1952-01-01

Synchronization of Brakes on Multi-Axle Truck-Trailer Trains 520241

THIS paper presents a discussion of tests and mathematical studies made during the past year in connection with the synchronization of brakes on truck-trailer combination units.
These developments point to a clarification of the many misconceptions and exaggerated ideas which have been built up concerning timing, steering, and braking necessary to offset the dangerous jackknife type of skid, as well as the slide which frequently occurs on slippery pavements. The writer describes two types of jack-knife which may occur if the braking power on certain axles builds up more rapidly than on others. A third type of jackknife may result from steering as, for example, in a sudden turn to avoid an obstacle, even with no brakes applied.
The writer points out that synchronized braking cannot offer anything spectacular in the way of shortening stopping distance unless build-up time is shortened considerably in the process. The advantage with synchronized braking is not in making shorter stops, but in minimizing that short but critical time in which a jackknife can develop beyond control. Equations are presented covering test data and hypothetical conditions analyzed to determine the relative value of the different force and time factors in stopping a train. After these more obvious factors have been corrected, steps may be taken to adjust the torque on each axle to weight variations and dynamic transfer.

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