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A NEW RANGE. OF MANN MODELS.

2nd February 1926
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Page 13, 2nd February 1926 — A NEW RANGE. OF MANN MODELS.
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Preliminary Details of Some New Designs Embodying the Standard Boiler and Power Unit, which Include a Six-wheel Tractor, a Roller and a Tractor-lorry.

DU.RING a recent visit paid to the works of Mann's Patent Steam Cart and Wagon Co., Ltd., of Leeds, we were interested to learn that a new range of products, apart from the steam wagons and agricultural tractor with which most of our readers are familiar, is being offered.

There are several models, all embodying the standard boiler and double high-pressure engine, which are used on the latest Mann Express wagon. By these means the company are enabled greatly to extend the sphere of usefulness covered by their products, these being no longer restricted to work requiring only steam wagons or agricultural tractors.

Perhaps the most interesting development is a short-wheelbase tractor having six wheels, four of these acting as drivers and being mounted on a semibbgie on reversed half-elliptic spring; which are pivoted at their centres. Reference to the illustration which we reproduce of this model will show that the axles are prevented from rocking by radius rods mounted above the springs. The engine is carried with its cylinders pointing towards the rear.

From the engine-gearbox unit a pinion drives a large spur gear which provides a big ratio of reduction for the differential countershaft, from which each wheel is driven separately through the medium of a roller chain.

To give extra adhesion, a 250-gallon water tank is mounted immediately above the driving wheels ; this also provides ample water for the boiler.

The driving wheels are each 4 ft. in diameter and 1 ft. (3 ins, wide, whilst the front wheels are 2 ft. in -diameter and Of the same width.

Steering is effected through tle front wheels only, and we shall be interested to learn from experience with an actual tractor what effect the short wheelbase. combined with the non-steerable driving wheels, will have o'n the steering of the whole machine.

This tractor is intended chiefly for use in undeveloped countries, and for heavy agricultural haulage, ploughing, etc-: The overall length is 14 ft. 10 ins., and the wheelbase (to the centre of the bogie) is 8 ft. 2 ins. 2 The ,second machine, which should prove of particular interest to municipal engineers and those concerned with road construction and maintenance, is a tandem roller. In this machine the engine is arranged across the chassis instead of longitudinally, and drives first through a bevel reduction gear and then via a spur reduction gear. to . the rear roll.

The boiler is mounted forward in what may be termed the usual steam wagon position, but it also is kept very low.

Steering is effected through a worm and quadrant, the worm being driven by a two-cylinder oscillating 6ngine, the steering movement being arranged to correspond exactly with the amount by which the steering wheel is rotated.

The main frame is of channel steel, perfectly straight, and carrying a heavy bracket for the front roll, which is divided in the centre to facilitate steering, and is permitted to rock sideways.

Apart from the six-wheel tractor the company have designed a four-wheel type which is convertible, when required, to a road roller. It is of interest to not that this model is equipped with stab:fa-operated brakes.

In this tractor, much of the weight

has been concentrated over the rear wheels by setting the engine at the rear with the cylinders pointing towards the front, so that the drive is carried from the rear of the vehicle forward to the driving wheels. Here, again, there is a large reduction by spur gear and a chain drive.

The front axle is of the centrally pivoted type, but has Ackerman-steered wheels, and there is a long cross spring.

When it is desired to use this tractor as a steam roller, the ordinary' axle and wheels are removed, and an extension bracket secured to the frame to carry the front roll, steering being effected through a worm and quadrant.

For the carrying of large quantities of goods there is a tractor-lorry. This consists of a short-wheelbase wagon with a two-wheel trailer attachment, the two being connected through the medium of a rocking bar carrying a small but strong turntable.

• Steam or Westinghouse-operated brakes can be employed, and the trailer portion is equipped with a Combined fronf support and jack which can be used for lifting the front of the trailer from the turntable and for carrying the weight when it is required to use the tractor with more than one container.

A few details concerning the combined power unit and gearbox will no doubt be of interest, as it possesses several unusual features.

Two changes of gear are provided, B29 but the cylinders have two distinct points of steam cut-off, and the unit thus gives the mechanical advantages of four speeds, so that the drawbacks of a heavy, slow-running engine on the one side and the unduly fast-running engine on the other are avoided. Normally, most of the day's running can be carried out on top gear, using the early

cut-off ; for moderate inclines, it is -unnecessary to change to the lower gear, the only alteration being to retard the cut-off ; with still more severe gradients, the low gear and early cut-off can be employed, and for exceptionally heavy work the low gear and the late cut-off.

The twin H.P. cylinders have poppet valves for both steam and exhaust, and these can be kept steam-tight in spite of a fairly high degree of superheating.

The crankshaft is a solid forging of high tensile steel running lb Hoffmann roller bearings, and is fitted close up to the crank webs to give maximum stiffness and support. Outside these bearings the shaft is splined to carry the gear pinions, and the overhanging per tion is carried by a third roller bearing. The whole of the engine motion work and the gears run in an oil bath. Girder-section connecting rods carrying large die-cast big-end bearings are employed, and separate camshafts are used for the inlet and exhaust valves, these being driven by spiral gears from the crankshaft.

Unusual construction is employed in the boiler. This is a vertical water tube type with a patented form of inner flue, which provides a good slope to the tubes. The flue centre is pressed to form deep, triangular section ribs of gat strength.

There is an ample combustion chains bar below the tubes and space above.

combined with a special domed cover to permit the fitting of a superheater of ample size, also a steam-drying Pipe, making a full circle.

The particulars regarding the gearbox refer to the standard wagon, but it is possible that they may be modified slightly in the various other designs to which we have referred.

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Locations: Leeds

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