Orion Speedtrike

Orion SpeedTrike Sponsors

Introduction: 
At the recent World Human Powered Speed Challenge (WHPSC), 2004 edition, I had my first chance to try out the chassis for a speedtrike design that I have had floating around for almost 15 years. The concept is to make a fully faired tricycle human powered vehicle (HPV) designed for high speed, and specifically to compete for prizes being offered for record speed through 200 meters with flying start (the .deciMach Prize) and distance covered in one hour (Dempsey-MacCready Prize).

When I was at the WHPSC ’04 event, held outside of Battle Mountain, Nevada, I was a little surprised by the amount of interest people have shown in my project. I have even been contacted by people who have seen only an early rendering of the project as it appears in the WISIL screensaver. I am excited by the design, and because other people seem to be as well, I thought I would try to keep some info and progress reports on the WISIL site, which Warren Beauchamp has very graciously offered to host, “as long as I promise to keep working on it!” Please consider this write-up to be my “official” promise!

You can click on most of the images on this page for a higher resolution view.

The Concept:
The concept behind the trike is to try and combine the stability of the three wheel design with the low drag of a two wheeled low racer. Two this end, I have come up with a single driven and steered wheel in front, similar to several successful two wheeled speedbikes, but with two non-driven and non-steered wheels mounted on a wide outrigger (which I call the wing) in the rear. Note that while the fairing is not a true surface of revolution, it is derived from one, which should have lower drag than an extruded surface. This is because the revolved surface has less skin area in the turbulent region than the extruded one, a very important factor when you are trying to achieve laminar flow over ~60 % of your length. Also, the revolved surface allows a more direct path for the air from nose to tail than a typical extruded type design The fairing is symmetrical top and bottom so as to half the amount of plug work required.
I chose to use 700c size wheels throughout. This option was selected because with my 34 inch inseam, I can still fit the 700c front wheel between my legs and reach the pedals. Also, a study I did suggests that the improvement in rolling resistance of the 700c sized tires available (for which there is a huge selection of very high quality options) will surpass the added aerodynamic drag of the larger wheel fairings. The larger wheel fairings also contribute to improved high speed stability, as described later.

In a recent test out on the country roads outside of Chico (see picture above in the ‘Concept’ section), the tail light and rearview mirror worked better than expected, offering a clear view of overtaking traffic, which obviously saw me from a long ways off, as they would change lanes hundreds of yards behind me. The cyclometer must have been broken though as it registered faster than expected cruising speeds, but slower than expected top speeds. Darn thing must not be working right.

I have a full sized lathe, and a small hobbyist sized milling machine that I have retrofitted with CNC. These two machines are invaluable in making all of the various frame parts and fittings.