Safety Features to Avoid Jackknifing

Trailers equipped with Ackerman type steering linkages are usually provided with stops that limit the movement of the tongue at points corresponding to the maximum cramp angles of the front wheels. Problems arise when the operator inadvertently attempts to move the tongue and tow-bar beyond this point, as frequently occurs when the tongue jackknifes while attempting to back the trailer, and during sharp turns if the towing vehicle has a shorter turn radius than does the trailer.

Recognizing this problem area, the military has included in specification MIL-M- 8090 the following provision: “The tow-bar and steering mechanism shall be so fabricated that additional turning force cannot be applied to the steering mechanism after the maximum cramping angle has been reached.

AEROL CO., has developed a device to accomplish this; the Mark II Limi-torq. When the tow-bar is turned to the point where the inboard wheel has reached its maximum cramp angle, the steering mechanism is disengaged, and the tow-bar is free to swing further without applying additional force to the steering linkage. If the tow-bar is then moved in the opposite direction, it swings freely to the position corresponding to the maximum cramp angle at which point the steering linkage is engaged, and during further movement of the tow-bar the wheels are controlled. When the steering linkage is disengaged from the tow-bar, the wheels are positively locked in the cramp angle position.