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el3ktr1k • Oct 31, 2008

# DC Motor Selection

I'm trying to build a remote control submarine and I need some help in selecting an appropriate DC motor. I'm not a mechanical engineer and I don't really know anything about fluids or motor selection. The shape of the submarine is cylindrical with about a 3 inch diameter. I want to be able to go at least 1 m/s. I found this website: How To Select a DC Motor that seemed somewhat helpful. They first calculate the power of the motor that they need based on the motor's rotational speed and torque. The problem is I don't know how much torque I need for the motor or it's rotational speed. I tried using this equation that I found on wikipedia: F= -1\2p* v^2*A*C to give me the drag force of the submarine and I figured the thrust of the motor would need to equal that. I still don't know how that would relate to the torque of the motor though or how fast the motor would need to spin. As far as the voltage source goes, I was thinking of connected two 7.2 volt batteries in series to give me 14.4 V. Thanks for any insight that someone could offer me.