My girlfriend recently bought a 2013 Chevy Spark. This car comes with a CVT (Continuously Variable Transmission). This is not the first time I’ve heard of this type of transmission. I find them very interesting and unconventional. How hard would it be to implement this kind of transmission into an e-board. The current e-board transmission is pretty limiting in that you only have one gear ratio, so sacrifices have to be made when considering startup torque or top speed. Some of the advantages I can think of having a CVT would be the ability to use smaller motors, having the motor run at it’s optimal rpm, and having better efficiency (longer run time). What do you guys think? Is this the future of e-boards?
Believe it or not i have thought this over more than a few times. Its just a little too complicated (read expensive ) to do successfully.
The good old keep it simple mantra always leads me back to the old toothed belt we all know.
I’ve thought about this too, however, there is no smaller size CVTs that I could find and implementing one would make an eBoard look really bulky. It works with Go Karts and I’ve seen some scooter versions, but making one for eBoards would be a challenge.
If you had a three wheel setup with a rear drive wheel over 10" it would be good for long trips but even with the softest wheels and smoothest roads you’d be better off with a scooter. The speeds you would be able to get wouldn’t be realistic for a plank of wood, handlebars are a must. If you built something small enough to fit under a board and work with wheels less than 100mm it wouldn’t be able to stay clean and the time spent on maintenance would outweigh the benefits.
My big idea is to have two motors with different kv and gearing, one for low end torque and one for high speed, but the gears would need to be freewheels like on a bike and the throttle signal will need to come from a custom flight controller.
@lowGuido Yeah, being complicated and expensive are definitely downsides, but it doesn’t necessarily mean it’s a bad idea. I’ve only heard of CVT’s in small vehicles: small fuel efficient cars, scooters, and go karts as @Pantologist also mentioned, so what smaller vehicles do we have than our e-boards? lol
@Pantologist The only thing I’ve found on a small cvt is this video from 2008
Even with it being that small, the amount of space between the center of the trucks to the start of the wheels is very limited. Putting a cvt system inplace of essentially the belt and pulley system we have now would be very hard.
you want a list of what I have tried and my thoughts on them??
single wheel drive
pros: light weight, economical, long range, simple.
cons: low on torque, not so great on loose surfaces, hard carving on the offside can lose traction.
Dual rear drive
pros: awesome torque, good hill climber, good for heavier riders. no traction problems.
cons: heavy, uses more battery, need wider trucks, more expensive.
Dual diagonal drive
if you set it up heelside rear and toeside front this makes the ultimate carving machine!
pros: same as dual rear except you can use narrow trucks.
cons: same as dual rear.
uneven dual drive
this involves the combination of a big motor and a small motor (in power not size)
this is like a twin turbo high speed boost super fast!
pros: low end torque combined with high end speed, super fast!!
cons: expensive, heavy, still only roughly equivalent to single drive torque.
direct hub drive
as far as I can tell so far these are king!!
pros: loads of torque, no belts to skip or snap, and looks a bit more normal
cons: High voltage required, large diameter is starting to get a bit too big for my liking.
I don’t trust hub motors because my riding style involves riding off curbs, staircases, and eventually boardslides. I don’t believe a hub motor is strong enough to outlast my satellite motor, and belts are still cheap.
I am wondering about using something like THIS as a 90 degree friction drive system. It could be mounted flat on top of the truck with a simple clamp and quad drive would cut the amps way down. My list of science TODOs goes on and on. Too bad money is still a thing. @lowGuido your stack is inspiring!
But direct drive motors don’t really have a gear ratio right? I’ve only seen one direct drive with a planetary gear system, but just looking at that thing screams hard to maintain because
the ones im testing have a 1:1 ratio being direct drive. but they are like 70kv or something…
actually that the only downs side… you need to run like 10S or 12S to get any decent speed out of them… I like my small 6S systems.
hah, I think @nowind could be one of the first ones to try this out (by making it)…
There just needs to be enough influential figure to impact this decision… I hope something does come along one day what would make @nowind to make this crazy mini-scale transmission for eboards.
From what I’ve seen, @nowind from machining perspective should be up for this job with no problems
Once it would be built some calculations could be made, such as: does it outweight the cost / use of sensored system vs transmission system (cost, max speed, energy usage etc)
Cvts seem ideal for combustion engines where the torque is limited to a smaller range of the possible rpms than electric motors are. With an electric motor you can get decent torque from almost a standstill and at much higher speeds, not so with a combustion engine without a variable gearbox or a cvt. They’re pretty efficient but seem an unnecessary complication with electric. Except if u have an electric motor that’s really small then I can imagine it would be a benefit. Seems simpler to get a bigger motor, but cvts are cool and love to see one on a board
