On one of my many projects (sticking a small engine into an old bicycle frame), I need to build a gear reduction, as well as reversing the direction of rotation. On some of the bike motors the guys just use a belt and two pulleys for the reduction, but due to the orientation of the motor I want to use, the rotation of the motor output needs to be reversed. I was thinking of using two gears to do this (I am open to other ideas though).

Of course the nice thing about a belt is it doesn't need any lubrication (other than the bearings on the jackshaft, which is simple enough). For the gears, I would guess they won't last very long without some sort of gear lube on them. While I could probably just do a "total loss" system where gear lube drips from a tank onto the gears and then just flies off onto the ground, I'd prefer to be slightly more environmentally conscious (well, not really, but I'm cheap and don't want to have to be refilling a gear lube tank with oil all the time). So, how much oil is needed to keep the gears happy? If the big gear (the driven one) sets lower than the small gear on the motor crankshaft, how high does the oil level need to be? Do the gear teeth just need to barely touch it, or should the teeth be submerged some mount in it? Also, assuming this gear is turning at 2200 RPM and is 5" in diameter, a certain amount of oil will be flying around inside the case instead of resting in the bottom, so I would guess that needs to be taken into account somehow.

Trial and error may be the best method to go about this, and I would certainly start with what I think would be too much oil, instead of too little, but I have no idea what would even be a starting point. I have never had a gear reduction unit apart to see how much oil is in one of them.

andy b.