Saturday, September 16, 2017

Tallbike frame

A hacksaw has revealed that the reason Healing bicycle frames weigh somewhat more than seven elephants is that they too were built with tubing of 1.6mm wall thickness. I was amazed. Makes for very easy welding, though. The downtube got its ends hacksawn and hammered to the approximate fit that is adequately hidden underneath Mig welds provided neither Mr. Knight nor Mr. English happen on them and make Adverse Welding Remarks.





Then to rummaging about in the Bike Heap for scraps to turn into chainstays. Elderly BMX frame produced 7/8" chainstays ready-fixed to a strange 40mm tube, and slicing off most of the Ashtabula housing and a healthy bit of grindery persuaded this to fit the Healing BB shell. Some ancient MTB gave of its chainstays which terminated in squashed 7/8" tubing. Some other shards of unknown rear triangle, chopped off long ago and forgotten, slotted into these bits of 7/8". With a gap of 2.75" between them filled in (with bits lopped off the handlebar sacrificed to plug the fork steerer tube) to maintain the pretense that this was unbroken tubing, all was ready to weld.

Plug-welded through 4mm holes

Slightly gnarly welded chainstay

Then to contemplating how to align everything for attaching to the mainframe. Easiest is a jig but then you're left with a jig afterwards. So out with the bike stand (thanks, Matt) and a spirit level and a bit of manuka-wood propping up the back wheel until it's about in the right place and about in line and about vertical. Amazing how accurate this can be. Doesn't have to be manuka-wood though. Other timbers would have sufficed. Oak, ash or elm - even a stick of lacewood at a pin- oh shut up. Idiot.

Once welded, on with the faux seat-tube for the front derailleur mech. This tube's critical angle is gauged by holding up another rear triangle and tying a stick across the severed Healing seat stays and lots of filing and welding and whatnot. Do we keep the existing seat stays? Not sure at the moment. A straight line goes from rear axle to top headset and by happy chance clears the top of the derailleur mech tube, as determined by a stretched bit of inner tube rubber. That may do the trick with a bit of beefing up. It may prove too twisty, however. Four long undiagonalised tubes are scarcely a torsion box. - Shut up, computer.  undiagonalised is a word. - So for the moment we'll leave the Healing seat stays dangling there in the wind, ready to be used if needed.

Tomorrow I shall be forced to disturb the neighbourhood with a bit of antisocial Sunday morning angle grindering like as if I'm a bogan, and weld together some more bits of frame to make seat stays. Yes yes yes, I know it would be easier to use pristine tube but that would defeat the primary object. I'm not a Zenga brother. I'm trying to get rid of bits off-ov the Bike Heap. Repurposing, it's called.

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