While the trend in running gear design has been toward individual wheel suspension units, the caster is still a very useful device, and in some instances has advantages over other mobility means. If the function of an item of ground service equipment requires accurate positioning, this can be accomplished simply by using four swiveling casters. The equipment can then be positioned longitudinally, laterally and rotationally. For movement from one location to another, the rear casters can be locked in the longitudinal attitude and the equipment may be towed safely.
Casters often provide the simplest means of mobilizing equipment originally designed to be stationary or to be moved on a separate cart or pallet. While the AEROL Banjo Mount and Vertical Mount were designed with such problems in mind, it is often desirable to use casters due to the structure of the item, lateral clearance considerations, or for the positioning problem previously discussed.
To comply with the requirements of specification MIL-M-8090, AEROL casters are available with parking brakes, service brakes and steering provisions. Spring-mounted casters are also produced in a wide range of load ratings to protect delicate pay-loads. Other available accessories include swivel locks, shimmy dampeners to prevent the catastrophic results of violent oscillation at high speeds, and pry-bar sockets to facilitate positioning of heavy equipment.
Dual and three wheel casters provide a means of supporting heavy loads, without resorting to the complicated and expensive steering linkages dictated by tandem front axles. Casters also simplify the design of equipment that must be capable of being towed in either the forward or reverse direction, or even laterally. By using eight position swivel locks on all four casters the desired route for large items through restricted areas may be programmed.
In addition to the wide selection of approved casters conforming to specification MIL-C-4751 (Casters, Rigid and Swivel, Precision Heavy Duty, and Shock Absorbing), AEROL CO., has developed many special casters for ground support equipment. Assemblies designed for use with AEROL Cushion Tread Wheels, and Industrial Pneumatic Wheels (Specification MIL-W-8005) in both single and dual wheel configurations are the most popular. As an example of the capacity of these casters, the dual 9.00-10 size (28 inch pneumatic) will carry a load of 8540 pounds. Many other caster assemblies use commercial, transport type, and aircraft pneumatic tires.
When loads are in excess of the capacity of AEROL Cushion Tread Wheels and Industrial Pneumatic Tires, the designer may elect to use casters with wheel treads of AEROLAST, AEROL’S trade name for polyurethane. This amazing polymer provides a wheel with twice the load capacity of the best cured-on rubber tire of equal size, and also exhibits very high abrasion resistance. A very popular AEROL Caster using two 12 inch AEROLAST Wheels has a load rating of 12,800 pounds, and a similar unit with three 12 inch AEROLAST Wheels is rated at 16,000 pounds. For applications where the designer wishes to use smaller casters for manually propelled equipment, and trailers towed at low speeds, AEROL CO., offers a wide range of wheel types in both swivel and rigid casters, with many available features such as shock absorption, shimmy dampeners, parking brakes and swivel locks. Spark-proof casters, non-magnetic casters, and wheels with conductive rubber treads are also produced. Casters with adjustable height or retractability are available in most sizes throughout the entire range.
If shimmy dampeners are not used, free swiveling casters should generally be restricted to speeds not in excess of five miles per hour. For higher speeds it is recommended that the swiveling casters be controlled by Ackerman type steering linkages connected to the tow-bar and tongue assembly. In addition to many standard steering arms designed for this purpose, AEROL CO., produces several caster models with steering arms that may be disengaged, permitting the caster to swivel a full 360° for accurate positioning of the load. A valuable accessory for shipboard use is a “dead-man” brake, available on many caster assemblies. This device comprises a cable operated parking brake, mechanically connected to a cam linkage on the tow-bar by a cable passing through a hollow kingpin. The linkage is designed so that if the tow-bar is dropped to the deck, or placed in the vertical latched position, the parking brake is actuated.