The Milsco Manufacturing Co.'s XL-100 seat with FA-100 suspension and fore/aft and side-to-side isolators (top) and with an optional swivel attachment (bottom).
Seating comfort
There is little doubt that some operators - especially those who spend the majority of the day in their vehicle - would plow fields or move earth being pulled by a team of oxen, as long as their seat was comfortable. Milwaukee, WI-based Milsco Manufacturing Co. dates back to 1924, when the company manufactured harnesses, collars, and other accessories for farm horses under the name of Milwaukee Saddlery Co. In 1934, at the request of Harley Davidson, Milsco helped develop a new two-passenger motorcycle seat called the Buddy Seat. Milsco is still today the sole supplier of original equipment seating products to Harley Davidson.
But much more important to the off-highway industry is that in 1936, through an employee suggestion, Milsco designed a tractor seat with a foam pad and leather cover, a breakthrough since most tractor seats consisted of nothing more than a metal pan. It was submitted to International Harvester, who offered the seat as an option in 1937. In the first year, 37,000 seats were sold. Milsco has since expanded its range of seating products to include virtually all off-highway industries, including military, forestry, and industrial vehicles.
The Milsco Manufacturing Co.'s XL-100 seat with FA-100 suspension and fore/aft and side-to-side isolators (top) and with an optional swivel attachment (bottom). |
The company has recently unveiled a new version of a seat and suspension to be used in large construction and agricultural vehicle applications - a combination of the XL-100 Deluxe Seat and FA-100 air suspension. With its compression-molded composite material cushion and backrest shells with black texture finish, the XL-100 is rugged and corrosion resistant. The FA-100 air suspension offers 100 mm (4 in) of damped suspension travel, a 76-mm (3-in) height adjustment, and uses either a self-contained air system or vehicle-supplied air. A remote switch can be placed in the right-hand armrest to control the height/weight adjustment, while vertical damping is also variable and adjusted by a control knob located on the main damper assembly.
The seat can be equipped with fore/aft and side-to-side isolator options to maximize the vibration resistance for improved operator comfort and reduced fatigue. Isolater travel in the fore/aft direction is ± 25 mm (1 in) and ±19 mm (0.75 in) side-to-side. For rotating capability on equipment such as backhoe loaders, a Milsco SL-200 heavy-duty swivel can be added. The swivel, fore/aft isolator, fore/aft adjusters, side-to-side adjuster, and side-to-side isolators can be mixed, matched, and stacked in different configurations as well as actuated either through the front-mounted cable-operated control or direct-acting handles.
The suspension may be center-mounted or offset to accommodate extra operator heel clearance while swiveling in narrow cab applications. The swivel may be assembled to latch at ±15, 30, 45, 90, and 180°, or any combination thereof. Also, the side-to-side isolator can lock in any of three positions.
Milsco completed durability tests on the new air-suspension seating system using a six-axis shaker table. Vibrations included in the testing were from seven different inputs that would normally be experienced in loader backhoe operations. The seven operations include bank digging and dumping, back filling, city- and dirt-roading, trench digging, set-ups and moves, and concrete breaking. Milsco also conducted additional laboratory testing that included a dynamic durability test designed to simulate an abusive ride in earthmoving equipment. The test was not restricted to vertical movement, with the seat-mounting platform rotating ±15° in both the side-to-side and fore/aft directions to simulate operation on hills and embankments. The system complies to ISO-7096:2000 EM3 and EM6 as well as EEC-78/764 Class I, II, and III vibration standards.
Milsco cites an advantage of air suspension being its increased life expectancy; an air suspension has fewer mechanical linkages and is therefore more resistant to wear than a mechanical suspension. An air suspension has a single air-spring component as compared to multiple mechanical joints and metallic extension springs. Wear in the cams and bearing joints of a mechanical suspension can shorten suspension life.
Air suspensions also are typically easier to service than a mechanical suspension as the air spring can be replaced by removing two bolts and an air line. Mechanical suspensions generally have springs that are preloaded and require several tools to remove. They also usually contain multiple pin joints requiring the removal of push nuts, threaded fasteners, or snap rings to service. The friction in an air spring does not change as it wears compared to an increase in the friction in a mechanical suspension as the joints in the spring mechanism wear. An air suspension can isolate low-frequency, large-amplitude inputs from operations as well as high-frequency, small-amplitude inputs coming from the engine and transmission.
