The First Chain Gearbox.
Page 5
Page 6
If you've noticed an error in this article please click here to report it so we can fix it.
Some Records which should Render it Unnecessary Further to Pursue the Controversy as to the Origin of this Successful Application.
Many of our readers will recall with interest that a certain amount of discussion took place, in our columns, some while ago as to the novelty of the principle adopted in connection with the evolution of the chain-drive gearbox, as embodied first of all in the omnibus chassis manufactured by the L.G.O.C., and, subsequently, in certain models produced atthe 1/aimler, Maudslay, and other works. Those who are in a position to realize the seriousness of the problem which faced the London motorbusoperating concerns in 1900-8, will say that the designers and owners were literally at their wits' end to know what to do to secure sufficient silence of working from their motorbus chassis to satisfy Scotland Yard licensing authorities.
The Public Carriage Office was rightly, as events have proved, very firm in its attitude, during the years leading, op to 1903, towards the necessity of Lilly permitting adequately-quiet chassis to be employed for stage-carriage purposes on the London streets. The engineers who had the problem to tackle were, at the time, perhaps, bound to feel a little impatient at what they considered the adamant attitude on the part of the official licensing body, although it was realized by them that considerable stipulations were necessary.
The Struggle for 'Silence.
One of the most obstinate characteristics of many of the original motorbus chassis, in respect of noise prevention, was the engagement of the lower or the intermediate gears. Other noises on the chassis were gradually and effectually eliminated, but the gearbox was left to be the subject of n.uniberless experiments, the results of which were invariably disappointing in the extreme.
We ourselves can recall such " last-ditch " ex pedients as the carrying out of various machining modifications to the tooth outlines, the filling of the spur-wheel discs with packing pieces, first of lead then of wood, fibre, and other materials, which, it was vainly hoped, would absorb the insistent and monotonous groaning of those intermediate-speed engagements. The insides of gearboxes were lagged with felt.; the outsides were treated similarly, and in one or two cases experiments were tried of boxing in the whole of the bothersome noise—with quite ineffectual results we may add. It was found practically impossible in certain classes of gearboxes finally and effectively to abolish the noise made by the engagement of certain pairs of wheels :
efforts to conceal it were equally unavailing. In some cases, these were the change-speed reductions
themselves, whilst in others the secondary reduction to the differential was found to be to blame. Suffice it to say, then, that practically everything that mechanical ingenuity could suggest was attempted, in order to secure the fiat of Scotland Yard for some of those early models.
Certain makes of chassis, of course, proved to be more obstinate than others, and it is evidence that it was at least possible to secure relative improvement of sufficient merit, that some of the earlier models have only recently been taken off service.
The 1.,.G.O.C. Answer to Scotland Yard.
Scotland Yard, with, perhaps—we take have to suspect—an optimism arising from a not too intimate appreciation of the extreme difficulty of the problem which then faced designers, stuck to its guns, and insisted upon silence, and rightly, too, as such policy has proved of great benefit, not only to the motorbus industry, but to most of the other sections of the commercial-motor business.
We do not intend, in the present short article, to attempt to allocate the credit which is due to the first brainwhich gave birth to the idea of employing chaindriven gearboxes on these London motorbuses. There has been a number of claimants known to us for the original suggestion. We must, impartially leave it that the engineering and constructive staff of the London General Omnibus Co.'s motor department, in 1909, did in effect conceive and design a silent gearbox, in which the change-speed pairs of spur wheels were replaced by pairs of silent chain-driven sprockets, the changes of gear being effected by dog clutches.
That approved chain-driven gearboxes are used on very nearly the whole of London's petrol-driven motorbuses at the present. time, is the outcome of that experiment. To the mind, whichever it was, that first conceived this possible solution to what had, been so long an extremely puzzling problem for the London owners belongs the credit of thus enabling the petroldriven motorbus not only to continue in operation in London, during a most critical period but, thereafter, so rapidly to climb to pre-eminence in respectof London's surface traffic organization.
The Chain-drive Gearbox in 1898.
What we have to record at the present time is that, although great credit is due to those who produced the London type of chain-drive gearbox as a solution in the time of emergency, and although, as we have said, there are not a few claimants to its parentage,
the actual genesis of the system stamps the 1909 adaptation as by no means a novelty. We hope that our investigations, which have been pursued in conjunction with the courteous officials of Hans Renold, Ltd., the well-known chain makers, of Manchester, will finally set at rest contentions as to the origin of the chain-drive gearbox idea.
Oa Mr, Spurrier's Steamer in the Crewe Trial, 1897.
The first mention which appears to have been made, of an attempt to use chains in connection with changespeed is likely to rest unchallenged in connection with a 6 h.p. steamer, which Messrs. Spurrier entered for the Crewe trial, in 1897, for which it was awarded a silver medal in a. walk-over, owing to the non-arrival of other competitors. This was before the Lancashire Steam Motor Co. was formally constituted. Of this wagon, we recall, "it had a vertical steam engine capable of developing, so it was believed (sic), 6 h.p., which had its crankshaft across the car, and carried three spur pinions and one Hans Renold silent chain pinion for the reverse."
But it was subsequent to this that what can effectively be claimed, we consider, as the first example of silent-chain gearbox was embodied in an actual chassis, and this appears to have been used first of all as part of the chassis of an omnibus which waz built at the early Leyland works for the Dundee Corporation, and the date of this construction, the first chain-drive gearbox, appears to have been 1898.
Through the courtesy of Hans Renold, Ltd., we are enabled to reproduce the original drawing of the design for this particular gearbox. This, again, has been obligingly supplied by Leyland Motors, Ltd., to whose principals, of course, Hans Benoist, Ltd., had supplied the chains. The particulars with respect to the number of teeth in the wheels, etc., which we are enabled to include, are from a dra.ughtsman's original sketch. The chains used were the original Hans Renold multiplelink silent type, No. 560, in. pitch and 1/ in. wide. Unfortunately, at the time of going to press, it has not been possible to ascertain from the Dundee Corporation. what was the actual behaviour of the machines in question. The bus had a body made by J. Stirling, of Hamilton, N.B.
As a later, but still early, example of the employment of chains in gearboxes, we are indebted to Messrs. J. W. Brooke and Co., Ltd., the well-known manufacturer of Lowestoft, for the information that it was in 1901 that the first car left the Brooke works fitted with roller chains in the chain-speed gearbox, and this method was continued right up to 1906, when the company built its first spur-gear-driven car.
We learn that the sole reason for abandoning the chain method was " owing to the prejudice of the public at that time against chain gear." Mr. M. Brooke writes: "Such a drive was undoubtedly extremely satisfactory, and we have ears which lave been running since 1903, which, so far as the gearbox is concerned, are running perfectly satisfactorily to-day. We, fitted three gears and reverse, the gear wheels being engaged by dog clutches, the dog clutches being operated from one cam, which was inside the gearbox. Our opinion is that we obtained much greater efficiency from our chain gearboxes than we do from the later type of spur gearbox. We certainly should not have abandoned the chain gear if the public had not compelled us to do so." The chain which was used in these instances was the Renold 1 in. pitch roller chain, with a breaking load of .1000 lb.