Paul is correct, those Vari-speeds are an accident waiting to happen.
I repair the motor shafts of roughly 15 to 20 a year and that is only from the Midlands area and I'm certain i don't do them all.
If we had had decent cheap inverter drives years ago then they would not have invented the vari-speed.
Also what many people don't know is the step speed and varispeed is interchangeable not as in complete head change the the Bridgy head is basically two units, the lower drive unit and the upper motor unit.
Once split from the middle three bolts you can easily swap the upper part.
I obtained a step speed head last year to replace my ageing varispeed. Fitted a brand new 3Hp motor but didn't fit it as I replace the complete machine with a new one.
I have this step speed top half and new motor as a complete unit going spare if anyone needs to do the same.