The Engineer. 30th May, 1902
Wolverhampton Tramways

It will be remembered that the Corporation of Wolverhampton is engaged in installing the Lorain system of surface contact traction on its tramway system. For some time past now, parts of the line have been at work. On Saturday last, two curious accidents occurred. In one case a wagonette and pair were being driven along Pipers Row when one of the horses suddenly jumped into the air and then fell down dead.

It was supposed that the animal bad come into contact with a "live" contact stud, but against this theory the Lorain Company's officials are reported to have examined the studs in the locality of the accident, after it had taken place, and to have found them dead. Furthermore it is stated that a veterinary surgeon, who made a post mortem examination of the animal, failed to discover that death was due to electric shock. Did this accident stand alone, therefore, one might well assume that the horse had had a seizure of some kind, and that his death had nothing whatever to do with electricity. A doubt on the subject may, however, be pardoned, on account of the fact that earlier in the same day two horses attached to a wagon belonging to the Great Western Railway Company fell suddenly to the ground in Bilston Road, "as if," to use the words of a local report, "they had received an electric shock."

A driver of this van is also reported to have gone to the hospital to be treated for a sensation like "pins and needles running into him." He was not, however, badly injured, and is, so we gather, none the worse for his experience. These statements would seem to point in the direction of some of the studs having remained "alive" after the passage of cars over them.

It is, of course, well known that in all surface contact systems it is the main endeavour of designers to ensure the immediate disconnection of the studs when the car is not actually over them. Mr. A. P. Trotter, when reporting on this system to the Board of Trade before it was passed for traffic, said: "When the car passes, the pieces of iron which produce the contact are allowed to drop. Should one of these fail to drop, a horse treading on the block would probably be killed, but a foot passenger treading on it would receive a shock which would not be dangerous to life, but which would make him stumble. . . . I have examined the details of the contacts, and I think an accident to a horse is unlikely, and the risk of an accident to a foot passenger very remote. . . "  The Lorain Company’s officials are reported to have said with regard to the matter, that any instance of a "live" stud cannot be due to inherent defects in the stud itself or in the system, but to the studs having been injured in some way by workmen whilst being laid down. If this is a true report of their sayings, it appears to us to form but a lame excuse. It should be the business of the company to see that no such results shou1d be possible, whether caused by workmen or in any other way.

The Engineer. 24th April, 1903
The Surface Contact Tramways at Wolverhampton

Many of our readers will be doubtless aware that the Lorain surface contact tramway system has been in operation at Wolverhampton for some time now. In fact, the first experimental mile of line was completed in January, 1902. There are now, and have been since last September, just over 11 miles equipped on this system, and the borough electrical tramways engineer Mr. C. E. C. Shawfield, A.M.I.E.E., M.I. Mech. E., and the borough engineer, Mr. George Green, A.M. Inst. C.E., have just issued a joint report on the way the equipment has behaved. As this report contains some useful information, it will be of interest to give a summary of its leading features. It appears that between 40,000 and 50,000 car miles are being run each month. There are some twenty to twenty two cars at work, and each car, therefore, does, on an average, between 60 and 75 miles per day. Daily records have been kept of everything connected with running, repairs, breakdowns, etc.

The portion of the report made by the borough electrical and tramways engineer is divided into five headings, as follows: 1. Safety to human beings and animals; 2. Reliability; 3. Consumption of electrical energy per car mile; 4. Cost of working; and 5. Cost of maintenance. As regards the first of these, the possible sources of danger are given as :- (a) Obstruction to traffic due to the projection of the metal contact plates above the street surface; (b) Risk of electric shock to human beings or animals from defective boxes. It appears that no accident due to slipping or stumbling on the contact plates has been reported.

As to the question of liability to shock, we find the following paragraph:- "I do not think it feasible to devise or construct a surface contact system in which there is absolutely no possibility of a stud being 'alive,' except when a car is over it, and it is a matter of common knowledge that cases have occurred in Wolverhampton where boxes have been found 'alive,' and instances are on record of persons and animals having received shocks therefrom. Mr. Shawfield does not appear to be aware of the line in Paris, described in The Engineer some short time ago, where for more than a year there has not been one single case where a stud has remained alive, or accident happened.

It appears that it is by no means an unusual thing for boxes to be found "alive" in Wolverhampton. Indeed, they have men continuously at work testing them with the object of finding which are alive and which are not. It seems that the great majority of live studs are found at particular points in what are, perhaps, the busiest portions of the town, and generally at points and crossings. These places have now become very fairly well known, and it is very rarely that a case occurs of a box being 'alive' at a dangerous voltage other than at certain known places. At these danger points a more careful watch is kept than upon the rest of the line, and the report states that in nearly every case a "live" box is discovered almost as soon as it occurs.

To better understand the explanation given of the way the studs become "alive" reference should be had to the accompanying illustration, which shows the Lorain track equipment by means of two sections taken at right angles to one another. The various parts are lettered, and may be recognised by consulting the index on the diagram.

Car Equipment

 
Track Equipment

The method of working will be understood and need not be explained. The report states that in the case of the first studs which went wrong, the cause could always be traced to defective installing, due to haste, the object being to get a part of the system at work by time of the recent exhibition. When these were weeded out, the troubles were practically all confined to one cause, the damage done to the cup, shown in the illustration at K and K¹ "by heavy short circuits, which are largely caused by scrap iron on the track."

These short circuits, with very few exceptions, appear to occur only at points and crossings. The effect of a number of short circuits on a box is to cause the interior of the top half of the cup to become burnt and charred, with the result that it loses its insulating properties, and allows a leakage to take place from the lower carbon to the top plate. The report continues:- "If it were possible to prevent the occurrence of these short circuits, or to minimise their effects, the number of boxes which would be found 'alive' at a dangerous voltage would probably be extremely small." The italics are ours. It appears, though no explanation is given, that some of the faulty studs have been found to have a much greater difference of potential to earth than have others.

A classified list of defective boxes is given. This shows that from May, 1902, to February, 1903, inclusive, 400 damaged boxes were reported. Of these 182 are given as having a difference of potential to earth of from 10 volts to 49 volts; while in 218 cases the voltage between the two was from 50 to 500. In another place we find "box found alive at 120 volts;" "box found alive at 510 volts;" "box found alive at 480 volts;" and so on. The above mentioned number of 400 spread over the period indicated, which works out to 304 days, means a failure of 1⅓ boxes per day in just over eleven miles of track. This seems a high average; but, apparently, only seven accidents in all have been reported, all of these occurring during May, 1902, and before the line was really properly at work.

The report is careful to state that this does not prove that no shocks have been received, but it argues that since they have not been reported, such shocks, if received, cannot have been of a very serious nature. Mr. Shawfield considers that there is less danger to human beings with a surface contact system than with overhead wires. He has witnessed cases of pedestrians stepping on boxes "alive" at 500 volts without apparently receiving any shock whatever, and, he adds, "in any case I think that the risk of serious injury to any person stepping on a 'live' box is so small as to be practically nil". Even to horses he does not think that stepping on a live stud will result in permanent injury unless the shock is sufficiently severe to cause a fall. On the other hand, it is pointed out that cases have occurred from falling trolley or telephone wires which have produced fatal results. In fact, to sum up his conclusions, he considers that the Lorain system offers distinctly less risk of serious injury to the users of the streets than would an overhead system.

Discussing reliability, the report states that out of a total of 376,600 car miles, 1,483 car miles were lost from all causes from May, 1902, to February, 1903. Of these, 595 were due to the Lorain car equipment, and 85 to the Lorain track equipment, or 87½ percent and 12½ percent respectively. During the seven months August to February inclusive, the percentage of car miles lost due to defects in the Lorain system was 0.13 or 1⅓, out of every thousand miles run. The opinion is arrived at, therefore, that on the score of reliability there is very little to choose between the Lorain and the overhead systems.

The consumption of electrical energy per car mile comes out about 0.25 units per car mile more than with the overhead system, the total power used per car mile being 1.4 units. This makes the Lorain system some 22 percent, or, with electricity at 1.65d. per unit, 0.41d. per car mile dearer than the overhead system. The cost of operation is taken as being practically the same for the two systems. As regards the cost of maintenance, this is discussed under various headings. The cables will, it is estimated, cost a very small annual sum for maintenance. The cable terminals and the cable terminal insulators, marked H and G on the plan, will not, it is thought, cost much to keep in working order either. The armature cups, it is calculated, will cost 0.2d. per car mile to keep in repair. Experiments have shown that a current of 1 ampere at 500 volts can be broken over 750,000 times without damage to the cup. A further experiment, when breaking 100 amps at 500 volts, showed that this could be done at intervals of a minute without apparent damage to the cup.

Two kinds of contact plates have been tried. With one of these the cost of keeping in repair works out at 1.12d. per car mile; with the other, in which only the centre portion is renewed, the cost is 0.094d. per car mile, a considerable difference. Inspection and testing costs 0.035d.; the magnets and magnet coils of the collector 0.089d.; batteries, switches and connections, 0.027d.; the collecting skate, 0.06d.; and inspection and adjustment of car equipment, 0.054d., all being per car mile. The total maintenance, taking the second kind of contact stud mentioned, amounts to 0.8d. per car mile, as against a calculated amount of 0.28d. per car mile for the overhead system. The difference 0.02d. added to the calculated extra cost of current, namely, 0.41d., gives a total against the Lorain system of 0.43d. per car mile. With a service of say, 540,000 car miles per annum, this means 232,200d., or, say, £967.

Or, in other words, and granting that all else was equal, Wolverhampton has to pay over £950 per annum more than it would have done with an overhead system. This sum is less than that actually shown in the report, which takes into account all renewals which are likely to be necessary over a considerable period, but which are included in the estimate of expenditure per car mile. The sums calculated under this heading for the Lorain and overhead systems are 0.499d. and 0.1l6d. respectively. Subtracting one from the other, we obtain 0.383d. per car mile as the difference, and this, added to the difference already alluded to, of 0.43d. per car mile, gives a total difference of 0.813d. per car mile. This, multipled in the yearly car miles, 540,000, gives, say, £1829 as the yearly difference of cost between the two systems. The sum would naturally increase with each extension. The tramways engineer concludes by pointing out that his task of comparing a new and comparatively untried system with one which is more or less standardised has been hard, and that the responsibility for deciding whether or not the advantages offered by the Lorain surface contact system are commensurate with the extra expense involved, rests upon the Tramways Committee and the Council.

The original offer of the Lorain Company was to equip about eleven miles of single track, and to allow the Corporation to work them for a year. At the end of that period the Corporation were to come to a definite decision as to the acceptance or rejection of the system. Their deliberations on the subject should be materially assisted by the present report. The borough engineer's portion of the report deals mainly with the granite casings of the stud boxes and with paving, and though it is of considerable interest, we need not further refer to it here.