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LAURENCE EVELYN WOOD POMEROY, “Pom,” for short, was an English motoring journalist who wrote one of the great books of automotive technicalities, The Grand Prix Car, published in two volumes, 1954.
As an example, The Motor, December 30, 1942, published Pom’s analysis of “The Type 35 Supercharged Bugatti,” No. 15 of the magazine’s “Milestones of Speed” series. The article is reprinted in Bugatti Type 10 to Type 251, a Brooklands Portfolio, compiled by R. M. Clarke, 2010.
Pom described the supercharged Type 35’s prowess: “In the latter form, supercharged, the engine has had successes in every country of the world where motor racing is carried on, and was employed right up to the outbreak of war.”
Three-Valve Heads. Like other high-performance designs, the Type 35 had three valves per cylinder, two inlet and one exhaust, actuated by a single overhead camshaft. These valves, Pom noted, “show clearly Bugatti’s typical interest in exhaust scavenging. Whereas most racing engines have larger inlet than exhaust areas, Bugatti reverses this, the figures being 1.34 and 2.70 sq. ins. per cylinder.”
Less Than Adequate Head Cooling. Pom’s analysis wasn’t short of criticism: “Partially as a consequence of the vertical valve stems, partly because of the valve area, the cooling of the head is, to say the least, indifferent.”
“The cross-section drawing shows how thin are the water spaces around the bore,” Pom continued. “Further, although the valve stems themselves are long, the valve guides are short and the proportion of their length which is in contact with the water is shorter still.”
A Unique Crank Design. The Type 35’s cylinders are cast in two blocks of four. “Both the firing order and the layout of the crankshaft are unique,” Pom wrote. The firing order “goes 1, 5, 2, 6, 3, 7, 4, 8, i..e., taking each bank of cylinders separately the firing sequence is 1, 2, 3, 4 on the front bank and 5, 6, 7, 8 on the back bank.”
This firing order is derived from the Type 35’s built-up, not one-piece, crankshaft; the back being identical to the front but moved through 90 degrees. Pom observed, “In this layout, the engine is well balanced except for a severe couple between the front and back halves of the shaft, which imposes severe loads on the centre bearing.”
He certainly didn’t talk down to his readers.
”Sparking Plug” Location. “As can be seen from the drawing,” Pom wrote, “the sparking plugs are heavily masked, the slot being rectangular. The location of the plugs on the inlet side is one more evidence of Bugatti’s talent for setting theory at naught, as the latter has always dictated a policy of firing the charge from the hot side of the head to a cool area and not as in this engine, vice versa.”
Pom’s Summary. “Taken as a whole, it will be seen that the design of these engines is entirely characteristic of Ettore Bugatti, being unconventional in nearly every aspect, demanding the utmost in skilled workmanship and fitting, and yet, at the same time, reflecting a severe almost brutally practical outlook…”
Thanks, Pom, for your erudition. ds
© Dennis Simanaitis, SimanaitisSays.com, 2019