PWC workshop: Play on the brake arms

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In this episode of the workshop series, we take a look at a fairly common issue seen at many old cars: worn out pins and bushings. In this case the play occurs at the arms that actuate the brake shoes. The same principle counts for leaf spring pins though, for which the same repair method can be used.

The pins are worn on one side because they always rub on that same side while being used. This causes the hole to become oval and the pins diameter to be reduced.

Originally, there is no bushing. Repairing this, the hole in the steel axle part needs to be reamed oversize to be round again and to be able to receive a bushing.  For durability, I choose a bronze bushing to be installed. Of course it is also possible to use a steel bushing if desired.

After boring the hole, a bushing can be made to size, but remember to keep the hole in this bushing slightly undersize before pressing it in, as it can shrink a little from pressing and we want to ensure that the hole is round and accurate.

Now we can add new material to the pin itself making use of welding. Or a new one can be made. I choose welding if the pins are still decent enough, which in this case they were. You can use any type of weld you want, I choose mig welding since it's the fastest way in my workshop.

After welding, chuck it in the 4-jaw and check the end of the pin to run concentric with the front, since it can distort a little from welding, it needs to be checked front and rear. Recut the center if needed to accept a live center and start cutting the weld to original size.

Then measure the final size, ream the bushing installed in the axle some 0,05mm to 0,10mm oversize to avoid binding and accept grease and the part is done.

Photos of this operation can be viewed in my photo album here (click).

Work, photos and text by Jos van Genugten.

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