A racing innovation

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Motor racing is intended to improve the breed of ordinary cars and give opportunities for experimentation. To this end there have been not only many variations of the four-stroke poppet-valve engine used in races but also sleeve-valve, rotary-valve, even rotary engines as in the current Norton motorcycles, and variants of the two-stroke engine. One interesting innovation was that tried in a Schmid racing car in that memorable 1924 French GP at Lyons, which Sunbeam were expected to win but, their magnetos changed on the eve of the race, they gave away to Alfa Romeo.

What Schmid used was a cuff-valve engine. It was an ingenious form of sleeve-valve power-unit and it seems surprising that it was not continued with, for production cars, getting rid as it did of the problems associated with the better-known forms of sans soupape. For what the engineer concerned did was to use short sleeve, or cuff, valves situated above the pistons, so that the interposition of long sleeves between cylinder walls and pistons was obviated. Such sleeves, until light steel ones were introduced, were heavy and their interaction between rising and falling pistons and semi-rotating sleeves had detrimental effects on lubrication, which they required in quantity, and which could result in gumming-up in such engines if they were laid up for a longish period.

The Schmid engine prepared for the 1924 French (and European) GP was a 2-litre 64.8 x 100 mm six-cylinder. Each cylinder had eight ports near the top, four inlet and four exhaust, the total area being almost equal to the cylinder circumference. Indeed, it was claimed that the ports had an opening of an eighth of the cylinder volume of 20 cu in. Each cuff valve consisted of a split ring nearly 2 in in depth, weighing 4 1/2 oz. These were made to uncover the ports as required by inverted steel T pieces working in guides in the detachable cylinder head, one per cylinder. To impart the reciprocating movement to the cuff valve, two eccentric shafts in an aluminium casing bolted to the cylinder head and driven by a train of gears at the front of the engine were used. A pair of short tubes, telescoping one into the other, were mounted on the eccentric shafts by means of a split bearing, one per cuff valve, and the telescoping tubes operated a bellpiece that turned the aforesaid T-piece, thus giving the irregular motion to the cuff valve, which remained almost stationary on the firing and exhaust strokes of the piston but rapidly uncovered the inlet and exhaust ports at the appropriate time.

French and foreign patents had been taken out for this ingenious and seemingly effective valve arrangement and racing was intended to publicise it. The SRO Ball-Bearing Company at Annecy, Haute Savoie, built the first of the racing engines, for Rolland-Pillain of Tours, but having had no success in the 1923 GP with their desmodromic-valved cars they turned to normal twin-cam engines for the 1923 and 1924 seasons, and presumably felt that cuff valves were too much for them, because they never used these engines for racing and passed them to Schmid for the 1924 GP. As it had been M Schmid who had patented the engine, he presumably had no alternative than to build a racing car of his own. He employed a modified 1923 Rolland-Pilain chassis, with an abbreviated crab-track but the same 8 ft 2 in-wheelbase of the 1922 Rolland-Pilains, which suggests that he may have used these chassis, especially as the dry weight of both was declared at 1,624 lb.

As on the Rolland-Pilains, the racing bodies were neat and well streamlined, left-hand steering as on the R-P was retained; it has been said that this originated because Albert Guyot had driven a Duesenberg with near-side steering in the 1921 French GP, which had also had hydraulic 4WD, which R-P likewise adopted. The Schmids were full-blooded racing cars, with an eight-piece crankshaft built up with cones and keys, running in two ball end-bearings and two special roller-bearings. The valve-actuating eccentric-shafts ran on ball bearings, there were roller-bearing big-ends, and dry-sump lubrication.

Naturally, SRO were responsible for the bearings used in the engine. Apparently the cuff valves managed without a separate oil supply but there was a feed to the eccentric shaft bearings, from which oil dripped into cups on the telescoping tubes. This oil then drained to the base chamber via the drive-gears for the two eccentric shafts.

Two Bosch magnetos fed two inclined sparking plugs per cylinder. Electron pistons gave a compression-ratio of 6.5 to 1. Instead of the Solex carburettors on the R-P engine, Schmid changed these for two Zenith carburettors, and discarded the Scintilla magneto. The engine formed a unit with the Ferodo-lined cone clutch and four-speed gearbox, three-point-mounted, the propeller-shaft was enclosed, but as only a single universal joint was used torque was transmitted through the back half-elliptic springs, and the hydraulic brakes favoured by R-P were abandoned and replaced by Perrot operation. Rudge-Whitworth wheels and Hartford shock absorbers were fitted.

M Schmid entered two of these cars for the Grand Prix at Lyons, naming as his drivers Giulio Foresti, who like Jack Fairman in later times would test and race anything that presented itself, and Jules Goux, who had won the 1921 Italian GP for Ballot and had finished first at Indianapolis in 1912 in a GP Peugeot. In the 1924 GP only Goux’s Schmid started. At one stage it was ahead of two of the Fiats and Zborowski’s Miller, which sounds excellent except that both Fiats were in trouble and in 18th and 19th places and the Miller likewise, a car for which Laystalt had had to make a new crankshaft and new gears for the gearbox almost before the car had been used.

After 19 of the 35 laps the Schmid was out, retirement variously attributed to trouble with the chassis, the radiator, or the engine, although one report generously said that “the engine was too new to show its powers and the demonstration of reliability of this substitute for poppet valves was successful, as the withdrawal was due to the chassis”. At Monza later that year’s Goux’s Schmid was flagged off when it was 10 laps behind the fourth of the victorious Alfa Romeos. Foresti was another three laps in arrears and this potentially promising cuff-valve passed into history. WB

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