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This Tipper Will Pull Itself Out

26th January 1962
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Page 57, 26th January 1962 — This Tipper Will Pull Itself Out
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Keywords : Bedford Ca

ly JOHN F. MOON, A.M.1.R.T.E.

Bedford Four-wheel-drive 5-cu.-yd. Tipper Proves Capable of Negotiating Terrain That Could not be Tackled by Conventional Rear-drive Machines : All-Vauxhall Manufacture Keeps Cost Down

iHILST all-wheel-drive tippers—as opposed to heavy-duty dumpers—are an accepted part of the scene in such European countries as Germany, Len and Switzerland, the operation of such types is still yely limited in Great Britain, partly because a tipper four-wheel drive is usually a considerably more expertproposition to purchase than a conventional rear1-drive machine. This is because the front-wheel-drive 'merit is usually a conversion by a manufacturer than the original chassis maker, a process which must tably add to the basic price.

deed, there is only one manufacturer of a medium4 x 4 tipper, that being Vauxhall Motors, Ltd., and standard Bedford 4 X 4 tipper with Bedford diesel le and Telehoist 5-cu.-yd. body costs £1,861 compared 11,450 for a TK tipper with 6-cu.-yd. body but the : gross vehicle weight rating. Thus the price gap is ciwed to reasonable limits, and the tipper operator who extremely difficult conditions to contend with can .d to consider a 4 x 4 model as within reach of his :et and not as an expensive plaything.

the extra cost, however small, of a four-wheel-drive !.r worth while? In many cases, no, but the answer is definitely yes if the site conditions include thick mud, loose or slippery surfaces, gradients steeper than 1 in 4, or any combination of these. The additional traction and steering control given by the driven front axle can effect a very worth-while time saving under such conditions, in addition to reducing the need for external aid from bulldozers and the like through tippers becoming bogged in, such " pushing " exercises invariably damaging the vehicle being pushed besides wasting the time of several employees.

So far as design is concerned, the Bedford RSH 11-ft.wheelbase 4 X 4 tipper comes from good stock, being derived from the R-type 13-ft.-wheelbase 4 x 4 model developed 10 years ago for military purposes and since built in considerable quantities for a number of armies. Apart from slight basic structural changes occasioned by the differences in wheelbase, the RLH and RSH models vary principally in gross weight ratings. The standard RLH, which has 11.00-20 (12-ply) single tyres all round, is limited to a weight of 8 ton cwt., whilst with 8.25-20 (12-ply) equipment and twin rears, the rating is raised to 9 ton 12f cwt. The gross rating of the standard RSH, however, which has 8.25-20 radial tyres as standard, is 10 ton 5 cwt. and this rating is not increased, when, as in the case of the vehicle tested, the standard tyres are replaced by 9.00-20 equipment.

Mechanically the specifications of the two types are almost identical, both models being available with either the Bedford 300-cu.-in. (4.927-litre) six-cylindered petrol engine, which has a gross output of 133 b.h.p. at 3,400 r.p.m., or the Bedford diesel engine of identical cubic apacity, the gross output of which is 97 b.h.p. at 2,800 r.p.m. (the new 330-cu.-in. diesel engine introduced late last year is not offered in R-type chassis). With either mgine the standard main gearbox is the Bedford wideratio synchromesh unit, and this drives through a short open cardan shaft into a remotely mounted two-speed transfer box, which has direct and 2 to 1 ratios. This transfer box is controlled by a single lever in the cab, giving the choice of either rear-wheel-drive only and high ratio, or four-wheel-drive and low ratio.

Both axles are fully floating units with hypoid-bevel gearing and a standard ratio of 6.8 to 1. The front axle has a load rating of 3 ton 7 cwt., the rear axle, 7 ton 12 cwt. Conventional semi-elliptic springs are employed at both axles, those at the front being 511 in. long, whilst the rears are 60 in. long and are augmented by seven-leaf helper springs. The front springs are 2+ in. wide and the rears 24 in. wide, whilst at both axles double-acting tele

scopic dampers are incorporated. The 16-in.-diameter brakes of both axles are hydraulically operated through a tandem-piston master cylinder, boost being provided by an upright-vacuum servo.

The chassis frame side members are flitched as standard, the main members being 0.22-in.-thick pressings with a maximum depth of 9 in. and 3-in.-wide flanges. The five cross-members, like the spring-hanger brackets, are coldsqueeze riveted in position. As is usual with 4 x 4 vehicles, the frame height is fairly high, the unladen dimension in the case of the standard RSH. on 8.25-20 tyres being 451 in., but whilst this has the slight disadvantages of raising the centre of gravity and making cab access a little more difficult, the high frame line gives the advantages of improved ground clearance and excellent angles of approach and departure.

Because of the age of the basic design, the R-type 4 x 4s are the only Bedfords in current production to retain the forward-control cab originally developed for the S-type models, and this design of cab, being nearly 12 years old, compares unfavourably with current Bedford cabs in accessibility, comfort and range of vision. With respect to forward vision the high line of the lower edge of the windscreen is a particular disadvantage when negotiating rough a24 country as, combined with the height of the fra means that there is a blind spot extending almost in front of the vehicle, and this is discouraging ft driver who likes to pick his way carefully over ground to avoid damage to either the vehicle or hi

So much for the vehicle's specification. Its per ance was ascertained while carrying b. toad of 1 cwt., and figures taken on normal roads showed have a very reasonable performance and quitt handling characteristics. Its off-the-road perforr also was very reasonable, bearing in mind that t by no means a true cross-country vehicle (for matter, neither were the original army models). rough surfaces caused a certain amount of stel wheel shake, even when taken slowly and, with the running at normal pressure, runs made over a pave track shook the vehicle and its occupants considerably. Although the Bedford could not sumn a 1-in-4 gradient in bottom gear (high auxiliary), bo low restarts were shown to be possible on a 1-in-3 g All the tests I conducted, both on and off the road, made at a gross weight of 10 ton 81 cwt., the Telf body being evenly filled with coarse gravel and the rest weight distribution being such that each of the wheeh almost equally loaded. Normal-speed fuel-consum tests were made over a six-mile undulating route, and out exceeding 32 m.p.h. an average speed of 26.5 n was achieved, despite two traffic stops. The resulting sumption rate of 17.1 m.p.g. is excellent for a vehicle

ning at nearly 104 tons gross weight, particularly in vies the extra tractive resistance given by the front axle am gearing.

A second fuel-consumption run was made over a 23-i circuit of motorway, and this course was completer an average speed of 45.2 m.p.h., full throttle being t the whole time and a genuine maximum speed of exa 50 m.p.h. being timed on level stretches of the motorv The test tank indicated a commendable fuel consump rate-13.3 m.p.g.—and the tipper handled quite stea at the comparatively high speed sustained.

Standing-start acceleration .performance was shown be quite adequate, despite the need to use all four ra of the main gearbox when accelerating up to 30 m.i because the maximum speed in third gear is 29 m.r the speeds in second and bottom being 13 m.p.h. and m.p.h. respectively. The direct-drive acceleration betw 10 and 30 m.p.h. also was quite satisfactory, although transfer box was rather noisy between 10 and 15 m.p.h.

Ithough the braking system of the RSH is somewhat of date compared with current conventional Bedfords, retardation performance was by no means poor, whilst handbrake efficiency from 20 m.p.h. was amazingly d, an average Tapley-meter figure of 42 per cent. being tined from this speed.

ison Hill, which is mile long and has an average lient of 1 in 101, was used for the road gradient tests, these were conducted in an ambient temperature of C. (42°F.) The engine coolant temperature before zing the climb was 73°C. (164°P.), and the climb took dilutes 48 seconds, of which time 1 minute 46 seconds spent in bottom gear (high auxiliary), the minimum at any time being 3 m.p.h. This climbing time is :e good, and caused the coolant temperature to rise only 77°C. (171°F.), showing engine-cooling arrangeits to be entirely adequate.

,s a check for fade the 4 by 4 tipper was coasted down 3 n Hill in neutral using the footbrake to restrict the xl to about 20 m.p.h. This descent lasted 2 minutes seconds, about minute being spent in top gear with throttle applied in order to keep the brakes working :re the gradient is not so severe. At the bottom of hill a full-pressure stop was made from 20 m.p.h., and produced a Tapley-meter reading of 31 per cent.,

which, by present-day standards, does not compare too favourably with the average figure of 77 per cent, obtained from this speed when the drums were cold earlier in the day. None of the drums was smoking and there was only a slight smell of hot linings, but the pedal travel had noticeably increased. The test does show that it will not be safe to take risks with these brakes on long down gradients, although not even the wildest of tipper drivers should be tempted to descend a hill of this length in neutral.

The facilities of the War Department's Fighting Vehicles Research and Development Establishment were made available to me to ascertain the off-the-road performances of the Bedford 4 x 4 tipper. Trials commenced on the special test hills, the least severe of which is 1 in 4. The constant-gradient section of the 1-in-4 slope is 197 ft. long, excluding the approach and departure curved sections, and the gradient was tackled from a standstill at the foot with bottom gear (high auxiliary) engaged. Engine power, however, was insufficient to take the tipper more than half-way up the slope, at which point the engine stalled. A restart in second-low was then attempted, but this failed also, following which an easy part-throttle restart in bottom-low was carried out. While stationary on this gradient I noted that the handbrake was only just capable of holding the vehicle, and then only after it had been helped on by use of the footbrake.

The tipper was then faced down the hill and again held with difficulty on the handbrake. A reverse-low restart was successful, but a following attempt to restart in reverse-high ended in disaster. With a loud crack the transfer-box mainshaft sheared, and this put a decided end to activities for the time being.

It transpired that the particular vehicle tested had an obsolete mainshaft of a type fitted in all R-models up to chassis number 38849 (built in October, 1961). Vehicles after that number have shafts with a higher carbon content and additional heat treatment at the splined end of the shaft, features which give a tensile-strength increase of between 20 and 30 per cent.

Several weeks later the off-the-road tests were continued with an up-to-date shaft in the transfer box, and this enabled the gradient tests to be completed.

The 1-in-3 grade, which is 139 ft. long, was tackled in second-low, but again engine power was insufficient to take the tipper far up the slope. After some difficulty with the handbrake I managed to make a smooth bottom-low restart on this gradient. Facing down the slope a reverse

a2F low restart was carried out successfully, although I to do some pretty fast foot-work on the pedals /new the handbrake just would not hold the vehicle on t gradient.

It was raining heavily during these trials, so it was w some trepidation that I approached the 1-in-2 slope, wh is surfaced with timber baulks for the benefit of the track vehicles which normally are the only ones to use t gradient. Apart from the slipperiness of the slope, 1 v worried about taking the vehicle on to this gradient any case because of the high centre of gravity, it not bei unknown for high-sided tippers of this type to hal somersault when negotiating gradients more severe th 1-in-3. Fortunately for my peace of mind, wheelspin p vented the tipper going beyond the approach curve.

This question of avoiding a high centre of gravity a vehicle with an already high frame line possibly expla the Continental practice of constructing shallow-sided t ping bodies on chassis of this type or even, for that matt or ordinary 4 x 2 types. To get the required cul capacity, the Continental body manufacturers make th bodies longer, and on reflection it seems that such hod must produce a more stable vehicle.

The tipper was then taken on to the suspension cours each of which is 300 yards long. The pave" track v tackled first and at all speeds up to 15 m.p.h.-the maximt a could be reached—the tipper rode very 'roughly, the ipenSion bottoming frequently and the steering being 7y fierce to hold. The battering that the vehicle received Lctured the exhaust system at the flexible section ahead the silencer, shook out both the bolts holding the left [e of the bumper to the chassis frame, loosened the per section of the radiator grille, and undid the catch lding the radiator-filler trap.

Emergency repairs were carried out to the bumper removing one of the bolts from the other side, after iich the tipper was taken down the 1-in.-11-in.-sett .ck, these setts being staggered to induce various pension periodkities. The ride over this track was ite reasonable, and the tipper was not difficult to mainn on a straight course.

However, on the 2-in.-24-in.-sett course, as on the pavd, ride was very rough and the handling difficult. Even owing for the tyres being at normal road pressures, it obvious that very rough surfaces will have to be taken Fwly with this vehicle if chassis damage is to be aided. Still, as I have said, this is not a cross-country hide, its usefulness being mainly its ability to negotiate eper-than-average gradients and difficult soft surfaces. The 4 X 4's soft-surface performance was ascertained

• the Bagshot Heath tracks, and the tipper ploughed its ty quite majestically through thick, slippery mud. At time was traction lost, even when hub-deep in mud, tithe front-wheel drive made it comparatively easy to tintain a fixed course despite deep ruts and so forth.

Mud-covered gradients of up to 1-in-3 severity were cen comfortably, but I avoided slopes steeper than this cause of the old trouble of the possibility of the tipper ming over backwards. Other than this, there seemed be nowhere on Bagshot Heath that the vehicle could be taken with confidence, even if slowly, and there no doubt about the Bedford's ability to cope with thick Ad, provided suitable tyre .equipment is fitted, of urse. The vehicle tested was shod with Michelin " XY " .es, which combine good grip with high flotation. In two respects the layout of the cab was disappointing for off-the-road work. One disadvantage is the high screen line already referred to, and the other is the position of the main gear lever. This is well to the rear of the driver's seat, as it was in the old S-types, and its location necessitates some awkward stretching on the part of the driver, particularly when changing down from third to second gear, a change which it is easy to miss through pushing the lever over too far to the left. The ability to change gear uickly and positively is an essential requirement of any off-the-road vehicle, as a missed change can mean that the vehicle quickly comes to a standstill.

Taken generally, however, and particularly in view of its comparatively low price, the Bedford RSH 4 x 4 tipper is a good bet for any operator who is having difficulty in getting a full day's work out of conventional 4 x 2 types. There is no suggestion of luxury about the vehicle: it is purely a working machine designed to give above-average tipper performance at the lowest possible initial and running costs.

In addition to being available as a complete tipper, with Telehoist all-steel body (with cab-protection canopy) and Telehoist TV5 twin underbody ram gear, the RSH is available as a chassis-cab or as a straight chassis with basic front-end metal work. In these forms it could find a market as the basis of a fire-crash tender, light snow plough, gritter or communications vehicle whilst, if speed is the problem rather than fuel economy. it should be borne in mind that the petrol-engined model is a good 10 m.p.h. faster than the diesel job.

The RSH diesel-engined chassis with standard 8.25-20 tyre equipment costs £1,406, or £1,501 when ordered with the standard S-type cag. As a complete vehicle with Telehoist body and ram gear the price is £1,861. In all cases petrol-engined versions cost £120 less. The optional 9.00-20 tyre equipment, as fitted to the test vehicle, adds 141 to the basic price. The 13-ft.-wheelbase RLH models are between /46 and £66 cheaper than the RSH types. partly because the chassis frames are untlitched.

Tags

Organisations: War Department
People: JOHN F. MOON

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