TNT's two-pedal parcels puller
Page 12
If you've noticed an error in this article please click here to report it so we can fix it.
• One of the first four MAN tractive units fitted with a fullyautomated version of Eaton's 12-speed Twin Splitter gearbox has now successfully completed more than five months in service with TNT.
The Eaton Automated Mechanical Transmission (AMT)-equipped MAN 17.332 has turned in an "impressive" performance, according to TNT Express (UK) group fleet engineer Alan Parker, on trunking runs between TNT's parcel depots and its main sorting hub at Atherstone in Warwickshire.
Since the beginning of the year, the four MAN AMTequipped tractive units have been running with different operators in the UK, including TNT, and a further two are expected to be added shortly. Eaton, however, stresses that the vehicles form part of a "two-year field evaluation progamrne", so AMT is not likely to become generally available in the UK until at least 1991.
While the first sextet of evaluation vehicles are all based on MANs, Eaton says that it is likely to adapt AMT to other chassis, once the software has been fully developed.
The AMT system is basically a conventional Twin Splitter multi-speed mechanical transmission, but controlled by a microprocessor unit with the gear selection carried out by air-operated actuators. The throttle pedal has no direct mechanical linkage to the engine, rather it is via a "flyby-wire" electronic connection to the microprocessor.
AMT is the third stage development of the existing popular Twin Splitter gearbox, the second being the SemiAutomated-MechanicalTransmission (SAMT) version which is currently offered by ERF, Foden and MAN (CM 4 April 1987).
While SAMT has been developed primarily by Eaton's European operation, AMT has been a joint exercise between Eaton in America and Europe. In terms of sophistication, AMT has double the microprocessor capacity as SAMT. All AMT conversion work has been carried out at Eaton's European Engineering Centre in Manchester.
Last week, Commercial Motor took the 243kW (326hp) 17.332FTS TNT tractor with AMT out for a test drive with an unladen trailer. The conventional three-pedal layout on the MAN has been reduced to throttle and brake, while the gear lever is replaced by a simple selector box.
To start, a driver shifts to "Drive", which normally engages third gear — for hill starts there is "Drive Low" option which selects crawler.
Once in either D, or DL, the only other thing the driver has to do is work the throttle pedal and footbrake, all gear changes are fully automatic depending on road speed and engine revs.
On the road the AMT normally changes up when the MAN's 12-litre engine reaches 1,800rpm, while downshifts occur at around 1,200rpm, ensuring that the best economy band is adhered to. The actual gear change process, whether up or down the box, is extremely smooth, and skip shifts — especially when running into a roundabout — are carried out automatically.
For added flexibility, the driver can select "Hold" on the gear selector and manually control gear changes by means of a rocker switch. The console also features a cruise control. gear, allowing the engine rev to build up, thereby getting greater retardation due to du increased back pressure.
To gain maximum power, there is also a kickdown on tl throttle as with normal automatic gearboxes. Adaptin to the two-pedal driving technique takes no time at all and a driver quickly learns to brake lightly when approachir a junction or roundabout in order to prevent too many down-shifts. When coming to stop, the AMT smoothly changes down without any assistance from the driver, selecting neutral as the truck comes to a halt.
Parker reports that it is sti very early to analyse any tote cost benefit from AMT — bu he is convinced that it does have the potential to offer fue savings by providing constant engine control across a wide range of driving conditions.
After a spell on the main trunk run between TNT's Carlisle depot and Atherstone where it produced good fuel results operating primarily at 28-tonnes GCW, the AMT MAN is now based at Byfleet and is used with one of the latest aerodynamic airsuspended TNT semi-trailers. E The first full production MAN 17.362 tractive unit to I sold with an Eaton SAMT ha: gone into service with Scottis based operator William Nicol. A full description of the Eator Automated Mechanical Transmission will be featured in a forthcoming Engineer's Notebook.