THE . EVOLUTION OF THE 6-TON MANN.
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A Steam, Wagon Embodying Notable Improvements, Including More Powerful and Efficient Engine, Large Boiler, Feed-water Heater, and Better Braking.
FOR SOME time past Mann's Patent Steam Cart and Wagon Co., Ltd., have been busy evolving two new steam wagons to carry 4 tons and 6 tans respectively, to. take the place of the 3-ton and 5-ton models hitherto constructed. These two vehicles incorporate many important improvements in detail, although, to outward appearances, the differences between these and the former models may seem to p be
slight. is most striking at the 'first glance is the removal of the water tank from its original position between the boiler' and body to the sides.
,Actually, there are two tanks, supported by cross-bearers and situated outside the longitudinal frame members and under the body, as is shown in some of our illustrations. This arrangement enables the platform space to be extended by some 16-, ins. and, thelead being carried more forward, little extra weight is thrown on the rear axle by the extra ton carried. The-actual load' ing platform is now 14 ft. by 7 ft. in the case of the fixed body, as compared with a length of 12 ft. 6 ins. in the old type, and 12 ft. 6 ins. by 7 ft. for the tipping body, against 10 ft. These figures, of course, apply to the 6-ton wagon, with which we shall deal in the main in this article, only referring to the smaller model where it differs materially in its construction from the larger one.
The makers, of the Mann wagon cars certainly be classed as pioneers so far as steam wagons are concerned. Their experience in this connection dates from 1806, and they have built wagons both of the overtype and undertype. For the first two. -years they built tractien engines only, and their first self-contamed steam wagon was supplied on January 27th, 1822, and was known as the Mann steam cart. At this time it had to be run as a traction engine with a man in front carrying a red flag.
• This vehicle had a single wide driving wheel between two idler _wheels, which merely prevented the vehicle from turning over. The first overtype wagon with side firing was supplied in April, 1909.
Even these early vehicles had many of the features which are retained in the Latest models. This applies particularly to the one-man control and the side firing of the boiler to which we have just referred. The third great feature embodied in the Mann is direct steering, which permits higher speeds consistent with safety.
So far as detail design is concerned, the Mann also presents several important points nob found in other vehicles. Perhaps the best of these is that all the gears run between the bearings, there being no overhang at any part, in spite of the fact that three different ratios are provided, and that all the gears are of ample dimensions, with generated teeth = of a special involute form giving ample strength. In comparing the new 6-toaster with its 5-ton predecessor, we find that the cylinders have been altered from 4 ins. and 61 ins. by 8 ins., to 4 ins., 7 ins. by 8 ins.in other words, an increase in the bore of the L.P. cylinder has been made. Apart from this, the cylinders have been designed with particularly large ports and straight steam passages; also the cat-off is later in the II.P, cylinder, thus keeping the expansion ratio the same as in the 5-ten model. This engine can be driven at much higher speeds without causing back pressure. The boiler has also been increased in size, and now has a total heating surface of 714 sq. ft. It is, as is well known, ofthe short loco, type with largediameter tubes, disposed so that there is ample space between them' and reinforced with ferrules where they are in contact with the flames. Short, stout stays are fitted between the upper part of the firebox and the boiler shell. Th's is permitted by the use of a circular outer plate over the firebox. Each boiler is tested to 350 lb. per sq. in., and its normal working pressure is 200 lb. per sq. in.
The engine is mounted on the top of the boiler, the cylinder being bolted directto the barrel and steam-jacketed. The eccentrics for operating the double D • slide valves are carried on the crankshaft, and use is made of Stephenson's link-motion reversing gear. The crankshaft and the gearshafts are car-' lied direct by the boiler hornplates, and the gear ratios provided are 5.4 to I on tep, 9 to I. intermediate, and 17 to 1 low. Final drive to the rear axle is by siegle chain of 4 ins, pitch acting through an enclosed differential gear with cut teeth.
The axle is constructed of nickel steel of 55-ton tensile strength. This is carried in bearings which are longer and bigger in diameter than in the previous model. The axle has not been increased in weight or size, the necessary extra strength being obtained by the use of the better material. The larger engine has permitted higher gearing, and the increased size of the boiler allows of long periods of heavy steaming without. forcing.
. The advantages of utilizing three speeds are, of course, manifold. In a two-speed wagon what is known as the intermediate would become the high; thus the extra speed now possible along fairly level roads would not be obtainable.
. The frame consists of two heavy, rolled-steel channel-section side-members, bolted direct to the hornplates and not, carried through to the smokebox, as the strength derived has proved to be ample, and considerable weight is saved by foreshortening them in this manner. These frame members are the same as in the 5-ton 'model, but they are greatly strengthened by the fitting of wide flitch plates above and below them, thus changing their shape from channel to what is virtually a strong girder of H-section.
Careful attention has been paid to the matter of springing. The rear springs are long, with their ends supported in case-hardened steel slippers, which are, of course, renewable.. Below the ends of the springs are bolts. These are merely to prevent the springs jnmping out of the slippers in cases such as when a wheel drops down a drain. These bolts ean be inserted in one of three positions to allow for any stretching which may oecur in the driving chain.
The chain adjustment is obtained by stout radius reds with left and righthand threaded sleeves. Rmaller sleeves of a similar type are used for adjusting the brake rods. The front springing is by two long, laminated cross-springs allowed to pivot at the centre. The front aide itself is also centrally pivoted, and the lower end of the pivot has a truss rod hinged to the front of the firebox.
The brakes consist of a powerful contracting band on the intermediate shaft, operated by a quick-acting pedal, and similar hands acting on the rear-wheel drums and eentrelled by a hand wheel. All these brakes are lined with Ferodo. In the case of the 4-ton model both brakes act on the rear axle.
At this point we may mention that the other outstanding difference between the 6-trainer and the 4-tonner is that in the latter case the frame side-menibers take the form of extensions of the boiler hornplates. these being strengthened by the nse of angle-iron flanges; also the .crosk.members. are of pressed-steel box section, whereas in the larger model the channel side-members are swept,out to the spring centres, and thus a powerful cross-member of this type is not reanired.
Continuing with the 6-tearer, steering is effected by a special sector" bolted to the forecarriage and operated through the medium of a hardened worm.
We recently had the pleasure of being present during a somewhat drastic test of the new 6-tonner, and of checking the results, step by step, in order to ensure their accuracy. The test consisted of driving the wagon with its 6-ton load over a measured distance of 22 miles, the equal of which, so far as its hilly nature is concerned, would be difficult to find in other parts of the country in an ordinary day's run, including as it did such hills as Leathley Bank and Pool Bank.
Careful observation was kept on the wagon in order to note its behaviour under all conditions. On that portion of the road leading to Leathley Bank the minimum speed was 18 m.p.h., and the maximum speed 22 m.p.h. The actual route was from Leeds to Harewood, thence through Arthington, across the Wharf e River at Peel Bridge, and through Leethlev to the famous test hill which is so well known to motorists.
All the way to this hill it was noted that the wagon was blowing off steam in spite of its excellent speed.. It ran quietly, without any fuss except for this, and appeared to be as simple to control as an ordinary car. The test hill has an average gradient' of 1 in 5 over the steep portion, and a maximum gradient of 1 in 4 at the bend. The wagon Was driven straight up without any difficulty, stopped in the middle for some minutes while photographs were being taken, and then restarted. This it did without any hesitation whatever, and performed the rest of the climb at a fast walking pace who witnessed its performance on this hill considered it excellent, especially as the wagon wasiabsolutely standard and carried its full toad.
Its climbing powers are greatly -assisted by the fact that, apart from its changes of gear, it can be eha.nged to double high pressure -when necessary.
The return journey was made through Pool, up Pool 'Banke--a hill with a' length of approximately a mile and an average gradient-of 1 in 9—to the main Otley-Leeds road, and thence via Headingley ta Leeds. The water and fuel had been checked off at the commencement of the test and were again checked at the end. So far as the consumption of either was con cerned, it is but fair to point out that the wagon was only running for 80 minutes during the 160 occupied by the whole performance; for the rest of the time it had to remain stationary, using . up fuel and water while phetography and checking operations were in progress. The consumption of coal—that being
the fuel employed—was 1 .cwt. 2 qrs. 16 lb. for the 2 miles. This works out at 8.36 lb. per.mile, or 13.39 riffles per cwt. The water used was 120 gallons, being slightly over 5i gallons per mile, or 271 miles for the full tank of 150 gallons. The average speed over the whole course was 161 m.p.h., after allowing for the time during which the wagon was stationary.
These results we consider eminently satisfactory. The conditions under which the vehicle was working were far from ideal, being considerably More severe than the average which would be encountered in the same distance over ordinary routes, and no special efforts mere made to save fuel in any way, as is shown by the fact, already mentioned, that the wagon was blowing off steam during most of the run.
Wo have no doubt that very much better consumption results could he obtained over ordinary routes if the wagon were driven with the idea of studying economy; in fact, previous trials have already proved this. For instance, in one rum of 47 miles with a load of six tens, the average speed was 13a m.p.h., and 154 miles were obtained per cwt. of fuel, including that used for getting up steam.. The wagon also ran 32g. miles on a tankful of water.
With a trailer carrying an extra four font, making up the total load to. 10 tons, the same speed was achieved, but -the mileage per cwt, was reduced to 11, and the mileage per tank of Water to 241.
It may be of interest to point out that during the whole of this run the vehicle was entirely controlled by one man, who was' able to do the stoking and attend to the driving, even in this hilly country, without experiencing any difficulty. The driving position, also, gives a clear view ahead.