimeters of space between the clutch gear and the side plate but it seems to have a decent amount of pushing force due to the physics of mechanical advantage i chose to operate the clutch using the left hand lever like a motorbike but this operates in reverse to a motorbike as pulling the clutch lever actually engages the clutch rather than disengaging it the reason for this is i don't want the clutch engaged all the time when riding because it requires a lot of energy to spin up the flywheel so pulling the lever in will add resistance and act as a break then when the bike is fully stopped the flywheel will continue to spin with its stored energy and i can simply pull the lever again to engage the clutch and bring the bike back up to speed i think it's time for a test ride i suppose i just ride like a normal bike wow these gears are noisy right so i'm gonna pick up some speed and then engage the clutch and see what happens [Applause] slowed me down i engage the clutch again hang on the clutch needs tightening it's not fully gripping pick up the speed pick up the speed and then we engage the clutch and now accelerate i think we still need to adjust the clutch a tiny bit it's not quite biting enough to fully lock so let me get some tools [Applause] oh that's a lot better that's slowing me down quite a lot actually let's see if i can accelerate again and that's that's not bad it's not bad i think what the problem is is that by the time the clutch fully engages it's already slowed me down by a substantial amount so i'm going to try and spin it up whilst pedaling to get up to really high rpm okay that's fast let's turn around and see that [Applause] let's analyze what's going on here imagine the two lines on the left display the relative speed of the bike and the flywheel whilst riding the bike is at high speed and the flywheel isn't spinning then as i engage to the clutch the flywheel starts to spin and the bike slows down until the point where the flywheel has matched the speed of the clutch from this point the flywheel can't spin any faster and so they both continue at a constant speed until i use the regular bike brakes to bring the bike to a stop now the bike has zero speed but the flywheel is spinning with roughly half the speed the bike had at the start so when the clutch is re-engaged the bike accelerates as the flywheel slows and they both meet in the middle again once their speeds are matched but if i bring the flywheel up to speed whilst riding the fly will control a lot more energy as it's spinning much faster and i can then use the regular bike brakes to bring the bike to a stop now we have a much larger speed difference between the bike and the flywheel so when i engage the clutch the end speed of the bike is a lot faster so that's the problem i can't charge it up just from braking it has to charge up from riding come on get it going get it good then we fully stop then we accelerate come on high speed high speed high speed high speed [Applause] and [Applause] and [Applause] that was a bit scary [Applause] had some tyre weights mounted here two 10 gram tire weights and one just came off and hit me in the leg must be traveling at pretty high rpm for that thing to come off right i found the tire weight i think we need to go in and make a cup of tea i love it okay let's run through some of the numbers of this flywheel bike setup the weight of the flywheel is about 5.5 kilograms and the fastest i got it spinning was 2300 rpm that's a stored energy of about 1 800 joules to put that into perspective a small aa battery stores about five to six times that amount of energy however you can't charge and discharge one of those batteries anywhere near as fast as you can as flywheel so they have very different applications in terms of the speed recovery achieved by the flywheel the initial braking technique only recovered about 22 percent of the original speed of the bike and the second technique of spinning up the flywheel before braking achieved a speed recovery of about 40 percent but the act of having to pedal to spin up the flywheel beforehand requires a lot of effort so that's where the extra energy comes from also because energy increases with velocity squared the actual energy efficiency never exceeds about 15 percent but a few years ago i ran some tests on my diy electric bike and its regenerative braking and during a straight line acceleration and deceleration test its efficiency was only about 15.7 percent so maybe flywheels aren't so bad after all if you enjoyed this video it'd be great if you could leave a thumbs up down below if you're new to my channel and want to see other projects similar to this then please click subscribe down below and a massive thank you to all of my supporters over on patreon.com for making this project possible i honestly couldn't make these crazy projects without your support so thanks once again thanks again for watching and i'll see you in the next video goodbye let's quickly test the gyroscopic effects of the flywheel it actually doesn't seem too bad

Channel: Tom Stanton

Views: 2,221,514

Rating: 4.8903003 out of 5

Keywords: engineering, flywheel, KERS, kinetic energy recovery system, bike, bicycle, cycling, physics, energy storage, kinetic energy, mechanical engineering, ebike, technology

Id: gahKxbwUcYw

Length: 12min 59sec (779 seconds)

Published: Tue May 25 2021

Reddit Comments

[u/HerpDerpinAtWork]

I'm not sure the wisdom of mounting a flywheel that close to one's crotch, but it's still an impressive bit of home engineering. Cool vid.

[u/SPiX0R]

Williams had this idea in F1: https://youtu.be/KPJwJfdzP9o

[u/anyonethinkingabout]

Forget about f1, I wonder if this is against the UCI rules for road cycling