Doc used a wiper motor and a driver board board from a servo that as I recall he utilized the signal output to drive some op amps. I will look for the thread. In fact I just got a recent response from him re this. Search that Dragon thread. I mentioned automating the prop and mentioned his power servo. He is in process of working on a prop using them.
Hi mate, the HS5475 board info says it provides up to 4.5A with 2A continuous at 6V. I'm aware that a wiper motor can pull more than this although I might do some tests to see just how much it pulls under moderate loads.
For smaller motors the HS5475 ought to be fine though - I'm going to trawl around and look for geared motors to play with.
Try this one. It works really well - it should be fine for light loads ~2 lbs - I will need to check the current though I think it is about an amp. I am using one for my peeper I can test the current if you like also they are using them for FCG
If you are wanting to stay with a standard servo motor system you should look here at the "Pan" and "Tilt" systems that servo city offers. These are essentially gear boxes bolted onto standard servo motors that get you a huge increase in torque. I have used their 'medium duty' pan motors for 2 props I built and have had no problems.