Auto economy
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IN RECENT weeks CM has carried two reports on automatic transmissions. The report on the IMechE/IRTE conference said that operators in the audience were disappointed by the lack of hard facts relating to comparative costs of manual and automatic boxes.
Around the same time it was reported that ICI were to buy 16 Seddon Atkinson 400s fitted with ZF Transmatic transmissions following successful trials with a prototype. Rather than listen to the various manufacturers, ICI decided to find out for themselves.
Torque converter The Transmatic system — it cannot be described merely as a "gearbox" — comprises four major components: an hydraulic torque converter, a lock-up converter clutch, a shift clutch and a fiveor six-speed ZF synchromesh gearbox. So at least in theory the driver has the best of both worlds.
The technique for starting off fully laden is to select second (or possibly third) gear in the usual way after depressing the clutch pedal. Releasing the clutch does not cause the vehicle to move as the slip between the engine idle speed and the stationary vehicle is absorbed by the converter.
Depressing the accelerator allows the vehicle to move away smoothly. As soon as a certain vehicle speed and its corresponding engine speed have been reached, the lock-up clutch is actuated automatically, providing a direct connection between engine and gearbox.
If required, the Transmatic can be driven like a normal synchromesh gearbox, ie depress the clutch, select the gear, release the clutch.
That's how it works in theory. How ICI tried it in practice was by installing a Transmatic in a Seddon Atkinson 400 Series tractive unit. The prototype installation was carried out by the ZF engineers at Friedrichshafen. Jack Chapman, ICI's transport manager and Ken Fenton, sales director of Scott's Commercial Vehicles at Nottingham (who supplied the chassis) went to Germany themselves to keep an eye on the experiment.
ZF removed the existing Fuller gearbox and installed a WS K 400 converter unit and a six speed synchromesh box with 6.4 to 1 bottom gear and direct top. A Scott's engine' drove the vehicle back to 101 premises at Teeside and con pleted the chassis delivery.
With three shifts per day, total of 20 drivers and rout( Southampton -Teessidi Liverpool-Teesside, the prot type has now covers 160,000km (100,000 mile with an average daily distance 640km (400 miles). The fu consumption monitored by 11 has been a consistent 35.3 100km (8.0mpg) independe of who was driving.
Previously the fuel consum tion of the standard manu machines had varied betwes 43.5 and 35.3 lit/100km (6 and 8.0mpg) depending on th driver. Thus the Transmatic hE an immediate "levelling up effect across the range drivers.
The front tyres were replac( at 88,500km (55,000 mile and the rears at 151,000k (94,000 miles).
ZF claims that this very sati factory performance has be( achieved by a combination factors:
El the converter is on operating up to 10 per cent the time before lock-up occurs El lock-up speed is set .1,32Orpm Di operating at the vehicle legal maximum weight, tl driver can achieve high avera road speeds by remaining sixth gear and only occasiona dropping below fifth when clii bing hills
Li providing the driver h selected the most suitable ge in the first place, the Transma allows him to go through cc gested areas without touchi the gearlever jj full engine braking is s available
The performance of the p totype has prompted ICI to orc 16 Seddon Atkinson 400s w Transmatics, all powered Rolls-Royce 265L engines-. T vehicles will be converted to ti specification by Scotts as SE don Atkinson has not got on-line production capability the option.
As the Transmatic is sligh longer than the Fuller box whi is normally fitted, a 3.1m (11 3in) wheelbase 400 has be selected. This particular Trai matic specification (VVSK 41 and S6-90 gearbox) is bei offered at £2,500 for the Si don Atkinson and has been 4 gineered for use with eith Rolls-Royce 265/265L Cummins 230/250 pov units.