“I can do that better” was the beginning of the sportscar project of Jurgen Stockmar. He already done a lot of research in the different car designs in the paddock. He found that something was missing, according to his theory.
Design a sportscar was easier than designing a formula car and he had a great interest in sportscar. And he loved the group 5 regulations. He had five goals: low aerodynamic drag, monocoque with high rigidity, optimal wheel suspension, good driver protection and simple structure.
He started by designing the right environment for the driver. He measured all his friends down to the centimetre: seat hight, arm and leg length, hip width, knee joint. So a seating box with maximum dimensions and the best pedal arrangement and steering wheel position was created. Then he started with making paper constructions of different models. He aimed for maximal rigidity and stable bulkheads in the front, the middle and behind the seat. He placed the fuel tanks in the sides of the self-supporting aluminium, made of aluminium sheet, riveted and glued.
The job up until now was too much for a one-man show. So in came a designer. That resulted in several successful aerodynamically favourable shaping’s of the outer skin. Then came the drafting machine. He realized there were concessions to be made to his ideas. And he had to start all over again sometimes. Stockmar was about to have the desired outer skin built by specialists in England, when he found an expert for the final attempt.
The idea was now definitive: a five-part body made of glass-fiber reinforced plastic, two door and all parts removable. He made first a gips model before constructing the real bodywork.
Then he optimized the kinematics of the wheel suspension. He used a computer program from Dr Ing Klaus Rompe and that costed two pounds of computer paper at that time. It resulted in a very conventional suspension. The front double wishbone suspension looked like those used by Chevron; the rear were inspired by March. He used coil springs and gas-filled Bilstein shock absorbers. He installed inboard ventilated brake discs at the front and the rear
Th final chassis parts had to be drawn in order to have them manufactured in a mechanical workshop.
And then, he ran out of money. And again, he found only one sponsor despite his advertising campaigns.
In came the money, but also requested tight schedule. Thanks to an experienced mechanic Gerd Hillen, who previously had worked for Ford and numerous trips to England for the supplies, the Rex SP1 was born. Despite the seemingly large dimensions of the cockpit, the car was really small. His length was only 4080 mm, width 1,80 m and the height of the cockpit only 93 cm.
Before loading the car on the transporter for the first practice runs, he found out that the Ford Engine did not fire up. Jumper cables then, but they got them wrongly polarized. And… that all before a TV camera crew.
Then the first two planned training sessions in England with Harald Ertl had to be cancelled. There was a strike in England and the registration documents were still missing. Then they moved all the stuff to the Hockenheim Ring. And there Stockmar became proud. His car was fast: in 3.6 seconds it reached 100 km/h and in 11.2 seconds it was at 200 km/h. Although the cheapest option, the water-cooled four-stroke, four cylinder Ford-DBG engine, originating from Swindon, England was good for 270 pK. A BMW engine would have been more expensive
The Rex car was driven by Helmut Bross, Harald Ertl, Freddy Kotulinsky and Derek Bell in 1975. Norbert Dombrowski raced it after that for the next 3 seasons. Eberhardt Enst used it in 1980; Bruno Heinzeller used the REX SP1 from 1981 until 1984.
