Friday, October 12, 2012

Towing hitch

Close examination of how the trailer hitch had been made showed that a lady's mixte frame had been sawn into its component atoms of iron, each of which had been bolted to the next with a miscellaneous gathering of stainless steel nuts and bolts, many of them matching. Predominant were those now wonderfully obsolete threads which are only used either on boats or in America, and are the reason you still have a 7/16 spanner dangling on the wall. Nothing was employed to stop the tubing from compressing when the bolts were tightened through them, but lest we all leap up and down and wail about engineering niceties, we must needs recall that all of this was done by a bloke without any arms. Mind, given how I gouge myself with an electric drill, maybe there is a lesson to be learnt here. Maybe I would be safer in the workshop if I first tied my arms together behind my back.

First, then, was the business of simplifying all this mess. I took a donor bike off a hook in the rafters of the shed and sawed off its top tube, complete with the seat post clamp. It had to be a mountain bicycle (gentleman's, perfectly good; slightly less good when deprived of said top tube) because the turnbuckle was of approximately an inch in diameter, and only old mountain bikes have one-inch inner diameter top tubes. When turned upside down the clamp is of course exactly the right angle to stick horizontally out of the back of the towing bike.

 It wasn't hard to find a pair of rear dropouts from the Bike Heap whose holes exactly matched those on the towing bike, and bolted in place, I welded on a set of seat stays from another donor bike.

Two things haunt me when sawing up old bike frames. The first is the remark of Mr. Knight, who once told me that the reason there are so few antique bicycles left in the world is that as each machine became obsolescent it went into a Bike Heap in the back of some shop and as newer machines needed repairs, the shopkeeper would wander out to his Bike Heap, as I always do, and select a donor bike and saw it up. The second is the fact that we are a grossly profligate species who really have no business to be sawing up a bicycle. If everyone lived like Westerners we would need 4.1 planets worth of resources, whereas if we all lived like Chinese we could probably scrape by with just this Earth.

With all the ends bolted in place before welding commences, everything fits nicely, which it doesn't do when I'm in charge of a steel rule.

Then to the trike axle itself which turned out to have three graunchy bearings and one bearing shell, all of which had to be replaced. The wheels themselves are also on bearings: those on the driven wheel act only as spacers, while those on the free wheel only have to allow slightly different speed of rotation when going round corners.
Ghastly worn groove in axle

 The shattered bearing had worn grooves into the solid axle, so I filled up the grooves with weld and then trimmed them down afterwards, which is what you have a lathe for.

Axle ready for machining

And then a happy hour was spent filing plate steel into 4mm keys to go in the keyways, and eventually the whole was reassembled with its rather elegant band brake, a neat little version of those great big ones you see whenever the Veteran Car Club goes cruising through town.

And, because I don't like holes through tube with bolts running through them, I welded transverse tubing into the holes in the axle mount itself, because I have a vague feeling I might need them to hold the trike frame onto the main frame of the machine. With a little luck not too much weld will have penetrated the tubes and I might be able to get some 8mm bolts through them tomorrow. We shall see.

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