Interesting Ruairidh, I don't know where it is but that photo was taken over a decade ago. Stuart beat me, the sole reason for fitting the 4 speed clutch release bearing was to reduce the amount of wear. Living in a town any trip meant lots of use of the clutch in traffic clogged roads and I found the 3 speed toggle levers ate their way into the 3 speed thrust bearing carrier. I seemed to be cutting new slots for the toggle levers on a regular basis. So any mod had to address all the potential wear possibilities.
When I fitted a 4 speed close ratio box to one of our 3 speed RN engines I test run the engine with the gearbox fitted, fortunately, on a test stand. At that stage it didn't have mousetrap springs and at a fast tick over I heard a unusual loud clicking noise. That was the toggle levers flying out to contact the clutch thrust bearing, I then realised why Austin fitted mousetrap springs. Stuart's photos illustrate the wear by using 3 speed toggle levers and no mousetrap springs. So I fitted mousetrap springs to the 4 speed toggle levers. This led to the modification of the 3 speed cars with 4 speed clutch release bearing & toggle levers, mousetrap springs and the spring to retract the thrust bearing.
When I fitted a 4 speed close ratio box to one of our 3 speed RN engines I test run the engine with the gearbox fitted, fortunately, on a test stand. At that stage it didn't have mousetrap springs and at a fast tick over I heard a unusual loud clicking noise. That was the toggle levers flying out to contact the clutch thrust bearing, I then realised why Austin fitted mousetrap springs. Stuart's photos illustrate the wear by using 3 speed toggle levers and no mousetrap springs. So I fitted mousetrap springs to the 4 speed toggle levers. This led to the modification of the 3 speed cars with 4 speed clutch release bearing & toggle levers, mousetrap springs and the spring to retract the thrust bearing.
