ORIGINAL: cmoulder
Not to throw a wet blanket on the geared drive topic, but rather just asking...........
If a geared drive is used, of course the larger diameter/higher pitched prop will require significantly lower rpm's at the top end, but is the mid-range torque going to be increased?
Just trying to understand how the power curve is affected by the gearing.
And perhaps how much power is lost with a belt drive.
Geared drives are not really practical for this purpose. These need a dampener (and possibly some type of clutch) between the engine crankshaft or gear and the output gear it is driving. A certain (high) percent of the torque pulse needs to be damped.
Belt drives are more practical...the belt serves as its own dampener. What belt size, type (Vee, toothed, flat) and how many belts is the question.
I think that for transferring 4HP, two vee belts in tandem should be enough.
Higher torque is transferred everywhere in the rpm envelope, but max torque will always exist at the same rpm that the engine develops its max torque. For the SAP max torque will happen at around 8500 most likely.
Dag, I do not have the information you are asking for. I don't have an engine apart at the moment.