Wednesday, November 26, 2014

Proa float or ama

Summer doesn't start for another five days yet there is a fly in the kitchen; therefore summer is here. A fly has a short lifespan without interference from six inches of rubber band stretched to two feet and thereafter released with a terminal velocity of 270 feet per second and a hasty wiping of alizarin splotches from the wall. Nevertheless and notwithstanding my vegan friends' compassion flies entering the kitchen need to vacate it swiftly because our kitchen is a dipteran war zone. And like Afghanistan, one that I never win. I offer to the world Middleton's Razor (like Hanlon's, only completely different): "There is always one fly left in the kitchen".

Summer is here and therefore I have no excuse to not glue plywood. I found a 6 metre windsurfer sail at the town dump with the boom and the mast foot but not the mast. I think 6 metres is square metres. It's 2m wide at the widest bit and fifteen feet long and that's about 47 square feet which is, I daresay, near enough for North Sails to call it 6 square metres. Here's a scale model:

The metaphorical Next Bit is the float, or ama as Mr. Dierking calls it. I have the plywood already sawn into four four-foot lengths and four eight-foot lengths and to make the float they need turning into four twelve-foot lengths. Mr. Dierking's book recommends a plywood float of six inches square cross-section. I did some calculations.

6x6=36 square inches x 12 foot = 5184 cubic inches ÷ 61023.37795 = 0.084951049 cubic metres x 1,000 litres x 2.20462 = 187 lbs 4 ½ ounces worth of floatation.

7x7 of all that = 255 lbs floatation.

8x8 of all that = 333 lbs floatation.

But I need to minus a chunk for the pointy ends. There are two pointy ends. A cone has a third the volume of a cylinder. (I think.) (Don't you wish you were a kid again and Cudgy Sims was teaching you geometry with frequent diversions into wind drift and the resultant flight of an aeroplane, he having flown Spitfires in the war, and Boyce's trouser leg was hitched just to the point where his ankle was perfectly exposed to the attack of a carefully folded 11-grain paper pellet which you knew would evoke a satisfyingly high-pitched anguished yelp when it struck home with the kinetic energy of two foot-pounds?) -

So we have to assume - for ease of calculation - that the middle three feet are a square box and the two ends are a third each of what I've calculated and therefore a six-inch square float will hold 104 lbs out of the water, a seven-inch float will hold up 142 lbs, and an eight-inch float will hold up 185 lbs. (I bet I got the maths wrong. I usually do.)

I weigh 146 lbs. I have suddenly realised that I could have made a far simpler 12-foot catamaran of two of these floats and stuck a windsurfer sail up and it would have weighed hardly anything and I could have been sailing all last summer. Damn.

A heap of 4mm plywood. Ends staggered 32mm apart. Sanded with a belt sander into a smooth slope.

First plank G-clamped to a length of smooth chipboard to stop it slipping. Merry besmearment of epoxy on the sloping edge. Second plank, similarly epoxied, placed so the scarfed joints overlap. Clamped in place likewise, and unclamped, and clamped again lots of times until the two planks are in line with the right amount of overlap. Plastic bag under and over joint for the epoxy to harden without attaching surplus bits of junk. Finally, piece of plywood clamped over the joint itself. Everything left for 24 hours.

 All disassembled. Two of four perfect scarfed joints. Me = smug.

And here's the scale model showing what an eight-inch float will be like:

 And I expect it will be like that too, all capsized and me wet and sploshing about in the water.

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Wednesday, November 19, 2014

Long wheelbase bike finished

I finished something. Nearly. Amazing but true.

Here's the bit I hate. The endless moving of brake levers and gear changers on the handlebar until
a) my hands drop comfortably onto them, and
b) the cables point in roughly the right direction, Bowden cables hating to go round sharp corners, and
c) the gear changer doesn't get in the way of the brake lever movement, and
d) they don't snag the seat when the bar turns, and
e) they don't snag my thighs when the pedals turn.

Cantilever brake lever for front, and sidepull lever for back brake. You straighten the sidepull lever by disassembling, placing lever in vice with steel spacer to stop crushing, and applying blowtorch while simultaneously applying light straightening-pressure with a steel tube. All of a sudden the aluminium softens, and the lever straightens. If pressure isn't maintained you can't tell when the plastic temperature is reached, and the whole thing overheats and crumbles and melts.
Note wooden tube plugs. Apfelholz, bien sûr.

Here's the bit I hate too. Selecting cables. The main object of this exercise, it will be recalled, is not so much to build a recumbent but rather to use up old bits from the Bike Heap. This includes cables and cable housing. Foolish, admittedly, but one must stick to one's intentions. Most of the Bike Heap cable housings are kinked and rusty inside and nobody but an idiot would think of re-using them but fortunately I am that idiot. Fortunatelier I once invented a sneaky trick which is to use short bits of good housing and join them end-to-end with empty .22 rifle cartridges. Swords and ploughshares.

The trick involves a blowtorch, some zinc chloride, and a dab of soft solder. You stand a cartridge on end and put a drop of ZnCl onto the flat bit without even bothering to polish it, add warmth and a touch of solder and it's instantly covered in silver. Then you add ZnCl to the same place on a second .22 cartridge, invert it onto the silvered one, add more warmth and you have a back-to-back tube with a soldered separator disc in the middle. This you pop into the 3-jaw, drill a 2.5mm hole through the separator, and now two short cable housings can become one long cable housing. I mostly like to do this because it helps obviate the worry of what to do with jamjars of empty .22 cartridges, which problem only manifests itself because I can't bear to see empty brass strewn all over the rifle range, which it is, which I happen to know, which makes rifle ranges so irresistibly attractive. One day the brass will all be gathered up assiduously by my children's children's children and melted in a home-made brazing hearth to re-assemble all the bicycles I've ever sawn up, I expect. But for the moment all they get used for is cable-housing-joiners.

Anyway, here's the machine assembled and I haven't snipped off the cable ties because the other bit I hate - painting - requires their removal. You have to fiddle about with a flattened spoke to wedge between the zip-tie's rack and the jammy-inny-bit and then you can undo them. Have a look at one and you'll see what I mean.

You may compare and contrast with the original drawing which I most kindly posted here because I am good and generous and conceited enough to think someone might be int'rested.

Of course as soon as it was assembled I had to ride it, but before doing so I judged it wise to weld a short tube behind the front fork to stop the wheel turning right round, which it was apt to do on account of being geared up to double the movement of the handlebar, which gearing turned out to be zackly what I hoped. And indeed the machine rode zackly as predicted. Which means either I now know how to design recumbents or I'm very lucky. (Clue: lucky.)

The end of the steering stop tube is reinforced inside it with a washer welded in place. An open tube end is too readily dented by the fork swinging round and giving it a hearty bash. I was going to use a wooden plug like those hammered into the ends of the seat tubes so they don't apple-core me in the event of a crash, but a washer is lighter. The washer didn't fit until I beat all round the edge of it with a hammer, and then it fitted a bit too tightly and I had to use the hammer to whack it into the tube. These are delicate manufacturing details I shan't publicly reveal lest you discover that my engineering is of the bodge-it-and-weld variety.

And here's the cockpit view, showing the usefulness of wide BB axles and those bent cranks that increase the Q factor and allow the steering rod to gear up the front fork without snagging the pedals.

How does it ride? Pleasantly languorous handling, like all long wheelbases. The seat angle is such that 20 miles doesn't give  lumbar ache with a straight seat back, nor neck ache without any shoulder or neck support. Comfortable on ye bumme, so the 700c x 42 back tyre really does compensate for no suspension.  32 lbs (compared with 44lbs for the Duplo Bike) so ditching the suspension does indeed save weight, and a lighter machine makes for lazy riding at low speed. Not especially fast so it's true that the BB has to be 5 or 6 inches higher than the sitzhöhe if you want speed; it's true that light weight doesn't compensate for a bigger frontal area.

But come summer the kids on the bridge will shout "Cool bike mister" because kids on bridges always like LWB recumbents.

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Monday, November 3, 2014

Freeing a rusty brake cable

The global obesity epidemic about which our physicians wring their hands is going to be overcome not by some pharmaceutical expedient but rather by the imminent diminution of food supply, which everyone knows about but which we all prefer to ignore. During the 1870 siege there was starvation in Paris and in the midst of it was a woman who kept her family well-nourished by feeding them worms. I imagine she had access to dandelions because under every dandelion there lives a worm. I only found this out because dandelions are taking over the lawn and while I don't really care about the lawn my life is so uninteresting that I have declared war on them.

My dandelion-grubber had a pathetic short wooden handle that rotted away, and faced with the twin difficulties of leverage - a short grubber doesn't have any - and what to do with all the sawn-up bike frames that litter the shed, I welded various otherwise worthless chainstays together to make a Fabulous New Invention which I am going to patent, and I am going to call it the Digging Stick, and I am going to use the Trans-Pacific Partnership to retrospectively sue all the Neanderthals and ¡Koi! bushmen who already had digging sticks but hadn't the wit to patent them. (Do they really spell it ¡Koi!? - I only do so I can use that upside-down thingy and be pretentious.)

My grubber has twin prongs to get either side of the dandelion's tap root and half the time it plucks the top off so I was interested to see Edith's grubber which is an altogether more simple chunk of mild steel with a wooden handle. It is 1 ½ inches wide and a quarter of an inch thick and otherwise looks like a crude knife, and it gets the tap root out 100% of times. Immediately back to the drawing-board welder for Digging Stick Mark II.

This grubber is a trailer leaf-spring, one of those items one sees at the side of the road and pauses to pick up on the grounds that were one ever to need a trailer leaf spring, making it would take longer than the loss of bicycling time stopping to pick it up. - Thus junk accumulates. - The lever/foot pusher bit is, of course, two of those bottom bracket tubes from a wossname crank - Axolotl - Attrition Warfare - Alexander Technique - Ashtabula, that's the one - two Ashtabula bottom brackets welded side-by-side making it far too heavy, but if I didn't use them here I'd have to think what else to do with them and that would use one of the brain cells that I don't have. And Mark II turned out to be brilliant, lifting divots of earth so deep that a rash of earthquakes has been reported in Lancashire. So, the lawn is a bit lumpy now, but who cares about that?

Edith's digging-stick reflects her approach to industrial complication: she doesn't pay it much heed, and as a consequence I was tasked with the business of restoring her 33-year-old Raleigh so her Swiss sister has something to ride when she visits in the summer. Bicycles do actually benefit from Routine Maintenance but the definition of Routine Maintenance is something that you can do tomorrow and there were a good many tomorrows in the last 33 years. Indeed the sum total of Edith's bike's maintenance has been the replacement of one cotter pin with a piece of rusted jelly, and the application of No Oil Whatsoever.

Replacing a 26 x 1 3/8 Dunlop-valve inner tube (no pump available) with a 26 x 1.9 MTB inner tube with a Schrader valve didn't work at all. Just gave me pinch-punctures as I struggled to mount the tyre. (Those with lewd imaginations may derive much happiness from re-reading those last six words.) Other than that, lots of cleaning and re-greasing seemed to do the trick.

There was, however, one small aspect that required thought. The back brake cable was frozen solid with rust. Easiest solution would be to buy a new cable and housing, but there is satisfaction in doing a Kenyan, which is to say making the original cable work; and since I predict that one day cables and their housings are going to become scarce, this is how you manage it.

First, lashings of oil. You hold the housing upright and wick the lightest, thinnest oil you can find down the cable. This has no effect.

Next you apply brainpower and recognise that though rust makes a strong joint, it doesn't have much shear strength. So you go along the housing, inch by inch, bending it this way and that, and eventually the cable and the housing become two separate items.

However this doesn't undo the thick wedging action of the rust. The entire cable has to come right out of the housing, and to accomplish this you nip the cable nipple in the circular bolt recesses of the vice jaws, and using a piece of sawn-up bike frame with a cable stop as a handle, steadily draw the housing off.

And since this doesn't work either, you apply more brainpower and realise that the housing itself, made of helically wound wire, is not a fixed tube. It can be slightly unwound which increases its internal diameter. So donning leather gloves, inch by patient inch you twist the housing anticlockwise against itself, and eventually the cable comes out, heavily encrusted with rust. Then you find a length of gear cable (thinner than brake cable) wh. you insert into the housing and poke in-and-out a zillion times, the end acting as a sort of brush-cum-reamer.

When this goes all the way through, repeat with the original cable and lashings of oil.

It takes a good hour and in an Industrial Society it's much sensibler to chuck the cable and buy a new one but if we were all sensible we wouldn't climb Everest or make experimental proas and how much fun would that not be?

Unfortunately a Bowden cable and a sidepull brake doesn't work on a lady's bike, so I threw it away and installed a centrepull brake and a seat clamp pulley instead.  Still, Edith is a violinist, and until her bike is perfect she has my undivided attention. Then (I promise) it will be back to proa-building. Or dandelion-extraction.

Edith's 1981 Raleigh, now sans rust. The basket was given to me by Lenny at the bike shop for free because he knows her husband runs the Community Gardens for free. Does that make sense? Edith's husband's called Ron and he's a New Zealander so he's pronounced Ron, whereas Edith is pronounced Aid-it because she's Swiss. (I felt you needed to know.) Actually Edith's pronounced Edith because nobody can cope with Aid-it. Eugen's Swiss too so he's pronounced Oigen but nobody can cope with Oigen either so he's pronounced Eugene. - He isn't anything to do with Ron and Edith, only their friend and mine. I am still pronounced Ruptured, which I quite like. You have to guess how Lenny's pronounced. - How ever did we get onto this? - The 1978 Sturmey Archer three-speed now has a 23-tooth cog, replacing the 18-tooth which, with a 46 tooth chainring, made the gear uselessly high for a shopping bike in a hilly country.

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