Here's another cool project by the designer of the Tri-Magnum:
Ground Hugger
A Recumbent Bicycle You Build From Plans
This unique human powered vehicle was developed and patented in the mid 1960s, and first introduced as "Ground Hugger" in a special plans offering by Popular Mechanics magazine. Ground Hugger's sleek lines and elegant mechanical design captured the interest of bicycle manufacturers, worldwide. But the benefits of the recumbent were not widely understood, and it would be another 15 years before high-end bicycle manufacturers began producing them. Due to today's popularity of recumbents, the original Ground Hugger plans have been updated and republished. And we've also developed the Ground Hugger XR2 - a computer-engineered carbon fiber machine utilizing the latest in cycling design and componentry.
A major benefit of a recumbent is the awesome power that a rider can deliver to the pedals. Nearly everyone has enough strength in their legs to lift up to twice their own weight, and some of us can lift as much as three times. A recumbent provides the rider with something to push against (the back of the seat), so total leg power can be delivered to the pedals. In contrast, a conventional bicycle limits the maximum push against pedals to roughly that of the rider's weight. This, in combination with its inherently lower frontal area and reduced air resistance, is responsible for the recumbent's greater speed. The speed record for a recumbent is over 65 mph. In addition, a recumbent naturally positions the body for improved blood flow because the heart does not have to work against gravity.
Safety in the event of a spill, and virtually zero stress on arms, hands, and low backs are other advantages. The attribute that receives the most accolades from new riders, however, is also the most difficult to justify in practical terms. The sheer thrill of gliding along at 30 mph just inches above the ground puts Ground Hugger in a class of its own. It's a sensation that has to be experienced in order to be fully appreciated.
Riding a recumbent is an entirely different experience. One's sense of balance has to be reoriented to the new seating position and close proximity to the bicycle's reaction point. Because the ground is a bicycle's reaction point, the conventional riding position high above the ground translates into greater lateral distances between opposing lean angles, which means slower reaction times. A recumbent reacts more quickly because of the rider's low center of gravity and close proximity to the ground. New riders initially sense this quick reaction time as instability. Normally, it takes three or four attempts at cycling before one gains enough confidence to make the full commitment.
Early versions of Ground Hugger were equipped with the Sturmey-Archer 3-speed hub; the type with a built-in coaster brake. Plans also show how to install calipers brakes, lightweight crank and head sets, and a multi-speed derailleur system. The original frames were built of inexpensive mild steel tubing. But the frame can also be built of thin-wall 4130-N or aluminum tubing to keep weight to a minimum. The cost to build Ground Hugger will depend on the type of components and materials you select, and on whether you purchase new parts individually or buy a used bike and take the components from it. So the rock-bottom cost-to-build will be on the order of $200 (mild steel frame with parts from an old bike). But a high-performance multi-speed road bike with a 4130 frame and new high-end components will cost much more - depending on the materials and components you select.
Plans may be purchased as CAD drawings in electronic format (dxf format on 3-1/2-inch disks), as large 24 x 36-inch prints on bond paper, or in a set containing both CAD and printed drawings.
Specifications
Length: 88 inch
Height: 29-3/4 inch (to top of handlebars)
Wheelbase: 66-3/8 inch
Font Wheel: 18 x 1.125 inch (optional 16 - 20 inch wheel)
Rear Wheel: 26 - 27 inch (optional cross-section)
Weight: 30 - 45 lbs (depending on materials and accessories)
Gearing: Optional (multi-speed derailleur or hub)
Brakes: Optional (caliper or hub brakes)
Adjustment: 4-inch longitudinal seat & handlebar adjustment
(Fits 64 - 72 inch rider height as shown. Frame may be shortened or lengthened for taller or shorter riders.)
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MultiQuote
I'm dying to build a lotus 7 replica with a Honda F20C from an AP1 S2000! 
~900 lbs, 240hp.. a surefire recipe for personal injury 
I used it for a month or so while I was trying to figure out if I should get blades, turns out you kind of need them to pass inspec here in MO. 
