Shaft Driven Opposed-Four Motorcycles
One Built by Brough ... and a Few Others

The photograph above of this fascinating motorcycle and the cut-away line drawing of its engine are from Ronald H. Clark's excellent 1964 book, Brough Superior: the Rolls Royce of Motorcycles. (Note: "Brough" rhymes with "tough.") The cylinders in the engine are stacked over each other (see drawing above), unlike in the Honda GL1000, where they are placed fore and aft. Here are some passages about this machine from Clark's book:

like some previous examples,had four cylinders, but there all resemblance finishes for here we have the cylinders arranged after an "H" on its side or, if one prefers it, two horizontally opposed twins one above the other and geared together. Perfect balance was obtained by causing them to rotate in opposite directions but with each pair of pistons (when considered vertically) reciprocating together. George [Brough] called it a "flat vertical"—flat for balance, vertical for cooling.

As first designed, the four cylinders each were about 68x68 mm., 996 cc., with the camshafts gear-driven ... Much development work was done on this engine and as might be expected many modifications resulted, culminating in the second design ... and it was this engine that was used in the first "Dream" exhibited at Olympia in 1938.

[Ed. note: Inasmuch as the contemporaneous BMW R51, and the earlier R5 and R23, all had identical bore and stroke dimensions of 68mm., one just cannot help wondering if George Brough might not have used some BMW parts in the development of his 1938 Golden Dream engine! Or perhaps this dimension is something like the Golden Mean—so immutable that it was destined to become the dimension for the perfect 247cc cylinder.]

Final drive was by the propeller shaft ... and an underslung worm and wormwheel on the rear axle, and even the propeller shaft was enclosed in a tube [this didn't happen to BMWs until 1955 - ed.]!

Quite apart from its original features, this remarkable engine had one advantage over all the OHV twins so far produced—the valves and springs are now totally enclosed. It was the most original and outstanding attempt to break away from the ... conventionalism in motorcycles this country [i.e., England] had, up to 1938, ever witnessed.

... four or five were produced during the early part of 1939 and with the four-speed box was being erected [sic] for Olympia that year.

Then, in September, England was at war for the third time this century, and for the second time the productive capacity of the house of Brough applied to the war effort.

The Brough Superior Dream above is on display at the British National Motorcycle Museum. It was heavily damaged in a museum fire in 2003 that was started by a discarded cigarette. (We owe so much to smokers.)

Brough Superior Dream Engine. Four cylinders: Bore 71mm., Stroke 63mm. -996 c.c. - compression ratio 6.5 to 1. The cylinders are arranged doubly opposed transversely in the frame (one cylinder above the other on each side.) With this arrangement all the cylinders are equally cooled, and the Exhausts, which face forward, give an uninterrupted stream of air cooling them in a manner impossible to achieve with any other arrangement. The cylinders and heads are not shielded from the air by the front mudguard as with other machines. The cylinder block is aluminium carrying liners of special wear-resisting material, and each pair of cylinders (upper and lower) has its own crankshaft. They are coupled together with wide-faced gears, the teeth of which are ground. The crankshafts are each in two parts, the driving side member having the crankpin and driving side journal integral. The main bearings are bronze, and capable of great endurance. The crankshaft arrangement permits the use of bearings of generous proportions, and the connecting rods are of light alloy, operating direct upon the crankpin in accordance with the latest racing practice. There are two camshafts chain-driven to give silent operation, and the cams operate mushroom tappets and have a gradual take-up of tappet clearance to give quiet running. The whole of the valve gear is totally enclosed.

Frame. This is specially designed to accommodate this type of engine, being welded together instead of the usual practice of brazing lugs. This frame also has a fully sprung (plunger) rear wheel which is fitted as standard on other Brough Superior models.

Forks. The Brough Superior—formerly known as the Castle—type of fork is fitted as standard on this machine.

General. The remaining specification, such as bulbous-nosed tank and its capacity, saddle height, ground clearance and wheel base, etc., is practically identical to that of standard machines. The Dream could be supplied with 3- or 4-speed transmission, and the final drive is by silent, underslung worm. The rear wheel and all driving mechanism could be detached from the machine in two minutes.

Allan Johnson, whose photos are seen above, adds this postscipt:

In an interview in the early 1960s, George Brough put his decision to not to proceed with the Dream Four as follows, “I wanted to go on with the Dream after the war but it was so complex that it would have absorbed all our production facilities. Materials were controlled and one had to undertake to export most of one's production.” (These were the requirements of the Labour government of the 1945-1950 period — only firms that exported large amounts of their production could get quantities of special steels and other critical materials.)

“It was hard to decide against making motorcycles but I had to think of my men ... most of them had been with me for the whole of their working life and I just could not take the risk. The Brough Superior name lives on but it now stands for the highest quality in precision engineering.”

Click here for information on Brough Superiors other than the Golden Dream.

Brough, the BFG-Citroën. and the older Wooler had stacked cylinders on each side. Zundapps and the later Woolers were air cooled with cylinders fore and aft on each side. Honda's famous Gold Wing is liquid cooled, cylinders fore and aft.

Below, on the left is a 1975 Honda GL1000 and on the right is a 1933-1938 Zundapp K800 at the Barber Museum Birmingham, Alabama. The GL1000 and its larger four- and six-cylinder Gold Wing successors have become among the most successful touring motorcycles in the world.

John Wooler started building motorcycles in 1911 and was a designer with many brilliant ideas, but all his creations were unconventional. Rather than conform to the norms, he wanted to do things his way or not at all. After World War II he built a variety of 498cc four cylinder machines with opposing cylinders transversely mounted and shaft final drive. These beautiful OHV machines were built in very small numbers. Wooler died in 1956, putting an end to his exceptional creations.

Allan Johnson sent me the photo below, left, of a 1949 shaft-drive, four-cylinder British Wooler. Allan reports:

It was announced at the 1948 London (England) Motorcycle Show, and was the most unusual model ever produced by the Wooler firm — and they were specialists in odd motorcycles. The suspension of quadruple plungers, front and rear ... The exhaust into the frame tubes, the tyre inflator hidden in the footrest shaft, the seat suspension inside the frame tubes, the rocker pedal left side shift, the shaft drive and the single wrench tool kit (there were only 2 sizes of nut and bolt on the whole bike) were just a small part of the novelty of this bike. The engine was a flat four with cylinders above one another, was an OHV rocking beam type. The 50mm x 63.75 mm pistons were coupled to a beam by short rods and teh beam rocked by the little end of the master rod. The engine was 500cc; the whole bike was to weigh 230 lb. and to cost 200 pounds sterling. Apparently few were made and by 1953 a revised conventional flat four was offered with the same gearbox and a simplified suspension.

The BFG-Citroën (left) of 1982 was powered by a boxer, stacked four-cylinder 1,299cc Citroën automobile engine and shaft final drive. About 450 of them were built in 1981 and 1982. One-quarter of them were purchased by the French police. The motorcycle's acronym derives from its three designers, Louis Boccardo, Dominique Favario, and Thierry Grange. The motorcycle was designed in response to a 1978 contest initiated by the French Department of Industry.