Reflections on the potential of human power for transportation

Friday, November 23, 2012

The Return of the Recumbent Bicycle

Last September, after allowing it to gather dust in the garage for the last six years, I started riding my Avatar 2000 recumbent on the road again. I had forgotten how much fun it was to cruise down the road sitting with a car-like posture and taking in the scenery instead of being hunched over the handlebars with only a narrow view of the road ahead. I also had forgotten how awkward hill climbing was; dropping into the granny ring and spinning as if my life depended in it. Yes, my relationship with my recumbents was a love and hate thing.
My relationship with recumbent bicycles began three years after I purchased my first derailleur bicycle, a gas-pipe-framed Schwinn 10 speed. I bought the April 1969 issue of Popular Mechanics because it had an article by the do-it-yourselfer extraordinaire, Robert Q. Riley. The article was about the construction of a low-slung bicycle he called the “Ground Hugger”. I had never seen anything like it and started thinking about how I could build one.

 
As the article said “You’re cradled in a bucket seat and as you lean into a long-banking turn, you have the exhilarating sensation of being on a toboggan with wheels”. To a cyclist, this was an exciting prospect.





Many in the non-cycling community believe that Riley invented the recumbent bicycle. Instead Riley had copied the essential elements of a bicycle designed and built by the ex-airline pilot and bicycle innovator Captain Dan Henry.
Henry, famous for the Dan Henry markers used to guide cyclists on organized rides, wrote an article for the May 1968 issue of Bicycle Magazine describing his recumbent. He designed it based on what he felt were the best characteristics of pre-WW2 recumbent bicycles.





While Riley never admitted copying Henry’s recumbent, the similarities between the designs are numerous, especially the long wheelbase and remote steering. While Henry used a chain and sprocket for the fork-steering connection, Riley used a Cardan universal joint from a socket set. Why neither of them used the much simpler connecting rod between an offset pivot on the handlebars and one on the fork, I do not know. One interesting consequence of the use of a u-joint is the coupling ratio varies with the position of the joint. This could be used to improve steering control by having the steering be least sensitive when the steering is straight and becoming more sensitive with increasing steering lock. (Riley may have seen that the preWW2 Velocar used a Cardan joint to connect the handlebars to the fork.)
(A note here that chopper-style kid’s bicycles like the Schwinn Stingray are technically semi-recumbent bicycles and, for that matter, the children’s Big Wheel tricycle and its variants are recumbents. Here I am only interested in the reemergence of the adult recumbent bicycle.)
Henry was not the first to experiment with recumbent bicycles since WW2. Gunnar Fehlau, in his book “The Recumbent Bicycle”, describes the obscure work of the engineer Paul Rinkowski on short-wheelbase recumbents starting in the late 1940’s and continuing on for four decades.
And then there is this fascinating picture of two riders on very-low Grubb-style recumbents in Popular Mechanics from March of 1952. Notice, in this case, that the remote steering uses cables to connect the under-seat handlebars to the forks.







In addition, Alex Moulton of small-wheeled-bicycle fame experimented with a Grubb recumbent prior to settling on an upright posture for his improved-bicycle design in 1962. Moulton found that recumbent pedaling produced thigh fatigue when pedaled for extended periods and rejected the recumbent approach. It was a lost opportunity for recumbent evolution, given Moulton’s innovative product improvement abilities.   
Henry’s recumbent bicycle may have influenced the east-coast arm of the subsequent human-powered vehicle movement, Prof. David Gordon Wilson of MIT. He must have been aware of Henry’s article, because he wrote an article, “Where Are We Going in Bicycle Design?” published in Bicycling the previous month. He also included a photo of Henry’s recumbent in Bicycling Science, the book he coauthored with Frank Roland Whitt in 1974.
From 1967-1968 Wilson sponsored a design competition for man-powered land transportation. The winner, W.D. Lydiard, designed and actually built an enclosed mid-wheelbase recumbent bicycle. Traditionally recumbent bicycles either had the cranks behind (long wheelbase) or ahead of the front wheel (short wheelbase). Those with a long wheelbase were inconvenient to transport and had a lightly loaded front wheel that could wash out on slippery surfaces. The short wheelbase designs had an overloaded front wheel that consequently resulted limited-front-tire life and in skittish handling. If the cranks are located in the ideal location, above the front wheel, the bottom-bracket height was usually so high that the rider is placed in an uncomfortable posture. I refer to the issues with these approaches as “the recumbent packaging problem”. Refer to “Recumbents and Convergent Evolution”, below.
     

To reduce the pedal height, yet maintain their location over the front wheel, Lydiard used a squashed pedal path generated by a crank-slider-type mechanism. Lydiard felt that this approach could be refined to eliminate the problem of interference between the feet and pedals when putting the feet on the ground.







Wilson was apparently quite captivated by Lydiard’s mid-wheelbase, squashed-pedal-path approach. In a private communication, Wilson shared 17 permutations on this design approach, the latest being dated 1977. To my knowledge, none were actually constructed. Based on one of Wilson’s drawings, I built up a crank-rocker or treadle mechanism for my EcoVia 2.2, but power-production limitations caused me to abandon the design. See “Transcending the Pedicar, Part 2”, below.
In 1972, while Wilson was designing linear-drive recumbents, H. Fredrick Willkie, being inspired by Wilson’s design completion, contacted him for a sketch for the design of an advanced bicycle. Interestingly, the recumbent that resulted from that sketch didn’t utilize a linear drive. Ultimately there were five iterations in this design exercise, culminating in the Avatar 2000. Willkie did two designs which he christened “Green Planet Specials”. The first version had handlebars in front of the rider’s chest connected directly to the fork and a high bottom bracket. The design was very similar to the preWW2 Rivat recumbent. Willkie found the compressed body posture uncomfortable and at Wilson’s suggestion, the second version had a lowered bottom bracket and a more leaned-back seat angle. In addition it had direct steering with the handlebars mounted beneath the seat. Wilson bought the GPSII from Willkie and continued to modify the design as the Wilson-Willkie. The seat back was made more vertical and the weight on the front wheel was reduced from about 70% to about 65%. The Avatar 1000 followed and the front-wheel loading was reduced to about 62%. Finally, with the Avatar 2000, the radical step was taken to move the front tire ahead of the bottom bracket, and the front wheel loading dropped to about 31%. Under Wilson’s guidance, two Boston-area bicycle builders, Richard Forrestal and Harald Maciejewski began manufacturing the Avatar 2000 in 1979, making it the first production recumbent since WW2. (A more comprehensive description of the evolution of the Avatar recumbent, including photos of the five vehicles above, can be found in Wilson’s article, “Evolution of Recumbent Bicycles and the Design of the Avatar Bluebell” in the proceedings of the Second International Human Powered Vehicle Scientific Symposium.    

The Avatar 2000 recumbent was very similar to the preWW2 British Grubb recumbent. Both use indirect steering with the handlebars coupled to the fork by a connecting rod. Differences were the Avatar’s seat was higher and more upright and the Avatar had a shorter wheelbase due to the use of a 16” front wheel.  The Avatar’s wheelbase is 63”.
So there is a circuitous linkage between the Ground Hugger and the Avatar 2000.
In 1984, after becoming somewhat bored with upright bicycles, I purchased an Avatar 2000 from Angle Lake Cycle in Seattle. It was serial number 085 and it had been sitting in the store window for several years.
I was disappointed with both the on-the-level speed and, even more so, the hill-climbing speed of the Avatar. On the positive side, the extreme comfort riding the Avatar on the level terrain somewhat compensated for the reduced speed by eliminating fatigue from secondary effects like a sore seat, sore back and numb hands.
I did make one component change that significantly improved its hill-climbing ability. I replaced the conventional cranks with a Power-Cam crankset which I had purchased several years before.

The Power Cam was invented by Dr. Lawrence Brown of IPD (International Patent Development). The design involved chainrings that could float relative to the cranks. A cam follower attached to the cranks rode on a cam attached to the bottom bracket and drove the chainrings through a gear sector. The inertia of the bicycle kept the chainrings rotating at a near constant speed and the cam mechanism caused the cranks to speed up and slow down relative to the chainrings as a function of pedal position. The net result was the mechanical power pulses during pedaling became shorter and larger than with a conventional crankset using round chainrings. As a consequence, the rest periods between the pulses (two per cycle) became longer. The longer rest periods are physiologically more efficient and, for a given oxygen consumption, the aerobic power output was increased. (More on factors influencing power production in a future post.)
Using a Power Cam on a recumbent was suggested by Edward P. Stevenson in his book “The High-tech Bicycle”. The Power Cam did not work well when standing up on the pedals and forced you to climb seated. On a recumbent you couldn’t stand on the pedals so a Power Cam on a recumbent made a kind of sense. Stevenson was correct and it improved hill climbing. The Power Cam had only two chainrings, however, so an adaptor plate was machined to allow the mounting of a third granny chainring.
The increased comfort of the recumbent posture allowed me to take longer rides than on my upright and I logged a lot of miles over the 22 year period between 1984 and 2006. I eventually added an arm-power attachment to the Avatar to scavenge some of the power I was loosing through the inefficiencies of my leg pedaling. See “Arm Power and the Avatar Recumbent” below.
In 2006 I started mountain biking regularly and put the Avatar in moth balls. I began with a hardtail and later purchased a full suspension bike. My hardtail acquired road tires and became my road bike. I didn’t ride on the road much, however, because of numb hands and tired back from sitting in one position for extended periods. I didn’t have this problem when riding on dirt because of a continuingly changing body position and the reduction of road vibration due to the full suspension. The level of comfort riding an upright bicycle off-road was acceptable.
It was on a car trip up to Snoqualmie Fall for breakfast on Labor Day that I was reminded of the number of time I had ridden the scenic hill climb up to the falls on the Avatar. I have never done that ride on my converted mountain bike because of the associated lack of comfort. Realizing what I had been missing the last six years, I decided I would ride the recumbent on the road and the upright on dirt, thus having the best of both worlds.
The first few miles back on the Avatar after the six year hiatus were a bit shaky and the long hill climb back home was a painful grind. But when riding on the flats what I was left with was the feeling of being in a touring car where I could comfortably view the scenery while exercising at the same time. For me, the recumbent bicycle has returned.
Hephaestus  



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