Transmission for Electric Vehicle?

[hacksign23]

Hey guys, I'm looking to get a transmission for an electric vehicle. The motor is around 8 hp peak, but I won't be going there. (probably 5 or so) I tried google-ing some stuff for electric vehicles, but I couldn't find anything. I thought the TAV2 would work, but someone pointed out that gas and electric motors have different properties. Therefore, I can't really use it anymore

Any info and tips? Thanks!

 

[B man]

just get a motor controller for wat ever its volt is. you don't need a transmission. but if you really need one the easy solution is a belt tensioner,

 

[hacksign23]

just get a motor controller for wat ever its volt is. you don't need a transmission. but if you really need one the easy solution is a belt tensioner,

I have a motor control. I need the transmission obviously for the gear ratios... (vehicle's all about efficiency and speed)

anyways, can you point out a link for the belt tensioner or some sort of info on it? Thanks! (i googled it and read the wiki and some random links. just want to see if i'm missing anything)

 

[robotmickey]

Electric motors are all torque, a chain and sprocket with like a 5:1 ratio depending on your wheel size should be fine. ESPECIALLY if it really is 5 hp, thats a ton in electric motors.

 

[hacksign23]

Electric motors are all torque, a chain and sprocket with like a 5:1 ratio depending on your wheel size should be fine. ESPECIALLY if it really is 5 hp, thats a ton in electric motors.

The vehicle that I'm building needs to run many miles without charge (a marathon race kinda thing), but it's going to be cross country so there's going to be hills and such (and down hills!), which is why I'm looking for a transmission. Thanks for the input!

 

[racerc2000]

electric motors and trannys dont mix. an electric motor uses the most power to start. not cruise. some people have worked on adding trannys but most conversions electric cars with a tranny...have the tranny pinned in 2nd gear

and if a full sized car doesnt require gears why would what your building?

that being said if its still a must for you. why not run a tractor transaxle or tranny. I believe a transaxle will be more efficent then a tranny with a chain drive to the wheels.

but basicly a 6 speed transaxle with a 1:1 or overdriven motor to tranny. should make it work more like gears are needed. and clutchless shifting should work with electric.

you can also make a series of pulleys with manual tension and have like 2 or more ratios. loosen one tighten another etc.


if you build it right you can coast down hills and gain a charge.

 

[DCProductions]

The tesla roadster has one of the largest ranges of any production electric car and some of the best performance. It has a single speed transmission though. I would suggest a CVT if you're gonna use any transmission. The consistent power curve of the electric motor and the constant change in the CVT should be a potent combination for speed and efficiency.

 

[wingnut]

CVT transmissions are very inefficient. They convert allot of energy to heat. They're good for IC engines because the over all efficiency is improved by allowing the engine to stay closer to its ideal RPM range where the engine itself is more efficient. Electric motor efficiencies don't change with RPM as much as IC engines so they would not be a benefit from this. In fact, any transmission at all is going to decrease your over all efficiency across the whole RPM range. The most efficient arrangement for an electric powered car is to integrate the motor into the wheel. This is what all the solar race cars do. If that's not an option then I think a simple chain drive will be your best bet.

 

[speedshopmike]

if you're chain-driven, and gotta have one, this is the one to have; it's supremely cool and very efficient:
http://www.fallbrooktech.com

 

[hacksign23]

if you're chain-driven, and gotta have one, this is the one to have; it's supremely cool and very efficient:
http://www.fallbrooktech.com

Thanks for the link. I think I've seen that before but I thought it was mainly for bikes. Do you have any experience with them?

any for everyone else: you guys seem to be giving me mixed info here... one says it's efficient and powerful, not says it gives off too much heat (heat = power) so.... o_o

 

[fowler]

i think an 8 hp motor will rip that thing apart

i hear they are great for bikes though

 

[wingnut]

Pose a difficult and highly technical question on a public forum populated by amateurs (I count myself among them) and nine different people will give you ten different opinions. I suggest that the best way to go is to do some more research. Google for electric vehicles that are similar to the one you're trying to build and copy them. If you're going for max efficiency, I don't think you'll find a better example then what the solar race car guys are doing.

 

[racerc2000]

Motors have the advantage that they can produce power at a wide range of RPMs while still retaining their efficiency.

For instance, a reciprocating engine cannot run at 0 RPM, but a motor produces its most torque at 0 RPM. Also, by varying the current going through the motor, it is easy to control the car's acceleration without shifting gears.


If you take an automobile Gasoline engine as an example and write down what essentially it does:-

Basically a Gas engine produces a lot of RPM but a rather small amount of torque, hence if you connected your flywheel directly to your driveshaft your engine would stall immediately. It would do this for two reasons:-

The Otto cycle is a reciprocating cycle, i.e the engine cannot do anything from stopped. When the vehicle is stationary it must be disconnected from the transmission to prevent the vehicle stalling

A gasoline engine produces little useful power or torque at idle and has a definate "power-band" where the engine is at it's most productive. This is usually between 2000-5000RPM

If you take RPM at the wheels for a given speed on say a car with 14 inch diameter tyres.

First I'm converting to metric so 14 x 2.54 = 35.56cm

Pi * 35.6 = Circumference of the wheel (distance covered with each revolution)
3.1517 * 35.6 = 112.2cm (or 1.122m of distance covered in each revolution)

Hence for a speed of 60km/h (roughly 40mph) (or 1km/min)

Distance covered is 1000 metres per minute, therefore 1000/1.122 = 891.265 RPM

As you can see the required RPM at the wheels is less than most engines idle at, doubling the speed to 120km/h (roughly 80mph, probably closer to 75mph guessing off the top of my head) would only require a wheelspeed of 1782.5 RPM.

Therfore we have to design transmissions with the limitations of Otto cycle engines in mind. As torque and RPM are interchangeable through gear ratios this isn't much of a problem.

Electric motors however are a completely different ball game, you could easily be able to buy an electric motor that would be able to give you enough torque throughout the rev range from 0RPM to 2000RPM (If the wheels are 14inch remember that equates to 0-80mph) without having to resort to gearing. The lack of a transmission would also improve power efficiency as power wouln't be lost in the transmission.

The biggest problem with electric powered cars has been the power source, taking a 150 horsepower motor is equivalent to around 110 Kilowatts.

Power = Voltage * Current

therefore

110,000 watts = (x voltage) * (x current)

from the amount of power needed, the numbers involved in creating that power from volatge and current need to be large also:-

110,000 watts = (110 volts) * (1000 amps)

110,000 watts = (11,000 volts) * (10 amps)

or whichever you like it, you can see though that providing a portable electrical power source that would power a 150 horsepower motor has proven to be incredibly difficult. And to think, you get that much power from a tank of Gas.

 

[speedshopmike]

Thanks for the link. I think I've seen that before but I thought it was mainly for bikes. Do you have any experience with them?

any for everyone else: you guys seem to be giving me mixed info here... one says it's efficient and powerful, not says it gives off too much heat (heat = power) so.... o_o

their bicycle hub unit is rated for an impressive 7 HP electric or gas; if gas must use a cush drive, esp if 4 stroke.
they scale their unit size to the amount of power it needs to handle; bigger units can eat more torque.
the company is very well regarded in the human/electric/gas biking world; from what i've seen, their hubs are the holy grail.
electric motors and transmissions DO mix when you're under-batteried (always the case in non-oem apps) or under-motored and/or excessively current limited by the controller (also usually the case).
elec motors draw the most current at stepoff, assuming there's a load; reduce that load through mechanical advantage and you can accell equally with less current draw - increases range and eases heat burden on motor & controller.
yes, as in any other power transmission system, there is some power absorbed & net efficiency loss - so on a solar machine or one used primarily for steady state speeds you'd be better off w/ direct drive, but nuvinci's hubs purport to be remarkably efficient by design.
i've no clue what your vehicle config is so cant add anything specific

 

[racerc2000]

(vehicle's all about efficiency and speed)

this is just an assumption but....

you tried your current setup and are not pleased with the performance correct?

if you havent and this is just planning and brainstorming ide suggest you try it.

if this is for a race and not just personal use what are your limitations? 4 wheels 2 wheels 3? # of batteries,voltage AH etc

one or 2 of the best ways to increase performance and longevity of charge would be to reduce drag and weight. weight is easy but costly.

what kind of handling does this vehicle require? expected top speed etc?

reducing drag comes in many ways.if it is planned to travel at a good rate of speed the aerodynamics could play a key role.

if it is a 4 wheel vehicle you can reduce parasitic drag. better bearings,low resistance tires, 0 camber

you can take some tips from a build like this http://www.youtube.com/watch?v=n8RN4DFAndU&feature=related

and other gravity racers. they would be pretty easy to add power to and the designs are already setup for max efficiency

only minor balancing would need mods with extra weight.


but again. I feel you should look at tuning your chassis before anything else. as even with the best trans,motor and batteries a bad high drag chassis will kill the benefits.

thats why most "converted cars" are the same if not worse then the factory setup.

 

[hacksign23]

(vehicle's all about efficiency and speed)

this is just an assumption but....

you tried your current setup and are not pleased with the performance correct?

if you havent and this is just planning and brainstorming ide suggest you try it.

if this is for a race and not just personal use what are your limitations? 4 wheels 2 wheels 3? # of batteries,voltage AH etc

one or 2 of the best ways to increase performance and longevity of charge would be to reduce drag and weight. weight is easy but costly.

what kind of handling does this vehicle require? expected top speed etc?

reducing drag comes in many ways.if it is planned to travel at a good rate of speed the aerodynamics could play a key role.

if it is a 4 wheel vehicle you can reduce parasitic drag. better bearings,low resistance tires, 0 camber

you can take some tips from a build like this http://www.youtube.com/watch?v=n8RN4DFAndU&feature=related

and other gravity racers. they would be pretty easy to add power to and the designs are already setup for max efficiency

only minor balancing would need mods with extra weight.


but again. I feel you should look at tuning your chassis before anything else. as even with the best trans,motor and batteries a bad high drag chassis will kill the benefits.

thats why most "converted cars" are the same if not worse then the factory setup.

well the thing is, the race is cross country so there's going to be hills and what not. that's why i want some sort of transmission on it. also, i think a cvt would work because i have a motor controller. anyone got a motor controller and the cvt didn't work? thanks.

 

[huklebuk]

I just had an idea for this. If you can find an old peg perago gator, you could tear apart the gear box and use that as a reference. I know on the gear box it has two speeds and reverse so you could use that as a reference, just copy the design and use heavier duty metal gears and such. (the gears in it now are plastic) They have them on amazon for only 12 bucks. If I was in the states I would take my son's apart because the gear box is stripped out anyway and needs to be replaced.

 

[Doc Sprocket]

I just had an idea for this. If you can find an old peg perago gator, you could tear apart the gear box and use that as a reference. I know on the gear box it has two speeds and reverse so you could use that as a reference, just copy the design and use heavier duty metal gears and such. (the gears in it now are plastic) They have them on amazon for only 12 bucks. If I was in the states I would take my son's apart because the gear box is stripped out anyway and needs to be replaced.

If that Peg Perego Gator is anything like all the other Power Wheels type stuff, don't expect too much. My kids had a Power Wheels Chevy Z71 pickup truck a few years back- which I converted to run on DeWalt 18 volt cordless drill batteries. It had the two forward speeds and reverse. The "gearboxes"- one at each wheel, were simply a reduction unit. The two speeds and reverse were accomplished electrically. A resistor was employed to drop the voltage for low speed forward, and a simple polarity-reversing switch built into the "shift" mechanism allowed reverse.

 

[kendelrk]

If that Peg Perego Gator is anything like all the other Power Wheels type stuff, don't expect too much. My kids had a Power Wheels Chevy Z71 pickup truck a few years back- which I converted to run on DeWalt 18 volt cordless drill batteries. It had the two forward speeds and reverse. The "gearboxes"- one at each wheel, were simply a reduction unit. The two speeds and reverse were accomplished electrically. A resistor was employed to drop the voltage for low speed forward, and a simple polarity-reversing switch built into the "shift" mechanism allowed reverse.

we picked one out of the trash that had no batteries, it was for my little brother, since there were no batterys,i took a car battery jumper, plugged it in the charge, put the terminals on the contacts for the battery and had some fun, he beat everyone on the block that had one, the motor didnt last long tho

 

[Doc Sprocket]

My 18v conversion worked well. I experimented with wiring the motors in both series and parallel- I can't remember the final arrangement. I found a small electrical box exactly the size of the DeWalt battery. The nice thing was that with both kids in it, it would run on a pack long enough to charge the next battery- they could go all day like that.