10/02/2006 - 06:00 am

Departure from the Norm: Skyjack compact RT scissor lifts drop differential drive but maintain trademark features

Part One

Skyjack, Inc., Guelph, Ontario, has always built a highly successful line of rough-terrain scissor lifts, but its new 6826RT (Image 1) and 6832RT compact units make a significant departure from the company's traditional design. The new RT scissor lifts do not employ differential drives.

Differential drive is a proven product, and Skyjack has produced tens of thousands of machines featuring these virtually indestructible systems. But as solid as they are, it's no big secret that differential drive limits the turning angle of the tire and how low the chassis can be positioned. These specifications ultimately dictate the success of compact rough-terrain scissor lifts, compelling Skyjack to make this change in its long-standing design philosophy to fully participate in one of the fastest growing segments of the scissor lift market.

The designation “compact rough-terrain scissor lift” describes exactly why this product is so popular. Its rough-terrain capabilities sufficiently work in the most challenging jobsites. Couple this with a compact height and width and a tight turning radius to make the machine more flexible, the compact RT scissor lift allows for application flexibility that is matched by few products of any size or model, indoors or out. It is also a reality that rental rates for larger platform-sized 26- to 32-foot scissor lifts have lagged behind the rest of the market. Rental operators need a product that will allow them to gain more acceptable levels of return.

As Skyjack stood by and watched Genie, JLG, and Haulotte deliver thousands of its compact RT machines to the global marketplace, Skyjack recognized and accepted the fact that its current differential drive system placed too many limitations on its ability to deliver a product that could meet all the market demands. Even if Skyjack could overcome these limitations with its differential drive, it would simply be too costly to allow for the kind of price point the market mandates. Changing its traditional design would be Skyjack's only resolution to enter this product segment

Two products make up this new family of compacts: The 6826RT, with a 68-inch wide platform and 26-foot platform height, and the 6832RT, which is the same product with an extra set of scissors and added ballast. Skyjack was accommodating enough to arrange for me to see one of the first test mules of the 6826RT just prior to it going into the field. Ahern Equipment Rentals is one of Skyjack's biggest and most loyal customers, and I had the chance to scope out this new compact entry at its headquarters in Las Vegas, Nev. (Thanks to the folks at Ahern for allowing us run of the place). Aside from designing a unit that conformed to the market demands, Skyjack went into this project with a clear objective: Carry over as much of its signature design features as possible. As Chris Dossin, director of marketing, explained, “We wanted to Skyjack it.” No compromises were made to the company's reputation for reliability and serviceability, he said.

I have been around Skyjack products for 20 years, and I can say that beyond the familiar orange-and-gray paint scheme, there is so much about the 6826RT that screams Skyjack • those characteristics will become apparent as we work our way through the equipment review.
 

Design departures

Skyjack uses what it calls a crossover symmetrical hydraulic drive system, and simply stated, it is a system that utilizes a flow divider that splits the hydraulic flow from front left wheel to rear right and vice versa for the other two. For these new compact units, Skyjack has opted to utilize a Barnes Haldex mechanical gear flow divider, which the company believes performs better in low-flow demands than traditional cartridge valves. I had the opportunity to give this new drive system a go and found the power to be impressive. Skyjack will publish the gradeability to be an eye-popping 50 percent. Top speed is a brisk 4 mph, and of course, the 5-foot inside turning radius afforded by the new drive system is a great improvement.

With that said, the only concern I had was the way power was transferred to the drive wheels. On a couple of occasions, I noted the system was not able to utilize all the power it had at hand (Image 2). Although I really didn't have a problem getting to where I wanted to go, I don't believe the flow dividers were performing at optimum levels. The system also made the drive feel a little jerky. Every time I lost traction, a muted squeal from the valves hinted that the flow dividers were not properly adjusted. But remember, this is a field test unit, and its sole purpose is to work out these kinds of glitches.

When you start looking at the 6826RT's overall construction, many unmistakable Skyjack features shine through. Starting with the construction of the scissor stack, the stack on the 6826RT is slightly narrower than other Skyjack RT scissor lifts to accommodate the need to position the stack lower and, at the same time, hold the overall 68-inch width. As with every Skyjack product, cast ears are utilized, and these are welded to 3/16” thick wall steel box tubes. The 26-foot unit is equipped with dual lift cylinders, and coupled with generous cross bracing, it adds up to impressive rigidity. As the platform rises, the scissors travel on UHMW slide pads at the top and steel rollers (Image 3) with needle bearings at the bottom.

Dual grab bars on either side of the entry make it very easy to access the 12-gauge diamond plate steel work platform. Fold-down guardrails are standard and can be knocked down in a matter of minutes. As I mentioned earlier, I have been around Skyjack scissors for 20 years, and for each and every one of those years, I have beaten up Skyjack over the design of the deck extension system (Image 4) • well, not anymore!

I am very pleased to say that the new system designed for this series is wonderful. Dual push bars allow you to easily roll the spacious 60-inch long deck out and lock it down in nearly two dozen positions. It is also important to note that you can drive either compact RT model at full height when the deck is fully deployed.

Another signature Skyjack feature is its very robust and easy-to-use all aluminum control box. In this application, it can be located on both the main deck and, for improved visibility, at the leading edge of the extension.

Next issue, I will continue my discussion of Skyjack's new design as we take a look at its serviceability and I delivery my final verdict on the machines.

Part Two

Skyjack, Inc., Guelph, Ontario, has always built a highly successful line of rough-terrain scissor lifts, but its new 6826RT (Image 1) and 6832RT compact units make a significant departure from the company's traditional design. The new RT scissor lifts do not employ differential drives. Last issue, I discussed the reasons behind their move away from differential drive to a crossover symmetrical hydraulic drive system. In this issue, I discuss the new machines' serviceability and take a look at some important optional features.

Skyjack serviceability

Flanking the machine is a pair of large component boxes constructed of heavy-gauge sheet metal. On one side, you will find the engine, and in keeping with tradition, Skyjack has gone the extra mile to make servicing the engine easy. Whether it is the sweet running Kubota DF 972 water-cooled gas engine or its sister diesel engine, the 902 D, both power plants are a snap to service • thanks to the swing-out engine mounting. This feature, often found on boom lifts, is perfectly suited for this installation. The photo below

(Image 2) shows that swinging the engine out 90 degrees allows the starter, alternator, and oil filter to be wide open. To help prevent the accumulation of debris in the radiator, the cooling fan is pitched to push • not pull • air flow.

The engine is a tight installation and could only be engineered with the use of a very short, all-aluminum bell housing and coupling. These are manufactured by KTR Corp., Michigan City, Ind.

On the opposite side of the scissor lift, you will find both the fuel and hydraulic oil tanks and the main hydraulic valve block. I really like the innovative way the valve block is accessed for service. Refer to Image 3 to see the clever solution to what could be a nightmarish repair job. Release a latch at the base, and the block pivots forward far enough to allow access to all fittings and valves.

Also visible in this image are the fuel and oil tanks, which look very similar. Although they are clearly labeled as fuel and oil, I am not convinced it is sufficient to eliminate the possibility of accidental contamination. I would sure like to see the oil tanks either cap bolted or locked in place. Also note the oil filter cartridge at the top of Image 3. This is the first time Skyjack has utilized a spin-off filter for the hydraulic oil system.As with all other Skyjack products, electrical wires are numbered and color-coded, and Image 4 shows the main electrical panel is located in an easy-to-access service box. Note the gas strut is designed to keep the door open and/or shut, but I have to believe this will become sloppy and allow too much water intrusion. A simple latch and weather stripping would be a nice fix. One of the most notable Skyjack design features is the way the lift cylinders are mounted.

These are trunnion-mounted, full displacement cylinders fixed to urethane cushion blocks with Fiberglide bushing.

Although it seems a minor consideration, Skyjack uses nylon collars (Image 5) on the bottom side of the outriggers' cylinders. These sweep away any mud or grit that might stick to the rod.
 

Optional considerations

With a market that demands platform power “on-demand,” engines specified to power an entire machine are spending most of their lives simply driving a generator that requires a fraction of the horsepower. For $2,000 (list price), you can get an 800-watt inverter produced by Dimensions Unlimited, Inc., St. Paul Minn., that will convert the 12-volt starter battery's power to 110 VDC. Upon additional investigation, I learned this inverter is 88 percent efficient in converting voltage. To protect from over-discharging, a sensor will cut the power supply when it reaches a level below the amperage required to start the engine. Once this level is reached, start the engine and power the inverter from the alternator.

I have two suggestions to enhance this great idea. For one, I believe that field tests will demonstrate the need for capacity that only dual batteries can deliver. Second, the system needs to be devised to notify the operator that when the current goes away, he has to start the engine to resume power. My guess is the operator's first thought about the machine shutting down will be that the system has failed, which could lead to unwarranted service calls.

The 6826RT test machine was equipped with optional hydraulic outriggers. The outrigger controls allow either independent or auto-leveling features. It doesn't matter how uneven the terrain is, this system will automatically bring you to level in seconds! All Skyjack compact rough-terrain scissor lift models are designed so the outriggers can be field installed. Other optional considerations are platform work lights and an extra propane tank and bracket to supplement the one that comes standard.

It is important to make it clear that these units do not replace any current models • Skyjack's 8243 and 8850 mid-size RT scissor lifts are still available. The 6826RT and 6832RT compact rough-terrain scissor lifts were officially unveiled earlier this month at The Rental Show in Orlando. Priced at $38,500 and $45,000, respectively, it would seem the 6826RT and 6832RT have answered not only the market's demand for a more competitively priced product but also, based on my observations, a more competitively performing product. With deliveries set to begin late in the first quarter, I'm betting lead times will jump out quickly.

Likes

  • The 6826RT's overall construction continues to embrace Skyjack's trademark robustness.
  • Swing-out engine allows for easy access to all service points.
  • The valve block's clever tilt-out design provides easy entry to an otherwise nightmarish repair job.
  • The newly redesigned deck extension system uses dual push bars to easily roll out the 60-inch-long deck and lock it down in nearly two dozen positions.

Dislikes

  • The gas strut on the electrical panel box door is designed to keep the door open and shut, but it may become sloppy and allow too much water intrusion.
  • The drive was just a little jerky.
  • Give me a securable cap for the hydraulic tank.

Verdict

  • Although a departure from the norm, Skyjack can be rest-assured that this is every bit of what the market expects from them.


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