OH BTW, it would be called an altinator.
You know, the ripple current source................................................
WTF is an altinator?
And, incase you know as much about cars as you do electronics, an alternator is driven by a mechanical force, in a vehicle, you have a pulley on the crankshaft and a pulley on your alternator, with a belt between the two pulleys. As the crankshaft spins, it spins the alternator. The alternator produces an AC voltage. And if your unaware of what AC voltage is, it pushes power through a wire, then it pulls it back through. Pushing power into a battery then pulling it back out doesn't charge a battery. Some circuitry is added to prevent it from pulling the power back out of the battery, so the battery can charge. But there are pauses in the input power. These pauses is what creates the ripple in voltage.
Now what you're saying is to take a smaller motor, and have a battery spin it. This won't create the ripple we need, its pulling power, it isn't generating power. You would need to make an rc alternator, and figure out a way to have the main motor spin it in a mechanical fashion (with gears, a pulley system, chain driven, what ever). Then, yes....maybe the ripple could be read if it was charging its own separate battery. As the main battery voltage isn't steady at all when its powering a motor through a modern esc. and i'm sure an RC alternator isn't very cheap to make.
I see no possible way, how powering a small motor form the power going to the main will generate electricity. We aren't trying to make the rpm's go from 20,000 rpm down to 2000 rpm so the sound racer has proper sense. It doesn't detect rpms from something like this. It detects the ripple in voltage that an alternator creates. Faking that ripple requires special equipment to detect the frequency at different rpms and how sinusoidal the ripple is. Then faking that ripple takes quite abit of circuitry and lots of trial and error. And the simple fact is, time invested into it alone, is not worth the investment for the extremely small market. JUST BECAUSE YOU WANT 20 OF THEM, does not mean its a heavy hitter. It is cool, but it'll get annoying, especially if it doesn't sound very realistic.
If this task is as simple as you think it is, then sit down a build it yourself with "print-out resist paper on an etch board!", do they even make that anymore?
Or am I some alien whose 20 buck membership means my thoughts are less than some 100 buck guy who just keeps saying things cant be done?
These 100 buck guys know what the hell they're talking about and sell to the rc market. They know how large the market is and what to expect in sells, they know the costs involved in producing a product, they know the amount of time it'll take to develop a product, they know how much it'll cost to develop a product. They aren't saying it can't be done, they are saying at the price you are requesting and the size of the market, its not worth it. 100-125ish, it be worth it. 50ish, hell no. Its damn near impossible to create a quality american made(as much as possible)/american designed product that cheap in low quantities. If we're talking thousands of units a year being sold, yea its 100% possible and probably worth it, but we're talking 50-100 units a year. At this quantity, they are no where near affordable to make, and minimal profit doesn't pay for the time and cost spent in developing and marketing the product.
From the sounds of it, you're retired and have plenty of time and money. So how about you get a blue star, and sell these. It shouldn't be too hard for you to get some "print-out resist paper on an etch board!" and make these.
If you want some cheap, barely functional pos sound generator, go talk to the chinese, otherwise deal with the higher prices.
