Crane Fruehauf's service engineering manager discusses some typical conversion costs,
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and reveals that the vaE majority of work is for tri-axles rather thal tandems
AFTER the doldrums of the past three years the trailer market (and particularly the conversion side of the business) is gradually picking up. The long-awaited decision on heavier gross weights put an end to a lot of speculation and finally told operators what they could and could not do.
Not surprisingly, most operators are converting existing vehicles to achieve the five-axle combination necessary to run at 38 tonnes. The business generated has been such that Crane Fruehauf now has a five to to six-week lead time for trailer conversion work. It was not like that 12 months ago I talked recently to Tony Haynes, who is the service engineering manager at CF, to find out some typical conversion costs. So far, Crane Fruehauf is finding that the majority of the larger fleet operators are specifying big singles for a trailer conversion.
As far as new trailers are concerned, 100 per cent are for this tyre specification. CF in fact advises operators to go for big singles with 70mm reverse offset wheels to get a good track with a subsequent benefit to roll stability.
The typical customer goes to CF for advice before he actually gets down to talking about the hardware. The first thing the CF engineers do is to check out the specification of the existing trailer to see if the suspension needs relocation or whether it is simply a question of adding an extra axle to the existing bogie. This is obviously no problem with a CF trailer because all the relevant information is in the data books and this also applies to most popular makes like York and Tasker.
The trailer will need to be stressed before any conversion work is undertaken to make sure that it is strong enough to take the higher loadings. Again this does not apply to CF products because the design strength of the trailer is known anyway. To a certain extent this also applies to the york and Tasker trailers if only because CF has converted enough of these makes in the past to know their capabilities.
With the lack of latitude on axle loadings at 38 tonnes it is obviously essential to get the suspension in the right place. The frame usually needs to be reinforced to cope with the extra scrub loading. Tony Haynes supplied an interesting statistic when he said that, on a dry road surface and a tight corner, the side load equates to the axle load on a tri-axle bogie.
On frameless vans, a subframe extension is required while, for fridge vans the weight of the refrigeration unit itself must be taken into account . before deciding on the bogie position.
There is certainly a lot more to converting a tipping semi-trailer than is immediately apparent. A lot of frame reinforcing is usually required and the bean need stiffening. If the conversi is not done properly then a 38tonner will be far less stable.
It is difficult to convert an existing tipping trailer to run with a three-axle tractive unit. The centre of gravity must be moved forward which means moving the body and ram forward as trailer necks do not like a bending moment betwef the ram and the fifth wheel.
For tandems to be used at 3( tonnes the front end has to be beefed up in many cases. This usually means moving the kingpin rearwards and reinforcing the neck to be capable of an imposed load of tonnes. If the kingpin is movec back then the landing legs nee to be moved as well.
As Tony Haynes explained: "Tankers are treated very muc as individuals. We will not quc until we see it."
Crane Fruehauf quotes £1,71 for a flat platform conversion, which involves adding an axle but without repositioning the existing suspension. This prio is for the situation where the operator retains the twin-tyre figuration and does not ude wheels and tyres for the d axle as CF has found that st operators have local tyre tracts. Chassis and trailer lufacturers are not allowed ass on tyres at less than the iinal equipment price so the rator can often buy them aper anyway.
iding an axle where moving aogie is involved adds £300 ie above price. This price ides cutting off the original :kets and repositioning the )ension cross-members, CF re-use the springs and ue arms but all hangers are aced.
) convert a tandem-axle er with twin wheels to a trion singles will cost £3,300.
e bogie needs repositioning the extra cost is again £300. ( way of comparison, the ent list price of a tri-axle flat form Crane Fruehauf trailer ingles is £8,700.
ir38-tonne operation, the en must be fitted with side rds for which CF quotes £150 )d) as an average price. The dard side guard is in steel adds 150kg (3cwt) to the iden weight but CF also rs an aluminium version weighs only 70kg (1.4cwt) costs £200. These weights Inclusive of the mounting :kets and are not for the side rd alone.
-eine Fruehauf is unusual in int to side-guard struction in that it employs a ed rather than a welded struction. As well as allowing use of aluminium, it also ins that individual rails can eplaced. Kits of parts can be provided for the operator o his own fitting. These are !able in lengths of 3.5,4.5, and 5.5m (11ft 6in, 14ft 9in, and 18ft) and are supplied slightly overlength so they can be "adjusted" to suit the individual trailer.
Most operators are staying with mechanical suspension because of cost. Crane Fruehauf, in fact, would prefer air suspension not only for its lack of sensitivity to fifth-wheel height but also for its excellent compensation. CF has its own air suspension although this has not been on general sale. Later this year the company hopes to offer full air suspension "at a reasonable price." Previously high volume was the usual path followed to keep the price down but as Tony Haynes explained: "We will stick our necks out, set the price and hope for the volume."
An add-on air-suspended axle is feasible according to CF but is considered complex to maintain. Crane will use its own air suspension to special order but only with a suspension that Offers good roil stability as the CF design has a high degree of roll stiffness. Tony Haynes does not see any reason for an operator wanting such an arrangement unless he needs a lifting axle.
One point which is being stressed by all the trailer manufacturers is the need to reduce the brake actuation when moving from a tandem to a triaxle configuration. It should be obvious that a 10-ton axle is somewhat overbraked when running at 7.5 tonnes. Accordingly in common with the other reputable trailer manufacturers Crane Fruehauf includes Type 20 actuators on the front and centre axles in its conversions.
If the operator wants an antilock system then CF will fit Girling although Tony Haynes admitted that he was not happy about Skid Chek's virtual monopoly since Dunlop lost interest in the business. This is not intended as a criticism of Skid Chek — CF worked for two years with Lucas Girling on Type Approval — but a general comment on monopoly situations.
A few own-account operators are fitting anti-lock braking but virtually no hauliers. The reason? "It is a £460 option that nobody wants."
Not all conversion work is physically carried out by Crane Fruehauf. A known operator can be supplied with a kit of parts for installation in his own workshop. CF does a quality check on the conversion as if it was an in-house job and issues a manufacturer's plate where the work is judged satisfactory.