Wheel Generator Brake Lights?

[user 35233]

Has anyone attached a generator to work when brakes are applied rather than applying consistent drag to the wheel? Is it possible to affix a generator at the right angles on brake hardware so that power is only supplied when braking?

 

[axeman88]

I think those "bottle" style generators we used back in the day are notoriously inefficient. They sure added a lot of drag. A favorite trick when I was a kid was to get in a race with somebody who had one of those mounted on their bike, pull up close enough to push the button that engaged their generator, then watch them drop behind like they had just dropped an anchor.

I was thinking of something like you are talking about, on a E-Bike build, sort of a poor man's regenerative braking. But I think I'd try to start with a generator hub. Magnets mounted on the rim of a wheel would be even more effective in producing power, I'll bet. With LED lighting, a battery to store power, and a few substantial downhill sections along the route, that would normally require braking, one might have a viable source of "free" energy.

I would expect the difficulty to be in implementing a "no resistance" mode. Seems to me that this would be with the generator coil shorted, not open, which would mean dissipating any power produced within the coils themselves, and they might not tolerate that. Anything with permanent magnets would produce some drag, I expect. A generator with a field coil wouldn't, but you'd need at least a small battery to get the system generating, although once it was producing power, that could be used to self-excite the field coil.

But, honestly, efficient LED lighting has made bike generators a solution in search of a problem. For $7, I got myself a set of lights that can fit in the palm of my hand, with internal rechargeable batteries that last me several rides between charges, recharge from a USB port, and put out far more light than any generator or battery light that I used back in the day. https://www.ebay.com/itm/234551292577

 

[rickpaulos]

Those bottle generators have so much drag they do a substantial amount of braking by themselves reducing the amount of braking needed. I have a 12 Volt bottle generator that has about 2x the drag and could power a regular semi truck trailer light if you want a really bright brake light. There was a lever actuated "power bell (I have one in a box somewhere). And there was a Sanyo type bb generator that had a cable running up the seat stay to a lever located below the saddle. The regular Sanyo control lever was below the bb so you needed really agile toes or had to get off the bike to turn the generator on/off.

Bottle generators are normally spring loaded to hold the drive wheel against the tire. Just the opposite of what you would want for braking. Remove the catch that holds the generator away from the wheel (a bit of filing or grinding). If the spring could be reversed, it would only work when you squeeze the brake lever. Or remove the spring completely and add an external return spring. Or can one be installed backwards so the spring would push the generator away from the tire? I think that depends on the construction of any particular model of generator. Some are more "modular", ie, many parts bolted together. They aren't all the same.

The direction of the hinge on the bottle generators is parallel to the bike. I think an L bracket attached to the outside of the generator (hose clamps) with the cable pulling up. A cable stop higher up on the bike so pulling the cable will push the generator to the wheel.

How to incorporate that with regular brakes. There are dual cable brake levers. Sometimes installed on tandems with 3 brakes or for 1-handed bike riders. Even some rare BMX gyro levers use 2 cables rather than a splitter cable. And use some barrel adjusters to fine tune the brake vs generator movement. Maybe a sturdy coil spring in the generator cable so when you squeezed the brakes hard, you aren't over doing the generator pressure.

Wire the generator output directly to your brake light. As you come to a stop, no more electricity so the light will go out unless you add a fat capacitor to the circuit. I've had generator head lights that have capacitors built in to keep the lights lit at traffic lights and stop signs. LEDs take less power so a smaller capacitor would be needed to keep the light going for the desired time. Too big of a capacitor and your brake light could stay on long after you are moving again.

I've seen some modern LED brake lights that detect a reduction in forward speed to activate. Same accelerometer technology in smart phones and game controlers and more advanced (electronic) step counters (fit bit). There are 3 main accelerometer technologies. Piezo electric, electro magnetic and coil all of which can be traced back to record player cartridges.

There are e-bike/scooter brake levers with build in electric switches. Those are normally connected to the controller to turn off the drive power. I suppose some ebikes have brake lights already installed.

"There's an app for that" or could be. Use the accelerometer in your smart phone to detect slowing, Blue Tooth control of a remote control tail light.

 

[user 35233]

Nice. Record player cartridges solves that Sanyo connection. I've been looking over their options, (thanks @axeman88), but didn't know there was a wire to lever controlled model. Your suggestions as to using specific models in place of brakes is extremely helpful. I'll be exploring both options. I'm hoping to store excess in a battery and hide LEDs around the bike with a switch. I appreciate being free of the grid, USB charging, short lived internal light batteries and plastic waste. Dynamo hubs are tooo heavy for my lightweights. This is the final fantasy in achieving my wholly roadside-maintenance free ride.