In normal running, esp if adjusted for modest output, or when prodding the cutout, the field magnetising current is modest. Possibly a full polarisation with the 3rd brush lifted off the armature and earthed directly, and battery applied to the isolated field terminal for a short while will make things more permanent. If the paint is not pristine hammering on the dynamo body at the same time may assist (Rivetted ships became very magnetised). 12v briefly would be OK.

(If anyone is referring to the Williams Special building book for polarising, the description there is wrong)

Merv emphasises an important point. On the car, most tinkerers press the cutout at some stage, but certainly a point to note off the car. Care necesary that polarity matches that in the car.

Location: Auckland, NZ

Dave Mann writes:

For those who really want to do the job right, here is a man sized tool for the job just a couple of hours to put together. Regards Dave Mann