Some years ago I built a model based on a small ferry that sailed on the St Lawrence between Canada and the USA. Only a modest speed was needed but a using a larger propeller than a small motor could directly drive. Direct drive was favored due to its silence and in the end a stock "540" motor was used, much to the initial amusement of spectators who probably expected the model to self-destruct on its maiden voyage! In fact it sailed smoothly and safely at full speed 'cos I was using a 2 Volt cell (from my days of starting glo-motors) to power it.
As this voltage was way lower than any of my ESC's (Electronic Speed Controllers) were rated for, the motor was controlled by a servo mounted resistance board and the receiver/servos used a separate six volt battery.
A little later and the idea came to replace the servo/resistance board with an ESC but still retain the six volt battery pack to power the RC circuits. My thinking was that as the ESC didn't have a low voltage cut-off, it still could still provide power to the motor with such a low drive battery voltage. But, control should be still maintained if the RC gear had a 6 Volt supply. The ESC's BEC (Battery Elimination Circuit) not being switched into the RC circuits of course..!
It worked and no problems were encountered, the motor running smoothly from "tick-over" to its modest top speed.
I be honest I have not had call to use this method in another model, the 2 Volt cell having finally expired plus my discovery of "Rock Crawler" motors (more turns for lower shaft speeds but still lots of torque) and my occasional attempts to rewind motors (something like a 100 turn 540 motor will cope with relatively enormous propellers). It is however a potentially useful idea that might get someone out of difficulties, I'm thinking of a kit based on a canal boat which was supplied with a 540 motor directly drive a large propeller, not a relaxing sail.....!
Glynn Guest