A brave toe in the water: the first ‘rotary’ car sold to the general public
Grand Design: NSU Wankel Spider A peek inside this revolutionary rotary ‘toe in the water’.
The development of the Wankel engine was a prolonged and complex saga. The impression left with the uninformed is of barely-understood technical issues, unsurprising failure and a comical name. The true story is one of huge international effort and investment in a promising new technology. The engine challenged materials science, machine tooling and corporate budgets, then came good just in time to be torpedoed by fuel crises and emissions regulation. The NSU Spider was an early chapter: the first ‘rotary’ car offered to the public. NSU was the German firm at which the technology was first developed. It was under pressure to present the fruits of its work, particularly from licensees such as Mazda, who were also nearly production ready and held back as NSU reserved the cachet of being first to the market.
Against this background, the Spider was unsurprisingly a work-in-progress at launch. Lacking a second rotor and the torque convertor that would arrive with the Ro80, it had to be driven in a very spirited manner to extract its performance and to avoid low-rpm roughness, early deterioration and failure. Brave customers weren’t compensated for their guinea pig role, either: the Spider cost twice as much as a Triumph Spitfire. Driven and maintained competantly by an engineer, however, the pretty and agile little sportster could give very good service.
Rotary principles
The two most familiar types of ‘rotary’ engine are unrelated. The engines of WWI-era aircraft were a form of radial reciprocating piston engine and rotary in the sense that the whole engine and propeller revolved around a stationary crankshaft. The principle that Felix Wankel conceived in 1934 also involved the body of the engine revolving, but it did so around one or more trochoidal rotors with no reciprocating components. With three spark plugs mounted inside the engine in the rotor, this was rejected by NSU on grounds of practicality.
Wankel engine
The tiny single-rotor engine forms part of a bulkier power unit with a broad sump, ancillaries and an oil heat exchanger. An eccentrically-rotating rounded triangular rotor creates three crescent-shaped chambers of changing volume. A four-stroke cycle is achieved, with combustion always occurring in the same quadrant. No valvegear is necessary, as induction and exhaust are managed by the exposure of ports. NSU opted for ports in the peanut-shaped chamber wall, rather than in the endplates as later employed by Mazda. Performance only arrived at 3000rpm and it was happiest above 6000rpm.
Fiddly hood
The soft-top is weatherproof and secure when up and slides neatly back under the rear deck when down, avoiding a pram-like look and making a cover unnecessary. Unfortunately, though, folding it is really a two-person job after freeing six fixings and, when up, it makes so much noise that conversation is all but impossible.
Lightweight body
The light unitary body is made of thin and easily-dented steel. Motor magazine reported noticeable panel resonance and body shake.
Warranty
Rolling out the untested little car internationally was, plainly, a mistake. NSU was determined to keep customers happy and replacement engines, at £550 apiece, were fitted without argument.
Oil and water
The hollow iron rotor is oil-cooled. Lubrication of the chamber walls is total loss with oil metered according to throttle opening, so consumption is not influenced by the condition of the engine. The oil remains very clean, and changing it and the filter at the recommended 9000-mile intervals seems almost overkill. The rotor casing is water-cooled, with a radiator positioned in the car’s nose.
Transmission
The close-ratio all-indirect all-synchromesh four-speed gearbox is light and precise. A low first gear just manages to enable a start from stationary on a one-in-three slope.
Brakes and steering
The 9in ATE-Dunlop front discs and 7.1in rear drums were described as ‘flawless’ by Small Car magazine. Direct and light but high-geared rack-and-pinion steering with 2.8 turns lock-to-lock gives a large turning circle, not able to be reduced because of significant wheelarch intrusion.
Fine handling
The compact engine weighs 125kg with all its ancillaries and front/rear weight distribution is about 40:60. Front unequal-length double wishbones with an anti-roll bar, rear semi-trailing wishbones and coil springs and telescopic dampers all-round give very tidy handling.
Modern electrics
The 12V system had a 240 watt Bosch alternator and eight fuses – a thorough specification in 1964.
Clever packaging
Despite its compact size and sports car format, the Spider has a wide, if rather shallow, boot at both ends. The rear drivetrain is so compact that a full width flat-floored compartment conceals it completely. A substantial load area behind the two seats amounts to a third boot – and the spare wheel can be moved from behind the seats to the front boot to accommodate large items.
Legacy
The Spider was the first Wankel-engined car to go on sale and the only single-rotor production car. It paved the way for the twin-rotor Ro80, launched in 1967.
Citroën followed a similar programme with its experimental single-rotor M35, followed by its Birotor. Mercedes-Benz developed probably the best multi-rotor engines, but they never went into production. Mazda launched the twin-rotor Cosmo in 1967 and went on to become the most prolific Wankel producer by far.
TECH SPECIFICATION 1967 NSU Wankel Spider
PRODUCTION 1964-1967
PRICE NEW £1391 (1965 UK)
KERB WEIGHT 699kg
DISPLACEMENT 498cc
MAX POWER 50BHP
MAX TORQUE 52LB FT
0-60 MPH 16.7sec
TOP SPEED 93mph
TOTAL BUILT 2375
MPG 28
Design Claus Luthe, Franco Scaglione, Walter Froede
