A Special Builder's Notes


The Special Builder's Breakfast Club

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06 July 2012

La Femme sur Vol.

20-odd years ago our verb conjugation may have been a bit suspect but we had a lot of fun with the old L4.....

.... more fun than I'm having with the brakes.

The adaption of Riley back plates to suit the Hillman front hubs is just not going to happen because it would be a full redesign of the whole set-up and the time and cost involved would far outweigh the perceived benefits. To replace the whole braking system would be the simpler exercise but then I'd be getting too far away from the original concept. After all, most of the pleasure of driving these cars is mastering and managing their inefficiencies and idiosyncracies.  So, I'm thinking about the principle of some sort of servo assistance.

In the system on my '29 Hillman tourer there's a Clayton-Dewandre servo and the brakes - fundamentally the same as the 1926 model - are excellent and compare favourably with a lot of  '60's cars of my experience. The Hillman 14 saloon belonging to Counsel is also not bad at stopping and that doesn't have a servo. So, although I'm putting a bigger engine in the car, one which will transform its performance, it's still down to the driver to understand and accommodate the limitations of 1920's drum brakes. If I add some servo assistance and use some decent brake shoe material, I think I'm going to have brakes that are at the very least adequate and, at their best, not bad.

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There are 2 places in the front brake system that present themselves as options for the incorporation of some sort of hydraulic help. The first and most obvious is the back plate itself though, what would be identified as the back plate is in reality,  just a dust cover and consequently a bit flimsy. However, projecting through this dust cover are the pivot bolts for the lower ends of the brake shoes and they together present an opportunity for mounting a bracket - probably 4 or 6mm thick - onto which a wheel cylinder could be placed. There would have to be a third stud to achieve rigidity but this could be easily arranged.

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I've sketched the new general arrangement with a conventional wheel cylinder but that would put the brake pipes on the inside of the bracket and make assembly difficult so, I've been looking at various types of clutch slave cylinders which, although generally a bit bigger, have the pipe unions on the outside and feature a couple of more handy mounting lugs. Of course, the fact that I now propose to employ a 'clutch slave cylinder' as a 'wheel cylinder' begs the question of 'what's in a name?'

I've done a bit of reading and consulted Learned Counsel on the subject of hydraulics and the consensus is that like eggs is eggs, hydraulics is hydraulics whichever way you dress them up and it's just a question of getting the piston volume, the piston stroke and the master cylinder and pedal travel matched and all should be well.


I honestly can't remember what the 2nd option was. Perhaps in Monaco, as I hurtle past the chequered flag and the sea wall looms large, it'll come back to me.

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