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| S. Heslop:
I bought a 100A controller but i'd still like to keep the amps as low as possible, with it being designed for RC planes most likely. So yeah 15mph might be a good bet. A nice thing about this drive idea is that I can easily just switch the contact wheel out for something smaller if needs be. To reach 185 rpm on the outer wheel the contact wheel would be 40mm diameter. Although at that size the motor would be getting uncomfortably close to the spokes so i'm going to try 50mm, giving the bike wheel an rpm of 230. One thing i'm wondering is how do things work in terms of using the speed controller to run the motor slower than 6000rpm? As in, would it put more or less strain on the controller/ motor? |
| vtsteam:
Steve, the ESC does run the motor slower than 6000 RPM when the throttle is reduced -- the ESC changes its timing to create the reduction in speed. The main strain on the ESC is if the amperage exceeds its rating. It takes about 24 volts to turn this motor at 6000 RPM. How much current it takes depends on the load at a specific RPM It might never reach 6000 RPM if the load is too great before that point. An ammeter and a fuse are important to have in line while testing. Check your current draw with the particular setup as you test. Gradually increase throttle while watching the ammeter. Stop when you get to 20 amps (or whatever you decide) This will give you a maximum operating speed for the current limit that you want to specify. Optimizing your setup by test would would mean that, if the maximum safe operating speed of the motor, by your specified current limit, is considerably below your 6000 RPM target, your gear ratio should be increased until they correspond. This will reduce the top speed of your bike until it matches your power specifications (500 watts @ 24 volts). Any further speed increase will require more power. If you are running under 6000 RPM at spec'd amps you are not sending effective full battery voltage to the motor, and are therefore running less than 500 watts. You are running at whatever amperage you show times the effective voltage. ps. that's my understanding -- could be a mistake in it -- others chime in, please! |
| vtsteam:
Let me just simplify that: Under test with typical load on the bike with a 24V system, approx 500 watt desired, 24 amp spec limit on a 250 kV motor: Test 1: Ammeter reaches 24 amps at 2000 rpm. Servo controller knob (throttle) is not at max. Conclusion: gear ratio too low, wattage less than 500 watts Solution: reduce diameter of rubber spindle on wheel. Bike speed should actually increase (even though gear ratio is increased) because you are absorbing more power. Test2: Ammeter reaches 24 amps at 6000 rpm. Servo controller knob is at max (full throttle). Conclusion: gear ratio correct for wattage. Full 500 watts available. But bike is still too slow for satisfactory performance. Solution: Increase spec for amperage and wattage. Since ESC servo controller is dialed all the way up in this case and you have no more throttle range, you will need to decrease the gear ratio. If you do that, 6000 RPM (and full throttle on servo controller) will then be reached at a higher figure than 24 amps. |
| S. Heslop:
Ah, thanks for clearing that up. Shame the speed controller is coming all the way from Hong Kong, that could take a good while yet. |
| kayzed1:
I have a pair of motorcycle sprockets here if you want them, not new but good, 420 chain size. Lyn. PS: may even have a new DID chain as well.. |
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