For short hauls it's 'yes' to auto lorries...
Page 44
Page 46
If you've noticed an error in this article please click here to report it so we can fix it.
AFTER two years trials with several tractive units fitted with different automatic transmission systems, Freightliners have now bought 20 Volvo F86s for long-term appraisal.
They were purchased from Ailsa Trucks Ltd of Irvine, the Volvo truck concessionaire in the United Kingdom.
The units supplied to Freightliners include the first five F86s to have been assembled in the United Kingdom; until the present time the trucks were built in Sweden.
Commenting an the new Volvo Fleet, Freightliner's chief engineer, Malcolm Filsell, said that Freightliners had been studying the suitability of automatic gearboxes for their work for some time.
"Trucks with a manual gearbox are usually designed for line haul and are not entirely suitable for the short-distance work btween customers factories and the local Freightliner terminals,he said.
-Short-haul work is tiring on the driver who may have to carry out as many as 200 clutch operations in one hour. Obviously this work can also create problems with clutches and gearboxes. Consequently a couple of years ago we instituted an automatic gearbox study programme.
Volvo is the first manufacturer to offer an automatic gearbox as a standard package fitted to a tractive unit for general road haulage use. It is available throughout the Volvo F86 range of trucks for use at gross operating weights of up to 32 tons.
Two Allison automatic transmission models are available — the MT 640 four-speed unit with converter lock-up in the top two gears and a five-speed version, the MT 650.
The MT 640, which in the F86 is suitable for use at a gross operating weight of 16 tons, has a single-stage three-element multiphase torque converter and the constant mesh spurtype planetary gears are 3.58, 2.09, 1.39 and 1.00 with reverse 5.67.
The five-speed MT 650, which is suitable for gross vehicle weights of up to 32 tons, has gear ratios of 8.04, 3.58, 2.09, 1.39 and 1.00 with reverse 5.67. Automatic converter lock-up applies in 4th and 5th gears.
Both models have built-in inhibitors to prevent harmful downshifts, engine overspeed and reverse shifts, To understand why Volvo decided to offer an automatic transmission as a factory fitted option it is necessary to look at the function of the Allison automatic transmission compared with that of a manual gearbox.
Forecast . . .
It has been forecast that within a few years most commercial vehicles will be fitted with automatic transmissions— not only vehicles for light and medium-duty applications but for most, including line hauliei Although there is a high initial purchase price consider tion there is an anticipati bright future for automatics. TI reason is to be found in the fir economic benefits that can I obtained throughout the life the commercial vehicle to offs the higher initial cost.
Throughout a continuous a praisal programme by Alliso there are indications that trar mission users may recover tl cost of their investment in tl first 12 to 18 months.
An automatic transmissic unit is a highly efficient piece precision equipment. It is d signed to work hard automa cally as and when speed am load demand and requires tl minimum of routine mainte ance.
Conversely a manual lor transmission has a lower init cost than its automatic trar mission counterpart mainly cause it is merely a mechanic sliding gear mechanism.
Automatics have mechanical clutch syste therefore there are no replac ment costs or downtime b cause of clutch repair. With manual transmission replac ment of a two-plate 35.6c (14-inch) mechanical clutch can be on average three or fo times in the working life of lorry. This is to be born in mil when it is necessary to hire use an alternative vehicle.
Fitting an automatic trail mission effectively reduces tl possibility of the engine I bouring because of its smoo transmission of engine torque. Automatic transmissions always provide a smooth and positive transference of engine torque as there is no sudden torque change from clutch changing when selecting the lower gears
Tyre wear . .
Tyre wear on the drive axle is found to be more uniform which results in fewer tyre changes over the life of the lorry.
Manual transmissions tend to give a harsher and more jerky action; even with an experienced driver, and this can result in uneven tread wear and a reduction in tyre life.
Because of the smooth flow of power through the torque converter there is less shock damage to the automatic transmission's drive-train, and added to this the absence of a mechanical clutch to repair or renew results in less downtime in the workshops.
Manual transmissions can be damaged far more easily than the engine because of overspeeding, over-loading because of "hanging on to too high a gear ratio" and sudden shock loads.