A Special Builder's Notes


The Special Builder's Breakfast Club

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22 August 2013

It Never Rains...

... but problems keep pouring in. The front axle wedge is too thick for the axle locating pin to do its job.

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The dotted line represents the pin that goes through the leaves of the spring and slips into a hole in the axle beam. With only the friction damper mounting plate between the spring and the beam, there's enough pin left to locate in the axle; add the wedge to get the caster angle about right on the kingpin and the pin doesn't get near. I could make the wedge thinner but that would weaken it considerably - it's about 1/16" at the thin end already. As I pondered a solution, Learned Counsel popped his head round the door and suggested that the damper mount could go on top of the spring - it would do exactly the same job and because the arms would be at a more acute angle, it might do the job more efficiently. This seems an excellent suggestion and gets me out of a bit of a pickle. The alternative is to remove the centre pin from the leaf spring and replace it with a longer one. I remember undoing a centre pin on a leaf spring and I recall I was lucky to get away with only a hole in the ceiling. Another way would be to redesign the mounting plate to wrap around the spring immediately in front of the axle. Whichever way I end up doing it, getting a positive caster angle is vital for steering stability. The Austin is about 3 or 4 degrees, possibly even 5 with the extension plates (and is a bit too stable) so if I aim in that direction I don't think I'll be far out.

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The damper mounting bolts arrived today - they're part machined and all I have to do is turn down the hexagon portion to length and add a 9/16" BSF thread for the chassis end.

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On the original chassis the dampers on the back were, in effect, check straps and I'd think not particularly effective in reducing roll so, using the mounting hole on the rear axle (conveniently tapped to 9/16" BSF), I'll work out a scheme with an angled bracket - the tapped hole faces rearwards - to mount the dampers in line with the front ones. I could mount them laterally - the easy option - but that might cause the dampers to become distorted as they take the fore and aft loads when the rear axle deflects. I may be dreaming all this up because of my experience with the Austin's rear-wheel steering but I think the dampers will look better if they're all lined up.

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The Hillman tourer's hood is finally complete but I've not had an opportunity to take a decent picture. The window went in reasonably easily (it was probably the fiddliest job on the whole thing) and the perspex is so clear it doesn't look as though there's anything in it at all. Still, it shouldn't take too long to be aged by road dust and general handling. There's a bit of a do coming up next weekend so a road test is in the offing.

And, of course, I shan't mind in the least if it rains.

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