Looks like an old two-cylinder tractor engine.

The big flywheel in front looks like its just for more gear reduction than anything else. Back in the old days when this was built there where limited numbers of high reduction gear boxes available that where small enough to fit on a homemade vehicle such as this.

The first stage power transfer is clearly belt drive and probably just used a simple idler pulley to put tension on the belt to start and stop the vehicle. I suspect it was only a single speed and only drove forward.

Looks like an early time machine locked in a transitory regenerative phase loop.

...early experiments with "flux capacitor"?

From the photo, both of those fellows appear to have all their fingers...

Kind of surprising, considering the drivetrain!

Yes, but we do not know why he is called "Mad Dog".

Check this out

It has no way to make a turn. They were just simply having some fun with that engine. Used it long enough to take a few rides and a photo.

Looks like the guy in back was there to lift the rear wheels to make short turns!

Back in the day my brothers and I extracted an old steel wheeled wagon from an overgrown hedgerow. We appropriated lumber to recreate the bed and had ourselves what my mother called a buckboard.

For power we took a pair of blocks and a long length of rope to form a block and tackle that we used to pull the thing. This gave mechanical advantage but he who was pulling had to run really fast pulling the rope. Brother power vs. Flywheel power!

Funny, back then I didn't realize how much I learned doing goofy things like that!