

May 06, 2012, 08:05 AM  

I'm a little curious about the formula and where the 63025 constant comes from?
I know for full scale cars the formula is: HP = (tq * RPM) / 5252 Rearranging for torque would be: TQ = (HP * 5252) / RPM * disclaimer, I know the "proper" formula is: HP = 2pi(RPM * TQ) / 33000, but 2pi/33000 is very close to 5252 (5252.1131220...) I found a couple sites that reference the same formulas for electric motors as well: http://www.electoolbox.com/Formulas/Motor/mtrform.htm http://www.wisconline.com/Objects/V...px?ID=ENG17504 All of this said, none of this helps you pick a motor. Since you need to know the actual current being drawn to make these calculations and not just the theoretical maximum you actually need to have the motor in the boat and be logging current draw. Prop choice, hull type and weight, etc will all effect current draw, so the motor will put out wildly different torque numbers with different setups. The manufacturers constant wattage output number is much more useful, since they give you a baseline to say how much power it will produce and still be happy. You can easily get double (or more) wattage out of it, but not for long before something goes up in smoke. 
May 06, 2012, 08:38 PM  

Oop wrong thead.

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