DC Motor and Gearing

[DonRotolo]

OK, that changes things a bit - I was thinking you had to overcome 400 oz-in of friction and THEN 350 oz-in of torque on top of that.

The motor you selected might work, but not at 2000 RPM. To start an engine of that type (at least, those that I worked with many moons ago) needed about 500-700 RPM to start, but (as you said) only for a second or three.

Looking at the photo, see how the motor gear is about 10 teeth, going to a bigger gear of about 40, which is stacked with a 20 tooth, going again to a 40? Just what you need.

For the $25 it'll cost to make it happen, I'd say try it.

If you can include some kind of clutch to disengage and engage the starter at will, you might consider a flywheel. A jet engine starter - thinking of it, a helicopter too - first spools up to speed with a flywheel, then uses the stored energy to turn the engine, effectively multiplying the torque considerably at the very first stage, where you need it the most. For this case, a 4 ounce 2" diameter flywheel on the fastest shaft will store considerable energy, almost enough to start the engine on its own. The motor will take a second or 2 to spin that baby up.

Don