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Chuan, Lim Kek, Penang, Straits Settlements.
Deane, Reginald, A.I.N.A., Irish Lights Office,
De Cosson, Claude Augustin, Public Works Department, Cairo, Egypt.
Dick, Alexander Frederick Henry, 41, Lee-road,
Faraday, Charles Arthur, 149, Stapleton Hall-road, Stroud-green, N.
Ffinch, K. H. Maule, Messrs. Tomlinson and Tian Fook, 1, Raffles-place, Singapore, Straits Settlements.
Fook, Chye Tian, Messrs. Tomlinson and Tian Fook,
1, Raffles-place, Singapore, Straits Settlements. Hong, Lim Eow, Penang, Straits Settlements. Ikin, Benjamin R., Alsager, St. Fillans-road, Catford, S.E.
Lal, Hon. Munshi Madho, Benares, India.
Rosendale, Otto M., Oregonian-building, Portland, Oregon, U.S.A.
Scanlen, Arthur Dennison, Salisbury, Rhodesia, South Africa.
Scott, Hugh J., Box 204, Middleburg, Transvaal, South Africa,
Shaw, Percy A., care of Messrs. Millers, Limited, Sekondi, Gold Coast Colony, West Africa. Thompson, Oscar S., 7, Billiter-square, E.C.
The paper read was—
STEAM CARS FOR PUBLIC SERVICE. By THOMAS CLARKSON, M.I.Mech. E. INTRODUCTORY.
The necessity for superseding horse traction. by mechanical power for public service is not only admitted, but is becoming increasingly urgent in view of the congested condition of the streets in large cities, and of the practical impossibility of improving and accelerating street service by present means.
Away from the cities facilities are needed to improve railway connections by the opening up of cross country routes, where in most cases there is insufficient traffic to enable even a light railway to pay, though traffic can be profitably developed providing the existing roads. are utilised.
We are taught at school that “England is covered with a network of railways," but we must bear in mind that some of the meshes of the net are large, and through these large meshes many sprats are lost which cannot be economically retained by the present heavy and cumbrous network.
Here is a great opportunity for the selfpropelled road vehicle, to make a lighter and more flexible network which can be spread over the large meshes between the iron roads. That this can be done without violating commercial principles seems to be no longer open to doubt, the indications being that such services will pay well in many parts already. When the blessings of improved facilities for transportation begin to bear fruit, that system can be further extended so as to include areas which at present are less promising.
One method of increasing the speed of locomotion in crowded streets, and at the same time of conveying much larger numbers of passengers from one congested area to another has, of late years, been found in the development of electric tramways. Suitable as these may be on wide main roads in the country, or in old-fashioned towns with broad streets and little traffic, the initial cost of laying down the permanent way and plant is very great, while their adoption is an impossibility in teeming business centres, partly owing to the enormous cost which the necessary widening
of the streets would involve,-a cost which even in suburban places has become almost prohibitive-and also because of the serious obstruction to the ordinary business traffic of the town, which becomes practically restricted to the narrow strips of the highway between the kerbs and the tram-lines. Cars therefore must be found that can mingle with the rest of the traffic, threading their way through the streets with ease and at any rate of speed that is desired, carrying large numbers of passengers or quantities of goods, but compact in design, and always under perfect control.
A very large reduction of the number of horses in our streets is not only possible, but desirable, on the grounds of economy, cleanliness, and humanity. The principal difficulty in realising these advantages hitherto, has been the imperfect character of the appliances put on the road, and it is clear that the severe nature of the conditions pertaining to the running of a regular public service have, in the past, not been appreciated by those engaged in constructing motor cars for this duty.
PRINCIPLES OF CONSTRUCTION.
Attempts have been made by taking an ordinary Chassis, the machinery of which is designed for a pleasure car, and fitting to it a public service body. It is not surprising, however, that these attempts have failed when we recognise that in the construction of machinery for pleasure vehicles so much of the construction is centred round the cutting down of weight to the minimum.
It is necessary to recognise at the outset that there is a great difference in the breed of a racehorse and an omnibus horse, and the same analogy holds between the machinery of a light pleasure car, and the machinery of a public service car. The pleasure car being usually for intermittent service, no serious disorganisation occurs should the service be suspended, but a public service car must be continuous in operation, and as free from interruption and interference as possible.
The construction of the pleasure and the racing car resolves itself largely into an effort to combine maximum power with minimum weight.
The public service car needs first the economical and reliable production of power, and given this, the cutting of weight becomes not only unnecessary, but positively vicious.
During the recent reliability trials conducted by the Automobile Club, it was demonstrated
that the expense for fuel on the steam car, which will be described presently, reached the remarkably low record figure of 211 of a penny per gross ton mile.
The advantage in price of using cheap paraffin fuel instead of petrol, far outweighed the difference in theoretical efficiency between the internal combination engine and the steam engine.
The most economical of the internal combustion cars was 42 per cent. more expensive in cost of fuel per gross ton mile; and, moreover, the weight of the petrol car was less than half that of the steam car. This steam car was of more substantial build than any others in the contest, and yet, notwithstanding this, its weight might have been further increased 42 per cent. without making the cost for fuel per ton mile any more than the cost for the most economical petrol car.
Consider the effect of a reasonable extra weight as an insurance against accidents. Suppose the engine and the vital parts of the car are strengthened by the judicious addition of 5 cwt. of metal. The extra cost for fuel throughout a day's run of 80 miles is only 4td., or 053 of a penny per mile. Compare this with the loss of revenue and disorganisation consequent upon a car being knocked out of commission for a day. A day's revenue may be put down at from £3-£4, and in addition there is the men's wages to add as well as the loss of prestige to the service.
During the reliability trials an accident occurred owing to a light petrol car being steered into the steam car. Result :-The light petrol car was put out of commission for the rest of the day. The more substantially built steamer had scarce a scratch, and completed its day's run as if nothing had happened. The obvious moral is that "Superior metal commands respect."
In order to secure continuity of running with a mininum of stoppages, the machinery of a public service car must be designed of a most substantial and permanent character, with large safe limits in strengths and surfaces, in clearances and in capacities. Simplification must be carried through to the utmost extent, and the driver relieved from every operation which can be performed efficiency by purely mechanical means.
The driver is a very important factor in the design of the machinery of a public service car, and it is not desirable to expect that he should possess much mechanical skill. The type of man who is competent to drive a pair of omnibus
horses will generally be expected to drive a mechanically operated omnibus.
In addition to this the constructor must seriously consider to what extent he can provide against carelessness and incompetence in the driver. It may at first appear unreasonable to expect provision to be made for this in the construction, but something can be done to this end, and it does not seem possible for the designer to set himself too lofty a standard of construction. He must, therefore, seriously ask himself to what extent can the evils of neglect and incompetence be defeated. I do not pretend to say that these can be entirely vanquished, even by combining the greatest skill in production with the most careful examination and testing of the drivers, but much can be done to minimise the evil.
A general answer to this difficult proposition is found in a process of elimination, that is to say, in taking out of the hands of the driver, as far as possible, every operation requiring skill and experience, such, for example, as lubrication, which can be performed with much greater certainty and precision by the machine itself.
Owing to the improved methods of construction now available some of the old-fashioned duties of an engine driver may be entirely dispensed with. For example, the packing of stuffing boxes. This is an operation which, for its proper execution, needs a certain amount of experience, care and judgment, especially when high pressures and high temperatures are being dealt with, and a careless driver in attending to stuffing boxes would very soon injure the rods and make it impossible for the boxes to keep tight. This, however, is an operation which has now been removed from the duties of the driver, improved mechanical construction having provided a solution of the difficulty.
In general, the designer must work for cutting out adjustments whenever possible, in order to avoid imperfect adjustment. This principle is applicable both to bearings, which instead of being made in halves and adjustable, are now largely made solid and without adjustment, but of such liberal proportions and excellent material and lubrication, that adjustment only becomes necessary at very long intervals after many thousands of miles, and may then be done properly and inexpensively by a mechanic. The adjustment of valves and operative parts is also to be eliminated as far as possible. I do not suggest that all adjustment may be eliminated, but where
an adjustment cannot be eliminated, it should be arranged in the most accessible manner possible. This is a thing well within the power of the constructor to arrange, and by making the adjustment easy, increase the chances that it will be made properly. If, in order to make an adjustment, the driver has to make himself in a mess, to lie on his back, or work in an uncomfortable position, at parts difficult of access, those parts will surely suffer for want of adjustment. Let all parts, therefore, needing adjustment, be, if possible, in full daylight, and in such a position that the work can be done quickly and comfortably without trouble or mess. We may then, but not otherwise, reasonably expect that the parts will be kept in condition.
So much with respect to the general principles of construction of the machinery for public service cars.
DETAILS OF CONSTRUCTION.
Coming now to the details of construction. As already intimated, each of the details must be of the most permanent and substantial construction, and let me say at once that only the best in material, design, and workmanship is good enough.
As the strains brought to bear on the machinery are often very severe, and far beyond their normal load, the factor of safety must be ample in order to ensure that a considerable overload does not produce any permanent result, or the first time a car gets into trouble its character will be injured for life.
Another specially important consideration in the design of the machinery for public service cars is to reduce as far as possible the amount of time which it is necessary for the car to receive, not only when in commission, but also in the garage, that is, in cleaning and preparing for commission. It is therefore a sine quâ non that, as far as possible, every bit of machinery shall be enclosed within a dust proof and mud proof oil-retaining case, which, at the same time, obviates the necessity for the cleaning of the machinery, for to do this thoroughly would occupy a good deal of time every night in the garage, and there would be a great certainty of its not being done in the most thorough
I now beg to invite your attention to some details of construction on the steam car with which I am most familiar, namely, the "Chelmsford," some of the vital parts of which are before you.
In a steam car there is no necessity for a change speed gear and its attendant complication, the whole of the change of speed being done by the regulation of the supply of steam to the engine.
The machinery of a steam car comprises the engine, differential and transmission gear and pumps. The design of the "Chelmsford" set of machinery has been carried out in order to embody all these essential parts in one complete mechanism, which can be applied to, or, if necessary, removed from a car as a complete unit; the advantage of this arrangement is that should the engine ever suffer serious injury, it would be preferable to remove it completely from the car for repair, at once substituting a stand-by engine in order to put the car again in commission while its engine is being overhauled.
Another advantage of making an engine, differential gear, and pumps, for the driving mechanism in one unit, is that the arrangement for the lubrication of every bearing can be greatly simplified, one system of force pump distribution being then applicable, to supply in a positive manner the lubricant to every bearing; the enclosing case being designed so that the surplus oil from all the bearings drains back into a common well or reservoir from which it is filtered and again pumped to the bearings.
The arrangement for ensuring the feeding of oil to every one of the bearings is familiar to many of you, and may be described as pumping the oil into a circular box, from which there are a number of outlets leading to the bearings. A rotary valve operated by the engine switches each one of the pipes in turn into direct connection with the lubricating force pump, and thus, by feeding the oil service pipes seriatim, prevents the possibility of stoppage in supply to any bearing, which would certainly result sooner or later if some of the service pipes were in parallel. This arrangement has been found to answer admirably in practice, and has the great advantage of requiring no attention whatever from the driver; it lubricates each bearing in a regular and thorough manner, conducive alike to increased mechanical efficiency and an increase in the life of the mechanism.
A steam engine embodying the latest mechanical practice is, admittedly, the most positive and reliable of any engine, and there is no reason why the engine should ever make its existence on the car manifest, except by the satisfactory performance of its appointed
work. Given automatic lubrication and entire freedom from the necesity of packing stuffing boxes on piston rods and valve rods, and the engine will run for many thousands of miles without any further attention than, once a month, supplying a little more oil to the lubricating reservoirs, and changing the pump rings.
The bearings of the engine and transmission gear are perfectly plain, and are of hardened steel, the working surfaces being ground to the highest possible degree of accuracy.
The engine is arranged horizontally, with the valves beneath the cylinders. This arrangement in the design relieves the driver of the necessity for opening and closing the drain cocks at starting, the water of condensation automatically escaping out of the exhaust.
The crank shaft is provided with a steel spur wheel of liberal proportions, which drives directly on to the differential gear with the ratio of 1 to 2. The pumps are driven directly off the differential shaft, and the advantage is thus secured of running the pumps at a reduced speed from that of the engine. At the same time this arrangement enables the reduction of speed between the engine and the road wheels to be accomplished comfortably in two stages.
This constitutes practically the whole of the mechanism, the other vital part of the car comprising the arrangement for the generation of steam, which includes the boiler, burner, and superheater.
The type of boiler which has been adopted, after experience with many forms, is the plain, vertical, cylindrical, multitubular, the outer shell being constructed of two steel plates hydraulically pressed so as to form a tube plate and half the cylindrical shell in one piece. By this arrangement both parts of the shell are of the same size, which is conducive to excellence of manufacture, and there is only one seam in the whole of the boiler shell, this being in a convenient position and entirely removed from contact with the flame of the burner. The fire tubes are straight, and are expanded into a tube plate at each end, the protecting edges being afterwards beaded over so that each tube forms a stay. There is only one hole in the centre of the upper part of the boiler, and into this screws a steel header or connecting piece with independent branches leading to the twin safety valves and the throttle valve. The working pressure is 250 lbs. per square inch, and the