Interpretation ID: nht90-1.6
TYPE: INTERPRETATION-NHTSA
DATE: JANUARY 5, 1990
FROM: HANK KMIECIK -- STEERABLE CARRIAGES
TO: OFFICE CHIEF COUNSEL -- NHTSA
TITLE: NONE
ATTACHMT: ATTACHED TO LETTER DATED 3-13-90 TO HANK KMIECIK; STEERABLE CARRIAGES, FROM STEPHEN P. WOOD, NHTSA; [A35; VSA 108(A)(2)(A); 108(A)(1)(A)]
TEXT: On the advice of Robert Clarke and Michael Trentacoste, I am writing to inform you of our intent to manufacture axle steering systems for tractor trailers, long bodied straight trucks, buses and special application vehicles and ask you to review the syst em and advise us if it is in compliance with the applicable DOT regulations.
Description Axle Steering System
The axle steering system provides a method and means for steering the rear of a tractor trailer combination by turning the wheels of the trailer to increase the maneuverability of the entire unit during turning maneuvers, parking, provide additional mane uverability in congested traffic and under close clearance conditions. This is accomplished by means of a steering apparatus comprising sections of steel beams, hydraulic cylinder/motor assembly, 2- locking pin assemblies, steering pin assembly, manifol d assembly, air reservoir, battery and control panel.
The sections of steel beams used as the framework for the system are welded to one of the existing trailer axles for retrofit to an existing trailer or incorporated simply into the manufacturing process for new trailers. The steering/axle assembly is po sitioned under the trailer chassis and welded to it. The other system components are installed in their designated locations on the trailer chassis (see the enclosed illustrations) and the control panel to operate the steering system is located in the ca b on the dash panel for ease of operation by the driver. No modifications are made or required to the suspension system or the brake system of the axle.
The axle steering system requires approximately 16 man hours to install by a skilled truck mechanic and helper.
The system is not designed for full-time rear wheel steering at highway speeds.
System Operation
Assume the trailer has 2 axles on the rear. Both axles have an air suspension. The ideal setup is air suspension and lift kit on each axle. The axle steering system works with either setup, combination of or the non steering axle can be a spring axle.
For example, when the driver needs to make a right hand turn onto a congested road, the driver would bring the tractor trailer momentarily to a full stop, a short distance before the intersection and engage the axle steering system. Using the control pan el (Illegible Word) in the cab, the driver releases air from, or otherwise deactivates, the rear axle suspension system of the steering axle, effectively raising one set of rear wheels off the ground. The driver then selects the right hand turn button o n the control panel which activates a two way double acting hydraulic cylinder which applies force against the raised rear wheel steering assembly in the direction it is desired to change the orientation of the rear axle. After the steering assembly is turned in the desired direction the two locking pins are engaged into the locking hole positions on the curved beam firmly locking the axle/steering system into the desired position, air is readmitted into the rear air/axle suspension system causing the steering wheels to return firmly to the ground. Air is now released from the air/axle suspension system of the adjacent axle which raises the wheels of the adjacent axle and eliminates the ground friction they would create in making the turn. The drive r of the truck then proceeds at slow speed to make the desired turn or other maneuver with the one axle turned.
After completing such turn, the vehicle is brought to a stop and the driver repeats the above procedure in reverse order, removing the steering wheels from the road surface turning the rear wheel steering assembly to the normal driving position and engag e locking pins before resuming highway travel.
It takes 10-15 seconds from the time the driver stops the truck to complete the initial steering sequence and about the same time to return the axle steering system back to the locked position for normal highway travel after making the turn.
Enclosed is a short video tape showing the axle steering system in action.
If you require further information or a demonstration, please do not hesitate to ask.
AXLE STEERING SYSTEM
Steerable Carriages 1/10/90
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AXLE STEERING SYSTEM
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AXLE STEERING SYSTEM
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