MORE ON REAR-AXLE OIL SEALS I NOTE from your issue dated
Page 40
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January 16, 1948, that Mr. E. Stothard calls for my comments. I also refer to the letters on the same subject from the Associated Equipment Co., Ltd, and Mr. N. C. Kew.
Regarding the statement by A.E.C., that one pint per 10,000 miles is reasonable; if this could be attained, I am confident that many road transport engineers would consider that they had accomplished something worth while. But could this consumption figure be upheld under high-pressure service conditions? Onry recently you published a letter from me calling for users' experiences of rear-axle lubricant consumption, to which I received no replies. Surely such a disclosure could not be treated • as a trade secret—probably the answer to my query would not bear investigation.
A rear axle should be so designed as to retain the lubricant over the longest possible period, to lubricate the differential gear and final drive and eliminate waste caused by leakage. The two main sources of leakage are along the axle-shaft casing, via the hubs (in spite of oil seals) and from the worm-shaft gland. Dealing with the former—and, incidentally, the easier to rectify —I would suggest a lower level than under present practice, but to reduce this level would obviously reduce the volume of oil in 'the differential case, which, of course, would not be desirable. In fact, I would like to see rear-axle capacities increased by at least 50 per cent, on what is now the general practice. This, in my opinion, could easily • be achieved by designing the differential case accordingly. I could advance many more claims for increased capacity if space would permit.
Hub bearings are generally lubricated individually through a nipple on the outside of the hub, and, therefore, no longer rely on being supplied from the differential casing, but I am afraid that it does not always work out like that, The main source of leakage must, obviously, be from the worm shaft, and the seal employed here is taxed much more than are the axle-shaft oil seals, as it is working with a head of oil to contend with, and whatever type of seal be used, it certainly undergoes the acid test of oil sealing.
I have had correspondence with the Associated Equipment Co., Ltd., around the period when the bellows gland was introduced, and this company stated that the original adjustable-packing type had the disadvantage of suffering from heat and burning if it was over-tightened. Speaking from my experience of operating vehicles over huge mileages, I have never experienced a burnt-out packing-gland-type seal on an A.E.C. or Leyland worm shaft, except in cases which could be accounted for by neglect.
n6 With reference to the bellows-gland-type oil seals, I find that when these fail they have a nasty habit of giving no previous warning. When this type gives up, the leakage is not intermittent drops, but a free flow, which can empty the rear axle in a matter of minutes In the 'case of the packing-gland type, one always receives a reasonable amount of warning—on the garage floor during the garaging period—that adjustment is necessary.
If anything up to a tablespoonful has leaked overnight, a one-slot turn of the gland nut is sufficient to check it. Furthermore, this class of packing has given us remarkably long service and can be renewed easily and cheaply.
In conclusion, A.E.C. informs me that the stuffing box and the packing gland are now obsolete and superseded by the bellows type, but I am not so sure that the company has not thereby "exchanged 'its fiddle for a gee-gaw."
It should be noted that the above remarks do not apply to overhead-worm drive. W. EmMERsON.
Bishop Auckland. (For " O.K." Motor Services.) T.R.T.A. SECRETARY REPLIES TO MR. E. H. B. PALMER ITH regard to the letter from Mr. E. H. B. Palmer, published in your issue dated February 6, how one "whitewashes alleged irregular operations" is perhaps best known to Mr. Palmer. To one who has spent many years in Traffic Courts, I would expect my explanation of the provisions of the Road and Rail Traffic Act, 1933, to prove to be elementary. Why he should assume that everyone else is equally familiar with them, I do not know—anyway, that is not the case. I am well aware of the proverb, "There is no smoke without fire," but I am by no means assured that the allegations to which I have taken exception are necessarily based upon actual facts The "fire" may well be only what Mr. Palmer seems to accept—as do others—without real evidence or just complaints, bitter or otherwise.
I would ask Mr. Palmer to re-read my article. 1 would then hope he will agree that I have tried to explain clearly the work which may legally be done with a C-licensed vehicle; that I have expressed the view that some of the complaints made are without foundation and due to ignorance of the law; and that I have said, and I repeat, that the T.R.T.A. stands for complete observance of the law and does not seek to excuse lawbreakers, whoever they may be. We do ask for proof— not hearsay—which is all that Mr. Palmer appears to put forward; and we suggest that if proof of noncompliance with conditions attaching to carriers' licences be forthcoming, the evidence be passed to the Licensing Authorities, who will take appropriate action with the very full support of the T.R.T.A.
Mr. Palmer, when" inclined to accept the ` evidence' " of his haulier friends, seems to me, anyway, to be indulging in that " surmise " which he quite incorrectly attributes to my article. Perhaps Mr. Palmer would do as we ask—it is very simple—produce the evidence. If it be available, then he will have our full support in taking action to stop illegal practices, whoever, may be proved to be guilty of them.
Finally, I hope that Mr. Palmer's haulier friends are members of the Road Haulage Association. If not, surely they should be. Then they could pass any evidence they may have to the R.H.A., and it will be
dealt with properly.. F D. FITZ-GERALD, F.C.I.S.,
London, W.1. Secretary.
(For Traders Road Transport Association)