A 2-2i-TONNER OF STRIKING DESIGN.
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Particulars of the New McCurd Chassis, the Main Features of which are a High Degree of Accessibility, Efficient Methods of Lubrication • ancl Generally Clean Design.
ONB OF the most promising of the new chassis which have just been placed upon the British market is the 2-2i-to1i McCurd, built by the MeCurd Lorry Manufacturing Co., Ltd., Hayes, Middlesex. It is of particular interest as, with its introduction, its makers re-enter the commercial
vehicle field after a lapse of several years. The former McCurd was a large-capacity chassis and is now again available.
The company have had a long experience in the commercial-vehicle trade, first manufacturing McCurd lorries in 1913, and entering into temporary retirement immediately before the big slump in the trade which occurred a year or two after the war, but it is obvious that since that time close observation has been kept on the various modifications in design and the changed requirements of users. Consequently the new model embodies most up-to-date features and is a remarkably able example of commercial-vehicle engineering with cleanly designed units of pronounced accessibility. The most careful attention has been paid to the question of lubrication and the prevention of undue wear through the entry of dirt and water. Tecalemit lubricators are used throughout and four-wheel brakes are provided, with the addition of a powerful transmission brake operated by the hand lever and located behind the gearbox, both sets having a one-point hand adjustment conveniently situated.
The power unit is a four-cylindered monobloc of 4 ins. bore and 6 ins. stroke, the detachable head being a one-piece aluminium casting embodying also a hot-air intake Which draws air from over the exhaust manifold and conveys it through the head to the carburetter, which is bolted direct to the cylinders and has a control for regulating the proportion of hot air to cold air. The R.A.C. rating is 25.6 h.p., but 35 b.b.p. are developed at 1,000 r.p.m., 50 at 1,500 r.p.m. and 63 at 2,000 rai.m.
The power emit is suspended from an arched crass-member at the front and bolted to an extremely strong cast-steel cross-member at the rear. The pump and magneto are mounted at the ends of a casing situated above the timing ease proper and driven by a worm-geared cross-shaft. The dynamo is mounted vertically on the cross-shaft casing, and on a bell-crank lever pivoted to the front of this casing is mounted the fan, the V-belt drive to which can be adjusted by one setscrew pressing against the vertical arm of the bellcrank bracket. The fan is two-bladed and of cast aluminium; it runs on ball races and is so well enclosed that, according to the claim of the makers, it is necessary to pack it with grease only once a year.
The situation of these important details gives them the utmost accessibility and lifts them well clear of dirt and dust.
The water jacket is carried very low and the delivery from the pump is taken to the lowest point, the connection being secured by one MA.
As an example of neatness, the magneto-control rod passes through the crankcase, thus reducing the number of joints and mountings. The cap of the combined oil filler and breather is held in position by two tension springs and can be slipped off any moment, whilst the oil filter can be removed by disconnecting one pipe and removing one nut. No joints need be broken to remove the radiator, flanged fittings being employed for the water connections, each flange having four bolts.
At this point it is of interest to mention that not only are there very few nuts used, but all these are accessible to the ordinary spanner, no special tools being required.
There are no excrescences on the engine to collect dirt, but extra cooling area is afforded by providing wide, shallow ribs on the sump. The makers guarantee that after three months' service no oil will be found on the engine. This prevention of leakage is obtained by eliminating felt washers and using reverse screws wherever necessary.
A portion of the cross-shaft casing is cut away to expose the packing gland of the pump, and a simple spring-lock holds the gland nut in the required position. Chain drive is provided for the camshaft only, a jockey roller affording adjustment, but tests have proved this almost unnecessary.
Oil from the relief valve drops on to the worm gear of the cross-shaft and then fills pockets in which the gears dip, so that even when starting from cold the teeth are immediately lubricated. The worm drive to the cross-shaft is taken from the camshaft.
A light aluminium casting of large diameter, faced with Ferodo, formethe clutch centre. This has no spigot bearing, but the sleeve on which the cone is mounted can slide over two ball races placed 5 ins, apart and completely enclosed. and it is only when the clutch is withdrawn that it rests on these races.
The same idea is carried out in connection with the clutch withdrawal race, the operating fork for which is provided with pivoted blocks of fibre which only press against and arrest the rotation of the end thrust race collar when the clutch is withdrawn ; normally, the race revolves freely with the shaft. There are two enclosed Hooke's type joints on the clutch shaft, and the accessibility is such that the clutch can be dropped on to the floor in six minutes. This question of accessibility also applies to the starter, which is held by a swing stirrup and can be slid out in a few seconds.
Some interesting features are to be found in the gearbox, which affords four speeds and has alloy-steel shafts and gears hardened and ground. There are three selector rods,
these being locked internally by spring-held bolts. The shafts are short and stiff, and there is a roller bearing for the spigot-in the primary pinion. The box is suspended at three points from two cross-members, and only three bolts have to be removed to allow it to drop. The transmissionbrake shoes are anchored to a cross-member • they are of the loco. type cast in aluminium and with Ferjido linings. An adjusting sleeve-nut with a snap-face locking device is pro
vided. There are two Hooke's type enclosed joints on the solid propeller shaft.
A full-floating rear axle is employed, this being of the overhead-worm type, whilst the casing is a steel forging of the pot type, all the wheels running on floating bushes.
There are several differences between the passenger model A and the goods model B, although the price is the same in each case—to wit, £555. In the passenger model, Hotchkiss drive is supplied if required, whilst in the goods model the axle is provided with radius rods anchored to the frame side members and a special type of torque member having a spherical bearing on the upper portion of the worm housing and a two-way joint where it is secured to the rear crossmember of the frame. In this' case the springs are shackled at both ends, the axle being permitted to float under the control of the radius rods and torque member.
The disc wheels are shod with 36-in. by 6-in. Dunlop tyres, twins being provided at the rear.
Particular attention has been paid to the steering gear, which is of the worm and complete-wheel type with an eccentric adjustment for meshing. A simple screw collar on LAC column permits adjustment of the thrust races. The column is well raked, and another feature which gives good control is that the hand-brake lever is carried very low and the driver can haul it up instead of pulling it back.
In both models the frame is perfectly straight, the side members being of rolled channel steel, which is not only stronger, but lighter, than pressed channel steel. A special low-frame-level model will be available shortly.
To prevent damage to the radiator through any frame warping, it is carried on spring-tensioned bolts, and to avoid any possibility of binding of the change-speed lever through the same cause, this floats. The wheelbase is 13 ft. 6 ins., or to order ; track, 5 ft.; length overall, 20 ft; width of frame, 2 ft. 9 ins.