obrien1984

Does anyone know of such a thing on bikes? I've seen the little generators that spin against the tire wall used to power lights, but these obviously reduce efficiency. But what if the same idea were used for brakes, like in the new hybrid cars? Squeeze on the brakes just a little, and the little generator thingy (for lack of a more technical term) presses against the wheel, slows the bike, and maybe pumps a little energy into rechargeable NiHM batteries which would be used at night to power lights. If the brakes handles are squeezed harder for a more abrupt stop, the regular brakes would engage as normal.

Whaddya think? Has this been done? Is it more trouble than it's worth?

joseph

LittleBigMan

Joseph,

Others may call me crazy, and they may be right, but why couldn't it work?

Pete

MichaelW

There are systems that use the spinning hub to generate more braking force (obscelete Suntour cantelevers).

There may be a problem transferring the energy off the wheel. Roller systems need low resistance , else they slip, but low resistance means you dont get much energy off the spinning wheel.

Hub based systems may be effective, but you are adding a lot of complication onto a machine who's main advantages are simplicity and low cost.

If you are going to build a larger more complex hub, you may as well use a Schmidt Dynohub. Not many people are willing to use these, dispite being the best energy source for flat urban use.

mike

Of course, it is theoretically possible. There is nothing terribly difficult with designing a system to apply a generator of sorts to a brake lever. That's not tough.

I think the reality is that you would have to be braking too often in order to charge up a battery in any reasonable amount of time.

With the science available today, recharging a battery uses electricity which ultimately comes from a mechanical source like a generator. The mechanical load is translated into electrical power which is then used to reverse the electro-chemical reaction of a (rechargeable) battery.

Unfortunately, the energy for this process ultimately comes from the legs of the rider.

As an alternative, maybe you could rig a wind mill to your bike and have the energy of the wind resistance (which is available whether or not you are charging a battery) turned into electricity. It is still a mechanical translation of energy into electricity, but it would be afforded without additional energy coming from the rider. Of course, this assumes that the wind mill would be powered by wind energy that would be pushing against the rider & bike anyway.

Keep thinking. The bike world needs something new and cool.

MichaelW

The point raised here is to use the energy that is dissipated during braking (as heat, noise and mechanical abrasion), for some useful purpose, not to find another use for the pedalling energy that is used for propulsion.

A windmill on a bike would be an additional drag force which would slow the bike down (ie transfer energy from propulsion to something else). A windmill would only work if the wind was blowing from behind faster than you are travelling. If this is the case, then you hardly need extra enegy, you are having a free ride.

If you check at the patent office you will probably find scores of energy conserving mechanisms, none of which were really viable.

TriBob

Here is a different twist: Make a jersey with solar panels on the back like those on a calculator. They could power lights, cell phone, PDA etc. your own moble office

RainmanP

Or how about turning the entire wheel into a giant rotor with tiny magnets on each spoke (as for your computer pickup), passing 1 or even two small coils affixed to the fork, seat stays, whatever. Total weight would be probably little more than a dynamo. No moving parts. No mechanical resistance. Minimal wind resistance.

MichaelW

Sorry, wont work in the sense that you have just re-invented the hub dynamo.

When you pass a magnet over a coil to generate electricity you are converting kinetric energy into electrical energy. A magnetised wheel would slow down as it passes the coil, and would need more of your energy to maintain rotation.

There is no free lunch, the only source of energy is your legs. If you tap any energy from motion to something else, you will slow down. A good dynamo will slow you down perhaps 1km/hr.

RainmanP

Awww, man! Leave it up to someone to come along with so-called "facts" and quash a perfectly sound fantasy.

aerobat

Besides, with all those magnets you may not be able to ride past the first metal light standard!

MichaelW

but at least traffic lights will change for you