the Design and Construction of the


(PART 1)

(an Arm and Leg Powered Recumbent Bicycle)
Submitted by PAUL DUNHAM
in fulfillment of requirements for a



This report describes the process of designing and building the Wild Thing, an arm and leg powered recumbent bicycle. A discussion of design philosophy and objectives leads into a component by component description of the requirements of each major system: the frame, steering, drive, seat, and brakes. Mechanical details are explained in the text with reference to figures. The results are presented, discussed, and illustrated with photographs.{Commentary by the author, thirteen years later, is in curly brackets and italics}


It would take a long list of names to cover those who have had something to do with the design and construction of the Wild Thing. Assistance had come directly and indirectly, from people trying to help and from people who gave me inspiration merely by being who they are or doing what they do.
Any list of those who deserve thanks would begin with my parents. My father taught me how to tinker and imbued me with a passion for mechanical devices. My mother put up with the mess; from greasy hand prints on the refrigerator to rotting cars in the backyard.
I thank Doug Gibbs for building a fabulous and outlandish machine called the Interbaker. He proved to me that fantasy and reality can be make to meet through imagination and determination. I learned a similar lesson from John Curtiss, the craftiest man I have known. John did things with metal and machines that would be passed off as impossible by those less inspired.
Without the approval and support of Dr C. E. Smith, the Wild Thing would never have gotten beyond the fantasy stage. His legitimization of an admittedly offbeat project left me free to spend the time, energy, and money necessary for its completion.
Jim Byford has been indispensable in resolving many of the fabrication problems that have arisen. Without his expertise, cooperation and support in the shop the construction of most of the steering and drive systems would not have been possible.
Thanks to Keith Howell and Richard Rau for locating the rear hub, to Bugs Rezac for donating her beloved beach chair, to Pete Gothro for the parachute thread, Fred Baldi for the fork off the "Green Piece", Henry Fields for the big tie-wraps, and Mark Lightner for the crankset, pedals, and shifters. Chuck Meitle made the paint job possible, and it was Jack Clarke that pushed me down the hall for my first test ride. The list could go on and on. I'll summarize by thanking everyone who has taken this project seriously and supported my involvement in it.


The bicycle as the world knows it has a basic configuration that was developed over a hundred years ago. Its design, and original name, "Safety Bicycle", resulted from the effort of inventors of the time to replace the high wheeler, or "Ordinary", with something safer and less awkward to mount and dismount. The Safety emerged victorious from a period that saw hundreds of new and often bizarre bicycles. It became the standard.
Interest in further development of the bicycle did not die entirely, however. A bicycle with a fairing inspired by a dirigible broke existing speed records in 1912. A fully faired recumbent, in which the rider reclines as in a chair, set more records in the mid-thirties. But development of these new ideas was squelched by a ruling of the Union Cycliste Internationale (UCI), which governs bicycle racing worldwide. It was declared that bicycle racing was to be a contest of men, and not machines, and that records set on anything but a standard bicycle would be ignored. This ruling still stands today {as far as I know} and until around 1970, limited mainstream innovations to improvements on the time-proven ten-speed racing bicycle. The foundation of the International Human Powered Vehicle Association
(IHPVA) opened up a long-closed frontier. Yearly races are now held where inventors, tinkerers, and crackpots pit their contraptions against one another in a no-holds-barred competition for speed, innovation, and practicality. The emphasis is on speed, however, and record holding machines are elaborate, streamlined, ground-hugging affairs capable of speeds over 50 mph with a single riders, and over 60 mph with two or more. These machines are to bicycles as dragsters are to cars. They probe the limits of how human power can be applied to motion, but their degree of specialization renders them unusable on a public road.
This developmental history will bring the Wild Thing into perspective. The search for a safe, practical, and simple human powered vehicle ended with the safety, or standard bicycle, which has remained essentially unchanged for a hundred years. The search for a fast human powered vehicle goes on, but it is clear that any viable answer will be low to the ground and will sport a highly aerodynamic shell. The Wild Thing is something different altogether and the goals that predicated its construction differ from those that led to safety or high velocity bicycles. In this report I will define these goals and describe how I went about attaining them.


Bicycles are used the world over for basic transportation. As a means of transporting humans or small quantities of goods they are unrivaled for their efficiency. In many parts of the world a person's bicycle might well be one of their most treasured and vital possession. In more affluent parts of the world, such as the U.S., the bicycle is seen more as a toy, and its uses are more recreational than utilitarian. {I feel that this is even more the case in today's bicycle market, with it's emphasis on suspension gimmicks and cool-today, passe-tomorrow components}
Whether a bicycle is ridden with a destination in mind or not, though, its value as a physical conditioning device is apparent. Aerobic activity strengthens the cardiovascular system, and a cyclist who rides with any regularity at all will develop his or her leg muscles in proportion to the frequency, duration and intensity of the rides undertaken. The use of the leg muscles in making a bicycle go is natural enough - after all, they are the muscles the human machine has used for motivation since we stood erect. They are big and strong, and have a range of motion that makes them very well suited to a simple crank mechanism that drives a wheel through a chain. But the human body has many other muscles that might be tapped for mechanical work. The muscles in the arms, shoulders, and back are not flaccid when one rides a standard bicycle, but they are only used to resist the reactions of the legs or to support the body's weight. If the mechanical work needed to propel a rider were more evenly drawn from the various muscles of his or her body, the resulting muscular development would be similarly distributed. This is the primary design objective of the Wild Thing - to draw mechanical work from and condition the muscles of the upper body as well as the lower.
The other design objectives of the Wild Thing could all be related to safety and practicality. It must be compatible with public streets and traffic situations to the degree that the safety of its rider is not compromised. As mentioned earlier, the "state-of-the-art" HPV is very low to the ground, a characteristic that would make it nearly invisible to motorists. Most of the fastest HPVs have three wheels, which is a result of an effort to put the rider as close to the ground as possible and eliminate the need for balance. For a three wheeled vehicle to be stable in a cornering situation it must have a track width sufficient to keep it from rolling over. This extra width makes it incompatible with most roadway situations, where a bicycle must fit into the margin between the moving traffic and the shoulder, or a line of parked cars. The Wild Thing should therefore have two wheels.{Besides, three wheels is cheating!}
Many of my reasons for wishing to make the Wild Thing with only two wheels are emotional ones. I happen to like the way a two wheeled machine leans into a corner, and I've always been fascinated with the fusion of human and machine that makes the entire concept dynamically possible at all. Furthermore, many machines utilizing arm and leg power have already been built using three or more wheels and I wouldn't regard such an undertaking as significantly new or challenging. The Wild Thing is not the world's first arm and leg powered bicycle. Gary Hale of Eugene, Oregon built a machine that fits that category, although the Wild Thing bears little similarity to it. The major differences will be discussed elsewhere in this report.
Safety considerations go well beyond making the Wild Thing compatible with the existing roadways. Comfort, crashworthiness, and fail-safe features must be incorporated throughout the design. The primary safety requirement for the Wild Thing, however is that it be easy and natural to ride. Its rider must be in sufficient control to avoid or overcome hazards encountered on the road. My original goal in this area was to make a machine that anyone with normal bicycling skills could ride immediately. Upon completion of the Wild Thing, however, I found that I had to learn to ride it much as I had learned to ride a standard bicycle, or to roller skate, or to ski downhill. None of these activities can be thought of as "automatic". Each requires training and practice to master, and, until the necessary connections are made between the brain, equilibrium, and musculature the cyclist will wobble, the skier and skater will fall. The Wild Thing constitutes a new form of locomotion, and since at the time of this writing I have put fewer than fifty miles on it I am still a little wobbly. In the last section of this report I will discuss its riding and handling characteristics. {After I finished the Wild Thing, I met many other recumbent enthusiasts (including some very big names), and participated in the IHPVA meet at the 1986 World Expo in Vancouver BC. Virtually all were of the opinion that if a person couldn't get on and ride immediately, there was something critically flawed in the design. My standpoint was and remains that you can't do anything truly unique if you limit yourself to skills and knowledge that you already have. So there.}
The establishment of primary objectives implies the existence of secondary ones. Some things must be ignored, others compromised. The main thing the Wild Thing is not specifically designed for is speed. This is not to say that I intended for it to be sluggish, only that I don't expect it to be any faster than a standard bicycle. Speeds in excess of 20 mph are not required to achieve the full body conditioning requirement, and would definitely compromise safety.
Any human powered vehicle should be lightweight and mechanically efficient. In these areas a "state of the art" ten speed excels. For the Wild Thing to do what it must requires more mechanical complexity, with its attendant increase in weight and decrease in overall efficiency. Since the funding for this project has come from my own pocket I've had to build it within the constraints of my monetary resources and my skills in the M.E. shop. Each component, therefore, had to be designed not only to work, but to be made with materials and processes easily and cheaply available. This led to a "Design for Manufacture" approach that set a theme for the entire project. Without sacrificing performance, safety or reliability each component or system of components had to be as simple as possible, because simple parts are simple to make, and simple systems usually have greater mechanical efficiency.
Because of the inseparable nature of design and manufacture, the two processes had to proceed concurrently. Once I had convinced myself (through innumerable sketches and layout drawings) that the whole concept was possible, I established a sequence of events in which the construction of one component or system would dictate the design of the next. This approach, has several advantages. Since many of the problems with a part design are uncovered when the part is built, properly sequencing the design-construction process minimizes the effect that the required changes will have on the existing designs. In addition, I find my won design work more enjoyable and more reliable if I have something concrete to stare at for inspiration. I work best with dirty hands. The overall sequence, as described in subsequent sections of this report, became: frame, steering, drive, seat, and brakes.
Finally, the Wild thing is a prototype. Most parts were machined to fit rather than to specific design dimensions. Drawings are included in this report where they are necessary to illustrate the workings of the systems but they are loosely scaled and contain no dimensions.



You are visitor number