Avoiding pivot steering pitfalls
|
|
Subject : Gradall 534D9-45 telescopic handler manufactured by JLG Industries, McConnellsburg,
Pa.; featuring 9,000-pound maximum capacity and
45 feet of lift height.
Serial Number: 0744148
Date in service: 2001
Hours in service: 1,851
Equipment owner : Rental Service Corporation, Phoenix, Ariz.
Service location: Arizona
Date of review: 5/21/04
Best known for their ability to pivot steer, Gradall telehandlers are built in New Philadelphia , Ohio , under the JLG Industries' umbrella. The 534D9-45 is no exception. Independent hydraulic-drive motors power each of the rear wheels enabling it to achieve 90° pivot-steering. This translates, however, into a few more service points than found on other axle configurations. But when properly maintained, as this unit has been, the operational advantages of pivot steering outweigh any related service issues.
Pivot steering maintenance issues
|
|
The front axle is a rigid, limited-slip design supplied by Carraro. A separate pedal on the floorboard of the cab is used to lock up the axle. When this pedal is depressed in conjunction with the accelerator, the flow of oil between the front and rear axles is split. A separate set of relief valves protects the rear-drive motors from any pressure spikes.
The steering linkage for a pivot-steer machine is more complex than a conventional design. There are lots of grease points, which if not given diligent attention, could lead to the need for bushing repairs. Additionally, the hydraulic hoses that supply the two drive motors receive severe flexing, yet after close inspection, I found all the hoses on this Gradall 534D9-45 to be good-condition originals.
Tire wear is probably the most unique maintenance issue attributed to pivot steering. Certainly, foam-filled tires are not cheap to replace-up to about $800 each. On this machine, the problem is further exacerbated by the hard and rocky ground typical of the southwest region. It is evident that the operating environment has taken its toll. What's more, the loader lug tread found on these tires is not well-suited to the environment. This wear can be minimized with the use of optional rock grip tread tires, which Gradall offers.
Service issues
|
|
The boom rides on UHWM slide pads-two each on the four surfaces of the boom. Although they are intended to be greaseless, I found a small amount of grease that was likely leftover from what the factory applied to break in the boom. I found no uneven or excess wear on the pads. During operation, I detected a minimal amount of boom deflection, but otherwise, the boom seems to be holding up beautifully.
Four hydraulic lines powering boom function run on the outside of the boom's underside. You can see in Image 4 that these lines are really drooping. A closer look showed that the skin of the hoses was peeling back at the bracket location exposing the wire braid.
The fork carriage leveling cylinder is tucked away in the boom's horse head, which has done a good job of protecting it from damage.
Current production models of the Gradall 534D9-45 are equipped with a John Deere diesel engine, but this unit was powered by an easy-starting and quiet-running Cummins B39C-110 turbo-charged engine.
The engine cover is made of a robust sheet metal and does a good job of protecting the hydraulic oil- and fuel-fill locations as well as all the filters. Access to the starter and alternator are also made from this location. The cover does not lock, however, which creates the opportunity for inadvertent or intentional damage.
One gripe I have, directed at nearly all telehandler manufacturers, is the dinky little ignition key. On the day I visited RSC, there were five telehandler models from three different manufacturers in the yard. The key switches on all but the newest one had been replaced. According RSC's branch manager, the key often breaks off in the ignition switch, a problem I've heard of before. In my opinion, operators, often wearing a pair of work gloves, need bigger keys to handle.
Overall appearance
|
|
The telehandler's blue paint, decals, and operational icons remain bright and legible after more than 1,800 hours of service. And although the seat's upholstery has held up reasonably well, the bottom cushion was shot. I'll bet eight hours in this cab would leave any operator feeling saddle sore.
The load chart, mounted on the dash, looked good as new; and all control switches, levers, and joysticks showed very little wear. A pilot-pressure joystick controller means no electronics are involved in boom operation. I've shown this simple joystick, see Image 6, because I was so impressed with the precise command the system still delivered. With the boom fully extended, when I asked for 1/16 th of an inch of lift, that is exactly what I got. No wavering, no jerking, no over adjustment. What's more-it's just the right size and placement for comfortable operation.
The service records on this telehandler showed only one major service expense-replacement of a rear tire. More than likely it experienced the same kind of wear that I saw on the unit's existing tires. With the exception of service due to customer damage, all other work was normal preventative maintenance.
