3 speed electric kart?

[bluetangkid]

I was wondering if it would be possible to have a 3 speed electric kart, as I wanted to have a kart that would be able to manually shift during a race for a competitive piece, and in case I happen to have 4 extra people hanging onto the side of the kart(or when I race a gas kart, and it breaks down) I have some experience with the transmissions of small r/c cars, but these aren't r/c cars(I'm sure somebody will argue that point).

 

[Arkparkp4]

Electric motors make power at all of its rpm range.. which makes it pointless to have gears if you always get instant power at most rpm. So it would be unnecessary to have gears on an electric vehicle since it has power at any rpm up to the top speed.

 

[bluetangkid]

I know, but it would help for the max speed, and manual shifting would be fun. and, think for towing: i could significantly increase the torque and lower the speed, and for racing i could significantly reduce the stress on the motor by using lower gears in the beginning and shifting up. I just dont see how your argument applies to my application.

Edit:"So it would be unnecessary to have gears on an electric vehicle since it has power at any rpm up to the top speed." Unnecessary but very helpful from what i understand

 

[Jrgunn5150]

BUt most BL RC car's don't have transmissions, for exactly that reason.

Any of my 6s BL trucks can backflip from a stand still and top out around 55-60 mph, so they are well balanced.

Tesla car's, one of the companies my company supplies, have single speed transmissions, and go 1mph, or 130 mph. And that's a real 1:1 car, with some very smart people engineering it.

Electric trains, pulling 5,000,000 lbs? Single speed.

If you need more power in an electric car, you literally add more power Volts, Watts, Amps, less turns on the motor, less KV on a BL, not drop a gear.

 

[bluetangkid]

I would believe that it is cheaper to have a transmission, it would result in lower temperatures on the motor, and have a higher top speed.

 

[Jrgunn5150]

I would believe that it is cheaper to have a transmission, it would result in lower temperatures on the motor, and have a higher top speed.

Well, every electric locomotive, Traxxas, Arrma, Losi, HPI, Thunder Tiger, and Tesla Motors all disagree with you.

So, that said, rig one up and show us, and them, that it makes sense.

 

[bluetangkid]

Oops. i double posted

---------- Post added at 08:27 PM ---------- Previous post was at 08:21 PM ----------

Well, every electric locomotive, Traxxas, Arrma, Losi, HPI, Thunder Tiger, and Tesla Motors all disagree with you.

So, that said, rig one up and show us, and them, that it makes sense.

Ok. When you have the gearing closer to 1:1 in any electric thing, the motor runs hotter because of the new stress, and if you were able to reduce that stress by giving it a momentum previously to running closer to 1:1, there would be less stress from starting the kart, and you would be able to have a higher top speed, right?

 

[Jrgunn5150]

You reduce the stress in an electric thing by dropping KV on the motor and adding more volts though.

Electric motor's make 100% of their torque, pretty much at stall. Or as commonly stated, instantly. There is no power band to keep an electric motor in, no need to gear down. You pick the speed you want to run, and choose the appropriate motor and batteries. They WILL perform down low, because they can perform up top, because there's no difference to an electric motor.

So, if you want to haul four friends, or another kart, simply factor that into your motor and battery choice, and it will be appropriate when you aren't as well.

 

[Poboy kartman]

Well...it's not completely crazy....if you think about it.

Electric motors may have a nearly flat torque curve....but...what y'all are missing is

.they turn a CONSTANT maximum RPM!

Now....I understand what you're saying ...but...if the motor is underpowered for take -off and incredibly high geared....are you saying it makes no difference?

Sorry ....just messing around a little bit with the Poboy crusher I found I needed a jackshaft.... So really? If an electric motor turns a specific RPM....and the wheels are geared 1:1....assuming the motor has enough power ....doubling the output shaft gear ratio is going to do nothing?

 

[Jrgunn5150]

Well...it's not completely crazy....if you think about it.

Electric motors may have a nearly flat torque curve....but...what y'all are missing is

.they turn a CONSTANT maximum RPM!

Now....I understand what you're saying ...but...if the motor is underpowered for take -off and incredibly high geared....are you saying it makes no difference?

Sorry ....just messing around a little bit with the Poboy crusher I found I needed a jackshaft.... So really? If an electric motor turns a specific RPM....and the wheels are geared 1:1....assuming the motor has enough power ....doubling the output shaft gear ratio is going to do nothing?

No, if it's underpowered for take off and incredibly high geared, you either drop gear ratio, or drop KV and add voltage to deal with it, not down shift.

What that situation would cause, is an incredible draw through the speed control, and likely would overheat it. Under gearing, causes to much RPM, and overheats the motor.

 

[bluetangkid]

No, if it's underpowered for take off and incredibly high geared, you either drop gear ratio, or drop KV and add voltage to deal with it, not down shift.

What that situation would cause, is an incredible draw through the speed control, and likely would overheat it. Under gearing, causes to much RPM, and overheats the motor.

And dropping Kv or adding voltage is cheap or fun? I mean, who would build a go kart for a purpose other than fun? shifting is more fun than holding a gas pedal, and lower gears and higher torque is fun for drifting in the rain, while a higher gear is more fun for racing, and i'm not lowering the Kv or raising the voltage with more batteries just to spend 30 minutes on a kart, then change it back. It just doesnt make sense to not make the kart geared. also, think of how useful this would be for racing, again. So, the max RPM is say 1000(just for explaining) with a 0.5:1 ration it would be 500, then if you gear up to 0.75:1 you get 750 RPM to the axle, and if you start with 0.75:1 your motor would likely overheat faster, and again, who doesn't like shifting something?

Remember: these numbers are purely for my explanation

 

[Jrgunn5150]

 

[bluetangkid]

Also, when you said "underpowered for take off and incredibly high geared, you either drop gear ratio" why don't you drop gear ration for takeoff only, then raise it up after you get your speed up to reduce the stress that you would do the other options to reduce.

 

[Poboy kartman]

Also, when you said "underpowered for take off and incredibly high geared, you either drop gear ratio" why don't you drop gear ration for takeoff only, then raise it up after you get your speed up to reduce the stress that you would do the other options to reduce.

Yeah...that was my point ....

 

[bluetangkid]

Yeah...that was my point ....

yep, but i used theoretical math to help prove what you said, since he was still not agreeing to what we said. Now, is ther anyone who could help with the design of one? I am completely new to designing multi-speed transmissions.

 

[Jrgunn5150]

You don't need theoretical math to prove anything. I've never disputed that changing gears via a transmission doesn't accomplish what you are try to accomplish.

I merely stated that it isn't done that way, because using the proper motor and batteries for what you are trying to achieve is much simpler.

Electric motor's beat the crap out of transmissions, and, in case you missed it, don't need them when the drivetrain is properly designed. Multi-speed transmissions are merely a crutch for inefficient IC engine's.

If you want to use a transmission to crutch your improperly spec'd electric motor and batteries, it will work on paper. They don't use them, because they don't need them.

If you are dead set on designing a transmission from scratch because you feel that's easier than using the correct motor/battery/gearing combo from the start, then by all means, let us see how your project turns out.

 

[bluetangkid]

You don't need theoretical math to prove anything. I've never disputed that changing gears via a transmission doesn't accomplish what you are try to accomplish.

I merely stated that it isn't done that way, because using the proper motor and batteries for what you are trying to achieve is much simpler.

Electric motor's beat the crap out of transmissions, and, in case you missed it, don't need them when the drivetrain is properly designed. Multi-speed transmissions are merely a crutch for inefficient IC engine's.

If you want to use a transmission to crutch your improperly spec'd electric motor and batteries, it will work on paper. They don't use them, because they don't need them.

If you are dead set on designing a transmission from scratch because you feel that's easier than using the correct motor/battery/gearing combo from the start, then by all means, let us see how your project turns out.

Sounds fun to make, and the motor I would be using will be fine, I just don't want to replace the gears/sprockets every time I add or remove someone from the kart. It's just simpler. I still don't see what you are basing your information off of though. If you do it correctly it won't break, it's how everything works. I've seen transmissions done for them, just not with multiple speeds.

 

[Jrgunn5150]

I'm basing my information off of the past ten year's I've been employed as an engineer.

You are making a simple thing complicated. The con's of a multispeed transmission outweigh the pro's in an electric vehicle.

But, again, show us what you come up with, I'm interested to see it.

 

[Poboy kartman]

Transmissions....just not with multiple speeds?

Past your bedtime....you're getting goofy.

Speaking of goofy.....I have a neighbor with a lawnmower you plug an extension cord into.....REALLY? ???? DUDE!!!!!!

 

[Arkparkp4]

And dropping Kv or adding voltage is cheap or fun? I mean, who would build a go kart for a purpose other than fun? shifting is more fun than holding a gas pedal, and lower gears and higher torque is fun for drifting in the rain, while a higher gear is more fun for racing, and i'm not lowering the Kv or raising the voltage with more batteries just to spend 30 minutes on a kart, then change it back. It just doesnt make sense to not make the kart geared. also, think of how useful this would be for racing, again. So, the max RPM is say 1000(just for explaining) with a 0.5:1 ration it would be 500, then if you gear up to 0.75:1 you get 750 RPM to the axle, and if you start with 0.75:1 your motor would likely overheat faster, and again, who doesn't like shifting something

If you really want to shift, buy a motor cycle engine, they usually come with 6 gears... and a clutch. Double the fun. Less complexity. No need for a separate gear box.