# Double shaft or 12v accessory motor?



## Uncle Joseph (May 7, 2008)

I don't know which option I should go with. My Vibe conversion will keep power brakes and air conditioning, and maybe power steering (although I'll try to eliminate this if the donor car comes with it). 

I've decided on a Warp 9, but should I go with a double shaft model turning an accessory pulley, or a single shaft with accessory 12V motor running off the DC-DC converter? I can't decide if one is more efficient than the other. Seems the double shaft option would weigh less and perhaps be less complex/ However, it also seems this would rob drivetrain horsepower. 

Any guidance would be appreciated.


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## Telco (Jun 28, 2008)

You'd be better off with a second, smaller accessory-only motor to drive the AC and steering pump. This will only rob range, not usable motive power. Also, using the motor to run the accessories means no AC when you are "idling" in traffic. Likely you wouldn't get AC or power steering until you were moving along about 40MPH or so anyway, since those accessories do need to spin at around 800RPM to work. 

I think those cars have rack and pinion steering, might also see if you can get a manual rack in there with it to save on the motor size needed. This would also extend range on days when you don't need AC, with a power steering rack you'd have to run the accessory motor all the time but with a manual rack it would just need to run on hot days.


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