The semirecumbent Avatar 2000 has indirect origins in a design contest organised by Dr. David Gordon Wilson and the Journal "Engineering" in 1967-68. First prize went to a highly promising semirecumbent design by W.G. Lydiard. Dr Wilson, a professor of mechanical engineering at the Massachusetts Institute of Technology, subsequently provided drawings of an improved design to a student, Fred Wilkie, who made two prototypes. Dr Wilson purchased the later one and incorporated a number of modifications on the basis of extensive road tests. Thus evolved the `Wilson-Wilkie' recumbent. Dr Wilson then approached FOMAC, Inc. on the idea of manufacturing a production recumbent. Three years, four prototypes and ten thousand miles of road testing culminated in the Avatar 2000.
Delivery
To date, some 125 Avatar 2000 bicycles have been constructed. Manufacture is by hand and the current order-delivery interval is about six months. Our test machine is the property of the editor, who ordered out only the bare frame, steering controls and seat. All other components were obtained and fitted in the U.K. An accurate comment as to the efficacy of the manufacturer's assembly is therefore impossible.
However, we do know that aside from the front and rear wheels, seat and steering rod, the Avatar 2000 is delivered fully assembled, with brakes and derailleurs preadjusted. The accompanying owner's manual is extremely comprehensive and only quite basic mechanical expertise is required to shift the Avatar 2000 out of the box into road running order.
General workmanship and finish of the Avatar 2000 is extremely good. The frame welds are clean and smooth, and finishing of stainless steel and anodised alloy parts is exceptional.
The Avatar looks very much the part of a futuristic machine. Our only spot of bother was with the brazed bosses for mounting the cantilever brakes, which were out of line. The makers assure us that this dereliction has long since been rectified.
Design Analysis
The Avatar is no ordinary bike, and the frame, brakes, seat, handlebars and so on each have to be analysed and evaluated in relation to new design criteria. So:
The chief point in favour of a recumbent design is aerodynamic efficiency. A conventional upright roadster bicycle requires almost twice the energy input to maintain a speed of 10 mph as does a drop handlebar sports bicycle. Put another way, an energy input of 0.1 horsepower (75 watts), which is what most people can comfortably produce over a longish period of time, will move a roadster at 10 mph, and a racing bicycle at 15 mph1. Which sounds promising, until you realise that at 25 mph on a racing bike, some 90 percent of the rider's effort goes into overcoming wind resistance.
In cycling physics mechanical drag (frictional loss through bearings, drive-train, tyres and so on) is comparatively negligible when set against the ferocious strength of wind resistance. In these terms, shifting a racing bike along at 20 mph takes four times the effort to maintain 10 mph, and a speed of 40 mph will require a sixteenfold increase in effort.
If you isolate for the aerodynamic factor by subtracting the rolling drag of mechanical resistance, then it takes 203 watts (about 0.26 horsepower) to move a racing bicycle at 20 mph2. By way of contrast, only 64 watts (about 0.084 horsepower) is required to maintain a streamliner with a fully enclosed fairing at 20 mph. That's a staggering 69 percent reduction in drag. With an unfaired semirecumbent such as the Avatar 2000 the saving is rather less - about 20 percent, or an energy requirement of 151 watts (about 0.2 horsepower) for 20 mph - but still hugely significant.
The clear aerodynamic advantage of the Avatar's semirecumbent design is obtained through a semiprone lounge chair riding position. What is the effect of this on ergonomic efficiency, e.g., biomechanical utilisation of the human powerplant? The answer to this question involves several elements and starts with a few details about the Avatar's seating arrangement.
The
seat itself consists of a tubular frame made of anodised alloy and covered
with stitched leather with a nylon mesh insert. Six side-to-side rear tension
straps and a single vertical tension strap secured to a horn at the front
of the seat make very precise adjustment of the seat configuration a simple
matter.
Attachment of the seat to the bike is via two seat support rods fastened with retaining pins to studs on the chain stays, and at the front, via locator bushings on the seat frame that fit into a carriage plate assembly, and are held in place by seat clamps and hand-tight knurled knob tension bolts. It is thus possible, by slacking the tension bolts and removing the support retaining pins, to dismount the seat in a trice, without tools. This is very handy when transporting the Avatar by means other than pedal power.
The carriage plate assembly, to which the handlebars are also fixed, fits on two stainless steel tracks mounted on either side of the top tube. Movement of the carriage plate assembly along these tracks (and thus also the seat) provides positions suitable for riders with leg lengths from 27 inches (68.6cm) to 39 inches (99.1 cm). This covers nearly 100 per cent of the adult population. The arrangement also means that one frame size fits all, a fact that the makers quite rightly tout as a basic economy for mass production when initiated.
Although the seat of the Avatar gives a distinctly reclining position, the rider's back is firmly braced. This allows very strong leg thrust to the pedals. In an informal test of static impedance load capacity held by the makers, with riders pedalling the bikes against a set of bathroom scales mounted on a wall, the Avatar scored an average 70 Ibs thrust as against 40 Ibs for a conventional bike. This seemingly monumental advantage is however, subject to qualification.
A human being can muster a peak energy output of two horsepower. This falls off dramatically within seconds, and stabilises after two minutes (for a conditioned athlete) to an output of around one third horsepower.
On a semirecumbent such as the Avatar it is leg thrust or nothing. Shoulders and arms can add little if anything to forward motive force. So while utilisation of the leg muscles is efficient, there is less scope for total body effort. On a conventional bike, pulling with the arms and shoulders will increase pedalling pressure, and there is the further option of simply standing up and allowing body weight to contribute to the work of turning the cranks. On the Avatar it is push or perish.
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