19 September, 2009

My 13 year old son's home-built 'bent!

Kids these days... Graham's grade 8 solo project assignment at his Waldorf school was meant to stretch the students' concepts of what they were capable of; his decision to build a recumbent trike from scratch - on his own, with me at arm's length as a mentor - certainly opened his eyes as to what's possible when you don't give up, even if your hands are frozen stiff in an uninsulated garage. Many thanks to Cary Chen from Urbane Cyclist in Toronto for acting as the real mentor with real answers!

every frame piece was drawn out full scale... often several times.

The drawings were fastened to 3/4" ply, the wood cut out, and hot glue-gunned into position. Sometimes he needed encouragement to take an extra moment to reposition something, as an adolescent's opinion on what constitutes "close enough" can vary wildly from measurements.

He used a tubemitre program to create a stencil for the "fishmouth" shapes needed for a tight fit, then cut each joint out by hand, filing it until the gaps were small enough for the brazing to effectively hold. This was made extra challenging as we were using 4130 chro-mo "aircraft" tubing, which, although extremely thin-walled, was very very hard! No wonder they can fashion airframes from it.

An old Nishiki mountain bike frame was cannibalized for its rear triangle. You can see where the seat tube and seat stays were cut off, and the top tube now runs diagonally between them. Both the top tube & the original BB tube are capped with brazed steel plates.

Single chainwheel up front, 7 speeds in back. Front disc brakes (Avid mechanical) and rear V-brake.

Even the handlebars had to be fabricated, although they may get a re-working for clearance and alignment purposes.

Aluminum blocks were drilled & tapped to form seat mounts that doubled as chain guide supports. An old skateboard wheel earns a second life as a chain idler by way of a sawed-out centre groove.

Many thanks also go out to John & the crew at Oakville's Cyclepath shop for the helpful advice, not to mention the rear derailleur cable re-routing!

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