Step 1: Bill of Materials
- A bicycle
- A welder
- Extra set of bike pedals/cranks
- Extra bike seat
- 2 heim joints to make a steering tie rod
Step 2: Pedals
When pushing off, each rider will have their foot resting on the pedal closest to the frame in the bottom most position (left side rider - right foot, right side rider - left foot). So cut off the left side crank and weld it back on so as to form a U. Now remove each pedal and in its place, weld a 6" long by 3/4" wide steel rod. I initially had welded a 1/2" rod to the original bolt from the pedal but was not strong enough as it twisted some while pedaling. You then make a custom pedal that will fit the 3/4" rod.
Simply use 5" of tubing that will slip over the rod and weld two 3/8" bent rods as in the picture.
With the custom-made pedal in place, weld at a 90 degrees an extended crank and pedal. To make this extension, you will need to weld a rod to an extra crank to achieve the required double length -- about 13 inches. You will not want to place too much of your weight on the outside pedal so use the inside pedal for pushing off and when stopping.
Step 3: Seats
To the seat post, weld a tube to form a T. Using a tube that wil slide inside the tube just welded, cut it to the length you want the seats apart from each other. Slide it in and now weld 2 short new seat posts at each end to accept the 2 seats. You can make both posts adjustable or just .one as I did since the original seat post can also be adjusted. Drill a hole across both tubes, insert a bolt and tighten with a nut. If weight combination of the riders does not work well, remove the bolt and slightly slide the inside tube with the seats to adjust. Drill across the inside tube starting from the holes already drilled on the outside tube and reinsert the bolt.
Step 4: Handle Bars and Steering
Only the left side driver will steer the bike so the left side handle bar will have a steering linkage. Weld tubing as shown to the left side of the head post tube. I used another bike's bottom bracket to make the steering mechanism. I welded a heim joint to the underside as well as another heim joint where the original handlebar used to be. I then connected the 2 heim joints with a tube acting as a linkage to make the steering possible. You will want to trim down the length of your handle bar so it does not interfere with the other rider. You could instead use a tie rod or perhaps sprocket and chain for the steering mechanism. Install the gear and brake controls onto this handle bar. Now weld a fixed handle bar for the right side driver and you are ready to ride! Since all that welding requires removing of paint to expose the steel, you will want to prime and paint at this time.
Step 5: Riding
As the driver, place your right foot on the inside pedal (closest to the frame) at the bottom most position. Left foot on the ground. Hold the handle bars firmly while the passenger sits on the seat and puts both feet on the pedals. At this point, three feet are on pedals and the driver's left foot is acting as the "kickstand."
You then push off while releasing the brakes. I find a few pushes helps to get enough momentum for balancing. Get seated and start pedaling while the passenger begins to help with the pedaling. The bike will lean slightly to one side when there is a difference in the riders' weights but this is normal as it helps in maintaining good balance. Once stopped, both riders should place the outside foot on the ground. Now enjoy an exciting ride in the park with someone special while socializing all the way. Oh what fun it is to ride side by side!