From the Rolls-Royce experimental archive: a quarter of a million communications from Rolls-Royce, 1906 to 1960's. Documents from the Sir Henry Royce Memorial Foundation (SHRMF).
Overview of the 'New Little Marmon' car, detailing its eight-in-line engine, suspension, back-axle drive, and other features.
| Identifier | ExFiles\Box 32\5\ Scan234 | |
| Date | 5th May 1927 guessed | |
| 3 THE NEW LITTLE MARMON A Fine Small Car from a Good American Stable—Eight-in-Line Engine—New Spring Suspension and a New Back-Axle Drive—Low Loading a Feature THE designers and manufacturers of the Marmon car have always endeavoured to give a vehicle which is a little ahead of conventional design. Their cars have attained a reputation for beauty and luxury which is one of their distinguishing features. Hitherto the Marmon has been a comparatively big car with a big reserve of power. But the trend of latter-day motoring, especially in this country, has been in the direction of the development of a lighter vehicle, less heavily powered and yet with a high turn of speed and a full and comfortable accommodation. With the introduction of the little Marmon we have a vehicle which is just as fine in finish and relative performance as the bigger car, and which has the added refinement of an eight-cylindered engine of remarkable efficiency and flexibility, so that low or high speeds may be indulged in without any but a very infrequent use of the gear-box, and with a flexibility and pick up which is exhilarating. Messrs. Pass and Joyce, Ltd., of 373 and 375, Euston Road, who are the sponsors of this car over here, and who hold the sole concession, have now available the new, eight-cylindered Marmon, which is already attracting a great deal of interested attention. In the following we have been able to give some illustrations and a full description of the new car which should take its place among the fine cars of American design marketed in this country. Although it is known as the "little Marmon" and is described by its sponsors as "America's first truly fine small car," the vehicle is not skimped in accommodation. It has a wheelbase of 9 ft. 8 ins., with corresponding carriagework accommodating five easy going for five passengers and luggage. It is exceptionally low in loading, due to the deep dropped frame which curves up over the front and the rear axles. This low loading has been made possible also by the special design of the rear axle drive, to which we shall refer later, and which allows of a low engine and transmission shaft position, while yet giving rear wheels of good diameter and allowing for good clearance. This low loading feature enables the designers to supply a saloon model with ample head room, and yet having a roof line not exceeding 5 ft. 9 ins. from the ground. Dealing first with the chassis construction we have a long, low and very deep side frame of pressed steel curved up at either end to clear the axles, and well supported laterally by very rigid yet light transverse frame members of pressed steel. Seven of these members are incorporated in the frame, which is triple trussed in front to protect the radiator from distortion. Engine, clutch and gear are built up as a single-power and transmission plant, and the unit is mounted in the chassis by four hollow box arms integral with the engine. The cylinders are monobloc, the casting of the eight cylinders and the water jacket being in one with the crank-case, and carrying the bearings of the crankshaft so that piston thrusts are self contained. The head is detachable. The bore of the cylinders is 2 3/4 ins., while the piston travel is 4 ins., the total piston displacement being 190.067 cu. ins. The actual brake horse-power developed is 64 at 3,200 r.p.m., but the car is nominally rated at 24.2 h.p. The valves are inverted overhead and are of large diameter. They are operated by overhead rocker levers and push rods, the latter being actuated by a side camshaft. The design has been developed to ensure the maximum of silence and the adjustment, as our illustration shows, is simple and very accessible. The side camshaft is silent-chain driven and carried in five long bearings which are pressure-lubricated. The pistons are of a special aluminium alloy, with the new Invax strut construction which is designed to ensure a correct fit of the pistons under all temperatures and pressure conditions. The crankshaft runs in five big bearings, 2 1/8 ins. in diameter, while the crank-pin journals are 2 1/8 ins. in diameter. The drop forged connecting rods are carefully balanced against each other and are of special steel and drop forged and of H-section. A comprehensive system of automatic pressure lubrication is installed. There is a gear-wheel type oil circulating pump which is immersed in the oil supply in the sump and skew-gear driven from the camshaft. It supplies a full pressure feed to the main bearings, the connecting rods, the camshaft and up to the rocker arms operating the valves on the cylinder head. There is also included an automatic priming device which injects oil into the cylinders immediately upon starting the engine and so prevents scoring of the cylinders in cold weather and ensures an easy turning of the engine by the starter. This supply is automatically turned off as soon as the engine is in regular operation. An oil purifier is fitted which cleans, filters and purifies the oil as it is circulated around the system and thus conduces to a wonderful economy of lubricant consumption. An automatic carburettor with a suction extra air supply and of the vertical type supplies the gas to the manifold, which has been designed after numerous experiments and much scientific investigation with a view to ensuring an equal supply of gas to each cylinder under all operating conditions. This is effected by a new equidistant “downdraft” manifolding seen in our view of the off-side of the engine. By this arrangement each of the eight cylinders gets an exactly equal amount of gas and, it is claimed, in exactly the same degree of vaporisation. The gas travels exactly the same distance from the choke of the carburettor to each of the cylinders. The result is seen in the fine behaviour of the engine. The car can be one moment throttled down to almost nothing, giving a perfectly clean cut, even combustion at two or three miles per hour in top gear, and it will instantly pick up without flutter or staggering to the full throttle opening and leap to maximum speed. A hot jacket surrounds the uptake pipe from the carburettor mixture chamber to the new manifold. A vacuum tank lifts the fuel from the storage tank at the rear of the chassis. A quantity gauge connected with the rear tank is mounted on the dash. Cooling is carefully considered and the water circulation system has been designed to keep an anequable temperature on the cylinders under all conditions. A four-and-a-half gallon cellular radiator of a particularly attractive design provides the means of cooling the circulating water which is sent around the cylinder and combustion head and valve jackets by a centrifugal pump driven by a rubber hose-connected from the dynamo on the off-side of the engine and most accessibly positioned with only one stuffing gland to the pump spindle. A radiometer on the instrument board shows the temperature of the circulating system and a thermostat control is interposed in the uptake pipe from the cylinder head to the water head of the radiator. Cooling is further accelerated by a four-bladed fan, with an eccentric adjustment from the V-belt which drives it, the belt being driven from a V-pulley on the front of the engine crankshaft. This belt also drives the dynamo, which is conveniently mounted on the near side front engine bearer arm. The electric equipment of the car is by Delco-Remy three-unit system using coil and accumulator, the dynamo supplying current for the starting motor situated on the offside of the engine. The three-speed gear with central lever control is built up as a unit with the engine and the power is transmitted to it through the medium of a single-plate clutch with an elastic plate drive. The gears are of exceptional size, carefully ground and practically silent on the indirect gears. The gear-shift lever is centrally located and beside it is the hand-brake lever. The power is taken from the gear by an open shaft to a new type of live axle, which has the helical bevel pinion gearing. Image Captions: Details of the front spring bumper with rubber shock absorber on the little Marmon. The lower sketch shows the forward spring anchorage and frame tube. The four-door Sedan model of the new eight Marmon. It has a low loading and plenty of head and seat room. Part of the little Marmon straight eight engine showing the cover of the overhead valve gear removed. The fan and overhead valve and special manifolding of the inlet pipes are here clearly shown. The belt-driven dynamo on the little Marmon is accessibly positioned on the near side of the eight cylindered engine. The V-belt driven four-bladed fan on the little Marmon is eccentrically mounted for adjustment of the belt, which also drives the dynamo. The thermostat water control is also seen in this view. Near and offside views of the little Marmon straight eight engine, showing the accessible plugs, the water pump, the new special manifold and the thermostat valve on the water uptake. | ||