The Good Oil on Castor or Caster Measurement

The Austin’s suspension is somewhat lower than standard so the castor angle probably needed a tweek but how to measure it?  Initially I thought I would use some flat surface on the axle or the stub axles but are those surfaces perpendicular to the king pins?

So, after a little Googling I found another use for the bevel box (Digital Level) and I think it would make a pretty good excuse to buy one if you have not already.

The jist of it is with the wheels straight ahead and sitting on a level surface, place the level on something vertical (it’s magnetic) as in the picture and zero it.  Turn the wheel 20° right and record the result then go back to straight ahead and go left 20° and record that number, in my case it was 1.3° for right and 1.2° for left so to calculate the castor it was 1.3 + 1.2 =2.5 then here is the magic part x 1.5 = 3.75°

Evidently, it’s important that the wheels are moved only 20° each way and that it’s related to the 1.5 that you multiply the result.  I will have to go ask a Maths teacher (Ian?) as my brain hurts when I try to do the trig.

20° lines drawn on the floor the White wedge is a piece of wood cut at 20° on the drop saw and used as a template

A7 chassis with one radius arm in place, I needed a 4° wedge to go under the spring to get the castor right then the radius rod needed some work to match.

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