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Kingsnake

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"Overkill is good."
- CACox97

At the beginning, there was a plan to build another recumbent: 20/20 CLWB FWD OSS highracer with a big cargo rack between wheels, something like Bevo Bike. I had started to calculate, draw, buy parts and prepare to sell the Python, but then the circumstances changed and suddenly I needed a small bike with decent gears which could handle everyday commuting all year round and would fit into limited parking spaces. So the plan changed: an old Eska folder which was intended as a source of material will be assembled again and fitted with all the hi-tech components waiting to be used: eight-speed hub, disk brakes and a hub generator. Easy, isn't it?

That much for the theory. First trap were non-coaxial bottom bracket threads. Original cups were able to tolerate this error, but a new cartridge axle isn't. I had to weld one thread over, file smooth and tap again. Second trap was the ultralight front fork made of 1 mm steel which wasn't strong enough for a disk brake. I replaced the blades with 30×15×2 mm rectangular tubing, fork geometry stayed the same. Rear fork was spread out and a brake support welded on, nothing complicated (the originally straight seatstays are now S-shaped which is probably not good for their strength; luckily I'm not very heavy). Last trap were the riser handlebars that wouldn't fit brake levers and shifting grip, so I had to replace them by a straight "stick" and make a doubledecker stem for it to avoid having my hands too low.

Clip-on basket on the handlebars is the whole cargo capacity of the bike. With the original plastic support it was barely able to carry its own weight, so I added a steel strut underneath. Now it can carry anything that fits inside, the only limit is the ability to steer (inertial moment can be tricky). The bike is primarily intended for a city, so the lights are designed to warn other drivers and entertain random bystanders, they are not very good for forest trails. With the small 20-inch wheels, cobblestones are much bumpier than with 28" I was used to. But that's the price of the tiny size. By the way, the tyres are Marathon Plus - probably the most bulletproof type that can be found today. So far after four years of use (over 10000 km), there have been no punctures and very little wear. I've extracted several shards of glass buried 5 mm deep, which didn't even reach the first layer of kevlar :-). Grip on wet road is not very good, but acceptable if you ride carefully.

I preserved the foldability, but the front wheel now keeps pointing forward when folded. That way the handlebars don't meet the saddle and nothing but the central hinge needs to be loosened. When folded, the bike is about half its normal length and can stand on its own, so it can be stowed somewhere in a corner, out of trouble. Practicality is slightly hampered by the seventeen kilograms of weight (quite a lot for a folder), but fortunately I'm used to much more. The paintjob was not planned, I just had a can of yellow paint at hand and applied it to all bare metal spots. Then I didn't stop in time and soon all the black components were striped black and yellow. Then a friend of mine who knows a lot about snakes saw the bike and that's how it got its name.

Metal fatigue

After some four years of use (9639 km of mine and unknown mileage of previous owner) I found a two-centimetre long crack along the edge of weld bead between front half of main frame tube and the folding hinge:

I don't know how long it had been there - it was hidden under a layer of dirt, so I noticed it only after folding the frame, which doesn't happen more than a few times per year. Repaired by grinding original paint and bead away and re-welding it thoroughly from both sides.

Second crack appeared on the lower stem, right above upper headset bearing:

I found it while inspecting the bike after a crash (see below) and I don't know if it was made by the impact, or had already been there (it looks rusty, but that may be just the original black paint of the stem). The crack runs along edge of weld bead at the front left area, through the bead at the front right, and continues directly through the smooth walls of the stem tube on both sides. This is the most stressed spot of the whole handlebars (the longest lever) and the worst possible cases of cyclic loading occur here (alternating compression, tension and shear in various directions). Luckily there's the bolt pulling the stem into the fork neck, so the handlebars shouldn't fall apart even if the crack finished its round trip, but the cast iron wedge at the end of this bolt was developing cracks as well. Repaired by welding the crack and replacing the wedge; plan B (making a new stem) didn't have to be executed.

Crash test

With nonzero probability of being hit by a car, you just need to ride long enough for it to happen :-). The collision is described over there, here I'll add some details about how the bike coped with it.

I was braking as hard as I could before the impact, so rear wheel was probably in the air. So the knock from the car's side was divided between front wheel and handlebar basket, which worked as a crumple zone. The car was moving from left to right, so another part of kinetic energy was absorbed by both stems turning partially sideways. The result is slightly bent fork neck between headset bearings, only visible when disassembled. This threw the bearings out of adjustment and they started to drag, but a new adjustment and lubrication fixed it to the level of safely rideable (lesson learned: if your handlebars move freely around the centre point and begin to drag slightly as they turn further from it, misaligned headset bearings are the reason). Front wheel and fork survived without damage, as well as all my ugly welds on the stems.

I don't know what the bike was doing after first impact - I was flying on without it and there was no time to look behind. There must have been some knock either to the left pedal from the left or to rear wheel from the right because left crank started to rub against the chainstay (there was very little space already, I even had to file the crank down a bit during the build). The problem was solved partly by bending the chainstays back (I'm not strong enough to finish it without a vise), partly by more filing on the crank. Luckily, the cranks and pedals didn't get bent.

Rear brake started to drag which scared me a lot, but it turned out to be just a bent cable end near the lever where basket holder pinched it (the force must have been considerable because it torn the basket out of its retaining hook). Bent back with pliers, now it runs smoothly again. Last pieces of damage were bent rear mudguard and chainguard, both straightened in situ. I hammered the basket into more or less original shape, but will probably replace it because it's too crumpled now to act as a crumple zone again. Rest of the vehicle is OK, lights shine, brakes brake, gearbox shifts, I'm happy.

Conclusions:

  1. Front disk brake probably saved my ass. With anything weaker I'd splat over midsection of the car instead of its rear corner.
  2. Handlebar basket is an excellent bumper, front fork would probably get bent or broken beyond all repair without it (headtube-mounted rack would be even better).
  3. I'm glad I didn't skimp on the wheels: hubs, double rims and multitude of spokes all survived without any signs of damage.
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