AT THE HEART OF THE ROAD TRANSPORT INDUSTRY.

Call our Sales Team on 0208 912 2120

The tver

22nd September 1961
Page 66
Page 67
Page 68
Page 69
Page 66, 22nd September 1961 — The tver
Close
Noticed an error?
If you've noticed an error in this article please click here to report it so we can fix it.

Which of the following most accurately describes the problem?

Takes Si

Beating

by John

.I.R.T.E.

ALTHOUGH a 24-ton-gross articulated outfit cannot carry as great a payload as a rigid 24-ton-gross vehicle, the increasing world-wide popularity of the heavy articulated vehicle,is clear proof that many operators are prepared to sacrifice the ton or so of payload involved in the interests of more flexible working.

One of the most outstanding tractive units for operation at 24 tons gross currently produced in this country is the Leyland Beaver, from the Power-Plus range introduced in

September of last year. Tested with the more powerful of the two optional units, the Beaver articulated outfit displayed outstanding fuel economy, acceleration and hillclimbing, above-average braking, and safe handling, whilst the abundance of power-assisted controls made the unit a,. light to handle as any private car.

Because of their ownership of Scammell Lorries, Ltd., ,Leyland are in the unique position, for a' British heavyvehicle manufacturer, in having a semi-trailer maker within the group. Thus it is not surprising that advantage has been taken of this to develop a Scammell tandem-axle semi-trailer to match the Beaver tractive unit. In this way the complete Leyland-Scammell outfit can be regarded as a single entity, and this shows up in the overall performance of the vehicle, in direct contrast to some of the illmatched combinations frequently found on British roads.

The Beaver tractive unit, which has a wheelbase of 8 ft., is one of live Beaver maximum-capacity four-wheelers in the current Leyland Power-Plus range, haulage models with wheelbases of up to 17 ft. 6 in. being available, with solo ratings of 14 tons, but gross-train-weight limits of 24 tons.

Like other Power-Plus models, the right-hand-drive Beaver is available with either the 0.600 9.8-litre " economy " diesel engine, which develops 140 b.h.p. (net) up to 1,700 r.p.m. and 438 lb.-ft. torque at 1,200 r.p.m., or the 0.680 11.1-litre " high-performance" unit, the net output of which is 200 b.h.p. at 2.200 r.p.m. with a peak torque rating of 548 lb.-ft. at 1,200 r.p.m. Left-hand-drive models are not available with the 0.600.

With either engine a five-speed constant-mesh gearbox is standard equipment, with the option of a sixth overdrive ratio. There is another optional ratio of 9.31 to I, but this is offered with the 0.680 engine when the vehicle is to be used only on hard surfaces. There is no restriction on the use of the ratio with the 0.600 unit. This crawler" ratio is contained in the forward section of the gearbox, and drives the layshaft: thus it can be used to double up the main box ratios—a valtIable asset when working in hilly territories.

The rear axle is a double-reduction unit, with spiral-bevel

primary train and epicyclie hubmounted secondary gearing. There is a choice of three standard overall ratios-7.74, 6.06 and 4.82 to 1--and the vehicle tested had the 6.06-to-1 gearing.

Bolting is used throughout the assembly of the chassis frame, the side members of which are pressings, with a maximum depth of 9+ in. and 21-in. flanges. Frames of up to 1l in. x 3 in. x in. are used on some of the Beaver haulage models. Semi-elliptic springs are employed at both axles, those at the front being 3 in. wide. whilst the rears are 3+ in. wide, and telescopic dampers are standard equipment at the front axle. Also standard equipment is Mantes cam and double-roller steering with hydraulic assistance, whilst the driver's efforts are still further reduced by the air-assisted clutch actuation which is incorporated as standard on 0.680 engines, although it is not available with the 0.600 unit.

Bendix-Westinghouse air-pressure braking has been adopted, the Leyland .S-cam brakes being actuated by diaphragm assemblies through Bendix-Westinghouse slack adjusters. This braking system incorporates yet another labour-saving device as standard--a power-assisted hand

brake.

_ The standard cab is an attractively styled all-steel assembly, a particular feature of which is the low step ahead of the front wheel. An alternative version of this cab is available with plastics panelling attached to the same basic framing members: this costs a little more than

the all-steel cab, but saves over I cwt. in weight.

The matching Scammell semi-trailer has identical S-cam brakes to those used on the driving axle of the Beaver, although alternatively 15+-in. x 5-in, two-leading-shoe wedge-actuated brakes can be supplied. In either case brake operation is through a two-line air-pressure system, the air reservoir and brake relay valve for which are carried on the semi-trailer.

Two entirely new types of bogie suspension are offered on this semi-trailer, both being based on four independent triangulated arms which are interlinked on each side to reduce wheel hop when braking, with subsequent reduction in the rate of tyre wear.

Bellows-type air springs provide the suspension medium of one type of bogie, the alternative version having rubber springs, each spring consisting of progressive, self-damping stacks of rubber discs. The rubber-sprung bogie was fitted to the test outfit and this, like the air-sprung version, has rubber-bushed joints to eliminate all need for periodic lubrication, The semi-trailer frame is a particularly robust assembly, with 15-in. x x side members, braced by live cross-members-three of which are tubes-welded in place. Lightweight, vertical-screw support legs are fitted, and an S.A.E./S.M.M.T, fifth-wheel coupling is standard. Bodysupport outriggers-spaced at 3-ft. intervals-are welded to the side members, and the standard timber platform body affords a clear length of 25 ft. 7 in. when a tailboard is not fitted.

For, the home market the Beaver tractive unit is supplied with 10.00-20 (14-ply) tyres as standard equipment. and the Scammell semi-trailer was fitted with the same size of tyre. The semi-trailer can be specified with 9.00-20 (10-ply) tyres, whilst for export the Beaver is fitted with 11.00-20 (12-ply) equipment.

Ready for the road the Beaver, from which the spare wheel and carrier had been removed to make room for a fuel-test tank, turned the scales at 5 tons 4+ cwt., whilst the unladen weight of the semi-trailer was 3 tons 191 cwt. Iron weights totalling 14 tons 12 cwt. were placed on the body, so that with myself, a Leyland driver and test equipment aboard the gross train weight was exactly 24 tons. Distribution was such that all the tyres were loaded well within their retated capacities, whilst, were it not for the desirability of having the same size of tyre on all wheels. the semi-trailer wheels could have been equipped with 9.00-20 (10-ply) tyres.

Brake tests were made first, and the figures obtained are most satisfactory for an articulated outfit of this weight. There was no wheel locking during any of the tests, and the overall stability of the combination was impressive. The average maximum retardation indicated by the Tapley meter was 59 per cent.

Although the mean stopping distance from 30 m.p.h. was nearly 10 ft. greater than that obtained from the same speed with an Octopus rigid eight-wheeler (The Commercial Motor, June 2, 1961), the retardation was still good, delay in the system having been reduced to 0.25 seconds (during which time the vehicle would travel about 11 ft. when braking from 30 m.p.h., hence the difference between the performances of the rigid and articulated Leylands).

Two handbrake tests were made from 20 m.p.h. Using the tractive-unit handbrake a maximum retardation of 15 per cent. was obtained from this speed, which. is quite satisfactory. Application of the semi-trailer brake handreaction valve on the Beaver's steering column resulted in a Tapley meter reading of 29 per cent. —again quite satisfactory.

The acceleration times recorded from a standstill up to 40 m.p.h. are outstanding for a vehicle of this weight, and are almost identical to those obtained in June with the 0.680-engined Octopus. Good direct-drive times between 10 and 40 m.p.h. were obtained also, and again these figures were close to those recorded with the Octopus. This 0.680 unit has extremely good torque characteristics, and it pulls hard at low crankshaft speeds.

Four sets of fuel-consumption figures were taken, all while fully laden. The first two were made on a level stretch of road to obtain strictly comparative figures to show the advantages of the overdrive _ratio under such conditions. The difference was 14 per cent. —well worth the additional £30 for this optional ratio.

Next a run was made along a 10-mile circuit of narrow, undulating roads and, without exceeding 33 m.p.h., the trip was completed at an average speed of 25.2 m.p.h. The resulting fuel-consumption rate of 9.1 m.p.g. is remarkably good, and gives a time-load-mileage factor of 5,493—very high in view of the conditions.

It is obvious that on a twisty, hill route such as this, the reduced transmission resistance of an articulated vehicle with a single driving axle saves fuel compared with the higher resistance afforded by the double-drive bogie of a rigid chassis. For instance, the 0.680 Octopus returned 8.3 m.p.g. over the same course in June, although the average speed was only 0,2 m.p.h. slower.

The final test was made along a 17-mile circuit of the Preston By-pass motorway, and this was completed at an average speed of 47.8 m.p.h., 60 m.p.h. being exceeded in places. The resulting consumption rate was 7.15 m.p.g., giving a time-load-mileage factor of 8,222. The outfit handled in a most stable fashion at these speeds and, despite the rather severe grades (by motorway standards) to be found on the Preston By-pass, it was not necessary to change lower than fifth gear. In addition to the obvious economy given by the optional overdrive ratio, it also raises the top speed from 45 m.p.h. to 58 m.p.h.

Gradient performance was assessed on the /-mile-long Parbold Hill, the average gradient of which is 1 in 12. The clirrib, which was made in an ambient temperature of 71° F., occupied only 4 minutes 20 seconds, and second was the lowest gear needed, this ratio having been engaged for 1 minute 6 seconds, during the course of which time the road speed never dropped below 10 m.p.h. No exhaust smoking occurred during this ascent.

The engine-coolant temperature before making.the climb was 158° F., and the ascent caused this temperature to rise by only 16° F., showing the cooling system to be more than adequate for this type of duty. As a safeguard, the cooling system incorporates a " no-loss " circuit into which is fed any water forced out of the main system due to increased temperature, and from which it is drawn back into the main system as the temperature drops again.

Fade resistance was ascertained by coasting the Beaver outfit down this hill in neutral, keeping the speed down to 20 m.p.h. by use of the footbrake. This is a particularly severe test for a vehicle of this weight and it lasted

2 minutes 20 seconds. At the bottom of the hill a stop was made from 20 m.p.h. and the Tapley meter indicated that the maximum efficiency was only 4 per cent. lower.

I would call these brakes as near fade-free as humanly possible, and this sort of performance illustrates the wisdom of providing adequate drum and lining area, the complete outfit having a total frictional area of 1,381 sq. in.

The Beaver was then returned up the hill and stopped on the steepest section, the severity of which is 1 in 61. The tractive-unit handbrake, the semi-trailer air brakes and the semi-trailer ratchet-type parking brake were each applied separately, and all held the outfit on this slope.

A second-gear restart was then attempted, but this failed, too many revs, giving rise to clutch slip and too few causing stalling. An easy, part-throttle restart was made in bottom gear, however, without the accompaniment of tractive-unit " bouncing " or other undesirable side effects.

At all times the Beaver " artic." handled very well, and was in no way tiring to drive, although the possibility of driver fatigue setting in will be even more remote when some efficient form of acoustic insulation has been found for the engine cowl, power-unit noise being somewhat loud.

All the controls are easy to reach and light to operate, and the general cab layout is good, although, as I remarked in connection with the Octopus tests, additional grab handles by the cab doors would assist access into the cab.

For a short-wheelbase tractive unit the Beaver rode extremely, well, whilst the stability of the semi-trailer also was above reproach. The vertical wheel movement allowed by the geometry of the bogie suspension and the selfdamping characteristics of the rubber stacks combine to give a particularly smooth ride over bad surfaces.

All in all, there can be few maximum-capacity articulated outfits to match the performance of this Leyland-Scammell combination in terms of performance, handling, robustness and potential ease of servicing. The linking of these two famous names has produced an outstanding vehicle.

Tags

Organisations: US Federal Reserve
People: Beaver
Locations: Bodysupport

comments powered by Disqus