I believe that the “moped brake drum” adaptation for a clutch is a separate (earlier?) entity from the so called Mk1 clutch comprised of a cast iron horseshoe expanded into a recess bored in the countershaft large pulley. I have a S7 of the same vintage; this has a worn but usable “horseshoe” clutch which I have adjusted so it doesn’t let go. In other words I have defeated the clutch operation to achieve a reliable drive from the countershaft.
So does anyone actually use the clutch, and if so why?
I’ve read that the clutch was fitted to avoid subjecting the single phase motor to an excessive number of starts as the capacitor was inclined to give up the ghost. But replacing said capacitor isn’t much of a deal. I’ve also read that it’s to help reduce the wear on the starter winding centrifugal contact. This isn’t a production environment so I don’t see the reasoning.
I have also seen a suggestion that the clutch is a quick and dirty way of feathering to drive, for tapping into a blind hole for example. This maybe doable with the Mk2 clutch which has a cone and taper as the sliding surfaces, but I don’t rate my chances of making the horseshoe clutch perform this function.
I’ve adapted my S7 to have a three phase motor and a VFD. I’ve got used to using a simple on-off function instead of a clutch courtesy of my Colchester Bantam, which is operated by a saddle mounted lever. I don’t miss the gradual start offered by the Myford clutch, I’ve got a soft start feature programmed which makes a better job of it. I haven’t used the quick stop function available on the VFD; worries about unscrewing the chuck have made sure of that.
So what does the clutch offer to justify its attention and repair?
Seasons greetings one and all
Simon