A NEW DIMENSION IN THE SPACE RACE
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Ray Smith Demountable's Contar drawbar system is giving a Manchester distribution business greater flexibility. David Wilcox
reports
ALTHOUGH reducing the unladen weight of lorries has been an obvious target for truck manufacturers, it is being increasingly recognised that many operators are volume or dimensionally constrained.
Evidence of this is the development of features such as cab roof mounted sleepers to save deck length and thinwall insulated bodies to boost the usable internal width.
The advent of the close coupled principle for drawbars is another step in this direction for the already space-efficient drawbar configuration. Because of the wealth of drawbar experience on the Continent it is hardly surprising that the close coupling concept has come to the UK from there.
It was last spring when Ray Smith Demountables introduced the Dutch Contar close-coupling system into the UK. The system has been sold in Hol land for about 21/2 years and there are about 150 Contar equipped drawbars running there.
Ray Smith admitted that it took quite a time to sell the first Contar in the UK but, including those currently in build, just over 20 have been sold to date.
Harris Warehousing and Distribution in Heywood, Greater Manchester, was among the first customers and now has four Contar equipped drawbar outfits. A large part of this Transport Development Group company's business is distribution for a leading confectionery company and this is retail/wholesale multi-drop work. All four Contar drawbars (with Volvo F7 six-wheel rigid units) are engaged on this work and they went on the road two to three months ago.
They were the first drawbars of any description in the 120-strong Harris fleet and fleet engineer Geoff Broadbent and Heywood depot manager Sam Elliot explained why they had introduced this advanced type of outfit.
According to Sans Elliot, the drop profile of the confectionery distribution is changing, with a trend towards larger but fewer deliveries. Harris therefore wanted to move up from the existing 16-tonners and selected drawbars rather than artics for two reasons.
First, restricted access at some deliveries would pose problems for maximum length artics but could be overcome by drawbars which can drop their trailers if necessary.
Secondly, Sam Elliot explained that it is expected that the mix of the confectionery products being carried may change so that in future the Harris vehicles will be increasingly cube constrained_ So, with an eye to the future,volume-efficient drawbars were considered the best solution.
To be more precise, Harris did not need volume; it wanted platform space to accommodate as many pallets as possible. This led fleet engineer Geoff Broadbent to close coupled drawbars which optimise their length by running with a very small gap between the two halves of the outfit. Only when turning corners do they cunningly extend the gap to give the necessary swing clearance.
Crane Fruehauf has the German-designed Ackermann-Fruehauf GLZ system and, since the beginning of this year, York's new TEC division has had the franchise for another German system called PAL.
What attracted Geoff Broadbent to Ray Smith's Dutch Contar system was its simplicity. All the mechanism needed to extend the A-frame during cornering was contained on the drawbar trailer.
There is a large turntable on the drawbar's dolly and a secondary, smaller turntable in front of it on the A-frame. This secondary turntable is geared to the main one with a sturdy chain. Also attached to the secondary turntable is an eccentric coupling to the telescopic tube that slides in and out of thr A-frame.
So, during cornering, the drawbar dolly is displaced relative to the rest of the trailer and this causes the main turntable's chain to rotate the secondary turntable. Because of the eccentric connection on this the telescopic tube in the A-frame is extended to give the necessary swing clearance on corners.
The PAL system is broadly along the same lines but uses cogged wheels instead of a chain to link the turntables.
Even with a deeply recessed underslung coupling, most conventional drawbars need to run with a gap of at least 1,4m (55in) between the bodies. With an ideal installation Contar can reduce this to 600mm (24in). The Harris outfits cannot quite achieve this and have a gap of 660mm (26in). The little extra spacing is needed because the Harris units are six-wheelers and so the coupling cannot be quite so deeply recessed to maximise the swing arc. The body height also has to be taken into account — the taller the body the greater the gap to allow for vertical movement when negotiating a ramp.
The rest of the Harris drawbar specification is as follows; Volvo F7 sixwheeler rigid, conventional VBG coupling, York drawbar trailer, Ray Smith demount system on both rigid and trailer with Don-Bur Spacemaster sliding door bodies.
While the Volvo F7 rigids have the usual Ray Smith electro-hydraulic power pack for the demounting operation, Harris was able to dispense with this on the trailers. They have air-suspension which doubles as the demount lifting power.
The Contar system allowed the use of two 7.7m (25ft 4in) overall length bodies within the 18m limit. Similarly, the Don-Bur Spa cemaster body squeezes every available centimetre out of the 2.5m width limit while still giving the good access afforded by sliding side doors.
The Spacemaster is a flush-sided de sign with top-hung side panels which can slide out and over the panels next to them. This permits two 1,200mm-wide metric pallets to fit side-by-side.
On the Harris bodies this gives a theoretical capacity of 28 pallets (14 in each body). In practice, the company is loading 13 in each body because one row of pallets is arranged with the 1,000mm dimension across the body.
Geoff Broadbent explained that 14 pallets is possible but leaves little width for not-quite-perfect pallet loads. This is because the Harris bodies have some light insulation in the side panels to protect the chocolate confectionery and this steals a little internal width.
Harris specified the six-wheel F7s as the drawbar rigids because it wanted total interchangeability between fully-laden demount bodies, and four wheel rigids would not be able to match the weight capacity of the trailers (the demount equipment is an additional weight penalty).
With their six-wheelers the complete drawbar outfits weigh in at around 16 tons each and so allow a payload of a further 16 tons. While saying that a 38tonne gross train weight limit would be of no use to Harris, Sam Elliot commented: "I'm not an engineer, but I can't see any logical reason why drawbars are still limited to 32 tons and not 38 tonnes."
As it is, the Harris drawbars are in the optimum position of cubing-out and weighing out virtually simultaneously and so unlike many drawbars they are often nearing the 32-ton gtw limit.
Bearing this in mind, Geoff Broadbent feels their fuel consumption of 35.8-34.9 lit/100km (7.9-8.1mpg) is up to expectations. The relatively low bodies (6ft 6in through the door aperture) help and he wonders if the close coupling has a measurable fuel benefit because of the aerodynamics involved. The four Volvo drawbars still have little mileage on them and he expects their consumption to improve.
While one of the drawbars is kept on distribution work in the Manchester and North-West area, the other three service the confectionery distribution in the North-East. This involves each drawbar doing a loaded night trunk up from Heywood to the North-East where a day man takes over the vehicle to do the deliveries.
The operation is very flexible and each day driver can either take the whole outfit or drop the trailer or swap the demount bodies, whichever he feels is the best solution. Harris does not have a depot in the North-East, but can use other operators' premises for dropping trailers.
Then, a North-East based night man returns the empty vehicle to Heywood and returns to the North-East with a loaded one for the next day's deliveries.
Sam Elliot commended the drivers who are handling the new drawbars. He said they had a few problems at first, but went into the training with a "positive attitude and keen to learn-.
I spoke to one of these drivers, Pete Ogden. "I'm getting the hang of it. It follows well and its stable on the motorway. Going round corners its just like a short rigid. There's very little cutin. Reversing is the only problem. It's easier to uncouple and nose the trailer in but I'm determined to master it the proper way.
He also demonstrated how it is quite possible to unload through the rear shutter of the rigid without unhooking the trailer. Providing the space is available, it is a simple matter to jack-knife partially the outfit to give access to the back of the rigid.
It is easy to see how these drawbars are paying dividends to Harris. Instead of limited capacity 16-tonners trimking up to the North-East they have highly efficient, 26/28 pallet capacity drawbars which can also handle the daytime distribution just as well.
This productivity and versatility has not come cheaply. With their six-wheel rigids, demount system, sliding door bodies and air-suspended trailers these outfits were very expensive. The Contar close coupling system adds 0,000 to the final price of each one.
That said, Sam Elliot is sure that they will prove their worth and believes that if drawbars are ever permitted to operate at 38 tonnes they will absolutely mushroom.