CA20A rework

The CA20A is a sidewinder configuration with the Mabucci style MF08 motor with extended shaft at both ends. The shaft ends extend out to about the mid point on the rear tyres with about 1.5mm clearance to the tyre.

The supplied PT32 tyres are quite elastic, and fly off the rim at high speed, making contact with the extended motor shaft and gouge the tyre, not to mention slowing the car.

I know real men glue the tyres on, and these were glued on, but when the tyre releases for some reason, it results in damage to the tyre due to the long shaft which is not actually required on this model.

Before re-gluing the tyre and re-dressing the tyre surface, the shaft was cut down to minimise the risk of future tyre damage. The shaft was cut down for a shaft extension of 5.3mm on the bell end (pinion end), and 2.7mm on the can end. This allows sufficient length for the pinion (the shaft ends about 0.2mm inside the outer end of the pinion) and enough shaft at the can end to work in the pinion press, but no extension beyond the existing chassis limit.

The rear axle needs to be removed, then the motor popped out of its mount. Note the position clearance from pinion to bell end. The pinion can then be removed with a suitable puller. The motor shaft can be chucked into a battery powered drill, and the other end carefully ground to length against a spinning grinder wheel whilst slowly rotating the motor shaft, the objective being a nearly flat shaft end at right angles to the shaft axis. Likewise for the other shaft end, and then the pinion can be pressed back on to the clearance noted above.’s SP21 is an ideal puller / press.


Above is a view of the reworked pinion end of the shaft. The outer end of the pinion is flush with the line of the inner edge of the tyre. At the other end, the end of the shaft is flush with the line of the inner edge of the tyre.

The bottom edge of the tyre shows the gouging caused when it flies off into overhanging shaft.

The pinion was then greased, bushings oiled, tyre re-glued, and when set, tyres were levelled.