EPICYCLIC GEARING ACQUIRES NEW INTEREST.
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Whilst in Half of the Motor Vehicles in the World the Epicyclic Train is Employed, the System is Understood by Few and Little Appreciated.
By Henry Sturiney.
MHE fact that, as has been recorded recently in The Commercial Motor, several makers are seriously investigating the question of planetary or epicyclic ,gearing, particularly
when it is noted that two of these concerns are of the import ance of the Sunbeam Company and the Vauxhall Company, leads to the conclusion that, at last, the very solid merits of this system are beginning to be realized and appreciated, for there is no doubt that there is merit of a very high order in such gears. May it be hoped, therefore, that we shall see more of them as time goes en?
The application of the planetary and gearing to motor vehicles is by no means were not only experimented with, but used by several firms in the early days of the motorear movement. For instance, the original Benz Gars, which shared with the Panhard the honour of "opening the hail" in the motor trade, used a plane tary system for securing a reverse. But the type was more favoured in America at that period than in Europe, and pioneer motorists will remember that both the Duryea and the first Cadillac cars were fitted with epicyclic gears, and, of course, as we all know, the Ford chassis to-day is, as it always has been, so provided.
This ,latter fact is interesting, because Ford has made more than half the ears that are in use in the world to-day. He has made, in fact, 17,000,000 of them ; so that, although few people realize it, it is a fact that at least one half the cars on the road to-day are epicycle geared, even if they be nearly all Fords. Therefore, the wind is taken out of the sails of that type of critic who airily says that they are "no good," without really understanding anything about them.
In the early years of the century I had a very considerable experience with this type of gearing, as may be remembered
by old readers of The Oommercial Motor, for not only the English Duryea cars, for which I was responsible, but also the Loris ears and van which followed them, were so equipped, and. my recollections and experiences of Loris gears are unreservedly pleasant ones. epicyclie types anew, as such gears were commercially • The Long Life of Epicyclic Gearing.
When the gearing deficiencies of those early days are remembered, it may be hardly believable when I say, which is a fact, that during the years we were making those gears we had practically no occasion to make repairs, with the exception of one or two isolated instances of flawed material. I never heard of any Loris gear being 'worn out. They were, it is true, made with considerable care and, accuracy. They had to be. Epicyclic gears to be successful must be, and hence they were, as costs were then, expensive to make: which was doubtless one of the reasons why other firms did not adopt them. The other reason and the principal one which militated against their popularity was the fact that they provided only two speeds and .a reverse, and the demand was all, as it still is, for three and four speeds, and many an interested " prospect " turned our cars down because of these' two speeds.
I remember at one Show a man, after examining the ear with great interest, and being informed that it had two speeds only, remarking most emphatically, "I simply wouldn't have a car with only two speeds!' But, knowing -the merits of the gear, Ford proportioned his ratio of power to gearing as we did in order to permit of the two speeds being a practical proposition. The low price carried the day in his ease and everyone to-day knows that it is piacticable although it is admitted that,all other things being equal, a third speed would be a desirable acquisition. The great point about this type of gehring is, of course, that there is no movement of gears in and out of ,mesh while in use and no skill required in changing, All gears are in constant engagement with each other and the change from one speed to another is effected by applying brakes operating on drums connected with either one or other of the gear members. For all practical purposes it was, therefore, impossibleto damage a Lotis gear, even by wilful abuse. For example, our demonstrators, with a fully loaded 2tonner, would often, while running full speed ahead, apply the reverse brake hard, which had the effect of first pulling up the car and then, without a moment's hesitation, re-' versing its direction of movement. The ability to do this gave the driver enormous brake control through the gearing. Of course, to put in the reverse of an ordinary sliding gear while running full speed ahead, or even the attempt to do so, would simply result in wrecking the gear. This stunt, of course, eau also be done with the Ford, It speaks much for epicyclic gearing, therefore, that so shrewd a man as Ford should have adhered to it all these years and that one of the oldest high-class firms in the Country—the Lanchester Co. —should also have adhered to the principle from the beginning, as it must bb remembered that there is no finer motor engineer in the country than Mr. Frederick Lanchester. The Lanchester firm, however, has always employed a three-speed epicyclic gear, which involves some compounding, and I have always wondered why the Cadillac people abandoned this type of gearing when they did, because at the time they did so they had just perfected and introduced a very successful three-speed model.
But I believe public prejudice was really the deciding cause, as they found that, owing to this, they would sell more ears of the type which met the public fancy, although less efficient and satisfactory as mechanical propositions. I may mention that just when my old company 'collapsed, through being let in on a large contract, we had also just completed a three-speed model, and when epicyclic gearing is truly understood—which, as a matter of fact, it rarely is, even by engineers—there is no difficulty in making three or even four or more speed gears, although in doing so we get, away from the great simplicity of the single train of gearing.
The Need for Simple Control Gear.
'With this system, one set of gear wheels enables us to get any combination of three gears, and as a motorcar must always, of course, have a reverse, the other two actions give us the two forward speeds. As a matter of fact, if it were possible—which it is not—to control them in one mechanism the same single train of-gearing could be used to give five forward speeds and two reverse speeds, and if this could be done it would be a positively ideal gear for motor vehicles. Owing to the impossibility of suitably arranging the controls, however, the only way in which a greater number of speeds can be employed is by compounding some of the parts, or using combinations of more than one train of gears, and I may here mention that I have recently obtained five forward speeds in a bicycle gear with a combination in which, whilst a single annulus only is employed, the sun wheel and planetary system are duplicated. The well-known Sturmey-Archer and B.S.A. three-speed bicycle gears, of which several millions have been made, use a single epicyclic train, and I may further mention that in the first cyclecar, which I built in 1900 and which is now in the Motor Museum, I get three speeds forward with a single epicyclic train of gearing. There was, however, no reverse.
One limitation attaches to this type of gear: the combinations are more or less arbitrary. Thus, for instance, if a particular train of gearing gives a multiplication of speed of, say, 50 per cent., you will get a reduction of speed only to the extent of 331 per cent. As a matter of fact, few people understand this class of gearing and, therefore, the rough diagrammatic sketch may be useful.
Here we have the three elements of an epicyclic gear, viz., A the sun wheel, or centre of the system, B the planetary gears which revolve around the sun wheel and are mounted on bearings in a ring or cage, and C the annulus, which is an internal gear within which the planetary system rotates.
By so arranging these three members of the system that one or other of them may be connected respectively (1) to the power end of the transmission, (2) to the load, or (3) held in a fixed position and prevented from rotating, we get the following combinations
With A held fast to the ground or frame of the machine, E connected with the power and C with the ,load, we get an increased speed, as the planetary wheels, using A as a fulcrum, while revolving round it, propel C at a greater speed.
By reversing the cennections of B and C and applying power to C, we get a reduced speed of movement on the cage B in which the planets revolve.
By holding or locking the planetary system B and applying power to A, we get a reversed movement on C which we connect with the load, and by, conversely, applying power to C and connecting A with the load we get a reversed movement on A,. but in different ratio.
By locking the annulus (C) and applying power to A, we get a reduced speed on the planetary carrier (B), and by reversing this and applying power to B, we get an increase of speed on A, but in a higher ratio than in our first combination.
By locking any two of the members together—AB, AC, BC—the whole system is interlocked and revolves as one, thus giving us a direct drive. It will be seen from the above that this type of gearing offers a very wide field for ingenuity and inventive skill.