Motoring Notes
The Six-Cylinder Air-Cooled Franklin
THE " Spirit of St. Louis " and its intrepid pilot are now world-famous, and a consideration of the factors which led to his success must be considered by all who seek for further triumphs and advancement of aviation and engineering. One essential was that the weight of the engine should be the minimum that could carry a big load of fuel at high speed, and the choice of the aviator fell naturally on an air-cooled motor.
There are but few air-cooled engines used in the construction of the present day motor car, and the several advantages of such engines deserve attention. I will place these under two headings—lightness and efficiency. It is obvious that if the water necessary for cooling purposes and the jacketing neces- sary for its retention and circulation are eliminated, the total weight of the engine must be materially reduced. Secondly, it must be remembered that the running temperature of a water-cooled engine must be below boiling point, whereas the highest combustion efficiency is reached at a point in excess of the boiling temperature of water. As the boiling point of oil is much higher than that of water, it follows that an air- cooled engine in which there is no water used, such as the Franklin, is able to profit by the greater heat at which it can be run.
As a proof of the success of these theories I would point out that this car has been on the market for a quarter of a century on very much the same lines, though in outward appearance the makers have now adopted a sham radiator which conforms to that usual with water-cooled engines. The 25 h.p. engine has six cylinders which are separate and detachable, each with copper vertical cooling fins. A Sirocco fan at the forward end is driven by the crankshaft, and air is driven over, and deflected downwards between the cylinders, the air pressure increasing with the speed of the crankshaft, and effectually preventing heat in excess of that required for highest efficiency in running.
The high temperature at which the engine runs has an appreciable effect in lessening the formation of carbon, and the consequent need of frequent cleaning and valve grinding. The valves are in the head and are enclosed. The crank- shaft is 2?, inches in diameter, and rests in seven bearings, to each of which a predetermined quantity of oil is forced, under a pressure. If the oil is obstructed, it quickly rises to such an extent that the obstruction is removed. The internal cleanliness of the motor is further assisted by an air purifier, and a particularly efficient visible petrol filter. Another of the several useful and unusual features is an electric vaporizer which, I have good authority for stating, will start the motor quickly on the coldest morning. Ignition is by coil and battery, and the spark advance is automatic, thus doing away with the necessity of one control lever on the steering column. I now come to a feature which is distinctly novel ; namely, the frame, which is made of laminated ash. There are three advantages of a wooden frame : (1) it is half the weight of a steel frame of equal strength, (2) it is double the strength of an equal weight of steel, and (3) as each side member can flex independently of the other, road inequalities are more readily absorbed by the chassis. The next noticeable feature is the springing. All four springs are full elliptic, the total length amounting to twenty-eight feet, and the results, to my mind, fully justify their size and design. It is only fair to point out that, as the car is not designed for speeds much in excess of fifty miles an hour, the problem of suspension is vastly simplified. Regarding the performance of the car as a whole, I covider it is quite satisfactory for anyone who wants a reliable, quiet, and smooth-running engine, but does not expect high speeds. Actually, speeds in excess of fifty miles an hour are only attained, either on a long stretch or by altering the carburation and slightly increasing the petrol consumption from one which is normally very low, considering the size of the car.
The acceleration is not in any way unusual, but is up to a normal standard, and a rather higher average speed than one would expect can be maintained because the speed need seldom be reduced for rough roads. Pot-holes and rough surfaces appear to be absorbed by the springs and chassis to a remarkable extent, and I was not forced to slow down for any bad roads over which I travelled.
Braking is on the transmission, and two hand-applied brakes to the rear wheels. While I could not cavil at the way the car pulled up, and pulled up without any tendency to skid, I would strongly advocate a change to a reliable four- wheel braking system, and I understand that this may shortly be fitted as standard. The four-door saloon I rode
was absolutely without a squeak or rattle, and was nicely
finished. Windows which open all the way would be an improvement. The driving seat will in future be adjustable; and the right-hand drive is being adopted for use in this country. - In a recent article in this paper adverse comment was made to the length of time taken by makers and service stations to take down and clean an engine. The Franklin Company are specializing in-time and money saving in their service stations; so that one can turn in one's car at, say, eleven o'clock. leave it to shop and lunch, and return some three to four hours later to find the engine has been taken down, decarbonized, valves ground, and the chassis thoroughly oiled and greased. Further- more, the fixed charges for work done are very moderate indeed.
I would like to recommend the Franklin ear for women drivers in particular because, as it seems to me, it offers a combination of reliability, low running costs, and a simplicity of control combined with particularly comfortable riding.
PELIIAII COCH RANH.
[Since the above was written we hear that the Franklin car has climbed Bwlehygroes Hill, considered the greatest test of engine-cooling in Britain. When the car reached the summit the engine was perfectly cool.—Tnr. MototuNii
EDITOR.]
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