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lew Welded Tipper Bodies

24th December 1965
Page 27
Page 27, 24th December 1965 — lew Welded Tipper Bodies
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solely as a bed for the body when it is in the lowered position. The sub-frame is not therefore a lifting frame in the normal sense, essential features of the design being that the body is mounted on the sub-frame in such a way that deflections are not imparted to the frame: that the front bulkhead and hinge-pin assemblies are rigid structures and that the body structure is torsitinally stable.

Of the close-centre twin ram type, the heavy-duty front lifting gear acts as a stabilizer and the thrust forces on the bulkhead are distributed to the side of the body by virtue of the 'robust top rails and the use of a r•bbed form of external framing of the dumper type that in effect provides high-strength lower rails. Whilst therefore the elastic modulus of aluminium is one-third that of steel and the material can withstand higher bucket impact and rougher usage generally than steel, torsional deflection is uniform and resistance to deflection increases progressively. Bccause the longitudinals are not lifting Members their depth can be reduced to a minimum and the need for steel members is eliminated. The body is attached to the longitudinal by floor wells between the ribs, the cross-bearers being left unattached to the longitudinal..

For bodies with a length in excess of 20/23 ft. a Y-type stabilizer is normally fitted between the vehicle chassis and a platform-type frame welded to the body. Occupying a relatively small area the frame stabilizes the body as distinct from the longitudinal.

Applied to tippers as well as dumpers, bodies designed for lifting by an underbody gear are equipped with longitudinal members between the upper ram pivots and the hinge-pin assembly, and in this case the members act as a lifting frame.

The longitudinal may be extended forward to provide a bed for the body when lowered if this is considered preferable to fitting pads for its support at the front.

It is noteworthy that steel lifting members are normally employed in conjunction with aluminium tipper bodies by the majority of bodybuilders because aluminium members of sufficient depth to give the required rigidity increase the loading height to the degree of being unacceptable and are costly. The two types of structure described enable aluminium to be used throughout .without incurring either of these disadvantages. The practical worth of such bodies is exemplified in the tipper fleet of Hall and Co., all the vehicles being equipped with MIG-welded bodies.

Mr. Dartnell emphasized that it is essential to make provision frir the flexing of the vehicle chassis members in the case of aluminium boxvans and platform ktirrigs if high local stressing is to be ajibided. Pedestal mounting is recommended for both types to ensure uniform flexing with the qualification that if the sub-frame longitudinals of a van body are relatively shallow compared With the chassis members the Structure is generally satisfactory because the body frame does not resist flexing of the chassis. It is noted by Mr. Dartnell that platform body headboards of commendably robust construction are frequently attached to the body rails with a small number of bolts that cannot possibly give ' adequate strength to resist high braking loads.

One of the main problem in boxvan construction mentioned by Mr. Dartnell is the prevention of lozenging of the front bulkhead and of the framework of the rear opening, the latter being' exacerbated if a full-width opening is required for pallet loading. Bulkhead strength can be provided by the use of aluminium frame sections of adequate dimensions but to avoid costly forms of fabrication steel reinforcement of a fullwidth opening frame is recommended.

Conservative practices that are criticized by Mr. Dartnell include multi plication of the uprights of 'boxyan bodies to mate with the cross-bearers when the number of bearers has been increased to cater for high-floor loading. Mr. Dart nell points out that unless a hanging load is carried uprights are employed solely to support the panels and a light roof, structure and that a number of uprights sufficient for the purpose can be fitted at points remote from the end of the cross-bearers. This would facilitate standardization of body side section.

The extension of body panels to form skirts is also condemned by Mr. Dartnell because of the frequent incidents of skirt damage. A satisfactory type of detachable skirt could easily be fitted.

P.A.C.B.

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People: Dartnell, Dart

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