Foden: Road Locomotive
Note: This is a sub-section of Foden
Extract from Steam Locomotion on Common Roads by William Fletcher. Published 1891.
One of the engineering firms which has recently taken up the manufacture of road locomotives is the firm of Messrs. E. Foden, Sons, and Co., of Sandbach. Their first traction engine was turned out in 1880. During this ten years' experience, Messrs. Foden have (in the face of the keenest competition) established a well-deserved reputation, and their road engines have produced some excellent results on the trial field.
The Sandbach firm embodied several wide departures from current practice in their earliest engines, they were not content to run in a groove produced by their predecessors, and the successful records obtained at Stockport in September, 1884, and at Newcastle in July, 1887, proved conclusively that Messrs. Foden's original designs, although at variance with present practice, were based on correct principles, consequently their engines are economical and efficient.
Double cylinder traction engines were often constructed a few years ago, and were generally liked by customers, because they are so easily handled. They do not start so suddenly as the single cylinder engines. They start quietly and run slowly, giving the steersman plenty of time to manipulate the locking, without so much plunging and backing when two or three sharp corners have to be encountered. There is no stopping on the dead centre, occasioning the pulling of the fly-wheel partly round. They are less noisy and rarely prime. But it was generally understood that the double cylinder engine was not so economical in fuel as the single engine of equal power.
Messrs. Foden have revived the double cylinder traction engine, thus gaining the above-named advantages, and in spite of the impression respecting its wastefulness, their engines are among the most economical in the market, as was shown at Stockport and at Newcastle.
Messrs. Foden and Co. give the following advantages of the double cylinder: —
- First — The strain on the gearing is reduced to a minimum, or less than half required to move the same load with a single engine.
- Second — The annoyance of reversing is done away with, which is evidently a great advantage in starting, and is thus more under the control of the driver.
- Third — The slow rate at which these engines can be moved gives them an important advantage in hooking on, and being able gradually to start a heavy load, whereas with the single engine the load is started with a jerk, which often breaks the drawbars and pulls the under- carriage- work and numerous other parts to pieces, besides endangering the life of the man hooking on.
- Fourth — The strain on the gearing, and therefore on the travelling wheels, being uniform throughout the stroke of the engine, enables it to carry better over soft, greasy ground. The irregular snatching pressure of the single engine we have proved to be one of the prime causes of slipping.
- And lastly, but most important — Priming is entirely done away with, by drawing the steam off the water surface gradually instead of by snatches. These advantages equally apply to the compound engines fitted with our patent starting gear.
All Messrs. Foden's traction engines are mounted upon large driving wheels, nearly 7 ft. diameter, the rims are of tough cast iron, shod with steel cross-plates. A peculiarity of these wheels consists in increasing the number of the spokes and using a light section of iron for them. Wheels of such a diameter obtain a great amount of tread, giving them more grip on the surface of the road, thus rendering them much less liable to slip, and allowing the engine to pass over soft ground where wheels of ordinary diameter would sink.
Two travelling speeds are provided, the fast speed ratio of gearing being 16 to 1, the slow speed ratio is 27 to 1.
Fig. 105 shows a traction engine as made by Messrs. Foden, but since the block was cut a few alterations have been made in the design, which must be named. Messrs. Foden are making nearly all their road locomotives with piston valves, they have had them in work two years, and find they answer very well, the wear and tear being practically nil compared with the slide valve. If the feed water in use is dirty, as it very often happens to be, or if the lubrication is neglected, the flat slide valve is a cause of trouble, it wears away at a most rapid rate, and not infrequently wears the port faces away, which is a serious matter. Hence the number of expedients, which various makers have tried, to prevent this irritating wear and tear.
For instance, Messrs. Aveling and Porter, in 1880, fitted Webb's patent slide valves to some of their engines, this is a round slide valve, which is free to rotate in a hoop, and with improved means of lubrication, some portion of the valve face being always exposed to the exhaust steam. Church's balanced slide valves were used about this time by Messrs. Fowler and others. Everitt's ingenious balanced slide valve, as well as Carter's, have been adopted by some makers. Then the ordinary slide valve has been tried in all kinds of materials, to ascertain the best wearing metal. Brass, phosphor bronze, malleable cast-iron, steel, and hard cast-iron have each been tried, and have their advocates. Phosphor bronze is highly recommended by some traction engine makers.
Messrs. Foden and Sons mount all their traction engines on springs. In 1880 they tried flexible wheel spokes, which saved the engines from vibration, but defects soon showed themselves, therefore these flexible spokes were discarded; and in 1882 Messrs. Foden introduced the arrangement as shown by Fig. 106, which answers admirably. It will be seen from the sectional view showing the patent spring arrangement, that the vibrating shafts are so arranged as not to alter their relative distance, while at the same time allowing the weight of the engine to be carried by the springs. The bearings of the main axle and second countershaft A and B are connected by two levers Ft the whole sliding in two axle boxes 0, 0, preparation being made on the top of the two upper bearings for the reception of the two strong coil springs, contained in the cylinders D, D.
The bearings E E, of the main axle, and the third motion shaft, are of extra length, and parallel, and being coupled by the levers F, having joints at either end, the necessary oscillating or vertical motion is allowed to take place without locking or strain.
The great difficulty hitherto of accommodating the gearing on the stationary to the moving shafts, is overcome in a very simple and effectual manner. The third motion shaft A, which moves up and down, is fixed slightly below a horizontal line drawn through the centre of the second motion shaft, which is not affected by the springs, being fixed in bearings carried by the box bracket, therefore the up and down movement or vibration, which at the most is only half an inch, viz., one quarter of an inch on either side of the centre, does not practically alter the depth in gear of the two spur wheels.
The front part of the engine is provided with a similar spring, on the fore axle, contained in the cylinder, on which are cast stops, to prevent the fore wheels coming in contact with the barrel of the boiler.
Messrs. Foden say: “This perfect spring arrangement materially reduces the effect of shocks or vibrations caused by passing over rough roads, and it is conducive to the reduction of the wear and tear arising from such causes in ordinary traction engines, as leaky fire-boxes, tubes and joints, strained frames and the jolting to pieces of the motion work throughout. Moreover, this spring mounting arrangement adds very considerably to the comfort of the engine driver and steersman."
Fig. 107 represents a sectional view of Messrs. Foden's compound cylinder, showing the steam chests outside. The cylinders and the steam chests are combined in one casting, forming with the jackets a suitable steam dome, containing starting and equilibrium valves, the whole being so arranged as to make priming almost an impossibility. Fig. 107 also shows the new patent compound starting gear, the following being a description: —
The Compound Engine is provided with a special arrangement by which the compound action may be instantly suspended, and both cylinders may take high-pressure steam, exhausting directly and independently into the funnel, the steam being supplied in such a manner that each cylinder shall give off the same amount of power. The object of such an arrangement is to give increased power to the engine when starting or doing exceptionally heavy work, as on steep gradients or when getting over soft ground. It is effected in the following manner: — In the passage between the high and low-pressure cylinders, a three-way cock is fitted, this cock being actuated either by an independent lever or else by the starting lever. In ordinary work, the steam from the high-pressure cylinder passes into the larger (or low-pressure) cylinder, is there further expanded, and exhausts therefrom into the funnel.
If, in case of emergency, it is required to get more power out of the engine, the above-mentioned three-way cock is opened, so that the exhaust from the high-pressure cylinder passes direct into the chimney, which relieves that cylinder of the back-pressure due to working the low-pressure cylinder, and consequently increases its power. Live steam is at the same time admitted into the low-pressure cylinder; but as this cylinder is so much larger than the high-pressure one, it is obvious that if steam of equal pressure were admitted to both cylinders, the larger one would do the most work, and consequently the engine would run unevenly. To overcome this, a steam reducing valve is provided in the passage to the low-pressure cylinder, by means of which the power to each cylinder is equalised and the engine works as an ordinary double high-pressure engine.
The advantages of this starting gear are:
- 1st — It enables the user to obtain a great amount of power for starting purposes, getting out of soft places, or taking heavy loads up steep gradients.
- 2nd — In case of accident to either engine the one may be used independently of the other; for instance, supposing an eccentric rod broke on either engine, all the driver would have to do would be to uncouple both eccentric clips, set the side valve of the disabled engine in the centre of its stroke, and open the three-way cock, as for working double high-pressure; by so doing the engine can be run as a single high-pressure engine, until such time as it can be repaired. Thus by means of the starting gear, our compound may be converted into double or single high- pressure engines; the additional complications being only the three-way cock, and the lever for actuating the same.
A very efficient water-heater, forming a suitable foot-plate for oiling and other purposes, is fixed alongside the barrel of boiler, and containing three lengths of steam piping; a portion of the exhaust steam passing through this warms the feed-water, and what remains uncondensed passes on to the back tank, by which means the greater portion of the heat generated is returned.
The crankshafts are all made of forged mild Sieman's steel, turned out of one solid piece, the cranks being of the disc pattern, which greatly assists to balance the motion; the eccentrics, being also solid with the shaft, and cannot be moved or get out of position in relation to the crank-pins.
The six-horse power road locomotive crankshaft is 3.25 in. diameter, and the crank-pins are 3.5 in. diameter. Messrs. Foden's recent engines have the feed-pumps fixed to the barrel of the boiler. A circular tool-box for spuds, &c., is fixed on the leading axle.
We must now very briefly refer to the trials of traction engines carried out in September, 1884, at the Stockport Show of the Royal Manchester and Liverpool and North Lancashire Agricultural Society. There were eleven traction engines tested built by seven of the best makers. Each engine was supplied with 20 lb. of fire-wood for lighting up: and 20 lb. of coal per nominal horse power for raising steam, and going through the following manoeuvres: — Steam out of the show ground, and traverse a piece of good road sufficiently wide for the engines to turn round, and afterwards enter a clover field cut along the sides for the engines to travel over, then couple each engine to a trolley laden with bales of cotton (the trolley and load weighing about 4J tons), and run round the field until the fuel was used and the steam exhausted.
It is to be greatly regretted that the question of nominal horse power should have been used by the judges, the inconsistency of which was more than once referred to. One maker called his engine, having an 8.5 in. cylinder, a seven-horse power nominal, he was therefore allowed 140 lb. of coal, while two others called their engines eight-horse power nominal with 8.5 in. cylinders, and were consequently allowed 160 lb. of coal. During the trials Messrs.
Foden's double cylinder locomotive was most carefully driven, and every portion of the heat studiously retained, the blast from the two cylinders caused a more even draught, and the slides had an early cut off, quite independently of the driver minding to keep the reversing lever notched up. This engine consequently made an excellent run. The Engineer says:- “Messrs. Foden's engine was more economical than any other engine tried, and they have fairly beaten so far the most eminent firms in the trade. The writer was present at the above trials, and he greatly admired the way the engine performed its task. Messrs. Foden’s engine had two cylinders (not compound) 5.75 in. diameter, it was mounted upon large driving wheels, and hung on springs.
The following table gives a few particulars of the two engines Messrs. Foden entered for the Newcastle Trials July, 1887, which were conducted by the Royal Agricultural Society, both of which engines achieved excellent results, as we shall show presently:
TABLE OF MESSRS. FODEN 'S ROAD LOCOMOTIVES AT NEWCASTLE.
PARTICULARS. (Simple Engine / Compound Engine)
- Diameter of cylinders, in inches - 7.5 / 4.75 and 9.5
- Length of stroke, in inches – 10 / 10
- Revolutions per minute declared – 168 / 156
- Brake horse power 12 /18
- Diameter of boiler barrel - 2 ft. 6 in. / 2 ft 6 in
- Length of fire-box - 1 ft. 9 in. / 1 ft. 9 in.
- Width of fire-box - 2 ft. 0 in. / 2 ft. 0 in
- Height of fire-box over grate - 2 ft. 2 in. / 2 ft. 2 in.
- Area of grate, normal, in square feet – 3.58 / 3.58
- Area of grate at trial, in square feet – 3.00 / 3.00
- Number of tubes – 76 / 76
- Diameter of tubes outside, in inches – 1.625 / 1.625
- Length of tubes - 6 ft. 0 in. / 5 ft. 6 in.
- Fire-box heating surface in square feet – 19 / 19
- Tube heating surface in square feet – 177.6 / -
- Total heating surface in square feet - 196.6 / 201
- Heating surface per brake horse power – 16.75 / 11.15
- Heating surface per square foot of grate – 56.15 / 56.15
- Pressure in pounds per square man – 120 / 250
- Coal used per brake horse power – 2.555 / 1.84
- Water used per brake horse power – 25.63 / 17.37
- Time of running total - - / 4 hr 21 min
- Time mechanical hours – 4.5 / 4.583
Messrs. Foden’s compound engine worked at 250 lb. boiler pressure. The steam was cut off by a separate expansion slide working on the back of the main slide, the expansion slide gear was a modification of Farcots, and is suitable for the engine running either way. We quote the following from The Engineer respecting the workmanship of the engines at Newcastle: - "We believe that Messrs. Foden's works cannot compare in dimensions with those of the great Lincolnshire houses; it is the more creditable to them that the workmanship of the engines and boiler were excellent. Notwithstanding the enormous pressure of 300 lb., the pressure at which the safety valves of the compound engine were set to blow off, the boiler and all its fittings were perfectly tight, not a breath of steam or drop of water being apparent." The engine could be made to work non-compound as per Fig. 107.
We now allow Messrs. Foden to speak for themselves: - "The results show beyond doubt that by compounding, a saving of at least 25 per cent, is effected. We were competitors in these trials both with simple and compound engines, and in our case the actual saving in fuel by compounding = 29.7 per cent. The benefits of the system do not end here. A corresponding or greater reduction of boiler wear and tear is effected. Again, the consumption of water should not be forgotten; in the above trials the water consumption of our compound engine was only 18.23 lb. per brake H.P. per hour, whilst the best simple engine tried consumed 22.5 lb.
The water-carrying capacity of the tanks is 1,440 lb. exclusive of water in the boiler; this would enable the engine, running at 3.5 miles per hour (fast speed), and exerting 18 H.P. actual, to run 4.5 hours or 15.75 miles without water; and in confirmation of the above we may say that at the Newcastle trials, our compound engine drove an 18 H.P. load for 4 hours, 22 minutes, on 1,394 lb. of water, whilst the coal consumption was 184 lb. per brake H.P. per hour, the highest point of economy of both water and fuel yet attained by any traction engine.
The following remarks are quoted from The Engineer respecting Messrs. Foden's compound traction engine: - “Concerning the design and the workmanship of this engine we can say that both are as good as that of any other builder of traction engines, and the perfect way in which both boiler and engine dealt with the enormous pressure carried— 250 lb. on the square inch — is sufficient assurance that there is nothing gimcrack about this engine."
There are several points respecting the Newcastle engine trials to which we might refer, but we cannot prolong this notice. We have said quite enough to show that Messrs. Foden's engines are worthy of careful consideration.
Sources of Information