How does a friction motor work Like the ones on a 1908 tractor?

When the operator pulled a lever, it moved the engine and its large flywheels (which were always in motion while the engine was running) back into contact with the friction pulley, which was connected to the pinion gear which drove the rear wheels. It was largely unsuitable for any kind of heavy draft work (such as a plow) because the friction wheels would quickly slip and begin to wear out. The machine was used mostly for stationary work such as driving a threshing machine.