This is from a Reddit thread. A picture and discussion are at the link below. It was spotted on a highway.
It’s a pully attached to the right rear wheel. It’s attached by a chain to something in the bumber. Whether the same setup exists on the left wheel is unknown.
The consensus it that’s a device designed (by someone ignorant of the laws of thermodynamics) to gain energy by recharging the batteries of the electric Chevy Volt.
Onviously you can’t gain energy in this way but is there some other possible valid use for such a setup?
You could charge the batteries that way, if something else is causing the car to move, or if it’s moving but you don’t want it to be. But the thing is, electric and hybrid cars already have a built-in system to do exactly that: It’s called regenerative braking, and it’s a large part of why hybrids are more efficient than pure-gas cars.
I think it’s clear, in any event, that this is an aftermarket modification, and a rather slapdash one (the space for the alternator, or whatever it is, is cut rather crudely out of the bumper). I don’t think it’s a stretch to say that it was installed by someone who didn’t understand very well what he was doing. And if you accept that, then who knows what he was thinking?
Also from the “We don’t need no thermodynamics” dept.: there was a guy in Québec who would publish an ad on Kijiji asking for somebody to lend him an electric car for an experiment. It would have consisted of adding this sort of pulley to activate a device in the trunk that would recharge the battery. But the device wasn’t merely a generator, it was a tiny hydroelectric power plant, where the belt-driven pulley would pump water to the upper réservoir. He also explicitly mentioned that, since the pulley was attached to a rear wheel on a front-wheel-drive vehicle, it wasn’t driven by the electric motor, so the energy was free. There were, oddly, no takers.
Could that be an attempt charge it when it is being towed as a “dinghy” for a large motor home? I could see trying that. The drag would cause a little more fuel use for the tow vehicle, but you’d have a charged car when you get where you’re going?
Even if that was the goal, wouldn’t it be a simpler, cheaper, more reliable and probably more efficient installation to just draw electric current directly from the tow vehicle? That way you’re just running a cable instead of this mess of an installation.
Is it possible that, rather than the input to a generator, the pulley is the output of another motive force? Like pedals, or a hamster wheel, or a small petrol engine?
I’m halfway wondering if this pulley is actually inputting to a generator. It’s possible the owner wanted to seriously upgrade the cabin cooling power over the stock air conditioning. This could be inputting to a compressor unit to provide secondary cooling.
Mind you, I’m not saying doing so would be smart. He’s be better off mounting a small, roof mounted, RV style air conditioner (assuming the roof could take the load and it wouldn’t block a sunroof.)
The output of this contraption would vary enormously according to the speed of the motor home. The standard charging circuitry on a Bolt will accept a stable level 1 (120V AC), level 2 (240V AC) or level 3 (400V DC) connection on the charge port and manage the charge intelligently to avoid overcharging, overheating, etc. Maybe you could have some additional components to clean up the generator’s output and disconnect it when it’s not generating a proper voltage+current level.
But that system works only when the car is being driven, not when it’s being towed. I like the idea that this is a trickle charger for a towed vehicle (as KMS94 suggested). Yes, outputting 110 volts from the RV would be easier, but this is more interesting.
All true but this just takes the fun out of guessing.
Hopefully this indicates that most EV owners are smarter than the people who would dream up these experiments.
The belt is very clearly connected to an automotive alternator. The obvious conclusion is that it’s being used to generate electricity. Unclear for what purpose.
A great selling feature for a Bolt might be making the regen charging system work when the car is being towed. Add a level sensor for the car and it could regenerate going down hills but be neutral going uphills. So, the Bolt wouldn’t add excess drag when the motorhome was struggling to climb and it would ease the strain on the RV’s brakes when the RV was descending. Of course, GM would only spend the money to program, build, and document this system for users if they really wanted to go after the niche market of RVers who want an electric towed vehicle.
I had a thought once that perhaps a Stirling engine could capture heat from an ICE engines exhaust and turn it into… something. Even posted a thread about it here on the SDMB.
Thought that the sterling could get the cooling half from airflow, and the heat from the ICE exhaust waste gases.
Long story short, I don’t really understand Sterling engines and you don’t get something from nothing.
Shame to waste all that heat from the exhaust though.
The heat from internal combustion is part of the waste. It can be utilized. Sterling engines have been suggested for both exhaust and radiator heat. Similar to the way steam engine designers learned to use the exhausted steam to power a lower pressure cylinder. As long as you have a steady source of heat with enough temperature difference to the surrounding air it will work. The absolute temperature is not that important. Sterlings have been designed to work in the Arctic using the nearly freezing water under the ice as the heat source, dumping to the -40 degree air above the ice.
How much energy could be produced at what cost is a good question.
Yeah, there’s more to economics than efficiency. And existing ICEs are not necessarily designed to be optimally efficient, but they are designed to be optimally economical.
I was thinking that this was a fifth wheel used for testing the car (speed, distance, braking, etc) but looking at such things, they don’t seem to be attached to the existing wheels.
There also seems to be some kind of pipe installed under the rear bumper - as a filler tube? Drain tube? Exhaust vent? Whatever it is, it suggests more than purely electrical mods going on in there.
I’m thinking that this thread has reached the point where we need to start thinking even farther outside the box to try to guess how this guy is thinking outside the box.
I’m going to suggest that this is a DIY, and admittedly very primitive, attempt to build a home-made prototype Infinite Improbability Drive.
(I was going to guess Alcubierre Drive, but that would probably not be street legal.)
Is it just me, or does the blowed-up picture show no kind of retaining nut on the disc added to the rear wheel? I see a largish thru hole on the disc itself, and it looks like the belt tension and a bearing might be the only thing keeping the disc in place. Flying highway disc alert!
I sure love a good mystery, and this seems like one that we can’t solve until we get with the guy who did it. I agree that the downspout/filler tube indicates there’s something that requires fossil fuels in there. Others have suggested a small gas generator where the spare tire might have fit.