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Hidden Cause of Miscouple
Page 67
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BY HANDYMAN
UOLLOW1NG a period of snow and
slush during February, 1965, difficulty was experienced with several fifthwheel couplings in that they became lazy and could not be guaranteed to lock automatically on every occasion. There was nothing strange about this as the roads were waterlogged and salt-strewn, and despite mudflaps there was a constant deluge of water and road debris whirling around all parts of the tractor chassis and turntable.
Therefore, as things dried out, the defects experienced were considered to be no more than the need for normal lubrication. During the servicing, however, coupling jaw hinge pins were found to be in a semi-seized condition and no amount of lubrication would ease them.
Short of removing the turntable altogether, various methods were used to move and free the dragging mechanism and included in this exercise was the liberal use of a gas torch. Finally, the mechanism was free enough to satisfy the mechanics that lubrication was again doing its job, and in turn each of the machines was returned to service.
Within a short while, however, two of the five had iniscoupled repeatedly. Luckily this occurred before the landing legs were lifted, and when a further tractor ran a few yards and then dropped its trailer heavily, a halt was called and the tractors were taken out of service for the removal of the complete turntable.
On removing and upturning the first turntable, everything looked normal• and in working order, and there appeared no reason for trouble as the moving parts were again well lubricated and free. One of the problems, however, on removing any turntable is to make the coupling work, as when it is being coupled to the trailer pin. Attempts to push a spare trailer pin into the coupling jaws on its own is a most difficult task.
This problem can be overcome by attaching a spare pin to the centre of a 6 ft. length of steel joist or channel, and if provided with handles at each end two men can swing the pin home into the coupling jaws positively and easily. This rig was used on the turntables in question, and it was then found that in each instance the fairly strong coil spring that operates and holds the jaw lock in place was now dead and useless.
These springs had suffered from the effects of the gas torch flame, which had been offered to the underside of the turntable during the earlier easing-off exercise and it had escaped notice that the springs were on several occasions right in the flame path.