FRAMELESS ALUMINIUM TANKI H TWO-STROKE POWER PACK
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BROCKINGTON, REPRESENTING the first commercial application of the Rolls-Royce K60 opposed-piston, twin-crankshaft 6.57-litre two-stroke diesel to a load-carrying vehicle, the New Era Mk. II frameless aluminium six-wheeled tanker is a logical development by the makers, Thompson Bros. (Bilston) Ltd., Billiton, Staffs, of the Autotanker prototype eight-wheeler exhibited at the 1960 Earls Court Show. Built for B.P. Trading Ltd., the tanker is of the six-compartment type, has left-hand drive and is destined for operation in Denmark, where the gross vehicle weight will be limited to 19-6 metric tons. Its capacity of 18,000 litres (3,960 gal.) is identical with that of the Autotanker, and even if allowance were madefor the saving in weight derived from the use of gravity discharge in place of pump discharge, the ratio of payload to gross vehicle weight would represent a considerable improvement. It is pertinent that a favourable ratio is more difficult to obtain in the case of a six-wheeled tanker.
With a gross-vehicle-weight rating in this country of 20 tons, the estimated U.K. payload of the tanker is 14 tons, which corresponds to a load ratio of 70 per cent, the ratio of the eight-wheeler being around 61 per cent. A full-capacity load is restricted to petroleum products with a specific gravity not exceeding 0-765, the normal specific gravity of petrol varying between 0.71 and 0.73. In addition to the integral light-alloy structure and the lightweight two-stroke power unit. weight. saving features include aluminium wheels, radiator and oil-water heat exchangers. Developed for the New Era, new types of Metalastik leaf-rubber suspension at the front and rear also contribute to weight saving.
It will he recalled that the Rolls-Royce K60 diesel (see The Commercrai Motor, August 31, 1962) develops 240 b.h.p. at a crankshaft speed of 2,400 r.p.m. and a maximum torque of 375 lb. ft. at an output-shaft r.p.m. of 2,500 r.p.m. Dimensions of the engine include an overall length of 46-25 in., a width of 28-45 in. and a height of 32-25 in., whilst the net dry weight is 1,570 lb,
The unit is mounted vertically at the rear of the tank (the Autotanker was equipped with a Leyland Atlantean power pack) and torque is transmitted through an Allison Torqmatic fully automatic gearbox to the front axle of the rear bogie. Serck oil-water heat exchangers are incorporated in the enginelubrication system and gearbox cooling circuit, whilst the fan of the Serck radiator is driven by an hydraulic motor, the radiator being mounted on the left of the engine compartment in line with the rear wheels.
The same basic principle of operation applies to both the frontand rear-suspension systems, although the types of rubber element employed arc dissimilar. In both caseS Metalastik c4
rubber elements support the tare weight and the reaction of a leaf spring is added to that provided by these elements to accommodate the payload. Basic feature of the front suspension comprises an unequal wishbone assembly, the lower arms of which are mounted at their inner ends on Metalastik torsionally stressed rubber bushes (which are pre-loaded with turnbuckle adjusters) having a diameter and axial length of 6i in. and Sin, respectively. A single six-leaf spring spans the
:s and carries pads of polyurethane at its outer ends, which on brackets attached to the lower wishbone arms when veight loading is exceeded. Axle loading is approximately 0 lb. laden and 3,300 lb. unladen, the spring rates of the !.r bushes and leaf spring per in. of wheel deflection being etively 360 lb. and 1,740 lb. The• combined rate is, fore, 2,100 lb. per in.
ted with Metalastik conical-type rubber bushes, the ions are of steel box section and are mounted on the light-alloy cross-member, the entire suspension assembly removable from the vehicle after the withdrawal of 12 tensile bolts. The springs are damped by Armstrong .opic shock absorbers.
:talastik rubber springs of the multiple-sandwich type with separating plates (similar to those employed by the ind Red Co. on its independent front-suspension system) are used for the rear suspension of the New Era rear bogie, which is essentially of the rocking-beam type, a single trunnionmounted three-leaf spring taking the place of the beam on each side.
The axles are mounted on steel brackets, the upper ends of which are linked to rubber-bushed radius rods, whilst the rubber bushes of the lower ends are linked to the outer arms of the sandwich-rubber spring assembly and to a spacer rod. To resist buckling under compression and shear stresses, twinned sets of rubber sandwiches are employed, the upper set being attached to the central trunnion bracket which pivots with the leaf spring. The two sets are separated by the ends of an H-section steel beam of shallow U-form.
The inner sandwiches are located on a higher centre line than the lower sandwiches. the approximate angle to the horizontal in each case being 22 degrees. At their inner ends the radius rods are carried by a light-alloy bracket welded to the subframe. No shock absorbers are fitted.
Polyurethane pads on the ends of the leaf spring contact plates on the main axle brackets when the tare load is exceeded. Whilst the rubber sandwiches and bushes provide a spring rate of 2,060 lb. per in. of wheel movement, the leaf spring has a rate of 5.540 lb. per in. The combined rate is, therefore, 7,600 lb. per in.
A tubular bracing member is located between the trunnion brackets and is cranked in the centre to accommodate the propeller shaft, and this also applies to the box-section casing of the rear trailing axle. Both axles arc stabilized by a front-mounted Panhard rod.
A basically similar type of rear bogie suspension has been fully tested on a Leyland Octopus chassis and has shown that the system gives a comparable ride unladen or fully loaded.
Structurally the tank has a general similarity to that of the prototype eight-wheeler, but a number of modifications have been introduced as the natural outcome of the lessons derived from service experience in Belgium of the Autotanker prototype. These modifications afford a simplified and lighter structure of increased stiffness, and particular attention has been paid to the avoidance of local stress concentrations.
The all-welded shell is of modified rectangular section with a deep sump (the bottom being arranged with a slope of 3° to facilitate drainage), and features six ullage domes to comply with Danish regulations. NS6 non-heat-treated alloy plate is employed, varying in thickness from 0-125 in. to 0-15625 in.
Stiffening members of the original structure comprised two longitudinals of inverted top-hat section on the lower side of the tank which ran parallel to longitudinals of upright top-hat section welded at the top of the tank, and these were internally connected at each compartment bulkhead by channel-section vertical members. The division plates were of shallow corrugated section.
The only longitudinals of the New Era structure comprise base members of modified form, whilst internal bracing (to resist vertical loading) is mainly dependent upon the five corrugated bulkhead members and front cover, the pitch of the corrugations (which have a depth of 5 in.) having been reduced to 9 in. to aid stiffness. At both front and rear, internal bracing is, however, augmented by two welded channel-section struts, the front struts extending from the bottom of the cover to the top of the fist bulkhead and the rear struts from the load areas of the bogie to the top of the end cover.
Each longitudinal is built of two angle plates (two additional stiffening plates are welded to the shell below each bulkhead) between which stop blocks are inserted under each bulkhead, and the tank is reinforced internally with doubler plates for the entire length of the longitudinals. The brackets extend below the stop blocks and the space is employed at each end for mounting light-alloy sub-frame members, on which the cab, suspension and steering assembly is carried at the front and the power pack at the rear, including the gearbox and suspension units. Of box section throughout, the front members taper to the rear and the rear members are increased in depth in the area of the suspension, high-tensile bolts being used for attachment to the longitudinals. The overhanging section of the rear sub-frame is braced to resist cantilever loading by lippedchannel-section aluminium members bolted to brackets at the top of the tank and to the end of the frame members.
As mentioned in the original report of the transmission, the Torqmatic gearbox essentially comprises an hydraulic lock-up type of torque converter and four planetary gear trains, and provides four forward gear ratios (the box has six ratios, but operation is restricted to the four upper ratios to limit the maximum torque) which are divided into three ranges, the normal driving range being first to fourth ratios. The second range restricts operation to the three lower ratios for hilly terrain (to increase overrun braking), and the low range caters for mountainous running in first and second gears. The control system automatically senses and co-ordinates range selection, acceleration, engine speed and vehicle speed, and selects the most appropriate ratio as required.
An hydraulic paddle-wheel retarder is incorporated in the gearbox, which provides a substantial braking force when fluid is introduced into the casing (circulation of the oil being resisted by stator vanes), but ceases to absorb power when the fluid is evacuated. As an example of the braking force available, the
talent of 400 b.h.p. is absorbed if the retarder is engaged at .ph. in fourth gear.
atios comprise a bottom gear of 2-69 to 1, a second gear 94 to 1, a third gear of F39 to 1 and direct drive, whilst se has a ratio of 6-04 to 1. The torque-converter ratio is 1 and the final-drive ratio of the Eaton single-speed axle to 1.
e engine and gearbox assembly is mounted at the front on ted rubber pads attached to drop brackets which support Jell housing, and at the rear on a single twin-pad unit ed centrally on the rear cross-member. A rubber-cushioned y bracket controls the movement of the rear end of the 'ox.
complicated duplex three-unit exhaust system is employed ve adequate silencing, combined with efficient fire-arresting. s from the twinned exhaust ports on each side of the Le are fed into 10-in. by 24-in, expansion boxes with tudinal baffle plates from which they are discharged :ntially into 12-in. by 12-in, centrifugal type of fire-arresting tbers and thence into conventional high-frequency-ption silencers, to which the tail pipes are fitted.
e hydraulic fan motor and pump of the cooling system are le axial-plunger constant-capacity type employed in the known Serck-Behr system, the speed of the fan being varied rovide a substantially constant coolant temperature by a riostatically controlled valve, which automatically regulates mount of oil from the pump (driven from the front of the r crankshaft) that by-passes the motor. In this installation is no forced draught of air into the radiator when the fan )perative and automatic shutters are not required. A small tulie-fluid cooler is mounted on the face of the main tor.
C use of Dunlop forged-aluminium three-piece wheels (described on page 44 of this issue) affords a weight saving of 41-5 lb. on each of the front wheels and 32 lb. on the rear wheels, and increases payload capacity by 46 gal. of petrol. Dunlop RB6 rigidbreaker 10.00-20 tyres are fitted to the front wheels and 8.25-20 covers to the twinned rear wheels.
The cab is separate from the tank and double-skin panelling is employed throughout based on a frame of steel box-section members, the wheel-arch hoops being extended round the front of the vehicle. Having a core of glass fibre, the rear panelling acts as a fire screen, whilst Plasticell p.v.c. foam (bonded to the skins) gives thermal insulation in the case of the front panels and doors. which is considered necessary because of the absence of engine heat, and increases the effective efficiency of the Smiths heater-demister-air-conditioning equipment.
The driver's seat is framed in aluminium and is fully adjustable. The windscreen is of the wrap-around type and has a centre pillar, and the doors are of the conventional hinged type. The front grille of expanded metal has a surround of polished aluminium and feeds air into the heater-demister system. Kerb-view windows are included in the front panels.
Other features of the tanker include Girling drum-brakes with Clayton-Dewandre Airpak air-over-hydraulic servo and a Neate single-pull handbrake. An Adamant hydraulic steering servo is supplied with fluid from a pump driven from the rear of the generator. Mounted on the left side of the vehicle behind the cab, the aluminium fuel tank has a capacity of 55 litres. The firescreen at the rear is of Durasteel 3DF2 material, comprises two thin sheets of steel and a core of asbestos. A Cooper paper-type air filter is fitted to the power unit.
Overall dimensions of the vehicle comprise a length of 30 ft., a width of 7 ft. 10 in. and a height of 9 ft. 8 in., whilst the wheelbase is 18 ft. 9 in. and the front and rear tracks are 6 ft. 6 in. and 6 ft. respectively. The centre of gravity of the vehicle when laden is approximately 13 ft. 9 in. from the front of the cab, and is moved forward about 5 in. with discharge of the payload. It is anticipated that the vehicle will have an easy cruising speed of 55 m.p.h.