You can build a bike out of a commercially available bike extension cargo rack.
Normally this cargo rack mounts behind a standard bike to extent the back wheel 1.5 feet back and makes room for its own large panniers, it has a a wood deck on top and plenty of tie down points for heavy duty hauling.
This project is about minimizing the bike and having a compact "sport hauler" where the rider and passengers all sit on the rack. The rack is the only seat, but(t) it's big enough for a couple of people.
The other two bikes can be seen on my hobby website woodenbikes.com
Step 1: Start by Looking at What You've Got
This is the Cargo Bike I was given. The bike frame is too big for me. I had to turn the stem backwards to be able to reach the bars. The stick represents the ground line.
I wanted to make a compact sport hauler where I could sit on the rack and pedal semi-recumbent.
Step 2: General Layout and Cogitating Stage
I lay out various bikes and parts relative to a ground line (represented by the stick) and ponder the possibilities. I try a variety of old damaged bikes form the scrap pile, looking for ones that have the features and dimensions I want.
I used the cargo rack from the big blue bike and the black rear suspension triangle from the Mongoose bike and the front triangle from a different 16" girls bike.
Step 3: Conceptualizing With the CAD System
Because I live in the high tech center of Silicon Valley, I use a sophisticated CAD system in planning my bikes.
CAD (Cardboard Aided Design) employs a full scale cardboard cutout of my: arm length to wrist, torso, thigh, lower leg and foot, crank and area swept bu my foot as I pedal. It has brad pivots at the shoulder joint. hip joint. knee joint and pedal axle as well as at the crank/bottom bracket axle. The movable joints let me reposition it to look at different torso angles (recumbent position or upright or crouched racer position etc. different leg extensions, knee clearance toe heel clearance etc.
A stick represents the ground line and I arrange a few bikes and parts on the ground with the CAD system to get a picture and a feel for the design possibilities, problems, and solutions.
I got the idea for the CAD system from this well thought out design method by Bikesmithdesign.com
12 steps to design a recumbent
Step 4: Front and Back Triangles Bolted Together
After cutting up the little girls' donor bike and unbolting the rear suspension triangle from a mountain bike I connected them together. I used the seat binder bolt and two 1/4" by 3" U bolts to attach the little girl bike front end to the macho mountain bike back end. ( That reminds me... at Maker Faire a visitor looked at my collection of home built bikes and said it was like Syd's land of the misfit toys from "Toy Story" .) I resemble that remark because I do enjoy combining disparate objects to help people get new ideas.
Step 5: Move Cargo Rack From Big Bike to Sport Bike
Loosening 3 bolts removes the cargo rack and it can easily be moved to the new frame after the shifter cable and rear brake cables are disconnected for the move. It's a great product.
Step 6: Connect Long Shifter Cable and Long Brake Cable
Rear dÃÂÃÂÃÂÃÂ©railleur (attached to the cargo rack 1.5 feet further back than normal) is fitted with a new long shifter cable.
Step 7: 2 Chains Are Joined to Make a Long Chain
Step 8: Get the Handle Bar Grips Somewhere Within Reach
One method to raise the handlebars up where you can reach them, is to cut a regular stem and weld a piece of tubing between the 2 parts of the stem giving them the big height offset. You can also angle the cut to give you more stem forward or backward extension (called tiller) if desired.
In this simple stem I used a hacksaw straight cut and square cross section thin wall steel tubing the make the stem. I welded both pieces of the stem to opposite ends of the steel tube to make a tall stem.
A non-welded method is to just use very tall bars (like Ape hanger bars, or half moon beach bars turned up) and the regular short stem. You can also buy a stem extension that fits between the stem and the steerer tube.
Step 9: All Ready for Prototype Test Ride.
I can hardly wait.
Notice how compact the new front end is compared to the prior big mountain bike.
Step 10: Shakedown Cruise
The first test ride on the prototype sport hauler.
I noticed the bottom bracket was a bit low causing the pedals to scrape in the turns. So raised it by making some adjustments.
Step 11: Snugging Up the Joint Between the Two Half Bike Frames
The frames are held together by the blue bike's seat post binder bolt and 2 u-bolts.
Step 12: Take It to Maker Faire
I brought it along with nine other bikes to share at Bay Area Maker Faire and let about a thousand people ride them over 3 days in May 2008. People liked the togetherness of hauling their buddies or family around. It also has a faux Harley motorcycle geometry that feels pretty cool. I can't help but make motorcycle noises when I ride it.
Some of the students riding it on Education Day would get up speed, then stand on the deck and hold the bars while doing bike ballet and bike surfing.