A Special Builder's Notes


The Special Builder's Breakfast Club

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23 March 2012

How fast d'you reckon we're going then?

..... well, I happened to have the Hillman back axle to hand and, with the help of an assistant, I was able to answer this question. First we took a piece of chalk and made a mark on the tyre and the floor so we could see when the wheel had turned 1 complete revolution and make a second mark at that point Then we measured the distance between the 2 marks. That's the easy bit and it turned out to be a squeak under 8 ft with the 20" wheels provided for this experiment. As I'm using 21" wheels on the car, I can safely assume a swire over 8ft - so we called it 8ft to keep things simple.

As I was wheeling the axle along the ground, I noticed that the yoke for the propshaft on the diff wasn't turning so (and this is where an able assistant comes in handy) we heaved the axle into the vertical so as to stop one wheel from revolving. Turning the uppermost wheel - still with the chalk mark on the tyre, I was able to count the revolutions of the yolk - 2 .5 as it turned out - for one revolution of the wheel. We then returned to the workshop and got out the calculator. After some misleading information about the value of pi threw our calcs awry, we arrived at the conclusion that we were doing 36mph at 1000 rpm in top with the Hillman diff hooked up to the Morris 6 gearbox. That was really quite economical and, as part of the purpose of this project is to race a friend in his Jowett Jupiter to Monaco, I think I'm going to be leaving him at the first petrol station. I imagine he'll be unamused at this revelation.

So, pleased with this new and winning information (and with the assumption that it was entirely correct) I set about drawing up the proposed radiator mounting illustrated in an earlier post. With a couple of revisions and a full size sketch to make sure all was as it should be and that the ruler was behaving itself, I sent the plans off to the laser-cutting people. Again, it's going to be a fabricated channel like the front engine mount.

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The 'Detail A' is just another drawing with the particular dimensions for the ends. The 2 x 36" plates I've asked for will be welded to the top and bottom edges of the plate shown above, to form a channel. They're over-length to give me a bit of purchase on the bends and also so that I can trim them to the 2 degree angle of the chassis rails. The lightening holes will make it look a bit racy.

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Here's the Jupiter but, don't be deceived by its looks; he's got a bit to do on it yet.....

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next post Well, here's a thing....


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