You can remove the belt that drives the gearbox at this point - if this has worn out then only the high speed attachment will have been working. It will lift off nicely with a screwdriver.

The large gear then needs to be gripped, and the "dog" on top of it needs to be removed.

You'll need to keep the gear in place - either fit an attachment and wedge a piece of timber between it and the body of the machine or get someone else to hold onto it tight) and turn the dog with a spanner. Eventually you or the person holding will feel it release, and you can unscrew the final turn carefully so the spring doesn't fly off!

If using timber for the above a piece of dressed timber about 120 mm long (and 15 mm wide x 10 mm high) was used succesfully for this. It can be used to refit the dog by wedging it on the opposite side when refitting

Apologies for the cake/belt continuity errors in this set - some are taken during reassembly