WHY NOT 1 STILLAGES AS BODIES?
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sks P. A. C. Brockington, A.M.I.Mech.E. I,N the January 9 issue of The Commercial Motor I suggested that a standard air-suspension system could be modified at a reasonable cost to vary the level of the platform by about 6 in. to match the deck height without additional modifications to the equipment. Fitted with a suspension system of this type a bare chassis could also operate as a carrier of complete body stillages.
In the proposed design of a body-stillage outfit the frame members of the prime mover would act as support brackets for the stillage, the only extra vehicle equipment being a locking Mechanism for securing the stillage sub-frame to the chassis. After the vehicle had been backed under the stillage the chassis would be lifted pneumatically to take the load, the stillage locked to the chassis members and the frame returned to the normal operating level. The stillage -legs would be removed or automatically retracted after the support feet had been raised from the ground, the locks or actuating levers of the legs being released by the action of the clamping gear.
Given the availability of a suitable air-suspension system. the development of complete body stillages of this type would be relatively straightforward. It is, therefore. appropriate initially to examine the scope of such a development in preference to assessing the technical difficulties involved. .
To many operators, the body-stillage outfit would offer benefits comparable with those provided by semi-trailers and, taking the longer view, it is probable that the system would afford special or multiple advantages in some applications outside the scope of the semi-trailer. It is possible to envisage an extreme case in which a single chassis would be employed, in conjunction with a number of stillages, as a platform vehicle, tipper, van and passenger vehicle. Whilst it is unlikely that any operator would employ such a variety of stillages for one prime c16 mover, its adaptability might well be exploited substantially to reduce the cost of running a mixed fleet, as well as improving internal transport and storage facilities.
Apart from its potential value for stillage lifting, air suspension would have the outstanding merit of accommodating changes in load automatically up to the maximum rating and would not be affected by changes in stillage weight. No other systems, apart from the hydro-pneumatic type, could provide this advantage.
Examining a typical case in which a fleet comprises a number of similar prime movers and upwards of double the number of semi-trailers of a common type, the main benefit to the operator of employing articulated vehicles is that a tractor can collect an empty semi-trailer while the goods on the original semi-trailer are being unloaded. In some instances the semi-trailer is retained at a depot for storage for fairly long periods to obviate double handling.
Similar advantages could be derived from operating body-stillage outfits, with the possible exception of easy manceuvrability. If, however, a special lifting truck were provided to transport the stillage over short distances in the depot, internal movements would be facilitated, particularly if the truck were equipped with a turntable steering head.
Moreover, the relatively low weight of the body stillage, compared With the weight of a semi-trailer, would reduce difficulties of handling by an overhead hoist or crane. Equipped with castors for depot movements, an empty stillage could be easily manhandled.
Employed for storing goods over a limited period, body stillages would assist the solution of many short-term storage problems. Moreover, special storage stillages could undoubtedly be produced which catered for the individual requirements of the warehouse, but were suitable also for occasional transport by road.
This application of the body stillage offers a facility which is already provided by a container designed for loading on a standard vehicle by fork truck or hoisting gear. Containers cannot, however, be employed unless a suitable means for lifting the load is available at all the depots visited by the vehicle.
The inclusion of an extra depot, not equipped with the necessary mechanical-handling devices, could seriously upset the economy of fleet operation if the transport of containers were the main traffic. Whilst the body-stillage system would not increase mechanical-handling difficulties, its adaptability to manual handling, combined with selfunloading features, would increase flexibility to cover many unusual and emergency operations.
Another important operational aspect of the body stillage is that, in the event of a breakdown, it could easily be transferred to another suitable vehicle, whereas a container could be moved to the platform of the second lorry only if a hoist of the required capacity were available.
The body stillage also has the advantage, compared with the container, that the weight of a platform body is not added to the prime mover. The weight of a special storage stillage would be greater than that of a container, but there would probably be an overall saving.
The visit of an American articulated bus to this countr last July coincided with a leader in the July 11 issue of The Commercial Motor advocating that the authorities should seriously consider legalizing this form of passenger transport. Such a change in the regulations might, it was considered, assist country bus •operators to work economically in sparsely populated districts. If passenger body stillages were developed they would afford the same advantages at a lower cost. If other suitable prime movers were available (with the necessary licences), the breakdown of a tractor, or its urgent use for another operation, would not immobilize the passengers.
According to leading bodybuilders, the design of a bus or coach stillage would follow conventional practice and, although it would be somewhat heavier than a standard body, the additional weight and cost would not be serious. The main cost considerations would, therefore, be the development of suitable mounting legs and locking devices.
Reviewing the possibilities of a body stillage in comparison with the known merits of semi-trailers, a haulier with a large fleet pointed out that maoy operators employed semi-trailers because of their increased payload capacity and he emphasized that the greater weight of a body stillage would reduce the capacity of a rigid vehicle. This aspect of body-stillage development is all-important and would be a deterrent to some operators.
Nevertheless, a body stillage could be designed to incor porate a trailing axle and be employed to carry heavier loads than the rated capacity of the vehicle in its standard form. The suspension of the third axle would preferably be based on pneumatic units, but this would not be essential.
No serious attempt has yet been made to fabricate bodies the sections of which can be easily dismantled for conversion to another type of structure without complete rebuilding. Probably the nearest approach to this projeci is represented by the Neville body, the length of which can be varied by increasing or reducing the number of standard sections. The use of Meccano-type bodies may be fostered by the development of body stillages and could be associated with the production of collapsible bodies Recent progress in the design of collapsible containers is indicative of the trend.
The proposal that complete body stillages should be developed was first made by a well-known operator who was reviewing the problems associated with direct export to the Continent by semi-trailer. Employing body stillages for Continental traffic could eliminate one of the most serious difficulties in organizing collections at the ports of destination.
Although it would be necessary to equip collection vehicles with suitable locking devices and there would be a limit to variations in frame dimensions, the capital cost of the carrying equipment would be reduced and the Continental operator would, if the system were fully developed, have greater latitude regarding the type of prime mover employed. The joint development of body stillages by British and Continental operators would, however, be necessary before the full possibilities of the system could be realized.
Special export stillages could undoubtedly be developed for some types of traffic which would facilitate double stacking on the ferry vehicles and thus provide a means for exporting two similar loads for the freightage charged for a single load.
To develop foolproof mounting gear and coupling gear is of first importance to the successful use of body stillages. If the vehicle frame had to be placed within very fine limits under the stillage before it could be raised to support the load, the time taken in_ the operation would be serious.
Locating the Stinage
Ideally it should be possible to " collect " the body stillage as easily as a tractor is coupled to a semi-trailer. It would be imperative to develop some simple means for guiding the stillage frame into the correct position if the chassis were out of centre by several inches transversely or longitudinally. A substantial chassis-mounted pin, guided by a spring-loaded funnel member into a socket on the stillage, could be used to locate the body longitudinally. Clamping gear could take the form of contracting socket rings acting on the chassis pin and on additional body-mounted pins at the rear.
The most difficult problem, particularly with regard to weight, cost and safety, would be the development of suitable support legs. In the majority of applications to longdistance goods vehicles engaged on regular runs, removable legs would probably be the most practicable. For some operations, however, built-in retracting gear would be required. In this case the front legs could be mounted on pivots between cross-bearers and fold inwards under the chassis. The rear legs could easily be located transversely on the rear bearer to support the ends of the body frame.
If the operator required foolproof safety locks, they could be actuated by electrically controlled solenoids. For example, the detachable legs could be positively locked in position until an electrical connection had been made with the vehicle system and current were available to unlock them. The solenoid circuit could be closed by the final movement of the coupling pin, which would ensure that the legs could not be dislodged until the body was correctly located.
Power retraction by electrical means would also offer advantages if current consumption were reduced by using light-alloy legs. A system of warning lights could be fitted at small extra cost.
Unlike a body suspended from chains, a loaded body stillage on legs could not readily be moved a few, inches from its static position to register with locating brackets. Mounting the stillage on castors would, however, obviate repeated manoeuvring of the vehicle in coupling-up. Equipping the wheels with a lever-and-ratchet mechanism would assist the loaders to make final " inching " adjustments.
Wheel-arches a Problem
The case of the van and passenger-body stillage with wheel-arches offers a particular problem if wastage of payload capacity is to be avoided. If the floor of a Stillage were below the level of the tyres, the increased clearance required when the vehicle was being backed under the stillage would preclude the use of a standard air-suspension system to raise the chassis to the body-frame height.
It would, therefore, be necessary to fit the vehicle with special lifting bellows (this would not present technical dilliculties) or to employ special jacking legs. Modifying the body to allow the wheels of the vehicle to move rearwards at the sides of the body frame to the mounting position could be accomplished only by providing full-length box-section channels inside the van.