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Machine Matters

Machine Matters – March 2009

March 25, 2009 |

The beauty of the medium size skid steer is its compact, muscular performance in small spaces. Mid-size skid steers with a rated operating capacity of 1,751 to 2,201 pounds nimbly maneuver in confined spaces while providing impressive power for digging, lifting and carrying. Your skid steer’s lift arm geometry can be the deciding factor on your machine’s best use.

Skid steer genetics
The key DNA in skid steers is the ability to turn around in their own footprint. Because the left-side drive wheels work independently of the right-side drive wheels, skid steers can perform zero-radius 360-degree turns. This ability is invaluable on jobsites with little room to spare, such as demolition projects, confined space utility construction and moving material around structures and landscaping. The mid-size skid steer’s narrow profile and short stature allow you to work in areas with low overhead clearance and slim access points such as doorways and gates.

Mid-size skid steers produce bucket breakout forces as high as 7,532 pounds on Volvo’s MC80B and offer arm lifting forces up to 6,796 pounds on Komatsu’s SK1020-5 model. The machine’s hydraulic system powers the loader’s lift and drive functions while auxiliary hydraulic systems power attachments. Skid steers that offer high-flow hydraulics can work even harder, running hammers through concrete or drilling through frozen ground. Medium size skid steers can travel at speeds of more than 11 mph. The mid-size skid steers’ wheel base ranges from 40 to 49 inches, making them easy and economical to transport.

Family tree
Medium size skid steers are designed to optimize lifting or reaching. The skid steer family tree branches off at the lift arms. The difference between a vertical- or radial-lift arm configurations is the path the loader arms follow moving from ground level to full reach at maximum height.

Vertical-lift skid steers (sometimes called parallel-lift) lift up-and-out in a straight, vertical line. They maintain their forward reach by rotating the bucket (or attachment) at the joint but don’t move the bucket forward. Additional linkage allows the bucket to pivot, using gravity to keep the face of the bucket consistently level as the arm rises. The vertical lift keeps the load closer to the machine’s body and has a high reach, which can be helpful when lifting loads in areas that don’t allow forward arm movement.

Radial-lift skid steers lift-up-then-out in an arc-motion, starting with the bucket low and close to the skid steer body at ground level, and swinging up and out from the machine’s body as the bucket rises to its maximum height. Maximum reach is at the mid-way point of the arc. Radial lift skid steer arms are connected to the machine with a single pin on each side, so the bucket is in a fixed position and follows the arm’s movement up and out. The bucket’s face generally stays in the position it started in on the ground.
Modifications to these two common lift configurations tend to focus on providing greater reach and stability.

For example, New Holland’s Super Boom vertical configuration lifts the load up and away for maximum reach at maximum height and keeps the bucket level for less spillback. Its low center of gravity reduces tipping and increases lift capacity.
Self-leveling systems on radial lifts use load-leveling sensors to continuously monitor and adjust the bucket to keep it level.

Individual skills
Both vertical-and radial-lift arm machines will move and carry material around your jobsite, but each style has its own advantages.

Vertical-lift skid steers have more upward reach at max height, making them a good choice for lift-and-carry applications such as stacking pallets of heavy materials in storage areas. Vertical-lift machines carry their loads high, allowing them to lift and load loose material into a dump truck. The arm linkage that keeps the lift arms moving in a consistent, vertical path give you more control and power when using attachments that break, pound or grind.

Radial-lift machines use their arm muscles and resulting breakout force to dig into a pile of material and load it over lower barriers, such as a wall or into a trench. Because they carry their buckets low and close to the machine’s body, radial skid steers are good for moving heavy, loose material. The radial’s longer forward reach (at the greatest curve of the arc) allows it to load pallets or material deep into places, such as the back of a storage area, without bumping the body of the machine into the structure. Radials work well with attachments that trench, rake and pull.

Manufacturers offer more than 29 mid-size models in the 1,751- to 2,200-lb. class.

Bobcat
S185, S205, S220
Arm lift configurations: S185 vertical, S205 vertical, S220 radial
· Low-profile lift arm increases visibility
· Automatic shutdown system protects machine from catastrophic failure if fluids are out of normal range
· Choice of controls – standard, advanced control system or selectable joystick controls
· Power Bob-Tach mounting system standard on all three models.

JCB
180 Robot, 190 Robot
Arm lift configuration: vertical
· Single-arm design provides great visibility and quick daily maintenance
· 180 and 190 Robot models available with wheels or tracks
· Left side operator access to cab for safety.

Volvo
MC80B, MC90B
Arm lift configuration; radial
· Rugged one-piece mainframe
· Choice of traditional hand-and-foot or pilot-operated joystick controls
· Universal quick-attach to allow hook-up to almost all types of skid steer attachments.

LiuGong
365A
Arm lift configuration: radial
· Standard equipment includes air-conditioned/heated cabs and auxiliary hydraulics
· Short throw, low effort control levers ease operator fatigue
· Compatible with most North American mechanical quick coupler attachments.

Case
Series 3 420, 430, 435
Arm lift configurations: 420 radial, 430 radial, 435 vertical
· Case’s easy-tilt cab makes servicing easy
· Models 430 and 435 offer a two-speed option for quick travel around the jobsite
· Choice of H or ISO control pattern.

Komatsu
SK820-5, SK1020-5
Arm lift configurations: SK820-5 vertical, SK1020-5 radial
· SK1020-5 offers Komatsu’s closed load-sensing system hydraulics for precise bucket
positioning control
· Automatic Power Control anti-stall hydrostatic travel system handles tough applications
without stalling
· Universal quick coupler accepts most manufacturers’ attachments.

Gehl
5640E, 5240E
Turbo Arm lift configuration: radial
· Standard bi-directional auxiliary hydraulics with flat-faced couplers; high flow optional
· Optional Hydraglide ride control system for optimal material retainage
· Joystick controls available on 5640E Turbo.

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Machine Matters – March 2009