Regenerative Bike Brakes

For their senior design project at Arizona State University, these guys built a regenerative braking system for their bike. As they brake, the system spools up to give them a push back up to speed.  They achieved 25% efficiency on one run, which isn’t too shabby.

The site has all kinds of information. You can check out their different plans and ideas from before they decided on this specific layout as well as all their data from the test runs. Be sure to look at the piece by piece breakdown of what changes were made from the initial design.

[thanks Mario Gomes]

21 thoughts on “Regenerative Bike Brakes

  1. What’s wrong with using a garage door spring? You could even probably manage to wrap it around the bike frame or something. Those things are very powerful too, fling you right up to speed in no time!

  2. Hmmm i can jsut see some sat at traffic lights on one of those.

    “watch out for that tree” no “watc out for the bus coming out of the junction”

    Still it would be a great idea for having to stop at lights goign up hill

  3. I think the most impressive thing about their Rube-Goldbergian solution is that it actually works. I’m sure there are much slicker implementations that would be a lot more practical and possibly more efficient, like a high-speed flywheel on a clutch. The energey density would certainly beat the pants off a bungee or spring.

  4. I’m all for proving the principle, but I have to say that

    this is the least elegant engineering solution I have seen

    in a long while. Couldn’t they have at least designed it

    to the length of the vehicle? Or implemented it using a

    fly-wheel or something. Engineering should be inspiring

    and as much an artform as anything else. The Victorians

    could have come up with something more elegant. If this is

    signifies the cream of Arizona State University, then

    it’s a sad day indeed.

    I’ve seen better ghetto solutions at

    Sorry for the criticism, but there you have it.

  5. In fairness to the guys, follow the link. They consider a few optionas, and give reasons for choosing the design they went with. It’s easy to be an armchair critic, but they do actually answer some of the questions like “why didn’t they use a garage spring?”

  6. I think it could be made more compact with a pump and some hydrolics., I think a spiral spring would probably cost too much b/c it would have to be custom made. Garage door spirng would probably be too much tension.

  7. How about this? Continuously variable transmission. Get a beefy-ass spring (of whatever footprint) that takes loads of work to compress. Very high k, if you will. Then attach the mechanism that compresses it to a continuously variable transmission engaged by the slightest touch on the brakes. The harder the brakes are then pulled, the higher the gear ratio, and the more work is done on the spring during deltaT. That would give you variable braking much like normal brakes such that if you pull the brakes as hard as can be, your stopping distance is governed by your coefficient of friction with the ground. The footprint of the storage mechanism also wouldn’t be that large, meaning you could fit it within the footprint of the bike itself.

  8. Hey guys,

    I’m one of the students that was in this design project. I understand all your comments and concerns…especially with the flywheel (believe me, we tried) But given our budget and our given constraints, a lot of things didn’t work.

    As far as all the spring comments, there were two other groups that had this project, one used extension garage door springs and the other used torsional garage door springs. So contact hackaday to see if they can post them as well.

    A torsional garage door spring is very dangerous and I personally feel much more comfortable with a bungee cord under me then a torsional spring. You can’t wrap a spring around the frame because that will affect the original intent of the bike and for that matter, when a torsional spring is loaded, the ID of the spring decreases thus crushing your bike.

    As far as the extension garage door spring, it did work much better than the bungee cord, I’ll admit it.

    The reason for the extended length over the footprint of the bike, is that in order to achieve the necessary speeds in the given distance, we needed to have a huge extension to provide the load. If we worked within the footprint of the bike, the spring force would make you either pop a wheelie (where you lose energy) or throw the rider (in which injuring the rider is not beneficial).

    If we used a flywheel for this project, due to the characteristics of a flywheel, we would never come to a full stop, lose too much energy (we had to design for 50% efficiency) and would require a giant flywheel in order to store the amount of energy required.

    Lastly, this project was intended to be a low cost add on to a bike. If you do more searches on the internet, you’ll find some OSU guys that had corporate sponsors who made a regenerative braking bike that ran off an incredible hydraulic system. Their project was amazing! But, they had roughly 10x the budget and twice as long to design it.

    As far as the CVT comment, we had some blackboard ideas for a system, but in order for us to build and incorporate it into our formal design, we would have been over budget and past due. There is only so much travel to a bicycle hand brake that you can’t really incorporate a CVT for it unless you have a complete gear ratio for it which would both cost a lot of money and weigh the bike down too much.

    I hope I’ve been able to answer nearly everyone’s questions. But contact hackaday for links to the other 2 sites. They did great work too!

  9. Hello friends….I am Mallya from Banglore,India.I am doing project on Regenerative brakes for conventional car,is it possible to use flywheel next to wheel,to capture kinetic energy while braking and again boost the vehicle during releasing the brake pedal.Pls give me a suggestions on what type of device i have to use.

  10. Hi guys
    i’am using gas springs for bicycle Regenerative brakes, they are light weight, expand slow if they ever let loose, gas springs have the same amount of force thru there complete stroke. this makes it simple for good even braking, unlike steel springs that start out at 0 force and get tighter. 2 gas spring at 250lbs of force each (500lbs of force total) and 12 inches of stroke launch me (200lbs) quite well.


  11. Hey
    I am designing a mechanical regenerative braking mechanism for bicycle in my final year mechanical project. It would be of great help if you could share some aspects of your design. Plz do let me know!!! your help will be of great help

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