THE GERARD ROTARY ENGINE: 18??

Left: Basic operation of the Gerard rotary engine. This engine was used by the Compagnie General des Automobiles in a steam omnibus, who described it as an epicycloidal motor, systeme A Gerard. The motor consists of three discs D, running in separate compartments and keyed to the central shaft at 120 degrees to each other. Fig 50 at left shows steam admission. The cap H on top of disc D is angled to open the port in its centre, and allow steam in from the top inlet E. Fig 51 shows the expansion period. H has tilted so as to close its admission port. From The Automobile: Its Construction & Management by Gerard Lavergne, 1902; p79

Left: A detailed view of the of the internal construction of the Gerard rotary. This shows the beginning of the exhaust phase, with disc D about to uncover exhaust port F. B is eccentrically keyed onto the central shaft, and the disc D rolls around this on ball bearings. R,R are springs that press seals against the ends of the cylinder. It was claimed the engine could be run at any speed between 60 and 24,000 rpm. The lower speeds were attractive as they eliminated the need for reduction gearing to match it to road-wheel speeds. Consumption of steam at the first trials was claimed to be less than 55 pounds per horsepower-hour; a rate that is markedly higher than that claimed for the Hult engine. From The Automobile: Its Construction & Management by Gerard Lavergne, 1902; p80

Left: Transverse section of the Gerard rotary engine. A,A are partitions between the three volumes containing the discs D. Note the ball-cage around the middle eccentric B, and the sealing pieces L pressed outwards by springs. From The Automobile: Its Construction & Management by Gerard Lavergne, 1902; p81

THE ARBEL-TIHON ROTARY ENGINE: 1898

Left: The Arbel-Tihon reversible rotary engine was exhibited at the Tuileries, Paris in 1898. The inventors were Pierre Arbel and Pierre Tihon. Once again a "piston" rolls on ball-bearings around an eccentric on the drive-shaft. This time the central partition actuates the admission/exhaust valve as it oscillates. The smaller plug valves on each side are moved together to reverse the engine. An example weighing 308 pounds (140 kg) was said to give 6 horsepower with steam at 142 psi. This seems like a less than stunning power/weight ratio, but the definition of horsepower in France has always been rather perplexing. My Citroen Dyane gave a massive 36 bhp from its air-cooled flat twin, but for tax purposes it was 2 hp, as in 2CV- deux CheVaux. A gentleman called R Soreau left a brief description of this machine, from which I quote: "The joints are made tight with cork plugs driven with great pressure into pockets so as to be flush with the sides of the piston. These plugs swell from moisture of the steam, and form, says the inventor, excellent joints with very slight friction." Hmmm. This design suffers from the common rotary-engine problem of having a line contact between piston and cylinder to seal. From The Automobile: Its Construction & Management by Gerard Lavergne, 1902; p82

Left: The Arbel-Tihon rotary engine as depicted by the French journal Nature on 17 September, 1898. 1: The engine with the front cover removed. 2: A section through the middle 3: Section from the side with various parts cut away. R is the reversing handle, geared to the two plug valves seen in the section above.

De Lambilly exhibited a reversible rotary engine at the Tuileries in 1899. No other details currently available.

Bibliography: The Automobile: Its Construction & Management, by Gérard Lavergne 1st edn, 1902.