ROAD AND WORKSHOP by Handyman
Page 47
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Damage and Expense caused by Loose Wheel Nuts
THE PROBLEM OF damage arising from loose road-wheel nuts has occupied the attention of the engineer right through transport .history, and when he might have expected a little relief from this problem, via road improvements such as less twisting and turning, this benefit is almost cancelled by higher road speeds, heavier loads and, most important of all, the shorter working day, which gives less and less time to the driver for vehicle attention. Therefore, it is fair to say that damage arising from loose wheel nuts starts with their neglect, rather than from any design weakness. In fact, the cone and cup method of securing road wheel to huh leaves nothing more to be done other than regular attention to nut security—only a few minutes of the driver's time daily. Yet this same system of locking wheel to hub can become an instrument of destruction if nuts are allowed to work loose and motion set up between cone and cup, To explain this dearly, the cone is on the nose of each wheel nut and also on the shoulder of each stud. The cup is represented by the countersunk stud holes in the wheel centre or disc. Therefore,. on nipping up tight, the wheel discs are centrally poised on eight or 10 such cones at each side, making them very secure indeed. However, if the daily nip up is neglected the situation changes rapidly; any movement at all between cone and cup is quickly increased, and it is known that distances as short as 100 miles have produced instances of heavy damage and expense. The reason for this is that the fairly :bin and—on some models—sharp inner diameter of the wheel disc stud hole. can come quickly in contact with the threaded section of the stud itself, and each movement of acceleration or braking can promote a cutting action. From then on two things can happen, if the situation is ignored: The wheel centre stud holes can enlarge enough to allow the wheels to escape over the nuts, which means a sudden grinding halt and damage. or an accident, or both; or the studs can be loosened from their bed in the hub, and in a short time can destroy hub, brake drum, wheel discs and, on occasions, the brake shoes themselves.
The transport engineer is very familiar with this problem, and considers himself fortunate if he can get away with no more than a set of replacement wheel studs and nuts, but all too often he is faced with the total damage as described. Although able to rectify quickly the damage on each occasion, he is never at all sure that the lesson from this expensive incident has really got home to the driver.
Apart from the daily nip up, the driver has two further methods or warnings of loose nuts and impending trouble: a visual inspection of each nut, in which the loose one will show a definite fringe or area of rust around it, emerging from between cone and cup; or a pronounced creak or metallic groan every 10 ft. or so
at slow speed, which will indicate with certainty that a pair of wheels are on the move and require attention, The one satisfactory approach, however, is the daily nip up and where this drill can be followed, the problem of loose wheels will be solved. Nevertheless, for the had lads who will not he told, or just could not care less, let some facts—from recent case_ of loose wheel nuts on a Leyland Octopus first driving
axle —speak for themselves. Material costs only were:— One rear hub ...
One brake drum Ten wheel studs complete with nuts ...
Two 20-in, wheel discs ... Two rear brake shoes (lined) ...