Round the clock trunking for gearbox evaluation
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by T. R. Radcliffe, chief engineer,
Eaton. Yale and Towne (UK) Ltd, Transmission Division
IN little more than 15 years the haulage fleet operated by John Raymond (Transport) Ltd, of Bridgend, Glamorgan, has grown in size from two rigid eight-wheelers to 42 tractive units and around 80 semi-trailers. John Raymond, the founder of the business, has master-minded its development, one of the main features of which was to change from rigid to artic operation.
• All the Raymond haulage vehicles are maximum capacity 32-tonners. As far as possible the fleet is standardized on equipment which the company has proved to be dependable and economically efficient, to the personal satisfaction of Mr Raymond and his operating engineers. Change for the sake of change is avoided wherever possible. Since the company's expansion in long-haul trunking work began, Atkinson chassis and Gardner engines have proved to be a trouble-free and economical combination.
In terms of mileage covered, many vehicles in the Raymond fleet must be record contenders. Eight of the 6LXB-powered Mk. 2 Atkinsons are permanently assigned to the intensive "change-over" service operated between Bridgend and the London area. Although the company's only depot is in South Wales, 14 of its drivers live in the Witney area of Oxfordshire. Witney is a convenient mid-way staging post between London and Bridgend. Two drivers (always the same two) are allocated to each tractive unit. They alternate on day and night running from one week to the next.
For one tractive unit, a typical 24-hour cycleof operation is as follows: Driver "A" leaves Witney at 4 pm (with the laden outfit which has been brought from London by driver "B"). He reaches Bridgend between 8 and 9 pm where he drops the trailer, picking up a pre-loaded unit destined for London. He arrives back in Witney at about 2 am, having completed his shift. Driver "B" sets off with the outfit at around 5 am for delivery to a consignee in the greater London area. He may have to cross London to pick up his return load before setting off for Witney to arrive in mid-afternoon for the cycle to begin again.
Intensive running of this sort clocks up something over 400 miles in 24 hours. The average weekly mileage for Raymond's London "change-over" tractive units is about 2250, resulting in an annual tally of something like 120,000.
It is usual to replace the high-mileage change-over tractive units after only 12 months. Mr Raymond has found a ready market for his second-hand vehicles, the power unit being an important attraction for buyers who have been quoted protracted delivery dates for Gardner-engined chassis.
Evaluation of new equipment which becomes available is undertaken in individual chassis. A Cummins NH 205-powered Atkinson 32-tonner has recently been acquired for assessment in this way. And the only non-Atkinson tractor in the fleet is a Volvo F86 which has covered about 20,000 miles.
One of the most significant evaluations now underway is that on a Fuller Roadranger RTO-610 gearbox. Mr Raymond was primarily concerned with assessing its reliability on high-mileage work behind a 6LXB engine. He wanted a transmission with sufficient ratios to get the best from the 180 bhp Gardner engine at maximum gcw. With the opening of further sections of motorway between London and South Wales, the availability of a suitable gear ratio for any road condition has become more important.
At the same time it was essential that the gearbox should match the Gardner engine in another way—that is, in terms of longevity and reliability. So that a true picture could be formed of the transmission's ability to build up a high trouble-free mileage, the Fuller 610equipped Atkinson was put straight on to the London change-over service.
The scheduled replacement of the vehicle last August was postponed in order to accumulate even more miles. To date, the chassis has covered 176.000 miles. Wear and tear has proved negligible on the whole power-train Gardner engine, Fuller gearbox and Kirkstall driving axle.
Traffic conditions on the London change-over run are such that journey times are little affected by specification changes. The Cummins 205-powered tractor achieves similar average speeds to those of the less powerful Gardner-engined vehicles. And the Fuller 10 speed overdrive gearbox has not appreciably speeded the haulage operation.
However, conclusive proof of the advantage of having 10 ratios instead of six has been shown in the fuel consumption figures. With smaller ratio steps, the driver is able to make "finer adjustments" to his engine speed, thereby minimizing the number of -slog-or-scream" situations. Accurate records have been kept by Raymond's operating staff of fuel consumed by the 6LXB-powered change-over vehicles—which are invariably fully laden for the main out-and-return hauls. A 6.3 to 1 axle reduction is specified on the London haul machines. With the standard six-speed gearbox fitted, a consistent figure of around 8.8 mpg is recorded. The 10-speed range-change unit has had the effect of increasing this figure to an average of 9.2 mpg. The additional 0.4 mpg represents a 4 to 5 per cent improvement.
Easier driving Raymond's drivers have welcomed the range-change transmission as a step towards easier driving. Although the Fuller is a constant-mesh design, it has been found that because of the close-ratio steps, changing from one gear to the next can be accomplished without double-declutching. Malcolm Dix, one of the pair of drivers allocated to the vehicle, also comments on the low gear-lever effort called for, compared with equivalent synchromesh transmissions.
Mr Raymond's next task is to persuade Atkinson to offer the 610 gearbox as a standard option on its Gardner-engined chassis. At present it can only be specified on Cummins-powered machines, although it is understood that the Fuller will be offered on all two-axlcd Atkinson tractors later this year.