The Belsize Bradshaw
Having referred recently in this recall of rare makes to two cars with radial engines, it seems time to think about a light-car which had an unusual cooling system. The Belsize Bradshaw was the idea of that well-known innovator, Granville Bradshaw. He had been the designer responsible for the ABC Dragonfly aero-engine of WWI, which became notorious for being underpowered, overweight, subject to horrendous vibration and which SD Heron called “probably the worst example of air-cooling ever used on a production aircraft engine.” This 9-cylinder radial engine had been ordered in vast numbers and had to be quickly replaced by the excellent war-time Bentley BR2 rotary engine, etc.
After the war Granville Bradshaw did make more successful engines for light aeroplanes and he became quite renowned for his advanced ABC motor-cycle with ohv horizontally-opposed twin-cylinder engine and sprung back wheel, and his equally well-known ABC air-cooled light car. Whether it was the reprimand which the ABC Dragonfly aero-engine had received which turned this flamboyant extrovert to thoughts of using oil as a coolant for his next car engine I do not know. But that is what he did. Oil disperses heat in an engine as well as acting as a lubricant of moving parts, so why not, reasoned Bradshaw, use it to cool the cylinders, thereby dispensing with water and obtaining a quieter engine than most of the current air-cooled units?
At that time, in the immediate post-Armistice period, many first class car manufacturers were getting satisfactory results from small air-cooled engines — GN, Armstrong Siddeley with the Stoneleigh, Rover in particular with its popular Rover Eight, etc, apart from many other concerns which were striving to sell such simple cars. Nevertheless, and in spite of the wide acceptance of his ABC motorcycles and cars and his revival of the 125cc Scootamota, Granville Bradshaw pressed ahead with oil-cooling. He told how trouble had been experienced with the war-time Dragonfly aero-engine because the blast of air over the cylinders at 150 mph caused a temperature difference of some 200 deg C between front and back surfaces, which he said he reduced to some 80 deg C by copperplating the cooling fins, to a depth of nearly 1/16th in. (He did not refer to other shortcomings with this engine; I assume the 150 mph was an exaggerated reference to the 125 mph Dragonfly-Sopwith Snipe). During these experiments Bradshaw found that 25% to 30% of the heat from the cylinders and piston crowns was dissipated by the oil and radiated by the crankcase.
Granville Bradshaw had had noise problems with his ABC car engine, especially in its earlier form, from the oh-valve gear, but also from the use of machined-steel cooling-fins, stroking of which with a finger nail produced a musical note! But when he came to design the P & M Panther motorcycle engine he gave it cast-iron cooling-fins, and with its ohv-valve-gear totally enclosed in a well-lubricated casing, he had a reasonably quiet engine, which he thought was the first air-cooled engine to have such valve-gear enclosure (Comments, please, from Motorcycle Sport readers). However, Bradshaw decided that cast-fins would never cool as well as thinner steel fins. So how to get an effectively-cooled, quiet-running engine without resort to airflow or water-jacketing? The inventor asserted that water was one of the best conductors of sound, so that this offered no solution, sound travelling four times as quickly through water as through air, to quote GB. Thus, when the Belsize Company of Manchester asked him to produce for them a small car for the post-war motoring expansion, he chose to design an oil-cooled vee-twin power-unit. Apparently he first built a 350cc oil-cooled motorcycle engine which gained racing successes. In later times Bradshaw drained the water from a 40/50hp Rolls-Royce and from a Ford V8 and reported that they ran more quietly than when there was coolant within their cylinders! He also filled his water-cooled car’s radiator with oil to see what happened — fortunately the cost of such an experiment should debar our readers from emulating it.
Belsize Motors Ltd of Manchester had made some advanced cars before the war and its cars, commercial vehicles and taxis, the last-named well-known on the streets of London were generally well received. In 1920 its 2.8-litre Belsize Fifteen was all set to continue the firm’s reputation but the need to have a light-car to compete in this field caused it to turn to Granville Bradshaw, whose oil-cooled Belsize-Bradshaw was announced in 1921. Whereas the ABC car had an ohv engine of flat-twin formation, for the Belsize a 90 deg vee-twin was chosen, of 85 x 121mm (1392cc), giving a tax rating of 9hp. It seems that at one time oh-valves were intended, but in the end a side-valve engine was used, claimed to give 33 bhp on the even-for-those-days low cr of 4:1.
What Granville did was to enclose the cylinders for most of their length in a box-ike crankcase filled with oil, some reports saying 1-1/2-gallons of it, others two gallons. This was flung up both sides of the cylinder-bores and to the piston interiors and into the valve pockets, to provide the cooling required. In addition, the flywheel, which was at the front of the engine, incorporated a centrifugal fan which blew air over the ribbed tops of the cylinders protruding from the box-crankcase, and under the sump. Aluminium cylinder heads were used, and to obviate the cooling oil being sucked into the combustion chambers, the inlet-valve springs were shrouded. The central sparking plugs screwed into brass bosses and the exhaust pipes emerged at the front, allowing the carburettor to be placed behind the cylinders. There was pressure lubrication, the 1-1/2 in diameter crankshaft ran on white-metal bearings and had bronze balance weights, and the camshaft was driven by silent chain. Originally a magneto was fitted but some production engines had coil ignition. Granville Bradshaw said that the fan sent air over the exposed part of the cylinders at 50 to 80 mph and that oil was fed to the bearings at a rate of 1-1/2-gallons a minute. Engine oil was also fed to the gearbox; long before Issigonis and the Mini!
This unique engine was mounted in a simple chassis, driving via a 19-plate oil-immersed clutch to a four-speed and reverse gearbox with forward ratios of 4-1/2, 7 and 15 to 1. Final drive was by a prop-shaft supported on a ball-bearing in the main cross-member and suspension was by 1/4-elliptic springs. The brakes incorporated a transmission brake, unusual on a light car. The Michelin disc wheels were shod with 26 x 3 tyres. The wheelbase was 8 ft 3 in. The steering gear was worm-and-nut. Oil-less bushes and easily-detachable main components were intended to appeal to the new class of owner-driver motorist, it was claimed that it was impossible for the oil to leak, and that 40 mpg and 1000 mpg of oil would be achieved. Conscientious owners who drained the sump oil regularly were assured that the quantity was not much more than in a normal car, although two gallons might not be so regarded?
That was the small car which GB sold to the long-established Belsize Motor Co. It was to sell for £275 as a two-seater, with a rear locker in lieu of a dickey-seat, but a starter was £25 extra and an ingenious coupé-top (a hard-top by later definition) cost another £25. The inevitable sports model entered into the repertoire from the start; it was to have aluminium instead of cast-iron pistons, a higher compression ratio, a special camshaft and no driver’s door, which must have stiffened-up the body and saved, I suppose, an infinitesimal amount of weight. For this version 60 mph was forecast, or ten mph more than was expected from the standard model, and the price was the same. To disguise the fact that this was not a water-cooled car an impressive dummy radiator was fitted and the colours were a black chassis with dark blue bodywork. An unusual feature was that the rh brake lever was some six inches ahead of the rh gear lever, which nestled in a cutaway in the seat cushion.
True to prediction, a chassis and both the completed cars were at the 1921 London Motor Show. Later that year the first roadtest report was published, using a car lent to The Light Car & Cyclecar by Gordon Watney (one time famous Mercedes modifiers) of Bond Street but for too short a spell, the excuse being that it was in great demand as a demonstrator. Engine size was now quoted as 1289cc. The tester devised a drastic means of seeing whether the oil-cooling system was effective. He left the car stationary with the engine running for an hour! It survived. He also took the Belsize-Bradshaw up London’s steeper hills, such as 1 in 3 and 1 in 4 ascents onto Hampstead Heath and round the Netherall Gardens 1 in 8 hairpin, which was taken in second gear — this used to be a favourite test hill in those days. The special clutch-stop made gearchanging almost fool-proof and every other aspect of the new car was accorded praise, except for the rather inaccessible gear-lever.
Publicity was obtained when the actress Winnie Collins took driving lessons on a Belsize-Bradshaw. But no doubt the sceptics waited to see how the new small car would perform in the tougher trials. They did not have long to wait, because although the conservative Belsize Company eschewed the 1922 Scottish Six Day Light Car trials and the 1924 RAC Welsh Six Day Small Car Trials, G Brooks and N Keep finished the severe Land’s End Trial and Brooks and J Nuttal took gold medals in the London-Edinburgh. For 1923 an 8 ft 11 in wheelbase four-seater model was available. Changes included cast-iron cylinder heads, deeper finning, an oil spray to the valve springs, enlargement of the flywheel-fan, and a hot-air feed to the Zenith carburettor, while £50 had been lopped off the price. Later it was down to a mere £210 for the four-seater.
It all sounded very satisfactory — how often have you heard that before? — and even Lea-Francis were encouraged to list a 690cc Bradshaw oil-cooled flat-twin. As for Belsize, there was further evidence that “oil-boilers” stood up well to MCC trials, yet by 1923 Belsize was not at Olympia and Lt Col GP Mills, DSO, was called in to oversee car production. A new push-rod ohv 10/20hp model, water-cooled, a stab at an in-line, oil-cooled model, even they say, a 2-1/2-litre straight-eight, failed to save Belsize although the soldier had them back at the Show in 1924. In 1925 a Receiver walked into the Clayton factory, ending car manufacture which dated back to 1897. However, I wonder whether Keith Marvin wasn’t a little harsh in the Georgano Encyclopedia when he said the Belsize-Bradshaw had an unreliable and frail engine? I met a bandsman just before the war who was happy to carry his big drum about on the back of his Belsize-Bradshaw (although I think he would have parted with it for a few pounds — the car, not the drum), and one of these oil-cooled cars has survived in VSCC Light Car Section ownership. — WB
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