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Softly, softly
Page 74
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Page 76
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A survey of suspensions for bulk vehicles by Trevor Longcroft
AN IMPORTANT part of any bulk vehicle is its suspension. An expensive tank can suffer fatigue fractures if the unladen ride of the semitrailer is rough, and high centre of gravity tanks can be unnecessarily hazardous to drive if roll stiffness is too low.
Some thought at the specifying stage and a knowledge of the basic alternative suspension systems available can overcome these problems, and possibly save weight and maintenance effort at the same time.
The conventional leaf .spring suffers from having a deflection rate which is independent of load, and it can therefore only be effectively designed to give its best performance at one load — usually the maximum axle load — and part-laden or unladen ride is a noor compromise.
Single-leaf springs of the taperleaf type save a considerable amount of weight per axle and have mildly progressive rate characteristics. As a result they are becoming popular.
Rubber used in torsion, shear or compression has good ride properties laden and unladen and, provided the rubber parts are protected from sunlight and grease, has a very good life. Another small but increasingly important bonus is that rubber suspensions run quietly.
The ultimate from a ride point of view is the air suspension. A tandem-axle air suspension costs in the region of £200 more than rubber suspension, which itself is about £150 more than conventional steel springs, but where the unladen ride is critical the extra money would be well spent. Air suspension, although it has not escaped criticism from users, is very adaptable; bogie spreads, for example, can be made to suit any application as only pipes connect the axle spring units. Roll stiffness of air-suspension units may be altered by use of restrictions between lines of wheels.
Aeon Products (London) Ltd, 1 1 -2 1 N orth down Street, London Ni 9BW.
Using Aeon hollow rubber springs in conjunction with a normal leaf-spring suspension it is possible to maintain a small deflection between unladen / laden platform heights. The progressiv rate spring provides, says the company, good anti-roll characteristics. Kits are produced or will be designed to suit different vehicle applications.
Chalmers Suspensions Ltd, Bridge Road, Chatbum, Clitheroe, Lancs.
This company markets singleand tandem-axle running gears using a hollow-rubber-spring suspension medium. The single-axle version has a 10-ton capacity, the tandem 22 tons.
The bogie is said to have good articulation and to offer similar frequencies to air suspension systems — but without piping, valves and dampers. Four axle spreads are available: 52in., 62in., 72in., and 85in., and the running gear without axles weighs 6251b. Mounting height, unladen, is 17.25in.; laden 15in., and the spring-base width is 40in.
Crane Fruehauf Trailers Ltd, Hayes Gate House, Uxbridge Road, Hayes, Middx.
Single-leaf and multileaf single, tandem and tri-axle bogies and air suspensions are offered by CF.
The CD2 twin-spring or walking
beam tandem-axle suspension cater: for loads up to 30 tons and is design& for operation under arduous conditions.
For normal road operation there it the conventional single, tandem oi tri-axle running gear using multilea springs, though tandem and tri-axl: running gears may be fitted with single-leaf springs, offering ar increased payload capacity.
Single-axle running gear has 10-ton capacity, tandem up to 20 tom and tri-axle up to 18 tons.
Singleand tandem-axle air suspension running gears using Dunlof Stabilaire or Hands Neway equipmen are also offered, the tandem axle with maximum capacity of 20 tons, th: single 10 tons.
Dunlop Ltd, Suspensior Division, Engineering Group Cash's Lane, Coventry CV1 LIDS.
Stabilaire air-sprung running gear i produced by Dunlop and mounted or to sub-frames or chasses by companie such as Dyson.
Available for singleor tandem-axl configurations Stabilaire requires working air pressure of between 77 pi and 84 psi depending on suspensio type. Chassis height above axl centre-line is 15.75in. and th tandem-axle kit weighs about. 7251t the single-axle weighs 3681b.
Dunlop's Polymer Engineering Div sion based at Evington Valley Road, PI Box 98, Leicester LE5 5LY produce Metalastik rubber-bonded-to-met: springs. They provide lubrication-fre suspension and are manufactured in range of sizes and stiffness.
In the walking-beam type suspension the springs can be used t accommodate pivoting. Spring design include circular types with stei interleaves which are normally loade in shear. The Chevron spring hz different spring rates in vertica transverse and longitudinal directior nd is loaded both in shear and ompression.
A third design is cone-shaped. In the orizontal plane this spring is stiff nough to obviate the need for dditional axle control.
)yson supplies single, tandem or .i-axle running gears with either ingle-leaf, multileaf or air springs 3tabilaire).
In the air-suspension bogie, air prings are mounted between the axle nd sub-frame at each wheel. During ormal running the trailing links rticulate about their leading pivots and le shocks are taken by springs and ampers. When the vehicle rolls, say 'hen cornering, articulation occurs at le rear linkage points also. Linkages n either side of the axle move in pposite directions relative to the hassis, and, depending on direction of )11, each rubber spring is compressed r stretched offering resistance to roll. Roll stiffness is adjusted by altering le pre-load on each rubber spring.
Axle spread is not limited by iechanical linkages, the system is asically two single axles connected by ir pipes; axle spread can be altered by hanging pipe length and the position f axles on the chassis. When axles are ,idely spaced a self-tracking rear axle an be fitted. When fitted with wide ngle types the spring track can be 'creased to improve stability. omponents for single, tandem and i-axle versions are interchangeable. The single-axle bogie has a capacity 110 tons, the tandem axle 20 tons.
aton Axles Ltd, Victoria oad, Great Sankey, Warngton, Lancashire.
aton markets rubber and leaf-spring indem-axle running gears produced by le Hendrickson Manufacturing Co, of merica.
The RS running gear uses four ibber load cushions and a walking-beam parallelogram linkage arrangement at each side. Vertical pins are used in conjunction with the load cushions to support the weight and maintain stability.
Maximum rated capacity of a unit weighing 817Ib without axles and fitted with the 50in.-long steel walking beam is 44,000lb. Aluminium beams may be fitted.
The later AT and RU series running gears have a similar construction except that a leaf spring unit replaces the substantial inverted triangular bracket of the AS system. Rated capacities of the RT series are up to 50,000lb and the RTE version (the RT with extended springs) 38,000lb. The lighter RU and RUE series have a maximum capacity of 34,000113, but at 744Ib are 3001b lighter than the RT series. The RUE (extended spring version) is recommended for tank and bulk carriers which operate unladen for part of their life.
A similar design of running gear is also used for driving axles.
Hands Neway Ltd, Hucclecote, Gloucester.
Hands Neway offers a range of spring and air running gears for all trailer applications up to 45 tons ground load, and an Air Ride suspension for tractor/truck applications up to 10 tons per axle. All the suspensions are available in kit form, while trailer suspensions may be supplied as built-up running gear.
The company has three tandem-axle steel spring suspensions designed primarily for trailers. The Rubber Tilt suspension (RTS) incorporates a pair of balance beams and a pair of multileaf spring units arranged to produce a non-reactive suspension capable of carrying 20 tons.
The company claims good roll stability through rear-axle-clamp rubbers which, with the axle acting as a torque rod, provide roll stiffness yet offer limited axle tracking when turning, to reduce tyre scrub.
The TS system is a twin-spring tandem-axle suspension with load capacities up to 45 tons, axles being either overor under-slung.
The heavy-duty tri-axle TR running gear has a 40-ton capacity.
Hands Neway also makes air suspensions for both powered and dead axles. The 'AR I system, for non-powered singleor multi-axle configurations with loads of up to 10 tons per axle, incorporates an underslung trailing arm design with rolling-lobe air springs mounted to the rear of the axle, permitting low frame height. The axles may be spaced according to the C & U requirements for bogie loadings.
The ARD-L is a lightweight single /multi-axle air suspension for live axles. Single-axle capacity is 7 tons, tandem 13 tons.
The AR D-H, a heavier-duty model, has single-axle capacities up to 10 tons, tandems up to 20 tons.
Should one air bag not function, the air may be exhausted from any Hands system and the laden vehicle driven home on the rubber stops at speeds up to 45 mph.
A. W. Hunton & Co Ltd, Drayton Road, Norwich NOR 301.
Tandem-axle running gears using multileaf and taperleaf springs are produced by Hunton. Following conventional tandem-axle design, the suspensions are available in two axle spreads: 7ft lin. weighing up to 10cwt without axles and subframe and with a capacity of 20 tons: and 4ft 5.25in. weighing up to 9551b with a capacity up to 24 tons.
A single-axle version weighing a maximum 545Ib has a designed capacity of 13 tons. Taperleaf versions are up to 3001b lighter on a tandem bogie.
George Neville Truck Equipment Ltd, Lindleys Lane, Kirkby-in-Ashfield, Nottinghamshire.
George Neville produces a tandem-axle rubber suspension bogie developed primarily for tipping semi-trailers which require a low centre of gravity when tipping, combined with variable springing, roll stability and a large tilt angle.
The bogie has an M-shaped prefabricated beam to each side. The axles are located between each inverted V of the M by a pair of Metalastik sandwich springs at each wheel. The springs project from either side of the axle and are secured to each side of the inverted V. Torque rods from the centre solid V member keep the axles aligned. The body tilts about a fulcrum located 6in, below the tandem axle centres, about 14in. from the ground.
The bogie has an axle spread of 4ft and operates at 18 tons to C & U Regulations; design weight is 20 tons. The bogie complete with axles, brakes, lights etc, but without wheels and tyres weighs 24cwt.
North Derbyshire Engineering Co Ltd, Darley Dale, Nr Matlock, Derbyshire.
Norde manufactures three suspension units, one single and two tandem-axle, that use rubber sandwich springs.
In the single-axle version, the axle is supported at each wheel by a pair of inclined bonded-rubber sandwiches which are attached to brackets mounted on the sub-frame.
The close-coupled or walking-beam tandem bogie with a 5ft axle spread also uses bonded rubber sandwiches as the spring medium, but these are located as a pair to each rocking beam pivot. A stirrup and a bump rubber limit the suspension's vertical movement and add to the roll stiffness. Capacity is 18 tons. The relatively wide spring base — 3ft 10in. — assists vehicle stability. A typical weight complete with 6ft long sub-frame and wheels is just over 1.75 tons.
The lateral location and torque reaction of axles in all Norde suspensions are taken by an upper A frame which keeps the axles in constant alignment.
Rubery Owen-Rockwell Ltd, Darlaston PO Box 10 Wednesbury, Staffs.
The M series running gears are probably the most common fitted tc British trailers. Available in single-, tandemand tri-axle configurations, thE units may be fitted with multileaf oi taperleaf springs.
A typical tandem-axle suspension, the M42, has a capacity of 42,5601k and weighs 820Ib without axles anc sub-frame. Axle spread is just less than 5f1. and the unit has underslung axles.
The company also produces twc widespread tandem-axle running gears, a multileaf and taperleaf model, botf with two axle spreads: 80 in. ant 74.5in. Capacity of the units 44,8001b, a typical unladen weight o. the multileaf unit is 11001b. ThE taperleaf is over 300lb lighter.
Taskers Trailers, Cravem. Industries Sales Ltd, Annz Valley, Andover, Hants.
The Taskalastic walking-beam tandem axle-bogie rubber suspension available with plated design weights o 18.5 tons or 20 tons,
The axles are attached to the beam via U bolts which clamp, but still alloy for limited axle movement. Axil movement is further controlled b, triangulated radius arms connectei through a prefabricated bracket on ti the axle centre. Each joint i rubber-bushed and the assembly i lubrication free.
The lighter, 18.5-ton-capacity mock has 54.72in. axle spread, the heavie 20-ton models 74,54in. and 80in spreads. Unladen weight . of tlm suspension unit ranges between 80711 and 835Ib depending on the model.
York Technical Service: Ltd, Market Harborough Leicester.
York produces single-tandem an tri-axle running gears using leaf-sprin suspension mediums. The TS serie comprises the TS1 (single axle) whic has a maximum weight of 3761b, th TS2 (tandem-axle) 7951b, and the TS ftri-axle) 11 661b. Capacities range fror 20,000lb for the single axle t 45,000lb for the tri-axle an widespread version of the IS suspension.
For trailers where light weight called for, York have the Harc single-axle suspension with a capacii of 21,000lb and weighing 3031b. lightweight tandem-axle running gel weighing 585Ib and able to can 26,880Ib is also produced.
The company also makes th Supaleaf tandem-axle suspension usin four single-leaf springs. This runnin gear weighs 336Ib when fitted to Yoi axles, Many of the units can ha% springs underslung to reduce vehic platform height.