The Ultra Trifecta (Part 2)

November 17, 2004—The timing couldn't have been better for the release of the 1250AJP manufactured by JLG Industries, McConnellsburg, Pa. This self-propelled 125-foot articulating boom lift offers an up-and-over height of 60'6" and horizontal outreach of 63'2". A dual capacity work envelope available on this unit expands its overall working range—approximately 75% of which allows 1,000 pounds in the platform. Considering its reach and load capabilities, its 44,000-pound GVW is a pretty light machine. The third unit in the company's Ultra Boom series is sure to command the track in the mega boom market. Read on to get my full-evaluation. 
 
To learn more about its transport-friendly design and coordinated elevating boom technology, go to Part One: The Ultra Trifecta

Operator considerations

Beyond the spacious and easy to access 36"x96" side-entry work platform, JLG has gone to great lengths to make this a user-friendly product. The controls are easy to recognize and simple to command. Non-proportional functions can be metered by using the potentiometer dial on the operator's left-hand side. It also controls the main extension/retraction of the upper boom section.

 

Although the dial worked fine, I personally prefer to control the extension/retraction with a full-fledged proportional control for this function. Hall Effect joysticks, supplied by OEM Controls, control both drive and main boom functions and provide exceptionally smooth performance in all boom positions, and they also work in conjunction with Sauer Danfoss proportional control valves that incorporate valve spool position feedback technology. The actual position of the spool in the valve is measured and fed back to the control system for real-time corrections to valve response. This allows high precision metering of oil throughout the spectrum of flow rates from the maximum amount down to near zero. The hydraulic system performance can be maintained regardless of factors plaguing conventional systems, such as hysteresis, thermal, and load-induced variations, which is particularly advantageous when coordinating combined boom movements.

 

 JLG's engineers went to great lengths while developing the 1250AJP to ensure the robustness of these controls. The critical sensors used in the control systems are duplicated for constant sensor checking, as well as the addition of backup sensors and back-up hydraulic circuitry intended to maximize machine operation in case of malfunction.

 

Feedback is provided to the operator through the platform display panel and platform alarm. If the control system deems a function inappropriate and the operator attempts to perform that function, a warning light will flash and the platform alarm will sound. The operator simply needs to perform another function to continue.

 

Three different modes of steering can be selected on the fly with the platform control panel, including crab, coordinated, and conventional two-wheel.

 

The 1250AJP uses electronic steering control in lieu of conventional mechanical tie-rod steering systems. Each wheel has its own steer cylinder, Hall Effect wheel angle sensor, and proportional valve, which allows the control system to position each wheel to the ideal angle for all steering modes and commands. When the operator steers the machine, the inside front wheel moves in response to the control input, and its angle is measured by the control system. Then the control system calculates and adjusts the remaining three wheels to their ideal position. This creates several benefits that are otherwise impossible with extendable axle machines. Not only are the three available steering modes automatically executed at the flip of a switch, but the steering angle is completely controlled during drive out/in expanding axle operations. This allows the turning angle to be in coordination with either axle configurations. Additionally, the maximum drive speed can be modulated to match the ideal speed for the current turning radius. Thus, reducing the centrifugal forces created in the work platform when turning tightly at maximum speed.

 

This system also makes self-correcting steering possible. If you are in crab mode and select two-wheel steer, the front and rear axle automatically align. The same holds true in reverse. If you are in two-wheel steer and hit either the four-wheel or crab steer mode, the wheels automatically adjust to the desired configuration. In crab mode, the 1250AJP has a 1:1 turning ratio, which means for every foot it moves forward, it also moves one foot sideways.

 

There's also an operator directional orientation safety system, similar to the one developed by Genie Industries, Redmond, Wash. When the platform is rotated 45° off the centerline in either direction, the system requires the operator to depress a momentary drive enabler switch to ensure awareness of travel direction. Once activated, the operator has three seconds to drive before it resets. I've always been a big fan of this safety feature, and I'm glad to see it has been adopted by JLG.

 

The 8-foot Jib-Plus™ jib boom can move on two planes: vertically 130° (+75°/-55°) and horizontally 180°. This horizontal movement is really quite a trick feature that allows for increased access and area coverage without repositioning the machine. The jib is part of the electronic platform leveling system, which maintains the platform position based on the level sensor feedback as opposed to the more conventional response to transferred fluid from a master cylinder driven in response to boom movements. The electronic platform leveling system has the advantage of maintaining the position of the platform with respect to gravity not only while lifting but also during other movements, such as driving.

 

One minor observation I made while operating the boom lift is the platform can adjust itself after you have completed a function • this is something that gets your total attention when elevated at 125 feet. I asked JLG's engineers about this phenomenon, and they explained. As with conventional master-slave systems, leveling occurs while the boom is actually moving and not just when the joystick is being operated, which is necessary for the platform to completely “keep up” to the final boom position. Platform leveling movement after the joystick is released ceases when the joystick function completes the ramp-down (deceleration) period, which may be longer on some functions than others due to the optimized, or customized, controls for boom speed and smoothness. What this means is one function could have completed its movement before the basket leveling is fully ramped and made its final adjustment. But the delay isn't such a big deal once you've become accustomed to it.

 

Another feature improving the 1250AJP's productivity is the short amount of time it takes to get from the ground to the task. This unit features JLG's Quik-Stik™ elevating system to help improve productivity. Once the lower (tower) boom is fully deployed, the Quik-Stik system allows the upper boom and platform to elevate from the ground to maximum platform height in one continuous motion. JLG publishes a lift time of 95 seconds. During my evaluation, I couldn't get the time below a still-impressive 113 seconds, but who's counting?

Powering up

Standard power is derived from a Tier 2 compliant, Deutz BF4M 2011 medium-cooled diesel engine. The engine produces 87 hp (65 kW), and JLG operates it at a maximum of 2,800 rpm. The company also notes that a water-cooled CAT diesel will soon be an option. For cold weather start-ups, a glow plug is included, and a bypass is provided for those of you working in hot climates year-round.

 

The engine is mated to a stack of pumps. First in line are dual Rexroth hydrostatic drive pumps that displace 28 cc (1.7 cu-in) each. One supplies the two left-side drive motors, and the other supplies the two drive motors on the right. These deliver a generous 42 GPM combined flow at 5,000 PSI. They each drive four Rexroth 16 to 45 cc (1.0- 2.74 cu-in) displacement wheel motors, then they drive Lohmann (a division of Rexroth) 88.1/1 ratio planetary reduction hubs. Non-proportional functions are powered by a variable displacement 45 cc (2.74 cu-in) piston pump.

 

Massive 445-50D710 foam-filled, rim protector lug tread tires from OTR put the traction and stability to the ground. These are mounted on oscillating axles that adjust to the terrain changes with four inches of positive and negative vertical travel. JLG says the machine's gradeability is 45°.

 

I had a chance to tackle some of the obstacles located on JLG's test track with the 1250AJP, leaving me at nothing less than impressed. I have driven several JLG machines on this course, and I've never been disappointed • the 1250AJP did nothing to change that impression. The power and balance this drive system exhibited was truly amazing. Braking was positive without a hint of rolling back or a jerky release. My confidence to climb the steepest incline couldn't have been higher.
At your service

Regardless of whether you are the operator or service technician, there are many ways to monitor the performance of an Ultra Boom. An array of status and indicator lights are located on the platform control console indicating system distress, fuel level, 5° tilt, and foot switch status. Transparent to the operator is the ability to perform a detailed analysis of the machine's entire operating system with the JLG Analyzer. From default codes to the engine system status, this hand-held device interfaces with the EPBC management system to access information. Operational customization is also a feature. One interesting capability of the system is the ability to control the unit's platform work range. For example, you can limit this unit to a maximum reach less than its full capability.

 

Gull-wing hoods are used as a styling statement, but they also are quite functional. The large hoods swing skyward to allow total service access, and they are modular for easy removal. Made of virtually indestructible ABS plastic, a product I much prefer over fiberglass, they also are supported by a substantial internal steel skeleton. Although certainly not a high-tech feature, the swing-out engine tray makes servicing the engine a snap. It is also interesting to note that there is only one grease point on this entire machine, which is necessary to keep the superstructure's huge rotation ring bearing riding smoothly. Are we getting spoiled or what? I wonder how long it will be before we have a dry ring bearing? Then we can do away with that grease gun all together.

 

The 1250 AJP carries a net price of $160,000. For that tidy sum, you get just about everything you could possibly need: four-wheel drive and steering, traction and power to go any place you would ever need to; plenty of on-board energy for just about any power tool; a jib with unparalleled reach capabilities; and the exclusive dual-load capacity. JLG has a full-year head start on Genie's new Z135-70. Although JLG has a commanding head start this is going to be one heck of a horse race. It will be very interesting to see if the Genie has the legs to make up the difference.

Likes

• This mega boom exhibited awesome power and control.
• Side-entry facilitates optional attachments; inward swinging gate allows easy entry.
• Dual-capacity rating system enhances productivity.
• The unit exhibited rock-solid stability in any reach position.

 

Dislikes

• Non-proportional dial control for boom extension is less intuitive than fully proportional controls.
• Delay in basket leveling response could startle an unprepared operator.

 

Verdict

• The 1250AJP's drive, stability, and control instill confidence on all fronts.