SR1 Speedster

Back in 1990, a former work colleague and friend, Fred Onrust, and I teamed up to design and build a light weight, road legal sports car suitable for weekend club racing. Our skill sets were complementary and our recipe was to create a cross between something like an ‘aerodynamic’ version of a Lotus Seven and a modern interpretation of an AC Cobra. Dubbed the SR1 Speedster, the initial idea was to build a prototype and then put the car into low volume production as a 'turn-key' package.

The prototype used a Nissan Skyline drive-train (FJ20 2.0 litre twin-cam motor, gearbox and diff/suspension assembly), but the chassis was designed to take up to various small-block V8 combinations. The motor was set well back in the chassis to achieve the desired front to rear weight split, ending up with the front pulleys of the motor 300mm behind the centre-line of the front wheels and a drive shaft measuring only 200mm between universal centres. Front suspension is inboard coil-over shock with cantilever top arms.

The base chassis was fabricated using a combination of light and heavy wall 25mm square tubing which was powder-coated, then skinned with aluminium ‘shear panels’ (epoxy bonded and riveted) to ultimately produce a very stiff monocoque unit.  The voids between the aluminium panels were filled with 'cut to fit' 25mm urethane foam sheet, to reduce any vibration or 'drumming' effect from the aluminium panels.

We spent a considerable amount of time (18 months) creating the body ‘plug’ and moulds to a high standard to ensure the final moulded fibre-glass body parts only required minimal hand finishing prior to painting.  This meant it was simply a matter of sanding off the mould joint seams and then a light sand all over.

The ‘after hours’ design and build process ended up being a seven year ‘labour of love’, with the car 95% complete in 1997. As with a lot of these types of projects, it was the challenge of the design and construction that gave us the sense of achievement and we decided not to proceed to low volume production. (That area of the New Zealand car scene had changed significantly during the build).  However, we still own the chassis jig and the full set of fibre-glass moulds.

Around 2001 we sold the car to a friend of Fred’s, but Fred remained involved with the project to see it through the LVVTA Certification process to road legal status. His involvement also included adding a turbo/intercooler set-up and changing the rear suspension from the original Skyline sub-frame, with semi-trailing arms, to independent top and bottom A-Arms. With the car weighing only 850kg and the motor now making around 300hp, performance and handling were well up there. By capturing data on a laptop, via a calibrated ‘accelerometer’ attached to the floor of the car, Fred was able to clock a 0 to 160kph (100mph) acceleration time of around 7.9 seconds. Good enough. . . job done!

Fred also made some cosmetic changes, blacking out the wheels and some of the body trim, to update the appearance. Other mods are in the wind, but considering the car was designed in 1990, we still don’t think it looks too dated. Below are some photos of the car in its current form, plus a very abbreviated overview of the construction process. . . Enjoy!