ROSLYN TRAMS

Evening Star, Issue 18258, 24 April 1923, Page 5

ROSLYN TRAMS

TO TUB EDITOR. Sir, —Cr W. A. Scott, chairman of the Tramways Committee, in his election statement, ascribes tho recent breakdowns of tho Roslyn tram service to “ rope trouble.” Just a month ago wo addressed a letter to tho council protesting against the statement that tho breakdown of tho rope was duo to any deficiency in its quality, and giving reasons for oux protest. Two meetings of council have been held since then, yet our letter has not been before the council, and we understand it has not even been before tho Tramways Committee. Whatever may bo the reason for this delay, it is unfair to tho rope makers that our letter should bo suppressed while Cr Scott now reiterates the statement to which wo took exception. We enclose copy of our letter, and will ho glad if you will publish it.—We are, ote., Thomson, Bridger and Co., Ltd. Jas. Allen, Director. April 23. 1 [Enclosure.] Tho Mayor and Councillors, Dunedin City Corporation, Dear Sirs, —With reference to tho Roslyn cable, which has been so much in evidence lately, the manager was reported as say “ tho present cable had not been a good one,” and Cr Shaddock that “ the root of tho whole trouble was a very bad rope.” Tho cable in question was made by Messrs Bullivant and Co., Ltd., London, for whom wo aro local agents. W T o have referred the abova statements to Messrs Bullivant’s branch in Sydney, and we have also furnished them with a copy of Mr Hunter's report, also of newspaper publications referring to tho matter, and we now wish to convoy to you tho substance of their reply. Wo wish to enter an emphatic protest against tho statements referred to above. The rope supplied was made from tho very best quality of material of tho grade ordered by tho corporation. Mr F. Bullivant wrote on February 22, 1922, before delivery of the cable r ” Wo havo now got tho wires in for the Roslyn cable, and the tests are in every way satisfactory.” Unfortunately, no test certificates of this rope were sent out, but wa havo asked London for full particulars, and meantime we have a cable from them replying to our inquiry as to tests for torsion and tension. Torsion.—Tho average number of turns in Bin is given as twenty-six, Thin is very satisfactory. Tho last test sheet of Melbourne rope (Xo. 153) shows an average of 20.49 turns in Bin for a ropo 4in full circumference. Tension.—The average breaking strain of wires is given as 88 tons per square inch, tho limits being 85 to 90 tons (the specification called for 85 tons). Messrs liuliivant do not draw the wire, and this enables very strict specifications to be issued, and drawers have to conform. Messrs Bullivant are not novices at the work of making tramway cables. They have now supplied 159 ropes to the Melbourne tramways, havo made records In most of the sections, and continue to maintain their reputation. The Sydney manager has just been at Melbourne, and has received splendid reports on ropes now at work. During the past ten years over 1.7C0 tons have been supplied to Mel- ’ bourne, including 252 tons during 1922. , Messrs Bullivant are also largo suppliers to Edinburgh and Glasgow cable tramways, also to San Paulo Brazilian railway inclines, which are used both for freight and passenger trains, tho Incline being- 1 in 9.75. b Wo think wo are correct in stating, that tho previous Bnllivant’s cable used some wars ago on tho Roslyn lino gave the longest life of any cable used on that lino. Why then did this particular rope not give a reasonable life? Mr Hunter decs not appear to blame the ropo. On the contrary, he states that the conditions in the power house would cause damage to the ropo, and it is reasonable to assume that tho balance of his report, if made available, will bo found to show that the condition of the track, especially as regards the pulleys, was such as to contribute largely to the damage to the rope. lliere is no doubt whatever that tho rope would be distorted by treatment such as is referred to in Mr Hunter’s report. I ailm'G to bottom tho rope in the groove of the driver would cause tho rope to bo pinched between tho tapered sides of the groove, and this would undoubtedly distort the shape of tho rope. A high Melbourne authority, with thirty years’ experience, is very emphatic that" the rope being pinched in wheel would, ns ho puts it, “take the inside out of tho rope,” and no doubt bo responsible for putting tho ropo out of shape, sub feet lug it to hag usage from tho grips. The jerking of the rope through slipping would sot up a tremendous strain on it,'especially at the periods of heavy loading, and this would accentuate tho distorting effect, increase the strain op certain strands through the pinching effort, and cause uneven' wear. Tho extent of this straining is evidenced by tho two serious breakages which occurred to the machinery, the ropo, of course, experiencing precisely the same overstrain on those occasions. Tbri pinching and straining occurred to a rope which could not bo kept properly filled or lubricated. Lubrication ls essential lo the lifo of a tramway cable. i It has b«en demonstrated by actual tost in colliery winding that the load can easily bo doubled by a jerk caused through slack chains. Tho elastic limit of tho material is just over half the ultimate breaking strain of tho rope. If tho maximum strain does not exceed this limit tho steel returns to its normal condition when the load is removed, but, if tho strain exceeds the clastic limit, then a permanent set is put in the material, and it finally becomes plastic and pulls out. It is quite possible that, under {be circumstances of distortion, slipping, jerking, and increased loading, not to mention possible trouble with tho underground gear, tho elastic limit of the material lias been exceeded. This would seem to be indicated by the nature of tho trouble experienced. It is a fact well known to those having experience with metals that shocks affect their structure. In the case of wire ropes shocks are fatal to the life of a rope, and there is no doubt that this particular ropo has had a very bad time in this respect. The bunching of a strand in the rope points to direct damage having occurred, possibly cutting through several wires or the whole of one strand. If tho ropo was breaking up generally from ordinary wear ' and tear, bunching would not he likely to | occur, as probably not more than "two wires would be found parted at any one place in a strand. In Melbourne a bunching is found to bo usually attributed to ropeman’s failure to throw rope at curve. In this particular case it is extremely probable that the bunching was caused by strands being cut by the gripper, due to its fouling the distorted rope at a time when perhaps a jerk occurred through the ropo slipping. Wo asked Mr Farmer, Bullivant’s manager in Sydney, to como to Dimjdtn to inquire fully into this matter, hut we regret it is impossible for him to como here at present. From what has already transpired, however, it is Certain that the breakdown of the rope was not caused through any deficiency in quality, and it is duo to our principals that tho members of the council should recognise and acknowledge that fact.—We arc, yours faithfully, Thomson, Bridges, and Co., Ltd. March 20, 1923.