Using RC gear to drive a grain mill

[Sammus]

Hmm... RC parts are looking less and less attractive.

Does anyone know how to figure out the rpm of an electric brushed DC motor run at a given voltage, if you already know it at some other voltage?

The motor in question is http://secure.oatleyelectronics.com/...roducts_id=189 - it's 2500rpm at 36V, but I would run it at 24V. I'm fairly certain the relationship isn't linear like with brushless motors.

Cheers.