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Flanges

Sunday, October 10, 2010 10:44:21 AM Categories: engineering problems penny farthing trikes wheel hubs
Right, attentive readers of these notes - I flatter myself - the attentive reader of these notes - assuming there is one, which is more than improbable - is aware that I am obsessed with the thought that quite soon all the oil will vanish and everyone will have to gather logs for their cooking balanced on their heads like the ladies in Darfur do. - The logs balance on the heads, not the cooking. - But anyway it seems to me every time I visit the dump I discover some cheery mortal has thrown away three quarters of a BMX and the remaining wheel has a 14mm axle. Ever picked up a BMX with a back wheel? Heavy. Ever tried to carry one home on your head? Cumbersome. Like logs in Darfur. And even carrying one on another bike's no good. So I need a better vehicle for dump recovery operations.
 
The BMX the cheery m. had thrown away had a wheel which, when coaxed apart, had had the wrong size ball bearings fitted, and when I replaced them with the right size, which ran on the unpitted part of the cone, I suddenly had a smooth bearing on a 14mm axle.
 
It is a fact that your brain immediately says 14mm = stub axles, if you chance to be a serial recumbent tricycle maker. You cannot help this. It's a reflex action.
 
I dived into the bookshelf and recovered my 2nd edition Bicycling Science and found the Oxtrike on p 325 and then on p 324 read that in Asia heavy loads of perhaps 330 lb, or 150kg, are carried on a single speed trike with a cruising speed of about 4-7 mph (2/3 m/sec.) Blimey! that's handy. - Any time you forget what 4-7 mph is, you can just back-calculate from knowing the velocity in metres per second. I do like David Gordon Wilson. Well of course everyone likes DGW. He designed the Avatar 2000. Which graced Richard's Bicycle Book. (Which actual bicycle - Mr Ballantine's, not Professor Wilson's - is now owned by Mr Wray, my spies inform me.)
 
So, quick calculation: cadence of 60 and a fixed gear of 26 inches gives a cruising speed of 4.64 mph. So that's 2.074707788 m/sec, Dave G.W., if you happen to be reading this. And if I want to go at 3.12928 m/sec, I can always pedal faster.
 
I was very pleased with myself and immediately decided to build a grown-up's child's tricycle. The pedals attach directly to the front wheel and obviate gears and chains and so forth, and all you need is the basic technology of the penny farthing.
 
Now I'll tell you about my flanges, and it's this - I got an old steel back hub and chopped it in half and bored the flanges to fit a cottered 5/8 axle and adjusted the cross-slide by one thou right at the end of the cut and for some reason unknown it jumped four thou and created a big floppy hole, like a thing that is floppy and not a thing that isn't floppy.
 
'******* ******,' I said to myself, 'but you're a *******; you've ****** it up again.' (I often say this to myself, because it doesn't matter what I'm doing, somehow I always manage to **** it up.)
 
So I got another lump of 5/8 from my tin of worn-out cotter-pin BB axles, and I ground the cones off carefully and made it a perfect fit on both my flanges. Then being warned in a dream that a 150 amp MIG isn't enough to penetrate 5/8 steel, I coated it with borax paste ready for brazing, and tack-welded both flanges in place and d'you know what - Juno Watt - both were square and parallel but the spoke holes weren't perfectly alternate.
 
'******* ****** but you're a ******* etc.,' I said to myself, and set about breaking the tack welds. And d'you know what, they wouldn't break. Had to saw them off. So I thought the MIG will actually weld it; I won't need to braze. So I sawed off the second flange's tack-welds and scrubbed all the borax off and replaced them and welded them up, and d'you know etc. etc. etc., now they aren't bloody well square. They *******  wobble. So I ******* went back to the box of old steel hubs and d'you ******* know what, I had absolutely none whatever that were suitable to machine 5/8 holes in. So now I'm ******* well stuck with wobbly flanges.
 
'Oh Damn and Blarst,' I said to myself, 'Better not show it to that ******* Knight or he'll know that *once again* I've accomplished a piece of ******* bad craftsmanship.'
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