Now that brings back memories. In the mid/late 60’s I spent many hours behind the heavy duty rotary, cutting orchard grass. I seem to remember there was no clutch between the engine and the rotor, the rotor was one heavy piece of metal, and you developed good muscles pulling over the engine and rotor to start it. 3 speed Albion gearbox with reverse, if I remember correctly.

That was replaced when it wore out with the ride on mower, which did have a rotor clutch. You had to go to full revs before engaging the clutch, or the sudden load stopped the engine. In those days, no health and safety, you could set the revs, jump off and walk beside it steering if your backside was getting sore after a long day of cutting! Also 3 speed Albion and reverse.