June’s surface haul trucks article focuses on the latest technology developments. News that could not be included in the published article, due to insufficient space, comes from Allison Transmission, which has introduced a second reverse gear on all its 4700 and 4800 models produced this year. The second ‘deep reverse’ gear, in addition to the standard reverse, provides greater control and engine braking during operation on steep grades. 2nd Reverse also enables increased manoeuvrability when operating in confined spaces, allowing quicker operation cycles and boosting productivity performance.
“Customers in mining in particular, will appreciate the provision of a deeper reverse gear,” says Larry Love, Allison Executive Director of International Marketing. “The shorter ratios of 2nd Reverse will make up and downhill reversing much safer and easier in heavy duty applications, giving drivers additional confidence. This is another reason to specify an Allison fully automatic transmission, complementing features such as our adaptive Electronic Control Systems and integral retarder that aim to improve comfort and productivity for drivers and operators.”
When a vehicle is in 2nd Reverse, it will have a slow creep capability with high engine speeds. With a mechanical ratio of 17.12, it will have an effective torque converter multiplied ratio up to 32.5:1. The new 2nd Reverse feature provides overall better performance and enhanced applicability for a variety of applications.
The company has also added a raft of enhancements to its 6000 Series, including the new 6620 transmission. New hardware and software upgrades for the transmission used in rigid dump and specialist mining trucks up to 70 t are aimed at enhancing durability, lowering operating costs and simplifying maintenance.
Available in the second half of 2010 and replacing the 6610, this proactive design upgrade responds to changes in engine characteristics that are increasingly prevalent in the sector. Greater use of digital control for engines delivers sharper torque ‘response’ through the driveline, necessitating upgrades to protect the drivetrain. “We have made detail improvements throughout the product to further extend overhaul intervals and increase durability,” says Brian Reusser, Allison’s Off-highway Product Manager. “These include design, manufacturing and material upgrades.” For the flywheel, the use of FEA identified an opportunity to modify fillet radii and introduce heat treatment and reduce stress. Case hardening and nitriding other interfacing components such as the turbine shaft and hub, together with increasing the shaft’s diameter, is expected to increase their fatigue durability by over six times. Extensive in-field comparative testing has identified a significantly more durable bronze-based material for use in the lock up clutch.
The 6620 will feature a new CEC3 electronic control system when available that includes an extended CAN messaging set (J1939 protocol) and other electrical interface upgrades. This translates into advantages for both OEMs and end-users. Manufacturers will benefit from an easier and higher level of integration with the vehicle architecture, for example the choice of a proprietary shift selector as well as the Allison derivative will now be possible. The opportunity to ‘tune’ the transmission to an operator’s specific requirement is now easier, permitting increased performance or economy depending on the duty-cycle or application. “Against the backdrop of a challenging economy, the operator or OEM can perfect a vehicle to a specific drive cycle,” says Reusser. “Together with the OEM, Allison can optimise the vehicle for the best economy-productivity balance.”
