RT scissors that work inside too - is there a peformance trade off?

There is a growing number of rough terrain scissors designed for working both outside and inside a building, Maria Hadlow looks at the advantages and finds out if you trade performance for flexibility.

Scissors, which are designed to be suitable for both rough terrain and interior use, are growing in prominence in the market. They offer the ability to work outside and travel about the site without a trailer and, as a build progresses, can be brought inside to work the whole project.

MEC brought its Crossover ERT machine to the market about a year ago and according to the company's president David White it is already the company's highest volume selling product. It might be considered that the compact, no emission characteristic of an electric scissor might appeal more in the European markets but Mr White says it has been very well received in the US with a significant number of machines recently going into US rental giant United Rentals.

MEC's director of new product Gary Crook said, "With the Crossover ERT (Electric Rough Terrain) it is taking the place of RT engine powered to a greater extent and slab scissors to a lesser extent. It has started as a niche but all too often, as a niche develops and matures, it eventually becomes a segment in its own right. We at at MEC believe that we are seeing the beginnings of that phenomenon. The Crossover is proving itself as an all purpose "first on - last off" machine as opposed to a niche product."

If a scissor is going to work inside it needs to be electrically powered: emissions and noise considerations require this. However, can all electric machines really deliver the traction control for real rough terrain performance?

Electric RTs

Jeff Weido senior product manager of scissors at Terex AWP says, "Genie Electric scissors allow the user to operate in sensitive environments without the cost of diesel or the worry of emissions. Traditionally electric scissors have only been used on concrete slab type environments and are incapable of traversing rough terrain. The new Genie GS-69 DC scissor changes this paradigm as it uses efficient direct drive AC motors to give it RT terrainability while also delivering all day runtime and industry leading 40ft full height drive."

Mr Crooks of MEC cites the electric machine's advantages as: no pollution from exhaust emissions, no noise, and running costs significantly less than a diesel powered machine. He says, "As the industry matures more segments, that used to be the confines of engine-powered only, have changed to a proportion of them being electric. As the RT capability and battery duty cycle have improved so has the acceptance, and in some cases insistence, of electric powered 4WD machines. This trend will not only continue but will evolve to a wider range of machines. In summary there are compelling revenue reasons for both the hire company and the user for a 4WD electric - notwithstanding the environmental reasons too."

So what is the trade off for the all electric models? Mr Crooks says, "You sacrifice at the extremes in both situations. For outdoor all but the most difficult rough terrain jobsites can be tackled. For indoor it is only the most narrow and extremely tight applications that demand a 1.2m wide slab electric scissor that are sacrificed. The Crossover will tackle 80% of all outdoor and 80% of all indoor work tasks."

Other models that address the inside and outside working scenario use a bi-energy or hybrid power source, but even here you may sacrifice a little of your RT performance. Snorkel says, "The trade-off for that increase in flexibility is that you lose a little of your ability to traverse gradients (Snorkel SRT diesel lift gradeability is 35%, bi-energy gradeability is 25%) and you gain a small amount of weight. In the Snorkel BE series bi-energy lifts it's only about 300kg over the same spec diesel RT lifts."

Small Sacrifices

Mr Weido, however, says that the sacrifice is minimal,"With dual fuel options on both the Genie RT90 and RT69 series scissors and products like the new Genie GS-69 DC that runs an AC direct drive system you sacrifice almost no off-road terrainability and yet retain the ability to work indoors. If you have a double door to bring the units in through, these scissors offer the best of both worlds."

Added functionality rarely comes without additional cost and, as Italian manufacturer Iteco points out, more components mean higher prices, Snorkel agrees saying, "There is a slight price premium for bi-energy lifts because of the added complexity. There are two power sources that can turn the wheels; this increases both build time and the cost of the bill of materials."

Jeff Weido says, "Features like four wheel drive, oscillating axles, and higher load capacities do make the RT scissors cost more than a comparable height slab scissor, but they also deliver much more value on the jobsite."

Mr Crooks has similar views,"The leading MEC electric rough terrain is our Crossover series. The Crossover costs more than a 2WD slab scissor but is in all cases 10% less than a diesel powered equivalent. Having 4WD, a heavy duty battery pack and traction control are features gained for a cost premium over a 2WD slab scissor."

So what are the advantages of the dual function machine? Mr Crooks says, "Flexibility in use leads to higher utilisation. The Crossover can get around an unimproved jobsite that normally only engine powered RT machines can negotiate, yet stay on the project much longer as the construction closes in and can perform that vast majority of indoor aerial access work."

Snorkel says, "Contractors like bi-energy lifts because it's a one-off rental; hire the scissor to work on the exterior of a building, then switch to battery power and drive it indoors for the fitting out process. Also, the lower emissions of a bi-energy or hybrid model can help major contractors meet their green CSR targets. Emissions legislation for construction equipment will get increasingly more stringent and this will drive sales of hybrid and bi-energy machines."

Flexibility

"Anytime users need to do work indoors and outdoors with the same machine they need to consider the types of fuel and more importantly the exhaust they are creating," says Mr Weido. "But hybrids don't always have to include batteries. Genie's dual fuel option (engines that run either gasoline or LPG) allows users to get all of the runtime and performance of an RT machine with the ability to run the machine indoors."

So can the inside/outside scisor be all things to all people? - the answer is almost yes. The exceptions at one end being where gradability is a real issue or where the ground is very soft and rutted. RT scissor lifts also really shine when you need to lift several people and large amounts of material to the working area and the machine must be levelled on a slope.

At the other end of the scale it is where spece is extremely resticted, where floor loading is a real issue or where access to the building or via lifts is very restricted.

Common chassis

The Snorkel compact scissor lifts are available in DC electric/diesel bi-energy versions, as the S2770BE and S3370BE. These lifts offer job site flexibility as the operator can work on a building's exterior on the diesel engine, then switch to battery power so they can take the same machine indoors for the fitting out process. Bi-energy machines can also help operators to meet increasing regulations governing engine noise and exhaust emissions. Sharing a common chassis that is 3.36m wide, they offer maximum working heights of 10.3m and 12.1m respectively.