# Transmission vs Direct Drive



## major (Apr 4, 2008)

Bertzie said:


> More specifically, where is the line drawn? Is it gear ratio alone, or changeable gears that makes something a transmission. Keep seeing motors that differentiate between needing a transmission or not.


I gave you my opinion, which I think is generally accepted around here. 


major said:


> Typically, the context around here is: Transmission = device between motor and wheels capable of multiple ratios. Direct Drive = a fixed ratio between motor and wheels.


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## Bertzie (Oct 13, 2011)

Follow up then. (Since this is for a different project idea) Why are some motors suggested for direct drive, while others are suggested for transmission use?


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## Coulomb (Apr 22, 2009)

Bertzie said:


> Follow up then. (Since this is for a different project idea) Why are some motors suggested for direct drive, while others are suggested for transmission use?


I think it's mostly the TransWarp series that are suggested for direct drive, and then only because they have moderately expensive hardware for connecting to universal joints and driveshafts.

The TransWarp is apparently the exact same motor internals as the plain Warp, so it has nothing to do with the motor characteristics. So it's just the housing and shaft attachments.


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## TigerNut (Dec 18, 2009)

Bertzie said:


> Follow up then. (Since this is for a different project idea) Why are some motors suggested for direct drive, while others are suggested for transmission use?


If the motor's efficiency curve limits you to about a 3:1 effective speed range (which is where a gasoline ICE typically ends up), then you need a multi-speed transmission. If the motor can functionally support 5:1 or better then you can get away with a single ratio, provided you can get that ratio through some combination of intermediate and final drive ratios. 
If you want to do 'direct drive' through a single gear reduction, then you need a motor of either prodigious torque or high RPM capability along with a suitable final drive.
Doing direct-to-the-wheels (1:1 drive) is generally out of the question because it would require the motor to have really high torque capability along with acceptable efficiency at very low RPM, to handle standing starts on a regular basis.


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## Bertzie (Oct 13, 2011)

The WarP and TransWarp motors are rated for the same torque, but one is suggested for a transmission, the other for direct drive.


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## TigerNut (Dec 18, 2009)

Bertzie said:


> The WarP and TransWarp motors are rated for the same torque, but one is suggested for a transmission, the other for direct drive.


Okay... that's because the TransWarP has a TH400-like output housing on it and a splined shaft, so that you can directly couple a driveshaft to it. The WarP motor, on the other hand, has a conventional keyed shaft on it, and you have to use a coupler mechanism on that - which is what you'd do if you were connecting the motor to a transmission.

That's about mechanical convenience, not whether or not the motor is suitable from a torque or RPM range point of view.


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## Bertzie (Oct 13, 2011)

TigerNut said:


> Okay... that's because the TransWarP has a TH400-like output housing on it and a splined shaft, so that you can directly couple a driveshaft to it. The WarP motor, on the other hand, has a conventional keyed shaft on it, and you have to use a coupler mechanism on that - which is what you'd do if you were connecting the motor to a transmission.
> 
> That's about mechanical convenience, not whether or not the motor is suitable from a torque or RPM range point of view.


So the housing and spline are the only differences then? Cus you can get a slip yoke for a keyed shaft for like 50 bucks that will also hook right up to a driveshaft.


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