A DRIVER'S DELIGHT
Page 45
Page 46
Page 47
If you've noticed an error in this article please click here to report it so we can fix it.
The Atkinson Eight wheeler By Assembled With Well-proved Proprietory-made L. J. COTTON, Components, the Atkinson Eight-wheeler is a m.i.R.T.E. Robust Chassis, and Gives Economical Operation THE Atkinson eight-wheeler is a typical example of sound British craftsmanship and
design. It is an individually built chassis employing well-proved proprietary units, and has a spacious coachbuilt cab, which is appointed in keeping with the high standard of the vehicle.
The spaciousness of the cab was enjoyed during the 80-mile test, when three others besides myself were carried without discomfort or complaint (even from the observer seated on the bonnet). The full load might have tended to improve the soundproofing of the cab, but in any event it was obvious that the Atkinson is well insulated against the transmission or penetration of noise.
The chassis is powered by the Gardner 6 LW direct-injection oil engine, supported at three points, with absorbent packing pieces between the brackets and frame. It is mounted in conjunction with a David Brown five-speed gearbox and employs fabricated support brackets at each side of the flywheel housing. Fabricated engine and spring brackets and other supports are features of Atkinson design which afford strength with lightness and reduce overall cost. Hardy Spicer propeller shafts are used in the transmission to the rear bogie, which is of Kirkstall pattern, with overhead-worm drives and a third differential between the two fully floating axles.
The rear suspension system incorporates two trunnion-ended springs at each side, connected through a balance-beam linkage. The Atkinson automatic lubrication system to the rear bogie and shackle pins is employed fully to lubricate the moving parts.
Both axles of the front bogie are linked conventionally to the steering
drop arm, with a secondary drop arm pivoted from the frame and connected to the drag link and swivel arm of the second axle. Although the wheels are arranged to steer in correct 'proportion, the tie rods are adjusted for a parallel wheel setting to improve tyre life. Reports from operators confirm that this gives a greater tyre mileage without noticeably increasing steering effort. Mules cam-and-roller steering is fitted.
The Clayton Dewandre vacuumservo braking system incorporates a Lockheed hydraulic master cylinder I
and operating units at the first, third and fourth axles. A notable point in design is the compact layout of the reservoir and servo units, which ensures a minimum time lag between depression of the pedal and operation of the brake shoes.
The Lockheed hydraulic operating cylinders are attached to the stub axles on the front axle and to the axle casings of the rear bogie, the opposite ends of the cylinders being connected direct to the brake cams. These cylinders are accessible for bleeding. Adjustment. for wear on the brake facings is a simple fnatter of lengthening the operating units.
A Substantial Frame
As an individually assembled structure,' the cross-members are bolted to the frame, all holes being reamed during assembly. All the main cross-members are of fulldepth channel section, and secured to the top and bottom flanges of the side members by gusset plates.
The vehicle supplied for test was complete with a wooden platform body carrying nine massive weights, forming the l4-ton payload. Baulks of timber securing the weights in position, and test equipment, added 2f cwt. to the payload.
For a preliminary climb, the Atkinson was driven to Shaw Hill, a short stretch of 1-in-10 average gradient, which has to be negotiated from a standing start. Second gear was engaged when moving away from rest, and held until reaching the steeper section half-way up the hill, when the lowest ratio had to be
used The chassis put up a good performance during the test and scaled a 1-in-6 gradient at a road junction on full lock with a reserve of power.
This trial was too short to show an
52 degrees F., water 140 degrees F. During the climb, I sat on one of the weights on the body to observe the gradients recorded by the Tapley meter. Starting off in good form, second gear was held until the meter registered 1 in 10, when a change to bottom gear was required. The Atkinson slogged steadily up the hill in bottom gear for 31 minutes, maintaining a speed of 4 m.p.h. over the 1-in-8 section. Despite heavy going, the radiator temperature remained unchanged, and there was no indication of overheating from the engine.
Easy to Control
Then we travelled through Preston towards Southport. Because of the light gear change and excellent driving position, the Atkinson is an easy machine to control in traffic. The brakes are adequate for the load, although the acceleration, when compared with that of lighter traffic, is somewhat slower. The deep front windows and quarter-lights afford good visibility, enabling the driver confidently to keep position in a stream of traffic.
As Atkinson six-wheelers and eight wheelers employ a standard engine, transmission and braking system the results obtained in the test were slightly inferior to those yielded by the six-wheeler. There was no need to employ low gear when moving away from rest on level ground, and using the four highest ratios, the time taken to reach the legal maximum speed of 20 m.p.h. was 28 secs. It took a further 34 secs. to reach 30 m.p.h.
Top-gear acceleration was smooth and without trace of transmission whip at any speed down to 8 m.p.h. The time occupied from 10-30 m.p.h. in direct drive was 65 secs. This is an average result for a machine with a low power-to-weight ratio and weighing 22 tons gross.
The fuel-consumption trial, made over a 15.2-mile out-and-return course on the A.59 road, was reasonably level and, apart from three starts from rest, there was no other
occasion demanding the employment of the indirect ratios. The Atkinson was driven at a steady 2728 m.p.h. and returned an average speed for the course of 23.5 m.p.h.
I was surprised at the small amount of fuel required to replenish the test tank to the original level, and the ultimate consumption rate of 10.13 m.p.g. for the eight-wheeler was only 1 m.p.g. less than that obtained on my previous test of an Atkinson machine of 19 tons gross. The fuel consumption of Atkinson vehicles is better than average.
I drove back to Walton-le-Dale, travelling in a stream of traffic for most of the way. I managed to keep up until reaching the gradient up the main street of Preston, Where lighter vehicles were waved past, while the test chassis toiled up the hill in second gear.
The machine is a good steady slogger, whatever the conditions of the road, and with constant-mesh arrangements for the three highest ratios, the driver is not afraid to make a quick change and get the best performance.
Driving an eight-wheeler of this calibre was not hard work. As the initial stiffness of the power unit and transmission components was wear ing off, I did not spare the vehicle on its return journey, and took oil temperatures upon completion of the trials. The curvature of the engine dip-stick guide would not permit a stick thermometer to be inserted into the base oil, so I had to be content with checking the axle-lubricant readings. These showed the thirdaxle oil temperature to be 110 degrees F., and final axle 104 degrees F.
I noted that the mould line round the periphery of the front-bogie tyres was intact. The speedometer reading was 144 miles. This is a proof that a parallel wheel setting reduces tyre wear.