Staying mainly on the plain
In one of our recent Grassroots articles, we outlined the revival of interest in 500cc classes old and new in hill-climbing; my interest was aroused by some of the new machinery being built, and especially by the proposal to take some of these lightweight cars away from the hills and onto the track. Having seen the amount of interest generated when one of the new cars was displayed at the Racing Car Show, I have been trying one on the track.
There are two people building new 500cc cars for sale currently: John Corbyn has built a dozen Jedi cars so far, which have been a major part of the Phoenix 500 Challenge run by the 500cc Owners Association. This, however, has concentrated on hill-climbs and sprints, whereas the proposed Formula 500S would stay mainly on the plain.
Behind the circuit racing proposal is Andy Murdoch, who plans the one-make series for next year relying on what he describes as “a proper racing car for just £6000” — the Hi-Tech 500. The car’s designer is David Peers, whose engineering career includes working on productionising the Loran twincam engine at Norton Villiers, and designing the Johnny Walker Formula Four car of 1965 before Formula Ford swamped that series. He originally envisaged it as a kit which home-builders could complete to their own specification for hill-climbing, and it will continue to be available in that form, but Murdoch is convinced that a fixed specification and a regular series will offer good close racing for a fraction of the cost of Formula Ford, in something more elegant than a Formula First.
The simple chassis consists of a long box of square steel tubing clad in aluminium, the all-wishbone suspension attaching to the longerons which run front to rear. Four motorcycle coil-over shocks hold the 400 lb machine off the ground, and it runs on 10in x 6in alloy rims with Dunlop slicks or treaded wets. A miniature rack and pinion deals with the steering. Mini hubs in special cast uprights carry Minifin drums behind and tiny Cooper-sized discs with lightweight AP bike calipers in front, and the driveshafts also originate with the Mini. Light weight and economy have been in Peers’ mind from the start.
Powering the cars in what will be known as Formula 500S is a single-cylinder water-cooled two-stroke unit delivered in standard 63 bhp spec from Austrian manufacturer KTM. More usually found in competition motorbikes, and in karts in 250cc form, the installed package gives a power-to-weight ratio of an impressive 245 bhp/ton, allowing for a 10-14-stone driver. The unit is rubbermounted complete with multiplate clutch and five-speed gearbox, driving a duplex chain to a sprocket-driven Mini differential in a specially-machined aluminium housing. Ratio changes are simple, and cheap: the diff moves back or forward to keep chain tension constant, and a new sprocket costs around £5. No limited-slip differential is fitted.
This simple but nicely made structure is clad in an attractive GRP body incorporating two slim side-pods, one housing the small radiator at a shallow angle, the other a small battery for the fuel pump. Three gallons of fuel is stored behind the seat. Adjustable canard fins project from the nose, and a rear wing sits on vertical end-plates.
In short, it is a fully-adjustable miniature racing car, which Murdoch hopes will attract people from two fields. It seems a logical move from karts, offering experience of chassis and wing tuning for those used to suspensionless karting, and it may seem an attractive alternative to the other “starter” formulae for those who want enjoyment but have no plans to fight through FF1600 as a career.
My outing was at the Three Sisters kart circuit near Wigan, where we had the track to ourselves. That was not the original plan, for David Peers had brought his own hill-climb car, 500cc class-winner first time out in the RAC series this year. At Three Sisters it was running for the first time on methanol, but it expired rapidly with a holed piston. His car is air-cooled, and the idea of methanol was as much as anything to reduce the head temperature, but in the event he had to re-install an old faithful petrol unit for Shelsley Walsh the following day. Surprisingly, the air-cooled unit is no lighter than the water-cooled version at around 63 lb, and would never cope with ten laps of a circuit, though its simplicity makes it attractive for the hills.
Prior to my trial, the car (a development chassis being run by Murdoch’s 2-Spec racing concern) had run only a few shakedown laps, so first out was the car’s intended driver this year, Derek Rogers. Rogers was British 250cc kart Champion in 1988, and is leading the series as far this year, but plans to squeeze the 500 car in as well, with Andy Murdoch deputising for one or two events.Having tried several final -drive ratios, Rogers pulled in and vacated the cockpit for me.
Because of the simple box structure the car has cockpit space any Formula Three or even Formula One pilot would envy. Although the car is small, the flat sides make wriggling down into it simple, and there is more room around the tiny pedals than in my TVR. Not only that, but those pedals are behind the front axle line as RAC rules demand, yet it was a stretch for my 5ft 10in frame to find them.
Once buckled in to the six-point harness and settled on the long thinly-padded cushion, though, it all felt very natural, with one major exception — contrary to single-seater practice, the gearchange is on the left, because the control arm on the bike gearbox is on that side and it makes for a very simple linkage. A little Mountney wheel allows the plain round electronic rev-counter and a small water temperature gauge to show through its spokes, and there are only two other controls, a push-pull ignition switch and a little choke lever.
Because of its motorcycle provenance, the gearbox has a positive-stop action — that is to say there is no gate, the lever simply being clicked back repeatedly for successive upward changes, and forward for going down. From neutral, first is forward, and the other four are back. It is the same system as used on the Triking, the Guzzi-engined Morgan three-wheeler lookalike we tested some years ago, and I recall that as working very well indeed.
So far the 500cc car has no starter-motor, though Peers is currently working on shrinking a ring-gear onto the tiny flywheel. Meanwhile the starting technique was shouted through my helmet padding by two pushers: “Let it roll in neutral, foot off the clutch, then click it straight back into second. Once it fires, neutral, first and away”.
As soon as I tapped the lever back the engine fired, and the machine rolled out onto the narrow circuit. On this damp day I was running on treaded tyres and trying to identify slippery patches of oil or rubber — with neither suspension nor differential, karts leave a lot of Dunlop’s best behind. Yet I already felt confident in the little car’s chassis, and it was simple to click through the closely-spaced gears, starting with a modest 7000 rpm limit and quickly working up to 9000, leaving 500 in hand for mistakes.
This proved a good idea, since the first problem was not changing gear, but remembering which ratio I was in, lose track and it is hard to get back in the groove. Coming down I more than once changed deftly into neutral for the hairpin — though without letting the needle stray into the forbidden region. In fact, Peers decided later, the car was still geared a bit high for this track, giving me an excuse.
However, a few laps of the sinuous track gave me a feel for the correct ratios, and as the half-litre lump buzzed behind my head I began to use the full width of the track. Once or twice a bootful of second and a patch of oil conspired to push the rear out of line, but it was easy to catch and stabilise.
Considering how little setting up it had had, the car felt good, stable and grippy on this abrasive surface with no evidence of pitching. As the speeds built up it began to want to understeer in the tight bends, and when I eventually started to reach fifth gear regularly on the main straight the odd bump would unsettle it for a moment. But such tuning will be easily dealt with in another test session. Adjustments are very easy — with a man at each corner, the whole car can be picked up and trestles slid under it.
Though geared to a maximum of about 108 mph on this twisty track, Peers estimates that some 125 mph or more should be possible at Donington, the first race appearance of the cars, which will have taken place when this issue of Motor Sport appears. Further races at Pembrey (July 2 and August 6) and Lydden (August 13 and October 1) should put the idea to the public, but for the moment Andy Murdoch is faced with a chicken-and-egg situation. He cannot sell cars without running races, but neither can he run races without selling cars, unless a series sponsor is found. Currently Murdoch’s small team has some help from Lynton Trailers, which has provided a neat box trailer to swallow the little car and its equipment, and there is a proposal to offer a complete package of car, tyres and special trailer to customers.
Meanwhile the price of £6000 plus VAT brings the car complete with engine, gearbox and one set of slick-shod wheels. To that must be added belts, mirrors, extinguisher system, wet tyres and a steering wheel (a very personal choice for most people).
Several cars are now sold, but for this introductory year, while grids are small, the BARC plans to allow the 500s to run with certain Formula Ford classes. Since the weight of an FF car is well over twice that of a Hi-Tech 500, but with less than double the horsepower, a face-to-face match should be good to watch, especially as the smaller car will use slick tyres. The results should offer useful development feedback to Peers, and a vital shop-window for F500S if this newest of low-cost formulae is to make an impact. GC