# Transmission for EV



## GE11 (Oct 24, 2011)

Hey Guys,

Looking at doing an EV and wondering what are the advantages of going with a transmission and without a transmission. I plan on using a DC forklift motor.
What are your experience of using either, transmission or not transmission.


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## MattsAwesomeStuff (Aug 10, 2017)

*With* a transmission:

- Less to disassemble
- Clutch gives you a failsafe, mechanical disconnect without relying on electronics or fuses.
- Mechanical reversing, no need for reversing contactors, can advance brushes without worrying about reverse, not that you're spiking the current that high in reverse anyway.
- Easier coasting (direct drive is always turning the motor).
- Long hill climbing and towing won't murder your motor from high-current low-speed use, you can just gear down.

*Without* a transmission/Direct Drive:

- Less weight
- Less bulk (more room for batteries/whatever)
- No bell-housing plate to machine
- Probably easier coupler to machine/weld (take old forklift mate, weld it to U-joint, done).

I'm probably missing a few but those are the big ones.


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## Duncan (Dec 8, 2008)

GE11 said:


> Hey Guys,
> 
> Looking at doing an EV and wondering what are the advantages of going with a transmission and without a transmission. I plan on using a DC forklift motor.
> What are your experience of using either, transmission or not transmission.


Hi
I'm using direct drive - no gearbox 
Makes the whole thing dead easy and I can still spin the tyres

My forklift motor - Hitachi 11 inch - came complete with a parking brake on a splined shaft 
The splines were the same on both ends of the drive shaft so I made a simple plate adapter to adapt the middle bit of the parking brake to a normal propshaft UJ - easy!


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## gunnarhs (Apr 24, 2012)

GE11 said:


> Hey Guys,
> 
> Looking at doing an EV and wondering what are the advantages of going with a transmission and without a transmission. I plan on using a DC forklift motor.
> What are your experience of using either, transmission or not transmission.


Advantage for no transmission

Motor control adapted to optimal motor specs
Simple single speed coupling
Better acceleration behaviour

Disadvantage for no transmission

If the area has hills you need a bigger motor


Advantage with transmission

Usage of smaller motor possible
More adaptable to different terrain (hills, snow etc)
In my experience better efficiency and range (based on Induction motor, may not apply for other motor types)

Disadvantage with transmission

The motor control must make compromises to the clutch/gearbox/transmission 
(by not violating the recommended Torque/speed specs).


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## potvinguy (Jul 24, 2016)

I did my old VW bug. It has a transaxle, so is very easy to just replace the ICE with an electric motor. I use 2nd gear below 35 MPH around town, and go to 3rd on the freeways. I watch the amps with an analog meter and changing gears can minimize the draw. Maybe someone can explain how that works.


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## Duncan (Dec 8, 2008)

potvinguy said:


> I did my old VW bug. It has a transaxle, so is very easy to just replace the ICE with an electric motor. I use 2nd gear below 35 MPH around town, and go to 3rd on the freeways. I watch the amps with an analog meter and changing gears can minimize the draw. Maybe someone can explain how that works.


Hi
Changing the motor speed will change the motor voltage required for that load and current
Going down a gear will reduce the torque required and the motor current will go down 
But the motor voltage will go up (back EMF) - 

You will be minimising motor current - but battery current will not be changing that much


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## GE11 (Oct 24, 2011)

Duncan said:


> potvinguy said:
> 
> 
> > I did my old VW bug. It has a transaxle, so is very easy to just replace the ICE with an electric motor. I use 2nd gear below 35 MPH around town, and go to 3rd on the freeways. I watch the amps with an analog meter and changing gears can minimize the draw. Maybe someone can explain how that works.
> ...


BAttery current would not change? How would it not change if Motor current went down?


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## GE11 (Oct 24, 2011)

potvinguy said:


> I did my old VW bug. It has a transaxle, so is very easy to just replace the ICE with an electric motor. I use 2nd gear below 35 MPH around town, and go to 3rd on the freeways. I watch the amps with an analog meter and changing gears can minimize the draw. Maybe someone can explain how that works.


WHAt pack voltage were you running ?
What kind of motor was it?
What was the top speed?

Thanks


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## Duncan (Dec 8, 2008)

GE11 said:


> BAttery current would not change? How would it not change if Motor current went down?


Your controller is a power in - power out device

You will start with say 
500 amps motor and 15v motor = 50 amps battery and 150v

As motor revs rise you will need more motor volts

500 amps motor and 30v motor = 100 amps battery and 150v
Then
500 amps motor and 60v motor = 200 amps battery and 150v
then
500 amps motor and 120v motor = 400 amps battery and 150v

Until you get to
500 amps motor and 150v motor = 500 amps battery and 150v

Any further motor rpm increase will have a reduction in motor and battery current


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## potvinguy (Jul 24, 2016)

GE11 said:


> WHAt pack voltage were you running ?
> What kind of motor was it?
> What was the top speed?
> 
> Thanks


126 volts nominal (10 batteries)
D&D series DC. About 40 HP, i think. D&D is kinda odd to deal with; they claim to not recognize the model number on it and told me to contact the distributor, but I don't know where it came from.
Top speed is about 60 in 3rd gear.


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