Running Gear Terms and Definitions

The terms and phrases in this list are used to educate customers on the proper criteria and specifications that must be understood and taken in account when you are searching for Ground Support and Military Running Gear to use in your application.

• ACCESSORIES– Reflectors, tie-down rings, and related parts, Pintle hooks, and lunette eyes.
• ASSEMBLY– A crossbar support, the terminals of which are the spindles on which the wheels turn.
• BANJO MOUNTS– Wheels and spring suspension mounted on the side of the carriage. Spring suspension has rotary movement.
• BRAKE DRUM– A circular metal drum mounted on the wheel against which the brake shoes are dressed to slow or stop the rotation of the wheel.
• BRAKE LINING– The friction material used to line the brake shoes.
• BRAKE MOUNTING FLANGE– The metal plate is integrally attached to the axle spindle, to which the brake assembly is mounted.
• BRAKE SHOES– Arc-shaped metal pieces to which the brake linings are attached. Brake actuation forces these shoes to engage their lining with the brake drum to produce action.
• CAMBER– All Aerol straight axles over 70 inches long (2 1/4 square or less) will be cambered 11/2″ (nominal) at spindle. All drop axles are cambered 1 1/2″ (Nominal) at the drop.
• CAPACITY– All axle and axle component capacities are based upon gross load measured at ground.
• CASTER– Tilting of steering knuckle kingpin. (When tilt is backward, the caster is positive.)
• CHASSIS– Structural framework that is supporting both the load and the vehicle body where the suspension units are mounted onto.
• CRAMP ANGLE– The degree that a wheel may turn from the longitudinal plane. (A 45° cramp angle allows 90° full swing or 45° each way off neutral.)
• DROP AXLES– Axle beam of underslung configuration as compared to straight-through axle beam.
• FRAME– The assembly of structural parts which support the body and payload and to which the running gear Is mounted.
• FRONT AXLE ASSEMBLY– The axle assembly located at the front end of the vehicle and comprised of the front axle beam, kingpins, knuckle, spring, wheel, hub. brake assemblies.
• FRONT AXLE BEAM– The structural cross member to which the knuckle assembly and the front tongue assembly is attached.
• HANGER BRACKET, SLIPPER– The member attached to the trailer frame that supports the fixed slipper end of a leaf spring assy.
• HITCH- The member designed to engage the drawbar. This member may be an automatic coupler, pintle hook, etc., located on the prime mover and/or at the rear of trailers to be pulled in train.
• HUB ASSEMBLY– An assembly that interfaces the wheel assembly to the spindle. It includes bearings, grease seal, hub casting, stud bolts, lug nuts, and grease cap.
• HYDRAULIC BRAKE–  A brake system using hydraulic master cylinder to actuate wheel cylinders for brake actuation.
• KINGPIN– The pivot pin used to connect the steering knuckle to the knuckle support of the axle beam.
• MECHANICAL BRAKE– A brake system using mechanical linkages (cables and levers ) to actuate the brake.
• MILITARY RUNNING GEAR – In addition to Commercial Running Gear, AEROL manufactures an extensive line of mobile equipment components and assemblies that meet the requirements of Military Specifications.
• OVERHANG– Overhang for axle with a single tire is the distance from the centerline of the spring to the centerline of the tire. Overhang for axles with dual tires is the distance from the centerline of the spring to the centerline of the duals.
• PARKING BRAKE– A brake system that is used only when a vehicle is not in use. It helps prevent the vehicle from any unnecessary movement. Also not to be used for slowing or stopping the vehicle in any way.
• RATED CAPACITY– The gross load to be carried on the running gear, minus unsprung weight, in case suspension-equipped running gear.
• REAR AXLE ASSEMBLY–  The axle assembly located at the rear end of the vehicle and comprised of rear axle beam, rear spindles, springs, and mounting brackets.
• REAR AXLE BEAM– The structural cross member to which the rear Spindles are attached.
• RUNNING GEAR – The mechanical apparatus used to move and direct movement of an otherwise immobile object safely and efficiently.
• RUNNING GEAR ACCESSORIES – Includes limi-torq and surge type brake actuator tow bar.
• RUNNING GEAR STEERING – AEROL provides running gear with Ackerman steering, fifth wheel steering and synchronous steering options plus various types of tow bars.
• SAM SUSPENSION UNIT– Wheels and spring suspension mounted on the side of the carriage. Spring suspension has linear movement.
• SERVICE BRAKE- A brake system capable of decelerating and stopping the motion of a vehicle.
• SHACKLE BRAKE ASSEMBLY– The assembly attached to the frame that supports the movable end of a leaf spring assy.
• SHACKLE LINKS– The connecting link between the spring eye and the hanger eye bracket.
• SHIMMY– Rapid lateral wheel oscillation during rotation.
• SLIPPER HANGER BRACKET– The member attached to the trailer frame that supports the fixed slipper end of a leaf spring assy.
• SPINDLE– The axle beam or steering knuckle for linking to tie rods and steering assy.
• SPRING CENTERS- The lateral distance between longitudinal spring centerlines.
• STEERING ARM– The arm attached to the steering knuckle for linking to tie rods and steering assy.
• STEERING ASSEMBLY– Entails tongue, tow bar, and tie rod assembly which then work together to achieve the steering capability of the vehicle.
• STEERING GEOMETRY–  The angular relationship between steerable wheels and their actuating parts.
• STEERING KNUCKLE– An assembly consisting of a spindle and is attached to the knuckle support through the use of a kingpin.
• THRU-AXLE – Wheels and spring suspension are mounted on axles under the carriage. Spring suspension utilizes leaf springs.
• TIE ROD– The rod linking the steering arm of the steering knuckle with the tongue of the vehicle.
• TONGUE– The main steering assembly member to which the tow bar, tie rods (and/or actuating rods) and axle beam are linked. The tongue in effect, serves as a Pitman Arm as it pivots laterally about the tongue pivot pin.
• TONGUE PIVOT PIN– The pin about which the tongue pivots laterally, usually located centrally on the axle beam.
• TOWBAR– The vehicle towing member usually has a lunette eye ring for engagement with the hitch of the prime mover and attached to the trailer through the steering tongue.
• TRACK– Track is the distance in inches from tire centerline on axle assemblies with single tires. On dual-tire assemblies, track is measured at the centerline between the dual tires.
• TRACKING– The following of the rear wheels in the track or path of the front wheels, or in the case of vehicles towed in train, the following of all wheels in the track or path of the lead wheels.
• TRAILER AXLES – Aerol axles are manufactured from the finest quality of C1040 hot rolled steel and 4140 alloy hot steel. All axles are furnished with spindle nuts, washers, cotter pins and “Z” rings where required.
• WHEEL ASSEMBLY– All parts included in hub assembly, rim assembly plus tire/tube.
• WHEELBASE– The longitudinal distance between front and rear wheel centers.