MG’s final and quickest Land Speed Record car, dubbed the Roaring Raindrop, combined other-worldly looks with a supercharged engine
By Keith Howard
When talk turns to the golden age of British Land Speed Record hegemony between the wars and on into the 1950s, images of Campbell’s Bluebirds, Eyston’s Thunderbolt and Cobb’s Railton Special inevitably spring to mind. But others ploughed the LSR furrow no less successfully, albeit at a less elevated level, and none more notably than MG. With a succession of EX record breakers, from the EX120 of 1930/31 to the EX181 of 1957/59, the Abingdon sports car maker promoted its products by setting numerous records in the lower strata of LSR endeavour.
EX181 was the last and most spectacular-looking, like a half-pint version of Reid Railton’s ‘flying saucer on wheels’ design for Cobb. Conceived by chief engineer Syd Enever and realised by Terry Mitchell, the MG was a great deal simpler than Cobb’s car: it had only one engine, it was rear-wheel not four-wheel drive, and it cooled its engine conventionally rather than by carrying a tank of iced water. But its basic layout – driver ahead of the engine to permit a radically streamlined shape – was very reminiscent of Railton’s design.
Although dubbed the Roaring Raindrop, EX181 was not simply the teardrop shape that is known to give minimum aerodynamic drag at subsonic air speeds. In side elevation it had the cross-section of an aerofoil, and a specific aerofoil at that: a wing section of Polish origin that Enever had identified as ideal for the task. By running it at a slight negative angle of incidence, the natural lift of the wing was eliminated to leave a car with close to neutral lift characteristics. At least, that is what would have been aimed for in the Armstrong Whitworth wind tunnel where the aerodynamic testing was done, using an eighth-scale model built by Harry Herring.
But as this tunnel will have had a fixed rather than a moving floor, some uncertainty must have remained about how stable the car would prove at high speed.
Apparently its drivers didn’t have any great concerns in this regard, otherwise Stirling Moss would not have been able to set his 1957 record (245.64mph for the flying kilometre, 245.11mph for the mile) in a short timescale between racing commitments, and Phil Hill would not have been happy at the tail being removed for his runs in 1959, which culminated in a best of 254.91mph for the kilometre and 254.53mph for the mile.
Just how efficient the EX181 was at cleaving the air is not clear. If we accept a frontal area said to be 10 per cent less than the EX179’s 11.8 sq ft then figures of 145bhp for 200mph and 240bhp for 245mph suggest a drag coefficient of about 0.24 – too high for a body form like this, which ought to be capable of 0.15-0.20. So these figures probably include transmission losses and/or rolling resistance.
A factor contributing to Hill’s higher speed in 1959 was the fitment of an engine bored out from 1489 to 1506cc, which MG deployed to exceed the 1500cc limit of class F and so place the car in class E (up to 2000cc), thereby increasing its tally of records rather than supplanting those it already held. Most obvious of the many differences between the road-going engine and its record-breaking cousin was that the latter sported a massive Shorrock supercharger, driven by spur gear from the front of an extended crankshaft, which sucked air and fuel mixture through a pair of 2.5in SU carburettors. Blown at 32psi the 1957 engine reportedly delivered some 290bhp at 7300rpm – 195bhp/litre – and 516lb ft of torque at 5600rpm, with the spare engine capable of a little more because of a slightly higher compression ratio.
Developed by Eddie Maher, the supercharged twin-cam four-pot had a prodigious appetite for the equal parts petrol/benzol/methanol that was its diet, as Basil Wales – who worked on the engine as an apprentice at the Morris Engines Experimental Department in Coventry – recalls. “We had to put in a special fuel supply that we could replicate in the car. Almost by chance this ended up as a compressed air bottle, with a reducing valve, to pressurise the fuel tank. We put some needles in the twin SUs, started up the engine and it promptly backfired. We lifted the dashpot and it ran a bit better, showing that it needed a richer mixture. So we took the needles out of the carburettors, put them in a lathe, filed them down and tried again. We had to go through this process quite a few times before we could get the engine running properly. Then
we got some pretty good results from it early on.”
Cooling of the engine was achieved using twin curved radiators from the Avro Shackleton marine reconnaissance aircraft. Twin inlets at the aerodynamic stagnation point in the nose pushed air through ducts on either side of the driver to the engine compartment behind, where it provided flow to the radiators (which had faired-in outlet ducts on either side of the car), inlet air to the carbs and cooling air to the engine and transmission. Cooling for the single Girling rear disc brake was supplied by a small rear-hinged flap on the central spine of the car abaft the cockpit (visible on the cross-section above), which popped up when the brake pedal was pressed and also acted as an air brake.
Suspension was MGA-derived at the front – parallel wishbones, coil springs and lever arm hydraulic dampers – while rear suspension was by de Dion axle with quarter-elliptic leaf springs and lever dampers. Tyres were critical, as they always are on a Land Speed Record car, the more so as Enever wished to house them entirely within the body, without the wheel well bulges that interrupted the pure lines of Cobb’s car. As usual, Dunlop rose to the challenge, developing some unusually small 24in OD tyres specifically for the EX181, which could be inflated to high pressure – over 100psi (6.9bar) was reportedly permissible – to minimise rolling resistance and tread heating.
MG withdrew from LSR hunting after the successes of the EX181. Enever, who retired in 1971, was recently characterised by economist John Kay as the type of practical (rather than academic) engineer who contributed to the demise of the British motor industry. But the Roaring Raindrop was no small achievement to have on a CV.
Thanks to Basil Wales, Don Hayter and Jim Cox for sharing their recollections.