Here is an image of a recumbent bike I designed and was built by myself and the help of two guys from work. For the complete set of drawings (12 sheets) of the bike, just click on the link in the left menu. It is capable of 45mph on a good day and the design is for a 5ft 8" person. It could easily be modified to accomodate any rider by lengthening the main tube.The main frame is made from exhaust tube and the rear section from a road frame which has been cut up.It is very durable and easy to ride. The main difficulty in building was locating a plain bottom bracket (without lugs) and the cable guides. An internet search for bike frame builders may help.
A free set of plans is available on the left menu. Choose either .dxf or .tif format.
The rear wheel is from the road bike and the front wheel was purchased . I seem to remember it was from a Pashley commuter type bike. I modified the front forks by cutting them down from the road frame ones and re brazing them. The whole frame was brazed together, except the triangle under the seat. This was silver brazed. It has proved strong enough, but welding would be another alternative. The seat is made of wood with a little padding and is bolted at the base but mounted to a rubber bush setup at the back. The bushes are the ones used to hang car exhausts (cotton reel type bushes). They are comfortable and avoid the shock loading on your back from the rear wheel. This is a common phenomenon with recumbent bikes. The frame is good, but In hindsight could do with being a bit stiffer if you intend to do high speeds on it all the time. Im not sure if this is to do with the frame or whether the seat rubbers just give this impression when riding. I suspect the latter. It is only noticable at high speed (40mph+) when it can tend to hop a little over bumps. It is only slight however, it is a compromise between comfort or efficiency.
The seat suspension mechanism can be seen above, simple but effective
The chain is controlled by passing it between a pulley mechanism. This was made by machining two skate board wheels to a flat bottom vee form to take the chain. The skate board wheels have the added bonus of internal bearings to make the mechanism very free running. The total weight of the bike is 15Kg (33lb).
In April 2010 the bike you see here was sold to Jon Beel. Jon has renovated the bike and given it a new professional dayglow paint job. He now takes part in recumbent bike races.