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Old 03-28-2010, 04:05 PM   #1
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Questions?? Turns vs. RPM?

I know that fewer turns results in a greater RPM, but just how many RPMs does, say, a 20t motor produce? I'm trying to use some RC speed calculators online for my electric conversion 1/12 scale and I don't know what to put in the "max motor RPM" section, which is arguably the most important field. Thanks!
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Old 03-28-2010, 04:50 PM   #2
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it depends on input voltage also. that is what kv ratings are for. if you increase the input voltage on any motor the maximum rpm will increase. also, motors can be wound in different ways. a 20t is going to be different from different companies, sometimes even from the same company, especially if it is a brushed motor.
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Old 03-28-2010, 05:14 PM   #3
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Originally Posted by benben10 View Post
it depends on input voltage also. that is what kv ratings are for. if you increase the input voltage on any motor the maximum rpm will increase. also, motors can be wound in different ways. a 20t is going to be different from different companies, sometimes even from the same company, especially if it is a brushed motor.
Oh, right, forgot to mention that. Thanks for the info!
My motor is a Duratrax Photon Speed. 20t single wound. If anyone knows the Kv rating on this motor I'd love to know what it is!
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Old 03-28-2010, 09:47 PM   #4
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i would guess max rpm on a standard 7.2v pack would be about 20-25k. you will not find a kv rating on it. that is a cheap brushed motor and max rpm can very even between runs because of the condition of the commutator and brushes.

i would suggest finding max rpm by experiment. either with a baseball radar gun and calculating rpm from speed, or with some kind of tachometer (data logger or telemetry system), or even an RC airplane/heli blade tachometer and put a small propeller or stick of wood on the end of the motor shaft.

it might be more helpful if you ask for help with your primary goal. it sounds like you are trying use this calculator program to figure something out.
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Old 03-28-2010, 10:44 PM   #5
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i would guess max rpm on a standard 7.2v pack would be about 20-25k. you will not find a kv rating on it. that is a cheap brushed motor and max rpm can very even between runs because of the condition of the commutator and brushes.

i would suggest finding max rpm by experiment. either with a baseball radar gun and calculating rpm from speed, or with some kind of tachometer (data logger or telemetry system), or even an RC airplane/heli blade tachometer and put a small propeller or stick of wood on the end of the motor shaft.

it might be more helpful if you ask for help with your primary goal. it sounds like you are trying use this calculator program to figure something out.
Thanks. Well I was able to find out the other variables I was missing for the Dark Horse RC calculator, including the top speed of my car (24mph), so from there I am able to deduce that my motor is around 3700kV equivalent. Thanks for your help!
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