A few weeks ago I attended a race meeting with a difference. The atmosphere was terrific, teams of competitors working hard at getting their vehicles around the track faster than any other car could travel, design and construction techniques varying from the basic to the most sophisticated. The race was 24 hours in duration, the distance to be covered by the top teams over 1000km. But the difference was that instead of using an engine, these cars used either pedal propulsion or a mix of solar/pedal motive power.
It would have been easy for the ignorant to have looked at the huge number of weird and wonderful vehicles circulating the 1.7km track in Murray Bridge, South Australia, and to dismiss the drivers and the teams behind them as nothing more than a bunch of wankers. But that sentiment couldn't be further from the truth. The Australian National Pedal Prix is not for the faint hearted, either in engineering or human power terms....
So what's it all about? The Pedal Prix's own website puts it like this:
"This a competition where teams design and construct a human powered vehicle (HPV) and test it for a 24-hour period under race conditions. The HPV is mechanically similar to a bicycle - the driver sits in a seat and uses pedals to move it along. In addition, there are some hybrid vehicles in the competition, which also contain an alternative power source, such as an internal combustion engine or a solar powered electrical motor. The teams participating in the competition are mostly from primary and high schools, although there are some private entries. Each team spends many months designing and constructing their vehicle, aiming at safety, efficiency and reliability."
That last part's understating the case. Think about the engineering challenge. To win, a car needs to:
- go at full speed for 24 hours without a breakdown;
- be as light as possible;
- have as low an aerodynamic drag as possible;
- have the highest of efficiencies in the drivetrain;
- have the lowest rolling resistance;
- allow easy and fast driver changeovers;
- and have good lights and a good horn(!).
Until you really start thinking of the implications - how do you make the car strong enough while keeping its mass ultra-low? - it all sounds easy. But it isn't.
Some years ago, when I worked as a secondary school teacher, I joined a Pedal Prix team near to the end of their car preparation. The car - designed and constructed by the students - was heavy and un-aerodynamic, but it was too late to change any of that. But when that event was over - I think that we came about 70th, way behind the winner who set a new world distance record for a human powered vehicle - I started to think about next year's car. Unfortunately I was transferred to another school before that car was finished, but it certainly had me thinking.
With these race cars, the obvious isn't always the case. In this year's event I noticed one car with a full carbon fibre aero canopy. But the car was well down in the field, apparently uncompetitive. I saw another school car with a flag on top - great for waving the school banner, but pity the poor bastards who had to drag a flapping aero-brake around for 24 hours.... Generally, the cars looked over-strong - triangulated space frames, when perhaps a simple backbone chassis would do. The aerodynamics of some vehicles appeared to have more to do with whim than science - but others looked absolutely full-on in aero design, NACA driver ventilation intake ducts at the front and outlet ducts carefully positioned in areas of low pressure.
In the area of drive systems, some vehicles had chains which must have stretched to three or four metres in length, each link dragging away through friction a little bit of the pedaller's power. Others adopted a 'mid-engined' front wheel drive configuration, giving also the low polar moment of inertia necessary to dart in and out of the slower competitors. And why was that needed? Cos some of the cars were damn fast. I'd suggest that the ratio of the faster cars to the slower cars rose as high as 4:1 - some looked like they were doing 40 or even 50 km/h while some of the heavy, slow cars being pedalled by primary school children were probably closer to a quick walking pace.
As dusk fell, that speed discrepancy made for some ultra-exciting moments. The cars - especially the well-engineered cars - were quiet enough that you could clearly hear from trackside the driver's curses as a fast car was baulked by a slower one. While all cars had rear vision mirrors, not all of the drivers were very well acquainted with race car driving... something pretty much expected when the youngest drivers were probably about 12 years old. But the fast guys and girls - in their early twenties and probably professional cyclists - sure as hell weren't hanging around....
At one part of the street circuit a deep spoon drain stretched across the track, just beyond the apex to a corner. It was fascinating to watch the behaviour of the cars across this obstruction. None of the cars featured a suspension system as such (and rightly so - it'd be a major weight penalty) so the extreme movement had to be absorbed by tyre and chassis flex.
Some cars bottomed badly every time (remember, the lower the car, the better will be its aero drag) while one car was up on two wheels through most of the corner - including over the spoon drain...
In the pit area a PC monitor kept the placings of all in the field, each car carrying a transponder to allow it to be tracked. The teams had full headquarters set up in the pits, with accommodation, mains power generators, catering caravans - the lot. But not quite what you would normally expect to find in the pits of race meeting was the well patronised children's playground.... In short, watching the race was a quite fascinating experience. I've no doubt that team managers were employing tactics, and I've no doubt that the nerve and determination of some drivers broke over those 24 hours. Certainly, even in the first five or six hours, some cars failed, the engineering not up to the durability demands.
If you can get involved in this type of racing - especially at the design and construction stage of the vehicle - I suggest that you do. Almost everything that we love about making a car go harder, corner harder, brake and make the most of its available power can be found in this form of racing. It's just that you gotta be a lot smarter, because you can't simply bung in a bigger engine......
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