A Special Builder's Notes


The Special Builder's Breakfast Club

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06 February 2013

Design And Build.

This week, the final assembly on the front hubs and the knocking-in of the kingpins would see a major part of the chassis schedule put to bed. That all went without a hitch and I was happy to see that there was almost no play present in either side. Then I put the nearside kingpin cap on - fine - and the offside cap.... Blast! That wouldn't go on because the root of the steering arm fouls the cap and to get the steering arm out of the way, I have to dismantle everything again. I remember thinking that it was a dopey bit of design and that I should remember this little 'gotcha' when I was re-assembling the hubs; I should have written it down.

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This is the nearside front hub which demonstrates the brake cylinder set-up. The cylinder itself has a capacity of just over 20cc so, although I've yet to read up on the form, I'm guessing that a master cylinder of about 50cc should be adequate to operate both cylinders with a bit to spare. It'll be interesting to see how they behave because, as they're clutch slave cylinders, they have a larger capacity than a normal brake cylinder and so might be a little be slower - or softer perhaps - in operation; pure speculation, I haven't a clue but I'll find out soon enough.

And, still on the subject of wheels, I've been wondering what to do with the spare. Originally I imagined that I might be able to tuck it out of sight behind the seats somewhere or, failing that, the more traditional position - hang it on the back. The former takes up too much room in the cockpit - the hood mechanism and Miss X's wardrobe take priority, and the latter spoils the line so it looks like I'll be strapping it to the side - the nearside in this case because the handbrake is the feature on the offside. I did this on the Austin Special by constructing a pillar with a hub welded in the centre and then secured the top and bottom of the pillar to the floor and upper longeron with one-piece brackets. I carried the load to the opposite longeron by means of a tube running across the cockpit. It was a rather neat solution and I think I'll do something similar on the Hillman.

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I think it's one of the best bits on the Austin.

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Fortunately, on the Hillman, just eyeballing where everything might fall, it looks like I'll be able to utilise the bracing between the firewall and the windscreen pillar post to anchor some sort of fandango that'll do the job. It'll have to be a fairly robust affair as a wheel weighs a ton. I'm hoping that the cross-brace falls in the right position and that the line of the wing won't be compromised - if it is, I'll just have to design and fabricate something to get the wheel in the right place.

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And you'll notice I've drawn in the seat position. I wasn't able to get hold of the actual Avro drawing for the bucket seat but, I have in my paperwork a copy of the relevant page of the Schedule of Parts for the 504k. The seat is illustrated and I've been able to source enough basic dimensions to work up a sketch.

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The high sides of the seat made me feel very secure, especially when in the height of summer, I had to get across the country in the middle of the day and we were being shoved from pillar to post by the thermals. The sides are probably a bit too high for a car seat but a compromise between this and the Bentley seat, I think, is going to be just the ticket.

Maybe 'Design and Build' is a bit high-falutin'. 'Cut and Fit' is probably nearer the truth.

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