# Project Smoothie: Motor Selection



## bigmotherwhale (Apr 15, 2011)

my advice would be try to keep weight down to a minimum and to use the highest discharge cells you can find or afford


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## JoeJErnst (Nov 3, 2015)

bigmotherwhale said:


> my advice would be try to keep weight down to a minimum and to use the highest discharge cells you can find or afford


Yeah, it looks like the C rate of the batteries will be the key factor in whether or not this will work. If I need the same size bank of batteries as an all-electric vehicle then I'm essentially running two complete drive systems (ICE + EV). It might pencil out if I can find a small, lightweight battery that can dump most of its charge on one or two trips down the 1/4 mile.


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## bigmotherwhale (Apr 15, 2011)

ultracapacitors or li ion capacitors might be a better choice for very short bursts. Do a calculation based on your motor and expected 1/4 mile times.


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## dougingraham (Jul 26, 2011)

JoeJErnst said:


> I'm trying to select a motor for my proof-of-concept Project Smoothie. The basic idea is to give a 100hp boost to an ICE-driven car for short periods of time. (the same scenario as using nitrous oxide in a drag race)
> 
> It looks like the AC-51 with Curtis Controller might be a good choice if powered at 144v. Any thoughts on using this setup as an electric-assist motor?


The Curtis controllers peak out at just under 90 hp so this won't make your 100 hp goal.

And it strikes me that you are neglecting the spot where it will do you the most good which is the launch. Electric motors have almost full torque at zero RPM. Your ICE doesn't start to make much until you get to around 2000 or so. Not sure how you plan to tie this in Perhaps a toothed belt to the crankshaft on the front of the motor. You also need to consider the RPM band of the AC-51 goes from zero to around 4500. It starts to taper off at that point. You have a little over 100 ft-lbs at 4500 and that tapers off to about 32 ft-lbs at 8000 RPM. HP is about 88 at 4500 and that tapers off to about 49 at 8000. The AC-50 has less torque but the torque band extends up to around 5700 RPM.

You will probably want to look at your ICE dyno graphs to see where exactly this would help you out. But it seems to me that if all you want is a boost then why not just have it assist all the time? An additional 80 or 100 ft-lb over most of the RPM range would always help. But the additional weight will hurt you. Is the additional boost worth the additional weight? The battery pack to do 144 volts at 500 amps will weigh around 16 lbs using the Ampahaulic drag racing LiPo's. That assumes you parallel them by two but they would be loafing if you paralleled by three and the pack would weigh 24 lbs. The motor weighs 115 lbs and the Curtis controller weighs 12 lbs. Total would be more than 151 lbs. You would probably end up adding around 200 lbs to the weight of the car with this setup. Electric only range would be around 7 miles with the 24 lb pack if you could decouple the ICE.


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