MOPED ARMY

why not? Just check the rpm rating on the motor and go!

Yeah, without some sort of strobe hooked up, you're just going to see your clutch spinning really fast. You won't be able to see which shoe comes out first.

go to a place where they make/service electric motors. They should be able to hook up a circuit for you to run the strobe.

Tell them what you want to do and maybe it will take the guess work out of the project

Yeah, I dont know if the fan would do it.

Grinder might cut it.

Bicycle speedos just measure RPM, then multiply the rate by the circumference of the tire. They're basically just little computers. You also have to set them by giving them the radius of your wheels so that it can multiply by the circumference. There's some math involved, but you could make a bicycle speedo give you RPM.

The bench grinders I found on a quick search were like 1/3-1/2 hp, and rated at like 3000-3500 RPM with no load. To get it to spin up to the RPMs a puch will generate, we need more RPMs than that. I guess that's where gearing would come in.

Roald, what's the horsepower or RPM rating on the electric motor you guys used on yours?

it doesnt need to reach the highest rpms you engine will generate, right? i would think that something that spins a 3500 rpms would be fast enough. something like this should work pretty well i would think.

or you could just buy an electrical tach for 30 bucks and you don't have to do the math.

I would go with the bench grinder at first for the "Prototype" then once you get the mechanical theory figured out, then spend the money to make the actual machine. Don't blow a huge wad of money on something that you don't know will work...start small...like tuning.