DC motor questions

Hi, I’m new to the forum and to EVing but I’m interested in building a small electric motorcycle as a starter project and I was hoping someone here may be able to help me out. For starters, I was given a 24v series wound GE motor from a power jack. It’s rated for 46amps at 2000rpm for 60min (1.5hp), but it’s fairly large( 6.7" dia). Would this be enough motor to power a small bike( say500lb,bike and rider) to a top speed of 40-45mph? If not, can I raise the voltage to 36 or even 48volts to gain extra power without damaging the motor? What would the current draw go up to if i raised the voltage. I need to determine if this motor could work before I start investing a lot of time and money and find out It’s all for nothing. Thanks.

very doubtful

do you have any more info on the motor? how long is it? weight? is it series wound or permanent magnet?

It might not be able to handle the power you need. You’ll need 15 or so HP to get a large bike like that going, but you COULD gear it down and have a max speed that is around 35 or 40.

Need more info on the motor, you might be better off getting another one.

I guess I was’t clear enough, the 500lb is projected GVW not bike weight. I haven’t bought a bike yet but I was thinking 125cc to250cc size and try to keep the bike in the 275-325lb range. The motor is 9" long overall and the stator section is 5" long, weight maybe 30lb or so. The powerjack it was driving had a GVW of around 6500lb but only 3mph speed. It is a series wound motor with an externally controlled field. What about raising the voltage to increase the power?

Its not a very large motor, and I don’t know what the motor is capable of. Most times a motor can be used at 2x the rated volts, but you’re still limited on the amperage. It’d be nice if you could get more specs on the motor, maybe a datasheet.

You say its series wound, but the field is externally controlled… how do you mean? That sounds like a sepex motor. Do the field windings say S1 S2 or F1 F2?

The data plate says it is series wound. Terminals are labeled S1 S2, A1 A2.

then what did you mean by externally controlled?

are you sure its not just a reversing contactor?

I apologize for the confusion and my poor terminology. I’m learning as I go but I have a LOT to learn. Yes it was a reversing contactor arrangement on the jack that it came off of. That is what I meant. Anyway, thanks for trying to help. BTW, you did a really nice job on your bike Frodus.

I’m here to help get more bikes on the road :slight_smile:

It might be a good size motor, but it’d help to have more info, nameplate data, torque curve…etc.

Thanks for the feedback on my bike, still not finished, we’re working on upgrading batteries now.

I don’t have access to a data sheet and I can’t find anything on it when I google the p/n. Here is everything on the data plate. GE: p/n 5BC48JB772,
24volt, 1.1hp, 46amps 60min. rating, temp rating 40*c. Ins. class B, Wound:series, FR:48, GEJ:3122, 583/24-AU1851.
You said before that voltage can usually be doubled. If I ran the motor at 48volts, how would that effect current and rpm? Would they both go up or just one or the other? I know that may be a little hard to answer because it depends on load. Do you know how much horsepower the motor on your bike is producing at 40 to 45 mph? This would probably tell me how much I would need to go the same speed.

it SHOULD double the RPM, current would drop off at higher RPM, but would remain similar at lower RPM levels.

HP is a little hard to calculate on the vehicle without a dyno, but at 120V I estimate the max to be around 30Hp… but realize, electric motors have a flat torque curve, not bell shaped like an ICE. You get all the torque at 0 and it decreases as RPM increases. I think you should look for a slightly larger motor, but it all depends on weight of rider/bike and what acceleration you need.

Sounds like the motor is a decent size, I’ve got a 6.7" 10" long series motor that’s around 13 or so max HP and its a 36V motor, and its been run at 72V no problem.

Are the windings thick?

Hi again,
The windings seem pretty thick to me but I don’t have a lot to compare to. One thing I have noticed though is that the brushes seem pretty small (only 5/8" wide) which I’ve read will limit max current, is that right? If doubling the voltage doubles the speed, do you think that the motor would likely take it without blowing apart?