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| Mystery motor - how to measure? |
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| John Hill:
These are my thought, which might not be worth much!! :lol: OK, I doubt that insulation would be an issue at low voltage so the principal limitation on safe working voltage will be maximum current carrying capability and hence wiring temperature. So, I expect you could safely hit that motor with two or more times over voltage for a short period of time, maybe very short. I expect that if you could put a light load on the motor and increase the voltage from zero it would start and get faster with increasing voltage, at some point the rate of increase of RPM with voltage increase will slow and I suggest that would be close to maximum safe working voltage. Safe working voltage also varies with load as a light load would allow the motor to turn faster which would mean more back EMF generated which in turn limits the current and hence the heating of the windings. So it is all pretty complicated if you want to get technical. For me, 12 volts is probably a good guess for that sort of motor and if it does your job at that voltage well and good. |
| 75Plus:
There is a possibility that you have a 24 volt motor. I recently scrapped a scooter, branded Razor, that used two 12 volt batteries in series. The speed controller circuit included voltage limiting on the LOW end. Once the battery voltage dropped below 21 volts the motor would no longer run. Joe |
| hopefuldave:
Alternative to a tachometer... attach a piece of threaded rod with a nut on it to the motor spindle , hold nut with wrench: Imperial thread: run motor for x seconds and see how far the nut moves(Y"), multiply Y by tpi (so how many turns) and divide by x (giving turns per second), multiply by 60 (turns per minute = RPM)? Metric thread: run motor for x seconds and see how far the nut moves(Ymm), divide Y by pitch in mm (so how many turns) and divide by x (giving turns per second), multiply by 60 (turns per minute = RPM)? Just a thought, saves buying a tacho - although such a purchase needs *no* justification :hammer: Dave H. (the other one) |
| andyf:
You can use a "cycle computer" or speedo as a tacho by setting it so it thinks it is reading the speed in kph of a pushbike with a wheel circumference (not diameter) of 1667mm. Then, a readout of 156.7 kph indicates 1567 rpm. Surprisingly, some models will read up to 199.9kph (1999 rpm). Some models actually have an rpm function. Here's one, though I don't know its max reading: http://www.ebay.co.uk/itm/LCD-Bike-Bicycle-Cycle-Computer-Odometer-Speedometer-/140521739875?pt=UK_Sporting_Goods_Activity_Monitoring_MJ&hash=item20b7bf9663 I'm sure the Chinese seller will also supply to the US. Andy |
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