Timing belt drives

Any of you guys have experience with timing belt drives? I need as compact as possible 1 1/2:1 reduction from a 600 rpm 2.5HP engine (3600 crankshaft RPM with 6:1 reduction) then another 1 1/2:1 after that (so lower speed higher torque) ( total reduction 13.5:1).This will be driving a 20 inch diameter 2 inch wide tire/wheel.

How wide and how large do I need the small sprocket? For simplicity I would likely like both stages identical. This simplifies everything including tensioning Small sprocket on output shaft driving large sprocket on jackshaft turning small sprocket driving large sprocket spinning on output shaft of the engine/gearbox with wheel attached to that sprocket. Distance from center of small sprocket to outside of large sprocket cannot excede 7 inches.

Is this possible/feasible???

-------------------------------- I've designed only vee belt drives. Drive belt manufacturers provide detailed design information on line, which I studied after my guesses with parts already on hand failed. I hadn't adequately accounted for the high peak to average torque ratio of a one cylinder 4-stroke gas engine.

Vee belts have the advantage of being able to slip by engaging the idler clutch pulley gradually, to accelerate from rest. On my bandsaw mill the ex- motorcycle wheels need several seconds to get up to 60MPH. The $99 HF engine may stall during engagement unless running about half speed.

On an old Maytag washer the vee belt slips for quite a while as the drum spins up to speed in the rinse cycle. It's a special belt, a standard one with exposed rubber grips too tightly. The motor slides against springs to let the position of the separately driven water pump control the drum belt tension. Pushing the motor inward to loosen the belts reduces its starting current surge to let a 3KW generator run it.

I've seen some timing belt power transmission calculators online, which account for RPM, small pulley diameter, required torque, etc, but haven't done a design. The `AI Overview` from a google search for `timing belt drive power sizing` has about 6 bullet points, each with a link, that get to some design webpages or calculators.

I think an auto engine timing belt handles 15 to 25 HP, which you could scale down from or get parts from. Depending on what your app is maybe one stage of planetary gear reduction as in drill motors would work; and there are some inexpensive electric bike clutches that look like 4"-diameter planetary drives but might be irrelevant -

I didn't read all of that, but my problem with timing belts relates to CNC motor drives. If I didn't get the tension perfect they would either exhibit backlash or they would sap power from the system at a much higher than expected rate.

That being said I have seen a cog belt with cog pulleys used on a fairly powerful pulley with good effect. The 5hp motor on my Hurco mill uses a

I don't have the experience with them, but everything I've read indicates a harmonic drive is the magic sauce for some applications.

I've decided to just try a bigger engine - - -

Engine has 6:1 reduction - direct driving a 20 inch wheel to move 300 to 350 lb. New enginr is 2 9/16 bore and 2 7/16 stroke

That's similar, not identical, to the 6.5HP 212CC Predator I have on my sawmill. Bore 2.756", stroke 2.165". The bolt pattern is standard, the same as the 5.5HP Tecumseh, and stock and racing go kart accessories are plentiful.

In the words on Tim Allen, "More power!"

Original application was 2.5 x 2.5 inch (12.27 cu inch) engine running 8:1 gear ratio - f head, atmospheric intake. My first try was 2 3/8" x 1.75 L head with 6:1 - doomed to failure. Current attempt is 2.5X2.4 L head with 6:1. This looks like it stands a chance.Running Mikuni style round slide bike carb. Compression ratio is higher than the iriginal F head and the cam is in control of the intake, which should make it more efficient and hopefully higher torque ( not the 3 1/2HP I thought I was getting but a 5HP)