As I was contemplating the future of my children's vicariously living my best childhood, I came across a site where a dude had modded a powerwheels car with a $50 36V motor to go like 30 mph with a 230# man driving it.
Years ago I read about how some university was looking at replacing FWD cars' rear hubs/brakes with electric motors to help with the launch and thereby drastically improve gas mileage and performance.
So put the two readings together and what's to say you couldn't drop a relatively cheap motor on each hub (via chain drive or what have you) and get some similar gains of your own? Granted, a small car like an Impreza would weigh in at like 850 pounds per wheel, which is not 230, but still it shouldn't be an order of magnitude more expensive to go 4x more powerful, right? I would think to save money you could do it w/out a controller and make it an on/off switch like nitrous. And spare the drivetrain by doing it at each wheel instead of running it through a diff.
Also, if sub $2,000...
The "via chain drive or what have you" is the hard part. Some pretty serious engineering goes into packaging those sorts of setups, and then you have to invest in the batteries and drive inverter, etc...it's not like a Power Wheels car where you don't have to worry about brakes or suspension!
Now I'm not meaning a full drivetrain replacement, just a little extra something. Granted, I haven't gotten under the car to do some imagining regarding placement, etc., but I do have batteries by the boatload. I'm apparently missing something with the inverter need, however. What do you mean there?
In reply to P3PPY :
In EVs, motors are typically AC but batteries are DC. You can't just connect DC batteries to AC motors and expect it all to work. The inverter handles that conversion as well as the "throttling" of the AC motors.
Decent intro-level reading here: https://lightningemotors.com/whats-an-inverter/
I guess if the goal was just to add a full throttle boost you could probably use a DC motor? But I'd think you would want to boost the whole drivetrain and not just each wheel, since wheel speed can vary so much depending on how fast a car is going, and you would still need some sort of transmission for engage/disengage or the motor would have a ton of parasitic drag when not in use.
(FWIW, I'm not an EV engineer but I did work with industrial machinery electrical systems for a good chunk of my career, and I feel like your proposal would be a little more complex to execute than you're envisioning, but I would love to see it happen!)
Maybe rig up a Razor dirt bike controller that has been modified to it. I swapped out one of our MX650s to a 48V li-ion battery which is also lighter. LED display shows a 54 overvolt now when it's fully charged. I'd imagine the same type of motor rigged up to one of those would do the trick.
Okay I had a lot of time to daydream tonight while putting the kids to bed-- motors would be securely mounted to the trans and the rear diff and the gears would be affixed to the shafts immediately coming out of each -- before the first of the two inline CV joints. Chain would be encased in a box of sorts. Or instead of chain would direct gear teeth to teeth be better?
I perceive a big hurdle though that it's probably no good to have the motor spinning the whole time the shafts are spinning such as when going down the highway, yeah? I'm looking for a way to disconnect. I was thinking internal clutch on the motor's side like a snowmobile, but if you're looking for a hard launch you don't really want the electric motor spinning up to speed first and THEN kicking in the chain, yeah? Or would it spin up so fast that it wouldn't be a big deal? If so, then you could use that kind of clutch to disengage the motor after pulling electricity from it. Of course you now have a small chain indefinitely spinning at a good clip.
Less important to address is powering it but I had time to daydream there too. I'm totally onboard with 48V (or whatever) of DC batteries to power a DC motor, but since this would be a rarely-used thing (-maybe?), are there such things as capacitors that would recharge between use? Instead of like 48V of batteries constantly there? (Not like a smallish Ah set of batteries would be too heavy to be workable though...)
Well I'm going to replace the rear diff and as long as it's out I'm gonna look for mounting points. That's step 1. We shall see
There's tons of EV projects that small creators have. The Openinverter wiki has detailed pages on the reverse-engineering on the Lexus GS450h Transmission (a transmission that has electric motors built into the casing) or the Mitsubishi Outlander rear drive unit that like you're thinking, is literally the rear pumpkin.
As for hub wheels, you have Protean Electric which has several retrofitted Mercedes and some videos on Munroe Live's youtube channel, and Elaphe which is making motors for the Aptera. Particularly notable, is that Proterra motor's are Brushless DC and not AC, so they don't use inverters to power the motors; they have more of an Electronic Speed Controller like an RC car or some E-bikes, though I believe through my exprience with both this leads them to being noisier and having less off the line torque than typical electric motors due to back EMF.
Thanks for those leads, man!
P3PPY said:
Thanks for those leads, man!
No problem dude. I can gather more specific stuff for you depending on what you're wanting to try; there's lots of very simple motor combinations thanks to Indochina's need for Tuktuks and other small vehicles.
I totally get where you're coming from with wanting to power up your kid's Power Wheels. But it sounds like you're also thinking about some serious performance upgrades for your own ride. I like the way you think!
As for dropping a motor on each hub, it's definitely been done before with electric cars and hybrids. The tricky part is making sure everything is balanced and the weight distribution is right. You don't want your car to handle like a shopping cart with a wonky wheel!
And you're right that going for an on/off switch instead of a controller could save some dough. But keep in mind that without a controller, you might have trouble controlling the speed and torque. You don't want to spin out or burn rubber every time you hit the gas!
As for cost, it's hard to say. It really depends on what kind of motor and other components you use. But with some careful planning and a little elbow grease, you might be able to keep it under $2,000.
My current best case scenario is to attach small motors near the differential and somehow put teeth on the outside of the CVs and spin them with chain.
Instead of spending money on a variable throttle controller I was thinking that if I could somehow use the 3 mile an hour start switch my razor scooters have (so it doesn't supply power until it's already moving), and if I had an on off switch for the whole thing, ala nitrous, I could run it like a cheaper on-off switch but not break anything.
