# Yeah, I'm new and I have questions

I have had this idea of building an electric motorcycle. Something with about twenty a mile range and top speed of 70 mph. I do not have the bike yet, but I have been collecting some parts.
I have two dc motors

1. 48 v 70 amp cont 6" X 12"
2. 72 v 40 amp cont 6" X 12"
3. 28 v ni-cad batt from an aircraft that are good but are not airworthy anymore. Each battery can pull 80 amps for more than one hour on a full charge.

My questions are.

1. what type of controller is my best bet
2. are my idea of range and speed possible
3. should I try the 48v or 72 volt motor first
4. or just try something else first

Thanks for any help, I’m kinda clueless with this stuff.

The extent of my expertise is only enough to address questions #2 and 3, but here you go:

It’s impossible to tell what your top speed will be without a torque-speed curve at the given voltage for both motors, but here’s what you can tell:

Motor 1 is more powerful – about 3.4 kW (4.5 hp), whereas motor 2 is only 2.9 kW (3.9 hp). Of course the amount of torque you can get out of them and at what speed is a better indicator of performance.

Let’s say you put together a 80Ah 48v battery pack. That gets you 3.8 kWh, so you can go full throttle for a little over an hour. Figure out your top speed, and that’s how many miles you’d be able to go. (Of course you could also build a 160Ah battery pack is you have enough cells, and double the range)

Of course, if the other motor is able to get you up to speed, and you built a 80Ah 72v battery pack, you would have 5.8 kWh to play with, so you could go full throttle for about 2 hours. I have a feeling the top speed will be lower however, because the rated current is lower.

In short, if you figure out the top speed of each motor (by looking at the speed-torque curves and looking up how much power it usually takes to go a given speed on a motorcycle), then you can decide which one to go with.

~Chris Hammond