We just made a longtail cargo bicycle from a second-hand Ukrainian mountain bike. It was made in Haiti with a minimum amount of tools and measuring, but it rides well. This bike has carried three adults (400 pounds total) without catastrophic failure. It is currently being tested/abused by the teenager pictured. Check out more of our projects at www.annbekan.blogspot.com
Step 1: Find a bike
Find a bicycle for as cheap as possible then cut the seat-stays about here, and the chain-stays just behind the bottom bracket.
Step 2: Find some metal
Find some metal tubing. We found an old TV stand with strong tubing.
Step 3: Lay it out
Lay it out and mark the tubing for more precise cutting. Aside from the TV stand tubing we also used a tube from a women's bicycle frame to strengthen the rear end.
Step 4: Build a jig
I'm using the term "jig" very loosely. We found a piece of aluminium U-channel that was long enough and attached the frame to it in order to hold the frame in a straight line.
Step 5: Wire it up
We used bailing wire to hold everything in place. Clamps would work better.
Step 6: Measure
We used string and a ruler and a nail on the end of the string to build a plumb-bob. The goal is keep everything as straight as possible.
Step 7: Measure more
Measure some more and cross your fingers.
Step 8: Find a welder
We used this cheap stick welder and used 50-75 amps for all of the welding.
Step 9: Weld
tack weld then measure/eyeball everything for alignment and weld some more.
Step 10: Weld
Weld some more.
Step 11: Paint it and name it
We chose the name Cheval which means horse in Haitian Creole. Choose a font, make a stencil and paint it on.
Step 12: Admire it
Our western style font is awesome.
Step 13: Make a head-badge
Every bicycle needs a head-badge.