British
Human
Power
Club

 

Posts in Category: wheel hubs

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.'

Wagon wheel hubs 

Friday, March 19, 2010 2:08:35 AM Categories: wagon wheel hubs
 
Foreign wagons, large & small, in Motueka saleroom, with 'forks' on the front axles.
 
Wagon wheels have stub axles unless they're made by Foreigners. German wagons had forks both back and front. Bizarre. Motueka is full of ladies' mountain bicycles fitted with black wire baskets, the lower support attached to the front axle of suspension forks. Bizarre. (Of course the baskets break; what else can they do?)

Wagon wheels are properly made of wood and shod in iron but I go for tyre availability. Wheels I have aplenty: they're what you make when you can't think of anything else to do, like my mother sequentially buying Stead and Simpson green pastel sandals of which she eventually had twenty-four identical pairs. Bizarre. Old people get into odd habits. I merely build wheels.

The children's wagon originally had kiddies' bike wheels, and I just winched the cones over on the three-eighths axles thinking the children didn't weigh much and wouldn't bend them. Sean Greenhough put me right. Sean Greenhough was a small lad who you'd notice standing on top of the telephone kiosk, and after he battle-tested the wagon they got replaced with proper stub axles. Three-eighths is too small but some Phil Woods wheelchair hubs with a seven-sixteenths bolt, given to me by Peter Carruthers, have been fine. Wheelchair hubs are obtained from my wife's mother's wheelchair, which you leave propped up on bricks. - She won't notice. - Otherwise 12mm is the normal minimum.

 
Rear hub bored out & fitted with 6003 bearings

Certain alloy MTB hubs, both front and back, have enough metal to be machined out to accept 6003 bearings, with a five-eighths tube as a spacer and a 12mm bolt as the stub axle. One bearing housing has to be machined oversize and assembled with Loctite because there's no hope of accuracy if the hub has to be reversed in the chuck. Only metric bearings are cheap in New Zealand and attempts to get bargain half-inch ID bearings from America always founder when visiting friends-or-relations fail to show the required sourcing enthusiasm and expect me to thank them for a tee-shirt. Why do aunts buy the children socks for Christmas? Ever known a child grateful for socks? We have to do a lot of editing of their thank-you letters though frankly I prefer the originals. 'Dear Aunt, Thank you for the purple knitted woolly hat which I can really see my friends casting covetous eyes at', or 'Dear Aunt, Oh! how thoughtful. How did you know I lacked one of those small iron men made out of horse-shoe nails welded together and painted black?'
 
Front hub bored out & fitted with 6003 bearings

Nowadays BMX front wheels have 14mm axles and the cheap ones have cones which can be wound across to one side to make a stub axle. I found two 36 hole hubs but they're normally 48 hole. The expensive ones with sealed bearings have a shoulder machined on the 14mm axle and require more brain power than I have available to adapt to wagons.

14mm axle with cones wound over to make stub axle
 

Welding bolts into a dead axle with my MIG is tricky owing to low power. It's supposed to be 150 amps but I suspect Team Exaggerating Bastards were in control of the advertising department that day, so I cut the ends off my bolts, pop them in the 3-jaw, and machine them into tubes so they don't act as a heat sink when plug-welded into 5/8 mild steel tube. There is not a chance that the bolts will be in line, so I put the wheels on and rotate the dead axle watching the wheel rims wobble in and out, selecting for the top the point at which rim distance front and back is exactly equal as measured with my pointy-lecture-telescopic-pen-thingy.

14mm axle bolted through box section, with spacer inside to stop it being crushed

Mounting holes can be drilled through box-section tube, and over-sized spacers machined to a tight length-wise inside fit get poked down into the square tube so the clamping bolt pinches the spacer and doesn't just squidge the box-section. Parallel wheels are vital on a bike trailer for low rolling resistance but slightly less so on a wagon where one only seeks to reduce tyre wear. But welding axles so they're perfectly in line is fiendishly difficult, unless you confine yourself to theory. I would never, ever put a finished dead axle in the vice and straighten it with a big hammer. Never. Not ever. Not even once. Nope, certainly not. Unless I had to.

Copyright 2006 Blog Author