User:Mirek
From Openbike
My name is Mirek, I live in Czech Republic and am a big bicycle fan. I'm quite fond of homebuilt bikes, although so far it has always been just an assembly of standard parts. Actually, I think stock bikes are boring :-).
I like the idea of Python very much and have decided to build one too. The specifications are:
- Frame: welded, mostly 40x20x2 mm steel (the only convenient type I could find in the local shop)
- Steering pivot: 12 mm rod-end spherical plain bearings
- Suspension: none
- Gears: 3x5
- Wheels: standard mountain 26x2.0"
- Seat: plywood base + strings
- Purpose: fast heavy freighter
Current status: all welding, drilling, grinding etc. done, primer paint applied. Next weekend I'll add the top coat, and if it cures in time, assemble the whole thing. Can't wait :-).
Progress pics:
- Dynamo-powered LED lighting system is planned for this bike. I'll post the calculations, schematics and results here when they're finished.
- After 25 years of faithful service, our welding transformer finally died an honorable death (with a loud Boff! and a cloud of smoke). So I ran to a shop and brought a brand new Omicron Gama 166. Transition from AC to DC, from no automatic at all to "hot start" and "antistick", from fixed 60 A to variable current, and from 26 to 5 kg has been really pleasant.
- Note: Welding at very small currents (like 30 A) is tricky. You don't feel the arc in your fingers, because it doesn't have the repulsive properties it had at higher currents. It is thus quite easy to drown the electrode in the pool, extinguishing the arc.
- Note: The rod-end bearings are not easy to adjust. Problem is that they must be positioned almost perfectly - any imperfection and additional friction and strains appear. It's difficult to tighten M12 nuts while keeping the bolt in place with a micrometer precision. For the first time it took an hour, now I can do it in less than 15 minutes, but still far from ideal. If I ever get to redesign this, I must come up with some self-aligning, flexible design.
