AT THE HEART OF THE ROAD TRANSPORT INDUSTRY.

Call our Sales Team on 0208 912 2120

IF tailors the top torquers

15th January 1998
Page 20
Page 21
Page 20, 15th January 1998 — IF tailors the top torquers
Close
Noticed an error?
If you've noticed an error in this article please click here to report it so we can fix it.

Which of the following most accurately describes the problem?

If you increase an engine's power output you need a tougher, heavier, gearbox to handle it. Or do you? ZF is working on a new generation of high-tech transmissions incorporating "torque tailoring" that could give hauliers the best of both worlds...

by Brian Weatherley • Spare a thought for gearbox manufacturers. It's not enough that they've got to compete against those vehicle manufacturers who make their own driveline components; they've also to supply the ones that don't with ever lighter, more durable transmissions.

And as more electronically controlled engines come on to the market the interest in automated heavy truck transmissions that can "talk" to those electronic engines grows.

But does the average haulier really want a semi or fully-automated gearbox in his 38-tonner—or would he be happier with a more driver-friendly synchromesh box with shift loads to match a constant-mesh?

While the market makes up its mind, a is having to consider every option. The German gearbox manufacturer has already developed its own electronically controlled transmission range, the AS-Tronic, while still offering synchromesh manual boxes for everything from light trucks to top-weight artics.

Ecosplit

However, it would hardly have spent so much on AS-Tronic if it didn't see it as a transmission of the future. So where does that leave its long-serving 16-speed manual Ecosplit box? Is there an Ecosplit 4 version waiting in the wings?

According to ZF Great Britain marketing manager Geoff Buck: "Quite how we develop Ecosplit has to be decided. We've now got the 16S-251, which can han die very high torque levels. It's essentially the same as the Ecosplit 3 but with internal modifications in its detailed gearing arrangement."

The 165-251 is currently the only synchro box that MAN fits in its 600hp 19.603, because it can handle the 2,700Nm of torque developed by the mighty vee-10 engine (see roadtest, page 30). You can count the number of UK operators who can justify a 600hp tractor on the fingers of one hand, but Buck says the development of the 16S-251 reflects fleet operators' continuing demand for more and more horsepower.

The question is, what happens next? "Do we develop existing manual transmissions," asks Buck, "or do we look at alternatives like AS-Ironic because we're in a position to say 'OK this is Ecosplit 4'?"

Multi-speed

Electronically controlled engines have not only made automated multi-speed boxes more viable on heavy trucks, they've also allowed more control to be exerted over a normal manual transmission, providing extra protection against clriveline abuse.

Buck describes this capability as "torque tailoring". "In low range it's rare for an engine to be holding in a low gear at peak torque for an extended period," he says. "But in some operations

it can happen. A typical example would be a multi-wheeler working in a quarry and pulling itself out back on to the road. It's running in low gear with a lot of tough restarts on full power and you can get a situation where the gearbox performs perfectly satisfactorily—but it keeps wearing out first gear!

"With torque tailoring you have the opportunity with EDC to provide the engine with a signal that will limit fuelling to prevent full torque," he says. "OK the driver is not able to go balls-out up the steep hill, but he'll still have the driveability, and the wear on the box will be reduced."

Ecomat

ZF is already applying torque tailoring on its Ecomat autobox, and Buck believes it has potential across a variety of applications. "It's a way of getting bigger engines without bigger transmissions," he points out.

Transmission manufacturers are often conservative when it comes to speccing a box, says Buck, playing safe and overengineering the transmission. But with torque tailoring they won't have to go over the top. This will reduce the weight of the gearbox, so operators will benefit from extra payload. "Weight's critical for us," says Buck. "We have to get the weight down and the torque up. Manufacturers talk about horsepower; we talk about Newton metres per kilogram weight. It's about providing extra carrying capacity for the operator."

The weight of the AS-Ironic (it's 50kg lighter than an equivalent Ecosplit) is certainly a strong point in its favour. Its twinlayshaft design is more compact and lighter than the current Ecosplit; not least because on the constant-mesh AS-Tronic, synchronisation is controlled by the engine and gearbox electronics rather than mechanical synchroniser cones.

Buck is aware of the irony of ZF developing a twin-layshaft box while arch-rival Eaton is moving into the heavy-duty synchromesh market with its S Series. But there's no disputing the advantages of the twinlayshaft design.

"It overcomes all the problems of a single-shaft box such as longer units needing a yoke and with propshafts and so on," he explains. "As power has been increasing, the gearbox has become more noticeable in the chassis and we're looking to make it smaller and lighter. We really need to reduce inertia in the box, and twin layshafts allow you to do that" The one question that the truck and transmission manufacturers have yet to answer satisfactorily, is why put a twopedal gearbox on a 400hp tractor where arguably you hardly need to change gear at all?

Twin layshaft

"It's one of those things you can discuss deeply—we're at the cusp now with AS-Tronic," says Buck. "It can go dramatically higher in terms of torque; up to around 2,600Nm because it's a twin layshaft I6-speed."

Whichever way ZF goes, Buck stresses that it's the electronics that offer the greatest benefits: "We've got to look at this as an industry challenge," he says. "People go on about electronics being a pain in the arse—but you can protect the driveline in a way you never could do in the past."

SHIFT ASSISTANCE: HELPING WITH THE LOAD

• As torque inputs become ever greater, ZF has developed a pneumatic "shift assister" for its 16-speed Ecosplit box and 65-1600 six-speed coach transmission. The first truck manufacturer to offer shift assistance in the UK is Nino: at the last TipCon show its latest eight-legger (pictured, below) featured the device on an Ecosplit box. According to Geoff Buck: "It's a simple device. It essentially consists of a linkage yoke between the selector crank and the linkage system. As free play is taken up it triggers the pneumatic assistance, engaging the gear with minimal effort on the part of the driver." While the unit will help reduce shift loads, Buck believes the problem frequently lies with a misaligned or poorly set up linkage. "If you have a properly engineered linkage, shift loads on the Ecosplit are highly competitive," he says.

"Over the years we've tried to get the manufacturers to optimise shift linkages," Buck adds. "But we've said that if we can't reduce shift loads in itself we'll do it with shift assistance." • ZF's electronically controlled AS-Tronic transmission was unveiled at the Hanover Show in 1994. Since then ZF has been working closely with Iveco to develop it, and the First production version—dubbed the EuroTronic—was unveiled in Britain on a EuroStar tractor by Iveco Ford two months ago (CM 23-29 October).

However, the sole-customer agreement with Iveco runs out next year, leaving ZF Free to offer AS-Ironic to other European manufacturers: lsuzu has already taken 20 evaluation units. Will ZF users such as Daf and MAN be taking it? "We're talking to MAN," says Geoff Buck, but the lack of an electronic engine in Daf's heavy truck range means that it may take until Euro-3 before the Dutch manufacturer can fit it. "Our presentation of the AS-Ironic concept will very much depend on whether it's seen as reliable and durable," he odds. "It's also dependent on the pricing policies of the OEMs."


comments powered by Disqus