Dave Wilson and the Improved Safety Bicycle Part 1

 We can consider the late Prof. David Gordon Wilson, emeritus professor of mechanical engineer at MIT and author of four editions of Bicycle Science, the technical bible for all-things bicycle, as the father of the modern recumbent bicycle. 

Wilson was a life long bike commuter and environmentalist and rode a small-wheeled Moulton to work. When Wilson launched his bicycle redesign competition in 1967, his goal was to encourage the development of a safer bicycle.

http://lefthandedcyclist.blogspot.com/2019/10/david-gordon-wilson-father-of-modern.html

 With Fredrick Willkie, Wilson developed the Wilson-Willkie recumbent.

The Wilson-Willkie received national exposure when it was featured in a Mobil Oil commercial in 1976.

https://www.youtube.com/watch?v=lYbfz4vCczg

The Wilson-Willkie evolved into the Avatar 1000 and then into the Avatar 2000 which went into production in 1980, being the first commercial recumbent since the Second World War.

Wilson's efforts in recumbent bicycle development duplicated the efforts of inventors in the 1930s to improve on the third generation safety bicycle. These previous efforts were banned from competition by the Union Cycliste Internationale because they felt the aerodynamic improvements of the reclining posture offered riders an unfair advantage.

http://lefthandedcyclist.blogspot.com/2013/12/the-technical-history-of-bicycle-part-3.html 

As it turned out, the Avatar 2000 was too unwieldly to carry up the multiple flights of stairs to his office at MIT,  so Wilson returned to a shorter design, finally ending up with a timing-belt drive that coupled the cranks to an intermediate bottom bracket-chainring assembly.

Wilson felt that two design changes made his recumbents safer that the current bicycles. Lowering the seat height about 12" reduces the injuries associated with the rider falling over and placing the feet forward insures that the rider's feet strike a forward obstruction before the head.  All of Wilson's recumbents use under-seat steering which is not only very comfortable but also safer than upright bars. In the event that the rider was flung forward during hard braking, the rider is not hooked on the bars.

Now, because of what I refer to as the recumbent-packaging problem, Wilson's recumbents came with an undesirable consequence. 

http://lefthandedcyclist.blogspot.com/2012/03/recumbents-and-convergent-evolution.html

The Wilson-Willkie had a very highly loaded front wheel. This resulted in reduced tire life and the possibility of pitching forward in the event of an emergency stop.

The Avatar 2000 had a very lightly loaded front wheel that could loose traction and steering control on slippery surfaces. 

The chart above shows weight distributions for Wilson recumbents and conventional upright bicycles.

Now either of two approaches can be used to achieve a more optimal weight distribution. The first is to raise the bottom bracket above the front wheel to allow the correct wheel spacing without foot-wheel interference. Wilson resorted to this approach on his last prototype designs.

The second is to place the bottom bracket adjacent to the fork crown and use a large Q bottom bracket to maximize pedal-wheel clearance. To prevent chainring-wheel interference an intermediary bottom bracket may be required to achieve a high enough gear ratio. Since Wilson is using an intermediary bottom bracket with his timing-belt drive this would not be an extra complication. This approach would also reduce the wheelbase of the Avatar 2000 by 10in.

This is an approach I have used in the past and would recommend. A near ideal weight distribution front to back of close to 39/61% can be achieved.

So, like Wilson, I would conclude that the recumbent posture makes a safer commuter bicycle than an upright bicycle, as long as the rider's posture is similar to an automobile driver's. And after riding an Avatar 2000 for over 37 years I would add that it is much more comfortable to ride. Despite the above facts, 42 years after the launch of the Avatar 2000, recumbent bicycles are only a small part of the bicycle market, despite the fact that Trek, Cannondale and Giant produced recumbent bicycle models.

One should remember that the bicycle's popularity stems from the fact that it is a relatively simple device which can double the users speed for a given level of effort. Wilson's modifications to create recumbents increased the complexity of the seat and in some cases added an intermediate bottom bracket, but the overall simplicity was maintained.

Hephaestus