Flushed with the success of the wooden wonder, I nevertheless realised the limitations of prototyping bikes built from wood. So I purchased a cheap electric arc welding kit and launched myself naively and blindly (sic) into the new world of welding metal. I very rapidly discovered a number of things: (1) attempting to weld thin-walled bike frame tubes with an arc welder is not a sensible thing to do! The result is always messy, and invariable burns more holes in the tubing than applying useful weld to join them together; (2) using a cheap welding mask with dark filters renders totally invisible the join that you want to weld together as soon as the mask is flipped into place. This makes welding - for me - literally a blind art!
Unfortunately I don't have a garage or workshop (or any suitable indoor space) with good lighting to perform my welding, so my solution is to weld outdoors in bright sunlight. This means dropping everything and taking a forced break whenever a cloud obscures the sun, or when it passes behind one of the several tall trees in my garden. Welding for me is therefore a highly stressful activity, in which I rush to get my tubes welded before I lose the essential lighting conditions. My lack of training, coupled with the problems above, invariably leads to my welds being somewhat less than perfect. Some might even describe them (not entirely unfairly) as a complete and total botch! I try not to let this disturb me, and I have been totally amazed as how my prototype frames have held together with such seemingly inadequate welds, despite hurtling downhill at over 70km/h on the most irregular of french road surfaces.
Getting the frame alignment right requires a little ingenuity. Here I discover that, however well the tubes are aligned initially, the heat applied while welding invariably causes them to be out of true when the frame is finally removed from the "jig". Fortunately - just like steering angle - I discovered that perfect wheel alignment is surprisingly not a prerequisite for a well handling bike.
The seat unit is fixed on the frame by front and rear bolts passed through the side panels, so the weight of the rider is supported by these panels which have perfectly adequate rigidity in the vertical plane for this task. Finally, a sheet of closed-cell foam is cut to shape and taped down on top.
The result is a fairly lightweight (less than 1kg, depending on how many cross-members I add), rigid and remarkably comfortable seat. It is also very versatile, and - by repositioning its fore and aft mounting bolts on the bike frame - can be readily adapted to allow different rider positions on the bike. The seat back can be more or less inclined, the seat height raised or lowered, and the whole unit moved forward or back. I shall use this seat design for all my further incarnations.
Even more chuffed with my second - all metal framed - prototype, and first truly fully functional and road-going bike. This one's even got brakes front and rear, as well as a fully working set of 24 gears! (Yes, I'm still using an old 8 speed rear cassette.)
Just producing a bike that is rideable seems to me a major triumph and gives me a real kick! I am already experiencing the heady thrill of riding a home-built recumbent that will lead into a near-obsessional relationship with recumbent engineering that no doubt all home builders are familiar with. I have not yet considered or researched the implications for efficiency and power transfer of elements such as chain line management and idler quality. I am currently happy to make do with a derailleur cog on a bolt as the drive chain idler (!) and another on its sprung derailleur cage to guide the return chain line over the front wheel. All this will change in the near future!
