Friday, October 26, 2012

Recumbent seat build

Spring being here, and the option being perpetual grass-mowing, I have resurrected - and not for the first time, I am unkindly reminded - John's High Racer.

The seat frame, built back in May, looked all wrong and applying a ruler I discovered I had three inches clearance rather than two. Seats are hard to get for a recumbent and I don't mind having spares, so I thought I'd make him another one.

First was to cut the side members. I have acquired the use of an old steel-cutting bandsaw, and a splendid creature it is, saving a good deal of elbow pain. It has the option, with a lot of fiddling, to alter the vice angle so I can mitre tubes, but I am scared of altering vice angles in case I can't alter them back. It crossed my mind that - in an entirely hypothetical case that one happens to have a builder operating on the house - one could wait until the builder has gone home, and then hastily plug in his wood mitre-saw which has angles marked on it and is very accurate. - This is of course a hypothetical case and should not be taken to imply anything at all.

Anyway, what I have found is that the best angle of seat base to seat back is 57 degrees. This isn't a law of the Medes and Persians because people's backs differ, and 57 degrees for me may be 60 degrees for John. But it's a starting point and we have to start somewhere. If you want two tubes to meet at 57 degrees then they need to be cut at an angle of 61.5 degrees for a reason that I understood when I was thirteen but can't remember any more. And if you want two blocks of wood that will go in a vice and hold a bit of tube at 61.5 degrees then the bits of wood need to be cut at 28.5 degrees, which takes half a minute to set up in a hypothetical mitre saw and about five seconds to cut.

By a process we will not now discuss I possessed myself of two such blocks of wood and put a piece of tube in the bandsaw and found that when the vice was tightened, the blocks of wood slipped like wedges and didn't hold anything tight at all. A moment's thought, and I screwed a scrap of wood to the two of them with a single screw in each, so it would act as a pivot. Now tightening the vice resulted in the blocks jamming onto the tube, and everything was cut easily.

Linked angle blocks holding tube at exactly 28.5 degrees

Mitred tube welded at the corner isn't very strong, so I use a Lowing Joint which is a scrap of steel wended into a slot cut lengthwise into the ends of the tube.

Side member welded, and another ready to weld, with its internal Lowing Joint support

Now to the seat supports. After Mr. Knight's handlebar adventures I thought I'd show him how it's done and got a large spring with a ¾ inch hole down the middle, and whopped it into the vice and whopped the tube inside it and bent it smoothly into a curve and it took lots of force but about a minute to do and I don't know what all the fuss was about.


Then I tried to get the tube to slide out of the spring, and it wouldn't. It was stuck. I thought it was stuck forever, but after about an hour of twisting I found that the bending process had moulded a series of indentations inside the curve that exactly matched the spring, so I tried to unscrew the tube out of the spring. This didn't work because as I unscrewed, so the spring tightened around the tube, gripping it harder. After about another hour I managed to screw the tube the other way and when finally the straight bit was inside the spring and the curved end of tube was outside, it slid out with only quite a lot of effort.

A slightly crinkled bend

Well I jolly didn't fancy my chances on the other end. I thought there'd be no hope at all of getting the spring off. So I did the Other Thing, which was heat it up red hot and bend it in the vice using a bit of solid poked inside the tube.

This resulted in something so imprecise that it needed re-heating and whacking with a hammer, and after a lot more whacking I had something which my children, when young, would have described as a Shape*. This, I thought, qualified me to be a professional outsourcing tube-bender, but I decided it might be easier in the long run to make some welded supports so that's what I did, and it took ages. But it wasn't as fraught as bending the stuff.

From the top: 
support bent to Mr. Knight's standard of excellence
welded replacement support
support prior to welding
two side members

Getting the ends of these supports to wrap neatly round the side members relied on crown-cuts again, it being easier to bend them to shape than accurately to file them to shape, and it gives lots of metal to weld, which my MIG welder likes. The side members were used as guides, laid on the floor exactly twelve inches apart.

Finally to welding them in place. Now while thinking about what one can accomplish easily with a mitre saw it occurred to me that if I cut a bit of wood exactly twelve inches long, and exactly square at the ends - which is easy to do with a mitre saw - I could use that as a spacer to make two wooden jigs with scraps of wood screwed exactly a foot apart.

And then, to jam the tubes in place, I'd need to cut two bits of wood exactly an inch-and-a-half shorter than a foot, and the two three-quarter-inch tubes would make up the difference.

However I'm not going to tell you exactly how I did this. But it worked perfectly.

So the next bit is the webbing, which I'm not looking forward to at all, because it takes forever to do.

*(After boiling a ping-pong ball to remove indentations, said ball became greatly flattened. Child: "Not a ball any more, is it?" Parent: "No. What is it?" Child: "It's a shape.")

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Thursday, October 18, 2012

Tandem trailer finished

Right, the tandem trike trailer is now finished, at least in my department, and I can now reveal that it took me about 30 hours to do, which can partly be explained by my remarkable capacity for standing and staring at something for hours worrying about whether there's an easier way of doing something. (There always is, but being ign'rant I don't know what the easier way would have been.)

The judge came round to collect it and mentioned the tandem meet right here the other day which I didn't know about, and then I remembered the self-same other day I was in Motueka and saw a tandem go past and glanced at it - as you do - and it said ENGLISH on the grey frame in those distinctive caps that Mr. English uses on his machines.

So I said Bless my soul to myself, and it turns out that Mr. English did indeed build such a machine recently and it was indeed destined for New Zealand. The Diaspora needs to remember it is supposed to be colonising the whole world, not merely Motueka.

Since we were on the subject of tandems, he - the judge, not Mr. English - said he'd done a tandem skydive, and he had asked the instructor if he'd ever dived with a man with no arms before. The instructor had thought about it for a moment and said he'd dived with a bloke with no legs, and then after another moment he said 'In fact I've dived with quite a few fucked-up people' which delighted the judge because he told me he considered he now belonged to the Fucked-up People Club. And in fact that was the last skydive the instructor did, because just afterwards he was killed in the Fox Glacier crash that nobody remembers because it happened on the same day as the Christchurch earthquake. So my judge was a Fucked-up Person but his instructor was a dead one. - He told me - the judge, not the instructor, who being dead couldn't - that when the chute opened he shot down in the harness, and not having armpits to share the shock of the deceleration, the top of the harness wrapped round his neck and he thought he'd choke. - Obviously didn't, though. -

It - the tandem, not the judge - has been admired, I gather, by an engineer who sent compliments about my welding. This says only one thing, and that one thing is that the engineer was partially-sighted because my welding is about as bad as welding can be without something actually falling apart. An example of the unkind things that lurk beneath one of my welds is seen here,

where a series of mediaeval crown-cuts are made in the end of a bit of tube before prying them all apart to make a tolerable fit for an easier surface to weld over. MIG welders are very forgiving. - Or concealing. - But they do not result in beauty.

Anyway he has hied himself over to Dean from whom he begged the broken trike back end, and since I happen to know that Dean has himself built a recumbent, I know that he'll get attended to when it comes to cables and chains and whatnot. My final acts were welding on some bits of handlebar to accommodate a brake lever and a pair of gear levers which are to be toe-operated.

With knobs on. So he can brake, and change gear, with his feet.

It will be asked how much I charged for this utterly brilliant job and I can answer £0.0s.0d largely because it seems churlish to ask money from a bloke who only got you to do the thing in the first place because of a deficiency in the arm department, but also because as soon as you start asking money for things the relationship between you and the machine changes. Instead of thinking about how to do it better you start thinking about how to do it cheaper, or how to do it so it looks as if a Proper Person made it with Real Stuff instead of an amateur with old sawn-up junk. Luckily the armless judge is, like me, a keen fan of old sawn-up junk. The world has two schools of engineering - the proper one where you get proper stuff and make it properly, and the one where you look at the Bike Heap and try to work out what you can make with it. Artists refer to this as Found Objects.

Unfortunately John has noted all this activity, and if I don't now Get On With his high racer I shall have some explaining to do.

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Monday, October 15, 2012

Tandem trike rear stays

Shards of at least four bicycles

Saturday's progress on the main frame slowed as soon as welding became critical, as progress always does. It took me all morning and a chunk of the after-morning, which is luckily what rainy Saturdays were ordained for, to make anything worth savouring. - Most of the time was spent hopping about the workshop arranging new swear-words, because for reasons unclear the axle wouldn't lie perpendicular to the frame of the blue bike. In the end I caught some eyes of newt and toes of frog and the odd lizard's leg and boiled 'em up and that did the trick.

The new seat stays were sliced from two donor bikes, inserted - they're tapered tubing - and welded. This sounds delightfully easy and of course it is, provided you can get the lengths identical, which I struggle to do because I belong to the Haphazard and Careless school of engineering.

The trike axle was assembled in the place I wanted it to go, and the new stays lashed in place with a strip of rubber from the ubiquitous inner tube, and then I fitted a chain. - Because I have some experience in chains, that's why. - Shut up and stop interrupting. - The chain told me I needed to do some bending, because it impinged on the new stays, or the new stays impinged on the chainline, whichever you prefer. So off with the stays and into the vice and a little brute force and they were cold-set in their new position. Cold setting is what we say when we don't want to admit to bending things. It sounds delightfully technical, and makes retired members of the legal profession think you know what you're doing. It is a hideous and cruel thing to do but it is entirely effective, and is the reason sensible folk opt for mild steel rather than carbon fibre or chromoly. Well, that and cost. Especially if people spend their lives giving you old bike frames. Which they do, I find, as soon as they discover you made that funny lie-down bike they saw you on last Thursday.

Anyway that was, I hoped, the critical weld and everything else should be easier. Otherwise I felt Sunday would be down to liver of blaspheming Jew, gall of goat and slips of yew, if memory serves aright. - I have some slips of yew, come to think of it, and gall of goat shouldn't be too hard to get hold of. It's the liver of blaspheming Jew* that's the problem, given that I don't know any of those citizens of the Middle East with a propensity to strap improvised explosive devices to themselves and blow unsuspecting bus queues up. - Ah - but how would one know the particular piece of liver was from a blaspheming Jew? What if it was from a Coptic Christian instead? Very difficult to determine someone's religious orthodoxy from their abdominal organs.

No Jewish persons were harmed in the welding of this item

*Macbeth IV.I, you ignorant cretins. 

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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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Wednesday, October 10, 2012

Tandem trike trailer

Today I had occasion to cut up a Raleigh Twenty, something that should be done as often as may be, for in doing so one learns why Nottingham's district of Lenton is now full of students rather than Raleigh employees. The one-and-a-half inch main tube of a Raleigh Twenty derives most of its strength from the wall thickness, a hefty two millimetres.  And when you come to weld to Raleigh Twenty tubing you discover that among its other economic savings Raleigh dispensed with undercoat when painting the frame.  In these revelations lies the Great Secret of why bicycles aren't esteemed in Britain. When the accountants have control, they're crap.

This desire to saw Raleigh Twenties up is not a new departure, but I did happen to want a bit of meaty tube to form a link between two machines to create a tandem. This is not a tandem for me, you understand; rather it's a tandem for a chap who lives beside the aerodrome, whom I happened to meet one day when I saw him pedalling along on a home-made semi-recumbent trike, a machine blessed with two front wheels located on linked BMX forks.

I asked him who made it.
"I did."
"But you're disabled."
"No I'm not. I just haven't got any arms."
He turned out to be a retired judge. He'd been born with no arms. Nevertheless he had built a number of boats, and an ingenious, recumbent-ish trike with two front wheels mounted on Raleigh Twenty forks, linked with an aluminium pole, and a plastic school chair as the seat. I asked him how, and he said to my amazement
"Angle grinder."
Which he holds with his toes.

Anyway, he phoned me up recently to come and see the new tandem trike he's making. It isn't a trike so much as a self-powered trailer. The two wheels are from a ditched conventional trike conversion kit. The junk he'd screwed together to fix this to the back of his wife's bike was so chaotic - ingenious but chaotic - that I offered to weld some stuff together to tidy it up.

First trial by the builder, looking remarkably happy largely because he hasn't got a chain

As delivered to me in the middle of a rainstorm t'other day

His linkage is a chrome plated, slightly magnetic, turnbuckle. Maybe nickel-bronze? - Anyway, the bolt part of it is 7/16 (11mm) OD. It rotates in the thread to allow the bike ahead to lean. It has two other planes of movement and it does work - I rode the bike with him sitting on the seat behind - but I was worried, and discussed it with a consulting engineer who designs industrial machinery and who very kindly doesn't charge me owing to the fact that he's interested in unusual vehicles* and owing to the other fact that he's my brother.

We decided that since the turnbuckle isn't going to take much of his weight, which is carried mostly on the two wheels of the trike-part, it should be okay, but my brother suggested a safety chain or rope in case it breaks.

But we were both concerned with the aluminium tube from the turnbuckle to the back section, under the non-functioning rear steering head, so the Raleigh Twenty got itself turned into a sturdy boom with a sturdy quarter-inch-thick piece of steel squeezed and welded into it and then drilled out to take a sturdy bolt and I think that should do the trick.

*Here's one of the motorbikes he built

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