basic electricity 101 question

deacon

deacon

minor bike philosopher
Okay I took the 55 tooth pusher bike out for a run today. It was going up a very steep hill and I was pedaling to beat heck and it still slowed down then blew a fuse. I have several tests to make to see why and how to prevent that if possible with this particular motor.

It's raining now but tomorrow when it stops, I'm taking the 80 tooth model out to give it a try up that same hill. I'll carry a spare fuse this time though. They both have the same size wheels. This particular motor and sprocket combination has blown a fuse one other time when the bike got to slow and I hit the on switch. The 80 tooth sprocket bike never has blown a fuse but I never had it on this kind of hill.

If the 80 tooth makes it up the hill with the same setup then I know I can revert back to the 80 if all else fails. I have one other idea though. I am running 20 inch wheels on both the pusher bikes. I might just try running a 26 inch wheel or even a geared mountain bike to keep the speed up on the hill. That might be all it needs. Just to be able to get more speed on the sharp incline.

If you have any ideas please speak up.
 
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30amp... If it pulls anymore it burns the switch and wires up. I have done that before. It seems to do okay till it gets bogged down to an almost complete stop. I think a bigger wheel and maybe gears will solve the problem but I don't know. Tomorrow first thing I'm going to check the same setup with a bigger sprocket and see what it does. If that works, I think I will give a bigger wheel and or gears a shot. It's a matter of intellectual curiosity now.
 
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Too much resistance. Resistance=heat. Voltage=Current x Resistance. You are not changing voltage or current, your resistance in the motor is chaging. You are overloading your motor.
 
I should have updated this earlier.

I switched to a forty amp fuse, moved the pusher to 26inch bike with gears ran it in a higher gear with more pedaling on the large hill and solved the problem. Yes the motor was overloaded.

I was searching for a way to prevent that in the future and the combination of a high amp fuse and the bike/gear combination upgrade did it. It didn't get the wires but I got them pretty hot in the shop when it ran accidentally against the wall. Now that was overload.

So the electrical problem is more or less solved. The mechanical problem I think has been solved now on the second pusher motor with the small sprocket on the wheel.

It has a 450 watt motor.... I had been running it on a 24" mountain bike with a simple on off switch. The problem came when I started the bike on an incline and turned the switch on. Only in that situation would it throw the chain off. After a few days riding it I decided that the problem was the motor coming on at full power with too much resistance on the drive wheel. So I set up a three way switch. I have on 12 volts ...off ... on 24 volts. If I am right the problem should be solved.

The chain isn't hard to put on so it isn't really a deal breaker. Also I only have it happen one place and it's my fault. I mean I know when and where it happens I should be able to just avoid that situation.
 
so far so good. I got a chance to put the bike on the one mile test track. It starts without the jerking with the 12 volt leg kicked in, but it picks right up and when the 24 volt leg kicks in, it has good power and hill climbing.

I want to ride it a week or two then go with a 16" bike wheel instead of the 12 in scooter wheel. I have one of these in the 12 inch with a controller and throttle so I want to make this one a little different.
 
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The reason your motor is overloading when it comes to a near stop is because it is in a locked rotor condition. This draws 5-6 times the full load current of the motor. If you are in this condition for very long you will begin melting the insulation of the motor windings which will cause them to short out and destroy your motor.

When you are coming to a near stop I would suggest cutting power to the motor unless you are all-right with replacing it.
 
I did replace one... That makes perfect sense... I have not let the motor get in that position again. But who knows what might happen next week. It's all a learning experience.
 
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