|Paddle-type selector (or an optional keypad) allows |
various control functions, but isn’t needed to use
the two new clutch engagement features.
Saturday, April 30, 2016
Test Drive: Making Low-Speed Maneuvers Easier With UltraShift Plus
Feb, 2016 For years Eaton has been improving its UltraShift Plus series to make the heavy-duty automated manual transmissions do more things and do them better. Engineers and marketers have meanwhile expanded the range so it now includes 10- to 18-speed units for on-highway and vocational applications, and cut weight by automating its Advantage gearboxes. And they’ve joined with Cummins and certain truck builders to precisely tune engine and transmission controls to improve performance and fuel economy.
While today’s UltraShift Plus products are not perfect (what is?), they are so well behaved that it’s difficult to put them in the same class as their predecessors, which go back to the late 1980s. A notable change in recent years is a normal dry clutch that engages more positively than a centrifugal clutch originally used. That and refined software in the electronic controls help the trannies properly shift themselves.
The latest in the story of Eaton’s progress are two new low-speed maneuverability features for most UltraShift Plus models, which representatives demonstrated last fall at the firm’s proving grounds near Marshall, Mich. The features include special clutch engagements called Blended Pedal and Urge to Move. These allow precise movement of a truck to properly place loads, or for a tractor to more easily back under and pull away from a semitrailer, or to carefully maneuver in tight spaces.
Blended Pedal provides gradual or quick clutch engagement depending on the accelerator’s position. A light foot sends the clutch face partially against the flywheel, and releasing the accelerator disengages it. Mashing the accelerator engages it fully and quickly. This works when the transmission is in forward or reverse gears, depending on how it’s programmed. It is akin to a driver modulating the clutch pedal of a manual transmission to slip the clutch and move the truck very slowly and for very short distances, or to abruptly engage the clutch to get out of mud or soft ground.
In Urge to Move, with brakes off, the driver releases the brake pedal and the clutch smoothly engages at engine-idle speed (about 700 rpm), moving the truck forward or rearward and keeping it moving. The powertrain then is in “creep” mode and will continue to move slowly, or the driver can push the accelerator to gain forward or reverse speed.
I drove several trucks whose transmissions were programmed with these features and tried them under various conditions.
With Blended Pedal I stopped and started dump trucks and a mixer chassis on level ground, then on steep grades, easing on and off the accelerator to simulate what a driver would do while maneuvering a vehicle to properly place a load of gravel or concrete. I could feel the clutch nicely engage and disengage, and grab suddenly but smoothly if I jammed on the foot feed. (No matter what you’re doing with an Eaton automated product, clutch engagement is almost always consistently smooth and proper.)
I also used Blended Pedal in a highway tractor for a hook-and-drop maneuver, backing onto a trailer, then detaching it and pulling away. Both moves were done at extra low speeds, reducing the jolting a driver expects as the fifth wheel slides under the trailer’s nose and slams against its kingpin, then, with the fifth wheel’s jaws released, yanks out from under the trailer’s upper coupler until it’s free. Blended Pedal can make these moves almost gentle and less stressful on both vehicles.
Urge to Move was a little more interesting. With the transmission in gear, I took my foot off the brake pedal and felt the clutch engage and the truck began moving at engine idle speed. The transmission will try starting normally, and in a higher gear (4th was common with an LL type). It will change to a lower gear if it finds the ratio reduction is not sufficient, or a driver can choose a gear. All the diesels were heavy-duty models with strong torque at clutch engagement, and electronic controls on the engines fed enough fuel to keep the trucks rolling as long as I wanted. If I got on the go-pedal, the truck accelerated and upshifted as needed.
Most impressive was a heavy-haul tractor with an 18-speed pulling a loaded multi-axle trailer (gross weight was 125,000 pounds) on a 15% upgrade. Urge to Move started it repeatedly. OK, the front end hopped a little as the clutch engaged, but the rig started up strongly. (There was one hiccup: On the first try the engine died and had to be restarted. The demo driver said the 16-liter diesel had been acting up.)
Of course, a good gear-jammin’ driver can put a manual transmission in Low (or one of the Low-Low ratios, if it’s that kind of gearbox), ease off the clutch pedal and the rig will begin to move easily on level ground. On a hill it can still be done. But it takes a steady foot on the accelerator to avoid engine surging. And upshifting competently on an upgrade can be very tricky. A driver with some experience can do this, but a novice will have trouble, and while learning can burn the clutch or break a U-joint. Put him or her in a truck with an UltraShift Plus with these features, explain how they work, and with care the driver can do it correctly the first time.
However, to get the most out of driving an automated transmission with an automatically actuated clutch requires the driver to understand what a clutch is (some young people who grew up with automatic transmissions might not know) and how it should be respected. A driver also must know these new features are there and how to engage them. Eaton will send technical reps to help with these instructions, and there are videos on YouTube, some by Eaton and some by regular guys sharing tips and occasional complaints.
Eaton’s automated products have become affordable, with models costing about $2,000 to $6,000 more than a comparable manual, depending on the transmission model and the truck builder’s pricing intentions. Of course these gearboxes not only shift themselves, but also do it correctly much more often than an average driver can, and don’t tire out at the end of a long day. This saves money on fuel and prevents wear and tear on the driveline. The new features make UltraShift Plus AMTs more useful and versatile.
Tom Berg holds a commercial driver’s license and does Test Drives of all classes of trucks. He also writes about vocational and medium-duty trucks, trailers and bodies, maintenance, and alternative fuels.http://www.truckinginfo.com/channel/equipment/article/story/2016/02/test-drive-making-low-speed-maneuvers-easier-with-ultrashift-plus.aspx?utm_campaign=topnews-20160227&utm_source=Email&utm_medium=Enewsletter