The Power And The Glory
Looking back on this year's Human Powered Vehicle Championships, Stuart Morris considers the development of HPV design and looks at some of the endeavours to achieve that elusive mix - good handling and high speed
Even if you're cynical about Human Powered Vehicles that aren't obviously bikes and not interested in aerodynamics beyond the fact that rain capes are murder in a headwind, just look what's happened so far…

here already exists a machine, the Vector, which can be carted from country to country, set down on a short run-up race-track and return maximum speeds in the mid-forties to low fifties, and which can go on up-hill-down-dale courses of twenty/thirty miles and average around 30 mph. The Vectors have been dominating HPV events all round the world for the last four years and are the first of the classics in a new generation of road capable machines. The really exciting thing is that their domination is about to be overturned by a second wave development in HPV technology.

In fact technology is not really the word. The next stage will be more dependent on a far more subtle understanding of all the variables which go into building a high performance HPV. The balance between mechanical efficiency, transmission design and aerodynamic effectiveness should be the basis of the next exponential leap in HPV performance rather than pure technological sophistication.

NEWCOMERS

The whole business is too new for there to be a conventional wisdom about design or engineering. The Vector is a successful high-tech machine that has forced its way into new. territory. There are a host of machines slipstreaming behind, poised to overtake and explore further.

At Brighton this year, one unlikely low-tech contender nearly led the way. The entry of the Nosey Ferret Racing Team, Bluebell (which is in fact the Avatar 2000, an American production recumbent bicycle, clothed in a skin of plywood and stretched plastic; did serious damage to state-of-the-art concepts of fast human powered vehicles. Until Brighton really quick competitive HPV's had to have the low, smooth, classic look of the world record-holding Vector. That's a ground-hugging shape with a small frontal area that pierces the air with the minimum of effort and continues on its way with the minimum of turbulence or resistance. The tail-end of the machine is as important as the front and sculpted to aid the slippery progress and clean exit from that cloying tacky soup known as Air.

Last year without a fairing the Avatar 2000 with an Olympic standard rider, clocked 26.43mph for the sprint. This year with the merely Olympian efforts of Tim Gartside, it registered 46mph, less than 2mph behind the Vector. A better illustration of the anomalies of HPV design would be hard to find; beneath the Bluebell shell, the Avatar 2000 is a conventional bike with its frame squashed and stretched, and with an amazingly comfortable bucket seat - the only really unlikely feature being that the handlebar and chainwheel positions are transposed. Handlebars are under the rider's thighs and feet where the handlebars would normally be. All the other running gear is conventional lightweight bike equipment. The only change to the Avatar itself from last year is a tandem style crossover transmission.

Obviously the big change is the bodywork which was created by Boy, otherwise known as Derek Henden (every genius should have an irreverent nickname). Derek has some understanding of aerodynamics - the phenomenal improvement in performance proved that. The design was a form-hugging shape following the lines of the Avatar plus rider and naturally ended up as a completely different shape to the Vector. Viewed from the front the Bluebell has a droop snout; in profile it is twice as high as most of the Vector style entries, resulting in great vulnerability in cross winds. Looking like a clinker-built wing section from the side, it also acts like a sail and this is its major weakness. Even so, in gusting winds blowing from the sea across the sprint course on Madeira Drive, the Bluebell, like the Vector and the 2nd place British machine, Poppy Flyer III, returned high speeds in 13kph + winds, although the Vector and Bluebell ran better times at lower wind speeds. (Wind assistance appeared not to be a significant factor other than destabilising the machines.)

It's correct to say that Bluebell is more vulnerable in these conditions than the low Vector style (usually tricycle configured machines) but that is a problem for everybody. From behind they can be seen careering down the course wriggling from side to side. This is partly due to the flailing limbs of the pilot frantically trying to convert energy into movement - mainly at build-up speeds - and a good deal due to side winds. It's a paradox of HPV aerodynamics that unfaired machines don't go fast enough to be dangerously buffeted but the best aerodynamic shapes go fast enough to catch up with another bundle of design problems. Although it is something which doesn't matter too much in the 200 metre flying sprints, other than suppressing the upper speeds, it becomes much more of a problem in road races and certainly for the future of HPV's as personal transport.

POPPY'S PROBLEMS

On the track at Brands Hatch for the second day's event, the 20 lap race, the Vector again dominated. It can cope with a twisting plunging course just as well as the straight line sheer speed sprint. So far it's the only machine that has shown such versatility. Bluebell showed its potential by dramatically overtaking the Vector on the pit straight, pitching like a windsailer into the following corner then, equally dramatically, suffering a blown tyre and capsizing. Poppy Flyer III fared even worse in terms of performance although if it was possible to harness shout power it would have been at the head of the field. Like many in the race it had mechanical problems finishing 11th solo at an average 20.25mph. Poppy doesn't seem competitive except in a straight line, probably because of its weight (which is a substantial penalty uphill) and the overall handling abilities.

Steering, cornering, braking, stability, visibility and cooling (not to mention comfort for the pilot) are vital in the road races. For these reasons a conventional tandem with a clear plastic canopy, aptly named the 'Flying Greenhouse' performed remarkably well in the multi-rider category, coming second out of two contenders. That is last as well, but it's not as facetious a comment as you might think. Even a racing tandem with top class riders should have no place in this competition without very well designed streamlining - that the Greenhouse doesn't have. It does have a pedigree of more than 80 years' development, time enough to sort out the handling abilities, unlike the first place 'Highview Hurricane'. The Hurricane is quaint, ugly and only just on the virtuous side of inept; aerodynamically it must be better than the Greenhouse, but in all other ways it's inferior. Were it not for the wide-track outrigger wheels and the fitness and determination of riders George Clare and Peter Corry, it would probably not have beaten the tandem by 0.09mph. Fully clothed HPV's should leave semi-naked tandems for dead.

Hills are a grind for HPV's. As cyclists know, the more weight you are hauling uphill the harder work it is. Most HPV's weigh between 40 and 75 pounds and uphill they make ludicrously slow progress; aerodynamics count for nothing below 12mph and all that windcheating bodywork is deadweight. Therefore really light machines like the Hawker/Hudspith could be seen streaking up the hilly bits, overtaking everything else only to lose the advantage again on the level and downhill to the sleeker, heavier, and once again, faster, competition.


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