THE NEW PAGEFIELD COLONIAL MODEL.
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A Special Design with a Rear Axle Clearance of 16i ins. Worm Drive to Differential Shafts and Final Drive by Spur Gears.
WE HAVE, from the inception of the War Office subsidy scheme in 1912, repeatedly given expression to the opinion that the subvention type model was well on the way to being an admirable chassis for colonial and general overseas use in not too well developed countries. It is, as generally constructed, of sturdy build, and capable of surviving under much more rigorous conditions of road use than are generally met with in this country, or on the Continent.
The interchangeability as between one make and another of certain essential details is also a feature which must recommend itself to colonial users, handicapped as they are by being so far from the manufacturer's works, for even the best managed spare parts depot must, occasionally, find itself short of some essential detail, The designers of Pagefield vehicles have solved the problem of giving, for overseas requirements, even greater road , clearance to the W.D. subsidy model in a manner which, after accomplishment, appears to be so simple that one wonders why it has not been standardized long ago. A patent has now, however, been taken' out in *connection with this design, and there is no doubt that the makers should reap the benefit by means of increased colonial sales as the due reward for their progressive methods. The whole secret, as might have been expected, is contained in the rear axle case.
The difficulty hitherto has always been that, whether double reduction or worm and wheel driven axle has been used, the designer has always been faced with the necessity.for covering with the easing either the final drive wheels of the final reduction ,in the one, or the worm wheel in the other. The large diameter of these, called for by the high ratio of the gear necessary with heavy vehicles, has always militated against the reduction of the road clearance, provided the road wheels themselves were kept at a, reasonable diameter. Where chains have been used, although they have allowed of increased clearance under the body of the axle, they involve either chain cases or chain wheels rubbing along the edge of the gutters in which the wheels generally run. In the Pagefield Colonial model, the final drive is first by worm and wheel and then 'by spur gears, one pair to each differential shaft. The worm and wheel and the whole of that part of the transmission,,ineluding the differential, are practically normal, except that the worm thread is of the opposite hand to that usual. The whole of the gearing is carried in a easing bolted to the top of a special double banjo type roar axle. The .differential gear does not drive direct to the live axle shafts, but each sun wheel is splined to a short differential shaft, both of which carry a spur pinion.; each of these gears with another a little larger than itself and secured to the live axle shafts which transmit in the uoual way through the hollow axle to driving dogs in the rear road wheels. .
The wheels of pairs of spur pinions are very nearly alike in diameter, so that very little actual gear reduction takes place there. The effect ofthin arrangement is to keep small the diameter of the final drive gearwheel and, since this is centred on the rear axle, it does not project far below the axle, thus allowing a maximum possible road clearance, which is, as a matter of fact, the same to all intents and purposes as though the vehicle were chain driven. The whole arrangement will be understood if reference be made to the accompanying sectional illustration, wherein it will be seen that the final drive gearwheels are hardly any larger in diameter than the bearing caps which support the ball bearings on the live. axle shafts. They are just covered and protected by a thin pressed steel tray, and the distance from the ground to the underside of this tray, which is, practically speaking, the ground clearance is ins., half as much again as the amount allowed by War Office subsidy.
In order to carry through the same amount of road clearance, the front road wheels which, on the standard _model are 900 mm. diameter, have been increased to 1,050 mm., the name size as the rear.
Another excellent feature in any Colonial model is the provision of a differential lock. The one on the Pagefield is of simple but effective design. The differential shafts are hollow. At their inner ends they are enlarged somewhat, and formed as spur pinions. The star piece on the robust differential gear is bored in the centre to receive a collar which has internal gear teeth of a size which will eonveniently engage with those on the ends of the differential shafts. Inside the collar is a diaphragm to which is fastened a rod, which projects through one of the hollow differential shafts, and may be moved longitudinally by means of a claw, which is operated by a familiar arrangement of levers and coupling rods, by hand lever from the driver's seat.. The sliding collar within the differential star piece is of such a length, and so designed, that it is always in engagement with at least one of the differential shafts. In the normal position it is in gear with that one only-, and, so arranged, the differential gear performs its functions in the customary manner. Movement of the control lever, however' slides the collar along and causes it to engage with the other differential shaft. It does this,. more
over, without becoming disengaged with the first one. When the collar is so coupled to both shafts, the differential gear is locked, and the torque of the engine is transmitted directly to both road wheels. In the event, therefore, of the wagon getting into such
The differential locking gear. The a. position that central internally cogged sleeve isthere is a ten: permanently in engagement with one denoY for one differential shaft, and it may be slid driving wheel to into mesh with Ike other when the slip, it is only differential Is to be locked, necessary to put
this locking gear into operation, when both wheels will take their share of the drive, and that one which has the grip of the road will propel the vehicle.
It would not be fair to turn from our discussion of this rear axle without drawing attention2to the undeniable merits of its general construction. The worm wheel and differential gear are carried by two substantial roller bearings placed dose together and backed on either side by ball thrust bearings.
The final drive wheels on the ends of the live axle shafts are-each doubly supported-by a. pair of Skefko ball bearings. The load-carrying axle itself is a most substantial one. ' It is a forging on the familiar double-banjo type, ;type specially shaped so as to accommodate the unusually-arranged gears. Accessibility, so essential a feature here, is naturally much more important overseas, where facilities for overhaul and repair shops are comparatively few and far between. This feature accordingly has had careful attention, as may be seen merely by reference to our illustrations, and particularly that which shows the axle casing in various stages of erection. Removal of the upper case takes with it the worm and its bearings without disturbing the worm wheel or any of the other mechanism, while on removal the middle portion of the casing will, after withdrawal of the live axles, which may be effected in the customary manner with the road wheels, carry with it the whole of the remainder of the gearing.