SOME NOTES by T. W. DOMAN (In an Interview). See Motorsport March 1936, Page 17 for full article
Anyone who was associated with the sports car of ten or twelve years ago must be amazed at the change which has taken place since then. Nowadays, the designer is faced with no easy task, being asked to produce a smooth running car with luxurious coachwork, and to still preserve the snappy get-away of the modified racer. In 1922 we still had many things to learn about obtaining high power output, and so had to obtain our performance from a high power-weight ratio, and every part of the Frazer-Nash chassis contributed to this result. The chassis frame was very light and free from complications, simply two steel side members of channel section with three cross-members. Quarter-elliptic springing all round saved weight, unsprung and total, and the front axle which was tubular still proved itself strong enough to resist the torque of front-wheel brakes.
Then we were fortunate in the engine which was a side-valve Anzani. Weighing only 166 lb., with a compression ratio of 5.8, it developed a maximum of 47 h.p. at 4,500 r.p.m. These little engines were extremely reliable and seemed capable of giving their output indefinitely.
Unfortunately, for continued full throttle work, the very compactness of the engine proved a disadvantage, as there was not sufficient water round the bores to allow continued cooling to prevent local overheating, and we had to look elsewhere in our search for further performance.
The engine we chose was the four cylinder Meadows, a compact and strongly-built unit with vertical overhead valves operated by push-rods. It weighed 275 lb. and therefore increased our total weight by 1 cwt.:, but to balance that, gave a full 50 h.p. with the standard compression of 6 to 1. The performance remained much as it had been with the Anzani, but we soon found we could raise the compression by the use of " higher " pistons. Continuing our experiments with the Meadows, we evolved a new type of cylinder head which had lobes or deflectors in the combustion chambers to improve the turbulence. This brought our power up to an even 60 h.p., with compression raised to 10 to 1.
As a result of racing experience, we developed special lightened con-rods, light rockers and valves and a balanced crankshaft, and these refinements, especially the con-rods, are desirable if you want to get the best out of the engine. Finally we succeeded in taking the compression up to 14 to 1, when we got 74 h.p., running on racing Ethyl. This power gave us a Brooklands lap speed of 103 m.p.h. on a car stripped of lamps and front wings. Supercharged, with ten pounds pressure, Commander Grogan's engine gave off 120 h.p. which resulted in a lap-speed of 113 m.p.h. Here again, after more than doubling the original horsepower, we had reached the limit to which the engine could be brought without drastic redesign. Instead, we branched out into a 6-cylinder car. The engine used was a Blackburne, a double-overhead camshaft job with a capacity of either 1,500 or 1,660 c.c. At 4,800 r.p.m., the larger engine gives 75 h.p., while the weight, which seems to increase almost in proportion to power output, is just 3 cwt.
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