Philosophy

Through his Prototype Car Design (PCD) concern, Martin Ogilvie began this lightweight single seater project about five years go, since when the design has undergone a few metamorphoses. Then I met Rob Barksfeild at the Autosport International Show last year' explains Oilvie, 'and I told him I was designing a carbon fibre car. He was interested in graduating to (driving) a carbon car so we got talking. I thought it was a lot of money to do the project just for myself which is why it toddled along as a spare-time doodle until I met Rob and it all turned good.' Ogilvie had previously designed a lightweight Lotus 7-type car for himself, and subsequently penned the Westfield FW400 carbon chassis road and track car. But for a lightweight racecar the motorcycle engine format fitted perfectly. "I looked at the motorcycle engined-cars and decided that it didn't look as though people had tackled them in what I considered to be the correct way. They'd simply taken a racing car and put a motorcycle engine in it." He added: "Another interesting thing in doing a very light vehicle is deciding what sort of parts are appropriate. I set a target of 200kg, so you've got to say "what's actually required of this bit and what do you actually need for wheels, or a steeering rack." You can also say "it's only going to do x number of miles so we'll do a hollow aluminium rack instead of a steel one." And why take wheels from a 450kg Formula 3 car? You've got to do our own, just bite the bullet and do it."

"So that's where I started from. I worked out what all the weights had to be and kept checking as I went along, making sure I was still down to the target. This was meant to be 200kg with the oil-cooled engine variant, which would be a bit lighter with no radiators, and it came out at 208kg with the water-cooled engine." Ogilvie did all the design work and made the patterns for the composite components himself, everything else was sub-contracted. Meanwhile, Rob Barksfield was coordinating the engine weight-reduction and performance development work at Hampshire-based Debben Performance. This work was based on successfully running a Debben-prepared Suzuki GSX-R 1100cc engine previously in a Hi Teck single seater.

Design and Build

Martin Ogilvie's ability to ask fundamental questions and avoid conventional weighty solutions is in evidence thoughout the S1100. But an inevitable and important question people have already asked, because of its low weight, is whether or not it will be safe. Ogilvie is reassuring on the this point. "The interesting thing is that the rub is of sturdier construction than early composite-construction Formula 1 cars. Of course F1 cars have come a long way since, but the S1100 is a sort of halfway house." A carbon/honeycomb nose box provides frontal impact absorption and was chosen after Ogilvie expressed concern abouth the 'bits of bent aluminium stuck on the front' of some older hillclimb cars. The raised nose allows the front lower wishbone pick-ups to be placed under chasis. "I'm paranoid about having the rear leg of the lower wishbone going into the driver's legs. I put them underneath the chassis so, in the case of a shunt, they shear off underneath and the driver stays intact."

The carbon-honeycomb chassis construction (with aluminium hard ponts) reflects Ogilvie's thoughtful approach as he has minimisied the number of internal bulkheads. The front of the chassis constitutes the front bulkhead and the dash bulkhead provides the pick-up points for the rear legs of the front wishbones. There isalso a small 'mini-bulkhead' under the rear roll hoop stay, and a rear bulkhead right at the back of the chassis. The moncoque is made in upper and lower halves, each half having been done in a one-shot cure in order to preclude the need for extra film adhesive layers. Intriguingly the chassis extends over the top of the engine. Ogilvie says, "I don't know whether it's unique. But the regulations call up quite a study roll hoop and I didn't want a lot of weight high up. So I thought I'd make the roll hoop as small as I reasonably could and take the carbon to it. Then, if the carbon is up that high you might just as well pop it over the top of the relatively low engine and keep the whole frontal area down (by not adding side stuctures)." The obvious downside of this is that if a spark plug failed it would require engine removal to fix it. The counter-arguement, however, is that the type of plugs used rarely fail, and that most other 'top-end' failures would require raceshop rather than paddock repairs. In any case, engine removal is not really very long job.

Suspension

Asymmetric, convergent double wishbones and pushrods are used all round. A monoshock spring damper unit is used at the front, with small coil spirngs to react against roll. A separate Penske damper controls the roll springs independently of the damper controlling the mains spring's bump and pitch movements. The non-adjustable dampers are actually re-valved Formula Vee untis. The rear suspension uses twin coil-over damper unts, but there is no rear anti-roll mechanism. Tiny rod-end (1/4 x 5/16in) and spherical (1/4in) bearings have been used throughout the 'Saxon' and pick-ups are small machined steel brackets bolted at hard ponts to the chassis, or outboard to the fabricated steel uprights. Ogilvie's approach to suspension geometry is regreshingly uncomplicated: "I've basically taken fairly standard suspension geometry and allowed more movement, especially in roll. With a car that's very narrow the suspension pick ups are almost of necessity much further in, which means you can carry long wishbones, and I wasn't very keen on having outboard strucures for the top pick ups. So it is fairly basic and conventional. I think if you've got good roll centre control, correct camber change, correct weight distribution and good roll centre heights then it will handle anywhere.

Aerodynamics

The S1100 clearly has a very small frontal area, so drag will be similarly modest. The wing set utilises the same profile front and rear, although the front wing chord is extended as a single element device whilst the rear wing is two-element. Both have 1400mm spans.

"We've started off with a fairly basic package but there is a further aerodynamic package coming at a later date. Because we've got no sidepods, and it's a narrow car, we've got a lot of scope along the side and at the back of the car to fit what we like. What you want is to produce downforce with the right distribution. If you start having sidepod diffusers you have to have them quite high for them not to be too sensitive to ride height. Ground effect aerodynamics (and I was at Lotus when it all started off) depend on constant ride height, And you don't want an aerodymanic package wich is sensitive to the great variations that you encounter on a hillclimb."

Engine and transmission

The Suzuki GSX-R 1100cc engine is a popular racing option, not least because of the availability of donor engines, tuning parts and relevant tuning expertise. As Ogilvie explained the car was designed around the oil-cooled version with minimum weight in mind. Howver, he was persuaded that the performance potential of the water-cooled variant made that a better route, despite the weight penalty. An all alloy unit, this partuclar engine has a bore of 75.9mm by stoke 60.0mm, giving a swept volume of 1086cc and produces, in current specification, around 190bhp at the crankshaft at 10,000rpm.

The engine here is semi-stressed, and is connected to the chassis directly by its original mountings. At the front of the engine block two lugs bolt to a triangular section carbon/honeycomb structure which forms an extension to the rear of the car's monocoque. At the rear, four lugs on the transmission casing connect to the bulkhead. The machined-from-solid alloy sump connects to the rear bulkhead and to the base of the triangular carbon moulding ahead of the engine.

Ray Debben of Debben Performance descibed the process of tuning the engine: "It's basically about blueprinting and careful parts selction. Weight has been taken out of the major reciprocating masses but we've also had the luxury of doing about 50 dyno development runs. That subsequently allowed us to try all manner of ideas on carburettors, cam timing, ignition curves and so forth. With the cylinder head the trick seems to be to do surprisingly little work. With development we've found what NOT to do, and it's about removing little bits of

Martin Ogilvie

After graduating with a mechanical engineering degree from Birmingham University, England, Martin Ogilvie's first job was at Girling designing racing brakes for such teams as Brabham, Tyrell and Lotus. Then he moved to Lotus and stayed there for 13 years, starting on the Lotus 72 and finishing with the 100, being chief designer from the type 81 onwards. He left Team Lotus in 1990 and spent 18 months as chief designer (advance composites) at Lotus Engineering prior to joining Racing Technology Norfolk (RTN), which was then TOMS, where he designed a Formula 3 car and 'did a bit of Touring Car work'. He then did an abortive F3 car for Tedy Pilette, an outboard suspension car with the suspension inside the wheel. After that he returned to TOMS to do the GT1 Elise for the FIA and Le Mans series. After a couple of years he went back to RTN and then started work with Prodrive 18 months ago to help on the Mondeo Touring Car. Now he's working on a GT project with them.