Understanding JLG® Scissor Lift Technology
Scissor lifts have been cutting a path of productivity through the construction market since the 1970s. Although the designs haven’t changed drastically over the last four decades, at least until recently, the technology behind these job site workhorses has greatly changed, making scissor lifts more productive than ever.
Finding the right lift for the job requires selecting a machine that allows operators to complete the task at hand as efficiently and safely as possible. Taking a closer look at scissor lift technology allows construction contractors to make educated decisions about how these machines will impact the job site — from the inside out.
ELECTRIC AND HYDRAULIC POWER DISTRIBUTION SYSTEMS
There are now three power distribution systems used in powered lifts — hydraulic, electric + hydraulic and all electric. Hydraulic systems take electrical energy from the batteries and convert it to hydraulic flow to perform lift, drive and steer functions. While hydraulic machines typically cost less to purchase or rent, they can be less efficient and have more moving parts, and in turn, are more expensive to operate compared to electric drive machines.
Electric + hydraulic drive systems, or hybrids, have batteries directly linked to motors on the drive wheels, which makes them more efficient overall. These systems require less hydraulic oil since they are only performing lift and steer functions, which helps to reduce issues with oil viscosity, making them better suited for colder environments. Additionally, electric drive lifts significantly reduce the number of leak points because they reduce the number of hoses, fittings, manifolds, and other components critical to their hydraulic counterparts. Electric drive systems also boast increased battery life and fewer needed replacement parts.
All electric drive systems replace hydraulics completely and eliminate leak points altogether. Traditionally, our machines have been equipped with flooded lead acid batteries or IC engines where the maintenance cost are heavy for customers. But all electric machines have highly efficient systems and the power required to run these machines is cut by more than 40%, this opens the door to lithium-ion battery technology and all electric machines.
Replacing batteries on a scissor lift can be expensive, making it critical to have battery management software that allows the lift to consistently operate at peak performance. While contractors often try to maximize the run time of a lift, doing so may sacrifice the long-term durability and reliability of the machine’s batteries.
For example, when the battery starts to drain during a shift, the output voltage also begins to drop. The battery logic helps determine how low the voltage can drop. However, the lower the voltage drops, the more the long-term durability of the battery is compromised.
With newer lithium-ion batteries there is consistent performance in terms of capacity, and they can be used in temperatures varying from 0c – 40c. This significantly lowers total cost of ownership as it has an increased life cycle and lower maintenance costs. This is a huge benefit for the customer since current machines have high battery replacement cost whereas these batteries last the life of the machine.
All electric machines, such as the JLG® DaVinci™ scissor lift, have fully independent battery monitoring systems which monitor cell temp, cell voltages, and ensures an optimal state of health of the system. It also provides data in the terms of state of charge and useable life left in terms of kwh or cycles.
When it comes to charging, these highly efficient machines have lowered the power usage which leads to lower charging times. This also enables the opportunity for new technology such as quick charging. This refers to providing useable power to the machines in a reasonable short period of time when batteries are completely dead, this is especially useful in trouble shooting machines on a job site and also sending machines back to the service center quickly.
POTHOLE PROTECTION SYSTEMS
Pothole protection systems lower the ground clearance of a lift when elevated to reduce the risk of an accident if the machine hits a pothole. Some equipment manufacturers pin the system to the machine’s service doors, which can cause it to move in and out of alignment. Mounting the system to a stationary component, like the chassis, helps prevent alignment issues, resulting in less service and more uptime.
Additionally, many manufacturers rely on duplicate components (limit switches, plungers, etc.), which can increase the risk of system failure. Manufacturers that use one limit switch and one plunger help reduce the number of components needed to safely activate the system, leading to less service calls.
It’s also important to consider what the system’s limit switches can handle. Systems with lower tolerance can move the protection mechanism out of position, which may require service. Machines designed for high tolerance will help keep operators on the job site and increase productivity.
REACHING NEW HEIGHTS
As buildings grow taller, so does the need for lifts with greater reach. And, as a machine’s height increases, it would reason that its base must grow as well to ensure stability. However, a wider width may not be ideal for certain situations. One solution are center-pinned arms to help with front and back stability as well as keeping larger platforms evenly supported from underneath. With this approach as machines get taller manufactures are able to keep the largest platform area possible.
Another solution is advanced technology such as QuikLevel Advanced (QLA), which offers automatic side-to-side leveling capabilities with lift-to-full-height on side slopes up to 7 degrees. Machine sensors monitor platform load, platform height, front axle tilt, rear axle tilt, and chassis tilt to permit operators to drive at height under certain conditions. The re-alignment of the chassis and rear axle are then automatically calculated once a job is complete, to level the machine back out.
Variable tilt is another technology available for slab scissors designed to maximize a scissors lift’s height based on the slope on which the machine is positioned. Scissor lifts equipped with variable tilt technology provide a larger working envelope by allowing the machine to lift on side slopes greater than 1.5 degrees while limiting the maximum platform height automatically.
Additionally, load sensing systems, like Lift-Sense, offer a sizeable adaptive work envelope based on platform capacity, platform height, and chassis tilt. The color LCD display equipped platform control box helps the operator understand how platform load and chassis inclination can affect maximum allowed working height and also provides enhanced diagnostics capabilities should anything go wrong.
Combining these systems can help reduce side-to-side movement and increase stability at height, helping operators feel more comfortable and confident.
Solid-state electronics allow operators to get fault codes without swapping relays and fuses. Service diagnostic tools can be used to monitor the lift’s critical components and point technicians to the malfunctioning component or part, helping reduce service time.
Technologies that have emerged from the use of solid-state controls include better horsepower management, simple reconfiguration of a machine for different job sites, the ability to update software/hardware on a machine to comply with changing standards, softer stops for more operator comfort, and simplified calibration.
Solid-state controls have also introduced new opportunities, to tap into intuitive, smart phone-enabled diagnostics. Operators can take advantage of apps on their smart phone to view, diagnose and troubleshoot in real time, from any location, to maximum uptime.
There are two types of load-sensing systems (LSS): Force-based and pressure-based. Force-based acts like a bathroom scale by providing a reading that calculates how much the pin has been compressed, showing how much weight is on the scissor lift. Force-based LSS provides an accurate measurement that can be calibrated without any weight in the platform and without raising or lowering the armstack so the process takes seconds.
Pressure-based LSS measures pressure on the barrel side of the lift cylinder and translates that pressure reading into weight. While it costs less than force-based, pressure-based can pose a challenge in colder weather. Since hydraulic oil moves slower in colder temperatures, it is harder for the piston to push the oil out the rod-side of the lift cylinder to elevate the scissor. This increases the pressure in the barrel, making the machine “think” it’s trying to elevate a large amount of weight, when really the sensor is giving a false reading because the oil is so viscous.
To avoid this, some manufacturers have adopted a “dual-pressure sensor” LSS, which places an additional sensor on the rod-side to calculate the differential between the barrel-side and rod-side pressure. This reduces low-temperature error readings.
SIMILAR, NOT THE SAME
Choosing the right scissor lift for a job can be a complex decision. Understanding the technology behind these versatile workhorses allows contractors to choose the best lift for the job. Considering available technologies and features can deliver significant job site benefits and help lower total cost of ownership over the life of the machine.