Automatic satisfaction with Esso's 'extra'
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Dil-company fleet experience with automatic and iemi-automatic tankers has been good; now the noblem is that similar replacements are hard to get
ne Graham Montgomerie
ERSISTENT clutch failures on their elivery fleet at around 25,000 miles or ss led the Esso Petroleum Company to rok around for other means of translining the engine power and improvig the reliability. With this in mind they mse to go automatic and I recently disBsed the Esso experience in this field ith Mr Geoff Day, one of Esso's autototive engineers.
With the type of running involved in ical delivery work the average annual lileage for an Esso fleet vehicle is only 5,000, while 25,000 is the average in ich areas as West London. Thus with utch failures occurring regularly at, or low these figures and with complete utch overhauls costing at that time round £120, Esso chose Leyland eavers fitted with the semi-automatic wo-pedal" transmission and Dodges fitted with the fully automatic Allison box.
The Leyland Beaver was the only tractive unit in the fleet at that time and when Esso decided to eliminate the conventional clutch, the SCG semiautomatic which was virtually identical to the Wilson bus box was chosen. They
would have liked to try a fully automatic unit in comparison but none was available. So great was the original clutch problem that Esso were prepared to pay over the odds for the new transmission. The Leyland list price for the semi-auto Beaver at that time was £5,165 compared with £4,525 for the standard manual version. The first one entered the fleet in 1970 and there are now 320 semi-autos in service.
Reliability improved
The results have been most satisfactory. The clutch troubles were bypassed and the transmission reliability was now acceptable. Most of the problems which did occur were connected with chewed-up brake bands on second and third gears.
British Leyland suggested that this • might be due to lack of driver training leading to them starting in second gear and not first. The selection pattern did not help in this respect as first gear involves lifting the change speed control and then moving it left and forward. Engaging second merely involves pushing the lever forward, and excessive use of this gear for starting was thought to be the trouble.
As the drivers became used to the transmission the brake band reliability on second and third gears improved considerably. The recommended starting gear had a ratio of 7.25 to 1 whereas the second gear ratio was 4.28 which was far too high for starting when fully laden.
With the Esso policy of specifying their vehicles to be used at any of their depots throughout the UK rather than specific areas, the comparative fuel consumption figures for the automatic and manual versions are rather difficult to obtain but Esso say that the fuel consumptions are very similar.
In the main, the brake band wear rate in the Leyland boxes has been satisfactory with some units reaching 150,000 miles, although occasionally vehicles have had replacements at considerably lower mileages; even as low as 5,000 in isolated cases.
Driver acceptance has been good. Although some of the older hands were rather disgruntled as they thought the older manual boxes gave them a chance to prove their proficiency, most of them have come to prefer the two-pedal
control, especially in heavy traff conditions. In a way this has no become an inconvenience for Esso E there is now no similar box still i production and their drivers are havin to go back to manual boxes on the late: AECs.
Spares problem
The spares situation has been unsati5 factory but Geoff Day emphasized th2 this applied throughout the fleet an was not wholly attributable to the tram mission. Esso originally intended t have complete boxes available as spare: so if a failure occurred the complete un. was replaced immediately to get th truck back on the road and the offend ing part was replaced on the bend
owever, because of the policy of keep1g the smallest possible spares stock the are boxes were always cannibalized as 1st as they were built. A familiar roblem.
The semi-automatic on the Esso eavers will hold in any one gear — it is tally an assisted gearchange unit, not a. illy automatic change. Thus, for Kample, when going downhill there is o danger of the vehicle changing up as le vehicle speed increases. The selector
position determines the ratio.
Esso have been very pleased with the performance of their semi-automatic Beavers, the first of which, MBH 727H, went on the road in February 1970. In' fact they would prefer to stick with such a specification but non-availability has prevented this. Their current maximum-capacity artic is now the AEC Mandator with the Thornycroft manual box.
Automatic A Ilisons
The smaller tankers suffered from the same clutch malady as their larger brothers so the replacement programme called for Dodge K1100 twoaxle units with the fully automatic Allison transmission. This specification was devised by Mr Harry Townley, the automotive construction and maintenance manager of Esso.
Coupled to the Cummins V8 engine, this gearbox has eliminated the original problem and Geoff Day estimates that the Allison is good for around 200,000 miles — which is certainly acceptable, as the average yearly mileage of the Dodges is the same as the Leylands, at 35,000 miles.
The Allison has a range selection system with four ranges apart from the reverse and neutral sectors. These ranges are 3-6, 3-5, 3-4 and 1-2. Thus if the box is in the 3-6 range it will start off in third gear and change up through the gears until top is reached. If the 3-4 range is selected, the Dodge starts in third and then changes up to fourth but goes no further. This provides a hold facility when the truck is on a downgrade.
The Allison does suffer from one minor inconvenience in that the truck cannot be towed in the case of a breakdown without first disconnecting the propshaft (the same applies to the semiauto Beaver). The oil pump for the gearbox is driven off the input shaft, so if the vehicle is being towed, most of the gears are still turning but the oil pump isn't. Hence the warning which is displayed on the front of all vehicles fitted with the specialist transmissions "Towing forbidden unless propshaft is disconnected."
The overhaul procedure for the Allison box is simple — they are sent back to Allison transmission specialists instead of being overhauled "at home".
The 2,800-gallon Dodges are now being replaced by three-axle Leyland Bisons to increase the product capacity. The shortest wheelbase option has been specified to provide a 24-ton vehicle with the same basic overall dimensions as the Dodge.
Overall, the Esso experience with automatic transmissions is favourable. The only regret is that unless a complete "special" vehicle is ordered, there is now nothing suitable on the market.
There is one compensating factor — that improved clutches are giving better life than when automatics were first chosen. But it nevertheless seems a pity that a company which, like Esso, has taken the forward step of specifying automatic and semi-automatic transmissions, and has been pleased with them, should now find it so difficult to buy similar replacements.