The Clydesdale A REAL I
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DRK HORSE
Powered by the Albion Four-cylindered Oil Engine, the Clydesdale Tractor Operates With Smoothness and Efficiency. Outstanding Economy Obtained over a Stiff Course Without Detriment to Average Speed
By L. j. COTTON,
M.I.R.T.E.
THE. reputation earned by the Clydesdale breed of horses for possessing •almost unlimited strength is being ably continued by the Albion Clydesdale. On test, the Albion tractor showed an outstanding zest for hard work, performing its task with a smoothness that belied only a four-cylindered oil engine under its bonnet; its economy, in its class, is without comparison.
The Clydesdale is one of the lighter class of chassis built by Albion Motors, Ltd., having the engine, clutch, gearbox and other components of the FT range, and the sturdier frontand rear-axle assemblies of the heavier CX class. The four-cylindered direct-injection oil engine, developing 75 b.h.p. at 2,000 r.p,m., has fully automatic variable timing, which provides a flat torque curve and assists in fuel economy. Its cylinders are equipped with push-fit renewable dry liners, and the bigends of the connecting rods are split obliquely to allow of the rods being withdrawn through the cylinder bore.
Nickel-bronze shells, with a white-metal bearing surface, are used for the big-end bearings, whilst five whitemetal-lined main 'bearings carry the short and sturdy crankshaft. Crankcase and cylinder block are formed in a rigid integral casting of alloy iron. The detachable one-piece cylinder head carries the overhead valves and the inclined two-hole injectors, the former being operated from the camshaft via push-rods and rockers.
No exhaust pump is fitted to generate the vacuum for brake operation, as an automatic by-pass valve fitted to the air manifold, operating in conjunction with a throttle valve, performs the duties of the conventional unit.
B8 When the accelerator pedal is released the air valve closes, and a vacuum is built up in the reservoir, being opened automatically at slightly above idling speed to prevent the engine from stalling The gearbox is bolted to the engine casing to form a unit which is four-point mounted in the chassis, on rubber at the front and by a spring-loaded bell-crank system with rubber dampers at the rear. Gear changing is simplified by dog-engagement constant-mesh gears to all ratios. Providing a high factor of safety, the heavyduty worm-drive gear of the rear axle has worm centres of 8. ins.
An efficient and powerful braking system is installed in the tractor, consisting of a Clayton Dcwandre servo operating through Lockheed units to Girling two-leading-shoe assemblies. A vacuum pipe from the tractor servo is arranged for connection to the Carrimore automatic-contact-coupling valve to operate the brakes of the semi-trailer. The vacuum pipe on the tractor is auto matically sealed when the vehicles are separated. A reaction valve on the trailed unit ensures simultaneous operation of the brakes on the tractor and semi-trailer.
The Carrimore 22-ft.-long 8-ton semi-trailer, with Quickfit coupling arrangements and a retractable turntable gear, was used for the test, this unit having a dropsided body and a D-shaped front which increases loading space. Its main frame is constructed from channelsection steel, the cross-members and angle-steel truss bracing being welded in position. Spring brackets are fabricated into the frame. A solid high-tensile-steel axle is employed, with machined reaction plate seatings keyed and pressed to the axle beam. The design of the caststeel hubs is such as to accept wheels which are interchangeable with those of the tractor.
Turning circles of the complete unit were measured in the Albion service depot at Willesden before starting the test. As the Clydesdale has an exceptionally wide front track, a marked degree of manoeuvrability is obtained, the turning circles being approximately 40 ft. in diameter.
After leaving Willesden, the unit was driven towards Watford to test the tractor's climbing ability. I immediately noted the quiet operation of the power unit, which is toned down by the ,noise of the exhaust, the silencer passing across the chassis below the cab. When accelerating with full throttle, the purr from the exhaust was sufficient to cover all engine noise, and the usual "Diesel knock" was notably absent. I have heard many petrol engines that have been noisier than the Albion four-cylindered oil engine.
Peterborpugh Road, with a moderate gradient of 1 in 10, caused no difficulty to the Clydesdale, second gear being employed to negotiate the steepest section. Observing the abundance of power, I decided to risk the displeasure of the law by tackling the steep incline of Yew Walk, which is prohibited to vehicles of the capacity of the Clydesdale.
Starting from level ground and running immediately onto a 1 in 9 gradient, second gear was used and held until the severity of the incline increased to I in S. This enforced a rapid engagement of bottom gear—a mameuvre which was accomplished without the wheels coming to rest. The engine was accelerated to maximum revolutions, and there was an ample reserve of power to climb the 1 in 5-i section. These hill tests were made with such ease and rapidity that I neglected to take wator temperatures. With the cooling arrangements as on the Albion, it would have to be a long and steep climb to make any material difference.
I then drove the unit to Windsor, taking stock of the chassis acceleration, lightness of control and general handling on the way. The steering is at the right height and angle to permit long spells at the wheel without tiring, and remarkably little effort is required in driving. As the gearbox has full constant-mesh gearing, changes in ratio were made with facility, even if the engine and road speeds were not correctly aligned. I enjoyed driving the Clydesdale because of its easy handling, smooth-running engine and well-built Durarnin cab, which is arranged with a double seat for two attendants.
The speedometer was checked for accuracy by taking the time between mile posts at 30 m.p.h., which is just within the maximum governed range of the engine. Although the Albion was kept at peak revolutions for several miles, I found it operated smoother and more economically between 24-26 m.p.h., at which point it ran without the slightest roughness.
As a matter of procedure, I tested the brakes with an emergency application on a straight stretch and on a
curve. The results showed that there were high spots on the tractor brake facings, causing slightly heavier marking on the near-side wheels, and that the semi-trailer brakes required slight adjustreient. The total effect of the brakes on both units brought the Clydesdale to rest in just over 20 yds. from 30 m.p.h., giving an indication that speed could be maintained with safety.
Although I found the narrow and winding streets of Eton and Windsor well congested with vehicles, driving the manceuvrable tractor with its trailer unit provided no terrors, and I drove through the towns with confidence.
Series of " Pimples " The fuel-consumption trial, starting from Ascot and finishing at Feltham, was a course which would never be selected by a manufacturer to demonstrate engine economy. The first four miles was a series of" pimples" which called for the frequent use of indirect ratios, and in the first 15 minutes of the trial, fourth gear was used for 3 minutes, third gear for li minutes, and second gear for 1 minute 20 seconds. A good, straight run between Virginia Water and Staines improved the average speed, but the busy shopping centre in the town slowed progress to a crawl in the traffic stream. There were two half-minute delays before reaching the Staines reservoir, and from that point the Clydesdale was given the whip to increase speed to 30 m.p.h. Deducting the amount of stationary time, the 10 miles' trial was covered at an average speed of 19.7 rn.p.h., which is an achievement reflecting the flexibility of-the power unit.
My surprise came when replenishing the test tank, to find that 5i pints was sufficient to fill the tank_ This shows a fuel return of 14.55 m.p.g., which developed to
gross ton-m.p.g. gives a result of over 200, a figure normally associated with rigid eight-wheelers only. I had kept an eye on the exhaust during this trial, but as the economy shows, there was not the slightest trace of haze or smoke under any condition of load or speed—the Albion uses the fuel to a better purpose.
Oil and water temperatures were taken at the end of the trial, the readings showing the radiator water at 154 degrees F., gearbox 117 degrees F., back axle 120 degrees F., with atmospheric temperature of 63 degrees F. The curvature of the engine dipstick-guide prevented the insertion of a stick thermometer into the base oil. With these operating temperatures, all within 100 degrees F. of ambient, and the rugged sturdiness of the tractor semi-trailer construction, the Clydesdale should prove an admirable unit for overseas operation.
Good Mating with Engine
Acceleration trials, made between Feltham and Hounslow, showed the Albion to have a transmission ratio well mated to the engine power, from 0-20 m.p.h. taking 27.5 secs., and 0-30 m.p.h. 62 secs. For a low power-to-weight-ratio machine, the top-gear acceleration (direct drive) was more than reasonable, from 10-30 m.p.h. being reached in 63 secs.
I had already taken stock of the brake efficiency, and had made use of the brakes during the day to assist the facings to bed down. As a result of this the unit was brought to rest in 63 ft. from 30 m.p.h. From the tyre marking I made, it was apparent that better efficiency would be obtained with slight readjustment of the shoes at the wheels. Nevertheless, 48 per cent. braking efficiency is a good braking effort for a vehicle which is not completely run in.