# Gears or no gears



## locost_bryan (Aug 18, 2008)

What are the advantages of retaining an operational gearbox? Is it only needed for a DC engine, or does AC need it too?

Could I eliminate it altogether, and just use a differential? Could I use a rwd diff with the electric motor attached to it (aligned north-south where the donor ICE was east-west)?

Just wondered why some conversions retain the entire gearbox (like Gav aka KiwiEV), some just retain one gear (like Tom aka Carrott), and others do away with the box altogether (like Eelectric7). 

Presumably there are technical reasons that I, as a newbie , have yet to work through.


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## KiwiEV (Jul 26, 2007)

For me it was just simplicity. The gearbox needed no work (once I'd found one that _worked_ of course), and the motor just joined straight to it.
If I had more money I'd quite to try the idea of having no gearbox (direct drive). Would be tricky in a front wheel drive but surely not impossible.


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## locost_bryan (Aug 18, 2008)

KiwiEV said:


> For me it was just simplicity. The gearbox needed no work (once I'd found one that _worked_ of course), and the motor just joined straight to it.
> If I had more money I'd quite to try the idea of having no gearbox (direct drive). Would be tricky in a front wheel drive but surely not impossible.


iirc you crashed through the gears on the motorway in Auckland 

Do you use all the gears when you drive round town, or on the open road?

Mark Fowler kept the gearbox in his ADC9" powered Birkin, but only uses 4th gear, and was considering chucking it to save weight. Electric7 did away with the gearbox right from the start (and the 2005 site's been updated in the last few days!), and connected the AC motor direct to the driveshaft.

To avoid using a complete fwd gearbox, you could use an IRS rwd diff (MX5/Sylvia/WRX/Altezza/Triumph) and have the electric motor mounted longitudinally rather than transversely (space permitting). Depends how long your electric motor is....

Bryan.


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## KiwiEV (Jul 26, 2007)

locost_bryan said:


> iirc you crashed through the gears on the motorway in Auckland


That wasn't me! I swear! It was the testing officer trying to turn my manual into an automatic. In the same video near the end I demonstrate how you can change gear without crunching.
As for around town running, it's 2nd gear all the way. I only use 2nd when driving below 70km/h, and if we're heading to friend's places out of town we'll use 3rd for open road driving.


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## locost_bryan (Aug 18, 2008)

KiwiEV said:


> As for around town running, it's 2nd gear all the way. I only use 2nd when driving below 70km/h, and if we're heading to friend's places out of town we'll use 3rd for open road driving.


So, you could get away with a 2 speed? Perhaps just the hi-lo bit of the old Mirage Super Shift (the one with the two gear levers)? Wonder if that was just bolted onto the end of the 4-speed? Hmm...


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## carrott (Aug 19, 2008)

locost_bryan said:


> So, you could get away with a 2 speed? Perhaps just the hi-lo bit of the old Mirage Super Shift (the one with the two gear levers)? Wonder if that was just bolted onto the end of the 4-speed? Hmm...


I'm using that gearbox. It has an extra gear cluster on the input shaft. I haven't yet counted teeth to see what the difference in ratio is. See http://carrott.org/blog/archives/5-Input-shaft-removed.html and http://carrott.org/blog/archives/9-Input-shaft.html

The later gearboxes with a 5th gear are actually the same internally. Instead of a second gear lever they have a switch in the main selector system that operates the input shaft selector via a vacuum solenoid.


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## paulmo_on_tour (Aug 31, 2008)

Hey guys and gals,

Silly noob question here. Reverse? Doesn't anyone back up any more? LOL

Seriously, do you reverse the current, if so, how do you manage with an A/C motor? 

Thanks for being patient with me. 

Cheers,

Paul Summers


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## MaverickNZ (May 14, 2008)

paulmo_on_tour said:


> Hey guys and gals,
> 
> Silly noob question here. Reverse? Doesn't anyone back up any more? LOL
> 
> ...


With 3 phase AC motors you just reverse the polarity of one phase, if all 3 phases were reversed it would still revolve in the same direction.


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## carrott (Aug 19, 2008)

paulmo_on_tour said:


> Silly noob question here. Reverse? Doesn't anyone back up any more? LOL
> 
> Seriously, do you reverse the current, if so, how do you manage with an A/C motor?


 A Series Wound DC motor requires a reversing contactor set which reverses the field connections. Likewise the other DC variants need some way to reverse the field.



MaverickNZ said:


> With 3 phase AC motors you just reverse the polarity of one phase, if all 3 phases were reversed it would still revolve in the same direction.


 With a 3 phase AC motor you have to reverse the order of field excitation, as you say, this can be done by swapping any two wires, but with a VFD, you do that in software (or whatever you have driving the power stage).


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## Hadleigh Reid (Jul 22, 2008)

The other question is whether a clutch is required when retaining the gearbox. It looks like u (gav) can do this ok, and im assuming its alot easier to make the adapter plate and all that without the clutch?


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