This paper, from Transactions for 1885, Society of Engineers (London, England), was written by William Newby Colam, an engineer who participated in the design or construction of several UK cable tram lines. In this paper, he concentrates on London's Highgate Hill Cable Tramway, the first Hallidie-type cable tramway in Europe.
From Transactions, Society of Engineers (London, England).
May 4, 1885.
Paper read before the Society of Engineers.
As is now pretty well known it was in America that continuous wire cables were first adopted for the purposes of street locomotion. The author, however, in addressing English engineers on the subject of cable tramways, thinks he is best considering the wishes of those present by dwelling but cursorily on the birth, history, and construction of the cable system in America ; and in devoting a considerable portion of his paper to a description of the Highgate Tramway, which is not only the most recently constructed cable tramway, but the first ever made in Europe. In the case of all inventions which have eventually proved to be of great value, the honors of inventorship have usually been contested. Suffice it to say that the cable system of tramways is of comparatively recent origin, and that the author proposes to leave the question as to who originated it for others to settle. It is doubtful whether the invention in this case would, even at the present time, have been practically worked out had it not been for the fortunate circumstances that a few wealthy men living on the heights of the city of San Francisco had no means of easy excess (access? - JT) to their dwellings.
The idea of employing a wire cable for hauling vehicles is, of course, very old. and has been utilized in a variety of ways, but the novelty of cable tramways consists in the secretion of the rope beneath the surface of the road in such a manner as not to interfere with the ordinary traffic, and also in the gripping arrangement, which allows cars of the ordinary type to be used. No two lines on the cable system have as yet been constructed alike, but the principle of working has in all cases been the same, and may be concisely described as follows:
On the cars and under the control of the driver a gripping arrangement is fitted which is extended down through a narrow continuous slot between the rails and into a tube under the surface of the road. Here it is so manipulated by the driver as to close firmly or partially upon, and, when required, to release itself from, an endless wire cable which. is kept constantly moving by a stationary engine placed at any convenient spot along or near the line. The cable is supported on small vertical pulleys at suitable intervals on straight portions of the road, but at curves inclined or horizontal, pulleys are substituted according to the nature of the curve. Where very sudden and acute rises occur in the surface of the road (such as at crossings on the San Francisco hills) small inverted pulleys are used to depress the cable and keep it from touching the top of the tube. Such cases, however, are seldom met with in practice.
In the month of August, 1873, a few energetic and skillful men succeeded in overcoming the many objections and apparently almost insurmountable obstacles which invariably attend the introduction of new schemes, and the result of these labors was the construction of the pioneer cable line up Clay Street Hill in San Francisco. This hill is very steep, the severest gradient being as much as 1 in 6 ; and, like most hills around San Francisco, is leveled where intersecting roads cross, giving the longitudinal section of the road, a step-like appearance. The street length of this line is 2,800 feet, and the altitude risen to in that distance is 307 ft. The first cable used was 3 inches in circumference, and was worked at a speed of 528 ft. per minute for 17£ hours per day, and it lasted over two years. Owing to an agreement made with the local authorities, this line had to be constructed in about two months, consequently it was not built quite so substantially as others since. The line soon proved itself a great financial and mechanical success, and in 1877 extensions were made, but not in the same manner. The total length of cable at present in use on this line is 11,000 ft.
The Sutter Street Tramway Co. closely watched the results of the Clay Street trial, and three years and a-half after the opening of that line they had converted their line to the cable system, as it had ( owing to the grades) hitherto for many years been worked unprofitably by horses. This company has now over three miles of double stock, crossing two of the most important thoroughfares in the city. There are four cables employed, all working from one engine- house, three of which work the main line and one a branch line at right angles. The total length of cable in use is 37,- 736 ft., running at 780 ft. per minute. Near the end of the branch line the cars have to pass round a sharp curve, and no difficulty is found in doing so. One year after the completion of this line the passenger traffic had increased 962,370, and the shares of the company previously offered at £5 sold freely at £12 10s. The construction of this line demonstrated the ease with which ordinary lines can be converted to the cable without seriously interfering with the traffic.
In 1877 the California Street Co. was organized, and opened their line in April, 1878. As the route for this line was very steep, at places being as much as 1 in 5.5, it was decided to build it in a more substantial manner than the previous two, which had wood in their formation. The tube here was solely and wholly a combination of iron and concrete, forming a strong homogeneous mass. The cables adopted were also heavier than before, being as much as four inches in circumference, The total length of double track is 12,650 ft. The engine- house in this case is situated in a valley, and contains two engines, hauling two cables of 8,840 and 17,055 ft. long, at a speed of 537 ft. per minute. Geary, a most central and popular street, was the next route chosen for a cable tramway, winch was completed in March, 1880. The grades on this line are comparatively easy, the worst being 1 in 10.3. Here the engine-house was placed about half-way along a double track of 13,200 ft. This line has been very successful and free from accidents, notwithstanding it is crossed at right angles by three horse tramways, one of which also runs over its metals for a considerable distance.
In 1881 the Presidio and Ferry line of 13,000 ft. of double track was constructed. Some of the grades on this line are exceedingly heavy, the worst being 1 in 5.1. There is a curve at the intersection of two streets, the streets from both directions descending towards the curve, around which it was originally arranged for the cars to gravitate ; but improved methods have since been introduced, so that either the main cable or an auxiliary one, running at a reduced speed, can be picked up by the cars.
In 1880 the wonderful mechanical and financial success of the San Francisco cable lines excited the attention of tramway companies in other parts of America, and even in the distant English colony of New Zealand. In both places the authorities, having convinced themselves of the value of the system, lost no time in organizing lines, and in August, 1880, the citizens of Dunedin in New Zealand saw the first cable line (out of San Francisco) opened. Roslyn tramway is practically a single line of 3 ft. 6 in. gauge, with turnouts. It is 3,500 ft. long, and the total rise is 500 ft. The steepest gradient is 1 in 7. An interesting feature of this line is an S curve of 215 ft. radius. The success of the Roslyn line induced the Dunedin people to further invest their money in the Mornington Tramway, which was opened in March, 1882. This line is one mile long, and the altitude attained is 430 ft., the worst gradient being 1 in 6.25.
The next city to recognize the advantages of the cable system was Chicago, and on the results obtained there, under so vastly different circumstances and conditions of climate, depended the spread of the system further east, or the limitation of it to milder climates. It may be taken as fortunate that immediately after the completion of the line, in January, 1882, Chicago was visited with heavy falls of snow and severe frost. The cable was at once well tested, and proved to be easily operated, never losing a trip, when all other vehicle traffic was suspended. Again, this winter, the cable system has been uninterrupted, notwithstanding the exceptionally severe weather Chicago has had. The Chicago company had at various times tried all the well known tramway motors, and they finally reverted to the cable, although the city is practically a dead level, and the company was doing well, as their $100 shares were quoted at 1250. The cables on this line are worked from one engine- house, and are so arranged and actuated that three different maximum speeds are imparted to the cable, suitable for the respective districts through which they pass ; thus in one place the cable is always moving at 315 ft. per minute, at another 716, and at another 804. At the end of the main cable line instead of switching the cars to the up line, they are run (at half speed) completely around a square block of buildings which entails four considerable right angle curves. The Chicago company has now a line capable of carrying over 10,000 passengers per hour, and on more than one occasion 100,000 people have ridden on the cars in one day. The annual passenger return before converting was 24 millions, and the first year after 27 millions, with the working expenses considerably reduced.
Market Street, the last line in San Francisco that was converted into the cable system, is by far the most important in that city. For a long time it was thought it would be impracticable to have a cable line in this street, owing to its already very crowded state at certain times of the day. Experience has, however, shown, that out of the eight lines of tramways passing along this street, those worked by the cable are the general favorites, for numerous reasons, amongst others the more uniform speed at which they travel. From 1860 to 1867 this line was worked by steam engines, and by horses from that date to 1883, when the cable was inaugurated. This road has about 10 miles of double track, and several branches worked by 46 heavy and large cars. Five cables of 4 inches circumference traveling at 750 ft. per minute are operated from two distinct engine-houses. The total length of these cables is 90,810 ft., and they weigh over 100 tons.
A noticeable feature in this line is a curve of 80 ft. radius which passes in front of the engine depot, and around which the cars are hauled by an auxiliary cable worked at half the speed of the main line cable.
Lines have been made in Philadelphia, and also one across the Brooklyn Bridge in New York ; both, however, have proved failures from an engineering point of view, because in each case the authorities attempted to ignore the po- tents which cover the construction of good economical cable roads. In Australia the city council of MeIbourne has been so satisfied with the report of their engineer, who specially visited and examined the cable lines of America, that they have sanctioned the construction of 27 miles of line in that city, which is now well in hand. The city of Sydney has also granted a company permission to construct a test line of a mile long, with the understanding that considerable extensions will be permitted upon its proving a success.
A cable company has been formed in New York, and the Mayor of that city has granted a concession for the construction of a system 72 miles long, part of which is to be street tramways, and part to run above the street as the present elevated railway does. The decision of the council and mayor has not only been influenced by overwhelming evidence of the behavior of cable tramways, but they have carefully considered the rapid increase of population which is annually being enormously augmented, and they have satisfied themselves that the cable is the only system which will be able to cope with the traffic of a few years hence.
The author has abstained from giving descriptions of the various gripping appliances used on the lines he has alluded to, his object being not to weary the members with described explanations of complicated machinery. He has, however, furnished models which show the principles upon which they have all been made.
Fig. 1 shows the wrought-iron tube frames used at Chicago and some of the San Francisco lines, others have cast-iron tube frames of similar character to those at Highgate.
Having given some information as to what has been done in cable tramways abroad, the author will next proceed to describe the Highgate Hill cable tramway.
It is surprising that notwithstanding the rapid growth and great success of the cable system in America and our colonies during the last eleven years, it was not until May, 1884, that the first cable tramway in Europe was opened by the Lord Mayor of London, on Highgate Hill. To those who had worked hard in introducing the system into this country, it was reassuring to find how soon after the opening of this line the objections of the local authorities disappeared, and the inhabitants living along the route prepared to vote for further extensions. The power to construct a tramway up the Highgate Hill was obtained by the Steep Grade Tramway and Works Co. during the session of 1882. In the summer of 1883 that company requested the Patent Cable Tramway Corporation (who own all the important patents necessary for constructing such lines) to furnish the designs for and construct their lines on the cable system. On the introduction of anything new into this country the idea introduced has usually to pay heavily for the privilege, and this occasion proved no exception, for the surveyors of the parishes through which this line passed were very zealous in watching the interests of their respective districts, and on so small a line as this their several requirements proved serious and most expensive obstacles to the completion of it.
Highgate Hill is a well-known steep incline rising from the junction of Archway Road, Junction Road, and Holloway Road, in the parish of St. Mary's, Islington; about half way np the ascent it is intersected by two other parishes, viz., Hornsey and St. Pancras, finishing opposite the old historical "Gate House." The summit of this hill and its surroundings is a great holiday resort for Londoners, and on many occasions this line has been severely tested by excessive and sudden rushes of traffic, which would have proved too much for any other system of tramway to have met.
The principle of the system working at Highgate is the same as on all the other cable lines in operation, but the details of construction differ in many respects.
The gauge of this line is 3 ft. 6 in., and it commences at the foot of the hill just where the rails of the North Metropolitan line terminate. The total length is 3,800 ft., of which 3,300 is double track and the rest single. By a reference to Fig. 3, which shows a longitudinal section and plan of the road, a good idea may also be obtained of the direction of the track, and the position of the engine depot. The total height ascended is 239 ft., and the steepest gradient is 1 in 11. Fig. 2 shows a cross section of the track and tube for receiving the cable. The tube is made of good strong concrete, and is connected with the concrete required by the local authorities for supporting the set stones and rail chairs. Tube frames of cast iron weighing 120 Ibs. are embedded in the tube, at intervals of 3 ft. 6 in (Fig. 4). The object of these frames is to support the Z-shaped steel rolled beams which form the slot in the road for the Dripper shank ; these beams, which weigh 36 Ibs. per yard, are shown bolted to the sast iron frames. The rail adopted weighs 43 Ibs. per yard, and is that mown as Dugdale's patent. It is supported on cast iron chairs placed opposite each tube frame, to which they are connected by the bolts, firmly securing the gauge true to the slot. The slot is 5/8 of an inch wide. From the surface of the road to the bottom of the tube is 17 inches, and the width of the tube is 8 1/2 inches.
At intervals of 40 ft. recesses are made in the concrete for receiving the 12 inch cast iron pulleys which support the cable in the tube (Fig. 6 (Figure 6 is not available - JT)); the pulleys run loose on spindles screwed into castings, which are held in their places by bolts built into the concrete. The pulleys are kept on the spindles by check nuts, which can be easily taken off whilst the cable is in motion, and the pulley removed and replaced through the hatch in the road. The hatch covers are light cast iron boxes filled with hard wood, and are dropped into cast iron hatches which rest partially on one wall of the concrete tube, and on the bottom flange of the £ beam. The hatch is built in by the paving, and cannot be detected easily in the road. The pulleys are lubricated by Stauffer's patent lubricators screwed into the end of holes bored up the centers of the spindles. At the single portions of the track, where the cable runs in opposite directions through the same tube, the spindles are made longer, and two pulleys placed on them instead of one. These pulleys are inserted where the road curves, and can be removed in the way alluded to before. All the recesses are drained into the sewers.
There are three portions of single track, and at the junction of the double and single tracks two tubes have to verge into one. The slots in following the tubes also converge, and in doing so leave a portion of the road between the slots unsupported. The designing of these points in cable tramways will always require considerable experience only to be obtained by careful observa^ tion during the working of such tramways. The triangle formed by the junction of the two slots is a cast steel trough which is rigidly bolted to the I beams, and supported by a cast-iron frame from beneath. The apex of the triangle is a strong steel spring screwed to the steel trough. This spring is sprung under the top bend, and against the side of the I beam, where it is supported on a plate bolted to the side of the beam. Thus the slot is alwtvys open for the grip shank of the ascending cars. The inside of the steel trough is filled with set stones, thus reducing the metal on the surface of the road to a minimum.
The author will next proceed to describe the three brick pits under the roadway, and the machinery in them for diverting the cable at each end of the line, and at the point where it leaves and return to the tube in passing to aud from the driving gear in the engine-room.
1st. The terminal pit at the bottom of the hill, the position of which is shown in Fig. 3. This pit is rectangular in shape, 18 ft. long by 10 ft. wide, and 7 ft. deep from the surface of the road. It is strongly roofed over by rolled iron joists and concrete. It is lighted by gas, and access is obtained to it through a manhole in the road. The machinery inside this pit consists of a narrow cast iron pulley 8 ft. in diameter with V-shaped jaw; it is free to revolve horizontally on a pin vertically let into a cast iron carriage mounted on four wheels. The wheels rest on and traverse the lower inside flanges of two rolled iron joists set at an inclination, between and along which the carriage is free to move backward and forward. A chain is fastened to the lower end of the carriage, and is led over suitable gear to a heavy dead weight, the object of which is to keep the necessary strain upon the cable.
2d. The terminal pit on the top of the hill. This is also a brick pit 18 ft. long and 4 ft. 10 in. wide, and 10 ft. deep from the surface of the road. From the drawing it will be seen that the parts of the cable approaching and returning to and from this pit are quite close together ; the cable has, therefore, to be returned to the tube in a different way to that adopted in the lower pit. As the slot passes over a portion of this pit, the roofing is arranged to carry the castings or supporting the slot beams. In this pit are two cast iron pulleys of 8 ft. diameter, one placed immediately in front of the other, one revolves in a vertical plane, whilst the other is canted sufficiently to throw its top out of plumb the same distance as from center to center of cable when passing through the single track.
3d. The pit in front of the engine-house is also of brick, and is so constructed as to be approached from the engine-room. It contains four 8-feet pulleys. The tube slot runs the length of this pit. The slot beams here are bolted to special castings, which are mounted on short cross iron joists resting on longitudinal joists. This arrangement leaves the slot open to the pit beneath. The engine room is in the basement of the depot, the ground floor of which is used as the car shed.
In selecting the engine for working this line two important points had to be taken into consideration, first, that they should have a most sensitive automatic cut- off valve gear ; and second, that they should be powerful enough to do the work of an extension two miles long. The nature of the work on cable tramways varies so much and so quickly that within an incredibly short space of time the engines may be seen both working hard and hauled around by the load. The engines chosen were a pair of high-pressure horizontals, with cylinders 14 by 28 inches, built by Messrs. Graf ton & Co., of Cannon Street. They are fitted with Collmann's patent valve gear, which the author considers a very good one for the purpose, and he is thoroughly satisfied with the way these engines have always done their work, the valve gear being so effective that the brake arranged to act on the fly wheel is never called into play. The engines can be disconnected and worked separately when required.
On the engine shaft is fixed a cast iron helical toothed pinion which gears into a larger cast-iron wheel keyed on a countershaft, which also carries the grip pulley. It is this pulley which does all the work of hauling in the cable from the road. The jaws are of a long V shape, as shown in Fig. 5, and can be adjusted by thinning down or packing up the wood bolted between the segment castings which form the jaws. Although the author considers this class of pulley gives the cable a rather severe pinch, he is satisfied it releases the cable freely, which is a great point in its favor, especially when used as at Highgate. These pulleys were made by Grant, Ritchie & Co., of Kilnnrnock. Immediately in front of the grip pulley, and in line between it and the pulleys, is the arrangement for taking up the slack of the cable, which is something considerable when new or freshly spiced. Changes in the atmosphere will also affect the lengths of the cable. This tak- ing-up arrangement consists of two long rolled joists laid parallel to each other, 18 inches apart and a little above the floor level. On the top flanges of these joists are mounted two 8 feet pulleys, the shaft of the one nearest to the grip pulley turning in journals forming part of a horseshoe shaped casting, which is arranged to be moved either way along the tops of the joists by suitable screw gearing. The front pulley is fixed on a shaft which turns in journals bolted firmly to the flanges of the joists. This latter pulley can be moved forward from time to time and bolted down as before, the operation being repeated as often as the stretching of the cable has exceeded the capability of the sliding pulley to take it up.
The boilers for supplying the engines are those known as the Babcock & Wilcox sectional type, with water tubes, and are worked up to 100 Ibs. pressure. This class of boiler is being used very much in the States on cable tramways. For feeding the boilers, a small vertical donkey pump and an exhaust injector have been provided, the latter delivering the water into the boilers at a temperature of about 180° Fahr.
The author having thus far briefly described all the places and machinery through and over which the cable has to work, he now proposes to make one round trip with it, and point out its travel. The speed of the cable is six miles per hour. Starting from the top of the grip pulley, A, Fig. 3, the cable makes one half turn, and passes to the farthest and fixed pulley on the taking-up gear; it there makes one half turn, and comes to the top, and passes over the pulley in the horseshoe casting, where it is again sent down and straight off to the bottom of the left-hand pulley, which directs it up to the large pulley set in line with the tube in the road, whence it is sent on its way down the hill supported on pulleys. On nearing the bottom of the hill the tube is not led straight into the lower pit, but is carried round between the tracks of the first turn-out. The cable leaves the tube at this point, and passes through 10-inch pipes into the lower pit, and on to the horizontal pulley, which directs it into the up-hill tube, in passing through which it is supported in the same manner as in the down-hill tube. Upon reaching the upper terminal pit, the cable passes the first pulley on to the top and over the second, around which it makes a three-quarter turn, and is sent up to the top of the first pulley, which is slightly canted to return it into the tube, close to the up-hill portion of the cable ; from it tbe cable passes down the hill until it reaches the pulleys, where it is deflected downwards and into the engine-room, where it rises gently until it again reaches the grip pulley from which it started. The long length of cable which passes, in sight, through the engine-room, enables any fracture of a wire to be quickly detected, which can be remedied at once or at night as the importance of it demands. The cable used is 8,200 ft. long, and is 3 inches in circumference. It is made up of 114 crucible steel wires of No. 16 wire gauge, and formed into six strands wrapped around a hempen core. The guaranteed tensile strain of this cable was 80 tons to the sectional square inch.
Fig. 6 (Figure 6 is not available - JT) shows the lower portion of a car on the line with the gripper fixed in its place and the gear for actuating it attached. The gripper is shown with the cable in its jaws and about to pass over a pulley. It is made of cast steel, and consists of two principal parts, one of which is in the same piece with the lower and movable jaw, and the other with the upper and fixed jaw. The wedge shown, in being forced into or withdrawn from a shoe, raises or lowers the casting holding the lower jaw. The cable is thus seized firmly or slightly or allowed to run through the jaws, as it may be required that the cars should travel full speed, slow, or stand still ; and by opening the jaws wide the cable automatically leaves the gripper. The jaws are lined with soft pieces of cast iron, which can be easily and quickly removed and replaced. Two grippers are fitted to each car, one on each end.
The grippers have hold of the cable whilst descending as well as in ascending the hill, and only release it at the termini and in passing the pulleys in front of the engine-room. At the latter place, as the cars slowly near the pulley, the drivers open their grippers wide, and the cable automatically leaves the jaws. The cars then descend by gravitation along the few feet of deviated track, the object of which is to take the grippers past and clear of the pulleys. On the cars again reaching the straight track, the cable automatically slides into the jaws of the grippers left open to receive it, and the drivers have only to screw up their grippers. when the cars are again carried on at the speed of the cable.
This being the first cable line in England, for obvious reasons it was considered advisable to try more than one form of car, and at Highgate there are now four distinct types of cars working.
1st. An ordinary short wheel-base tramcar with inside and outside seats, but not arranged to carry a gripper.
2d. A dummy or open car which has a gripper each end. This car and the first are worked coupled together, and demonstrates the ease with which the rolling stock of other lines of any system can be attached to and carried on by the cable cars.
3d. A bogie car of an ordinary design with gripping arrangements at each end.
4th. A long bogie car to carry 60 passengers fitted with gripping arrangement each end ; this has proved a very remunerative type of car.
All the cars are fitted with two classes of brakes, one of common design which acts on the tires of the wheels ; the other a slipper brake (Fig. 7) which acts vertically on the rails. The latter brake consists of an iron frame firmly secured to the bottom of the car ; inside this frame slides a shoe fitted with a long block of hard wood, which the driver, through an arrangement of powerful levers, can quickly force down on the rails, thus utilizing a part or the whole of the dead weight of the cars and passengers. This brake was severely tested by Major- General Hutchinson of the Board of Trade, who tried it on a car which was allowed to gravitate until it acquired a velocity of about 20 miles per hour on a grade of 1 in 11, when the car was brought to a standstill within 30 ft.
The Highgate tramway has now been working most successfully for the past eleven months, during which time it has carried 563,408 passengers, with but two mishaps, which the author is glad to be able to say had nothing whatever to do with the system. Time will not allow now of a full explanation of these unfortunate occurrences, but the author suggests that all interested in the matter should refer to the Board of Trade inspector's report and be guided by it alone.
Engineers will doubtless see at once that the cable system admits of a large increase of traffic, with but small proportionate increase in working expenses. They may, however, be astonished to hear that the Highgate line has carried 100 per cent. more passengers, with an addition to the consumption of coal which was practically nil. It must be interesting to know that every cable tramway constructed and worked up to the present time has paid a dividend after the first year's working. The author cannot now give details of the comparative construction and working costs of cable tramways, but he gives it from his experience that a saving of about 50 per cent, can be generally obtained in a cable tramway of three miles, the cable traveling at 6 miles per hour, and a five minutes' service of cars, allowing also interest at 6 per cent. on cost of construction and equipment as against a horse tramway with an average speed of 4£ miles per hour.
There is little doubt that the time has arrived in England when horse traction on tramways must be superseded by mechanical motors. Therefore, in comparing the relative merits of the known systems able at present to compete, it will be important to remember that there is a large mileage of tramway rails already laid in various parts of the United Kingdom which would be too light to bear the heavier traffic of locomotives depending on adhesion, thus at the out set giving the cable system, even on level roads, an advantage over steam, compressed air, and electricity, an advantage which increases very rapidly with the severity of the grades, until a point is reached when the cable system only can ascend, and even then work almost as easily as on the level. The latter statement is perhaps at first hard to believe, but its correctness will be apparent when it is remembered that the cable cars in descending hills still retain a hold of the cable, thus utilizing their weight due to gravity in hauling up the ascending cars, a power which on all other systems is thrown away by the application of brakes in descending grades.
The author will conclude by tabulating some of the advantages of cable tramways, as follows:
1. The steepest grades are as easy to work as levels, the weight of descending cars being utilized to pull up ascending cars.
2. The cars when taking up or setting down passengers are absolutely stationary, the hauling power being practically detached for the time, thus in cases of necessity to avoid collision or danger to life the cars can be brought up instantly.
3. The method of working is noiseless. The stopping and starting of cars is performed so gradually as to be almost imperceptible.
4. Fewer cars are required on the road to do the same work, because the more uniform speed gives a greater mileage per car, and consequently a larger carrying capacity.
5. Sudden increase of traffic can be accommodated to a practically unlimited extent by merely bringing more cars on to the line, the motive power being already provided, and in action.
6. Considerable reduction in wear and tear of the surface of the road as compared with horse haulage, and of the rails as compared with lines on which engines are working; the latter often requiring about 100 per cent. more deadweight to secure adhesion.
7. The traffic is not affected by snow or frost, as evidenced by the following extract from a letter by the Superintendent of the Chicago City Tramway Company : "Though we had at one time frost (snow) two and a-half feet deep, we did not discover any bad effects in our construction or operation."
8. It is the only mechanical motor which does not introduce more weight into the cars than is required for horse tramways, thus saving a renewal of rails when laid lightly for horse traction.
9. It is the only system which prevents cars running away in descending a hill, when all brakes have failed.
10. Its very low cost of working, as compared with other systems, ensures its financial success.
11. It is the only system which is not seriously affected by the proverbial dirty tram rail.
12. Perfect cleanliness of carriage way, a very important sanitary advantage.
13. The extinction, wherever cable traction is introduced, of the barbarous horse system -- a cruelty unworthy of humanity and civilization.
The President, in inviting a discussion, remarked that the subject might almost be said to be a new one to the engineers of this country. Those who gave increased facilities for locomotion were deserving of the thanks, not only of the Society of Engineers, but of the world at large. The author had given thirteen reasons why the cable system was to be preferred to all others; and certainly the arguments which he had brought forward went far to support the reasons which he had given.
M. Manlee asked what arrangement was made for enabling two cable tramways to cross each other at right angles.
Mr. A. T. Walmisley said that the construction of cable tramways, where other systems were unsuitable, was one of the questions with which the engineer of the present day had to deal; but although the cost of working was less than that of other systems, the first cost was so much greater that an engineer would hesitate in many cases before recommending the cable system. For steep inclines, however, such as Highgate Hill, the system was very suitable. But in spite of the author's powerful arguments he was not prepared to endorse the opinion that for very crowded thoroughfares, or upon a level road, the cable system would be economically applicable. An Act of Parliament was obtained last year for applying the cable system in a tunnel to be constructed under the crowded thoroughfare of the Borough and under the Thames, for conveying passengers to and from the City. They would all look forward with very great interest to the execution of that scheme.
He was sure that they were indebted to the author for bringing before them such an interesting account of the Highgate Cable Tramway to which he was engineer. They must all agree that the Highgate system was very complete in its design, and that no point of importance had been overlooked in the consideration of the details.
Mr. Claud Scott thought that Mr. Colam had made a slight error in stating that 100 per cent. more passengers could be carried with the same consumption of coal. He (Mr. Scott) had had much to do with the Highgate line, and a very strict record had been kept of the coal consumption from the beginning. In the winter, when passengers were scarce, they carried somewhat under a thousand a day, and the coal consumed was about 35 cwt. On Easter Monday about 7000 passengers were carried, and exactly the same amount of coal was burnt. He put this down to the fact that rather more people were carried down the hill than were carried up. The assistance which was afforded by their weight helped to carry the passengers up the hill without an additional consumption of coal. During a heavy fall of snow which occurred one Sunday about six weeks previously, the cars travelled up and down the hill without the slightest trouble, whilst the horse-cars and busses running to the foot of the hill were not at work for 2 1/2 hours, while the road was being cleared of snow.
Mr. C. A. Knight said that where the system had been established it had been most successful. The chief doubt which was urged against it was that snow would interfere with the working, but experience in Chicago had proved that objection to be quite groundless. The snowfall at that place was very considerable, but it had never caused any difficulty in the working of the line. The economy of the cable system had been thoroughly established by the fact that the cable roads were paying a good dividend. The failure of the line at Philadelphia, which ran for a short time, was due to improper construction. He was well acquainted with the system in operation in Chicago, where there was one cable of about 21,000 feet in length. He fully believed that the cable tramway system would be a success in England, as it had been elsewhere, and would be generally adopted. Mr. Colam, in enumerating the advantages of the system, had omitted an important one -- the absence of the smoke and gases which emanated from the ordinary mechanical means of locomotion. This characteristic was particularly valuable in connection with the application of cable tramways on underground lines, as no special or artificial means of ventilation would be required where that system was used. In reply to an inquiry made by the President, the speaker added that he believed that the longest cable in use was 24,000 feet, the length of the line itself would be about half of that.
Mr. W. S. Lockhart said that he had taken some interest in the Highgate tramway, for it passed his door. He should like to know from the author of the very interesting paper hew the ropes were spliced. He noticed that the paper stated that the ropes passed automatically out of the grippers, and automatically into them again ; but at Highgate he had observed that at the end of the line, after a station was passed, the conductors went forward with hooks, and a sort of fishing for the rope went on. He wished to know whether that was a normal circumstance, or was merely due to some slight but remediable error in construction. The author spoke of the sheave at the bottom of the hill as a sheave. He supposed that as a matter of fact it was simply a U-shaped sheave, having no gripping action on the rope. He did not notice much in the paper about the cost. Perhaps the auther would give a few details on that subject. He (Mr. Lockhart) believed that in the construction of the Highgate tramway there were some abnormal circumstances increasing the cost, and that the grade of the road had to be considerably altered in parts. The author, indeed, had alluded to the requirements of the district surveyors. But putting aside such special expenses, what would the line cost under ordinary circumstances?
As a mechanical system, the Highgate tramway was a marked success, but he could not altogether endorse what the author said with regard to the wish of the inhabitants for its extension. The route of the Highgate line, also, was much more noisy than it was formerly, because the roads had to be pitched in consequence of the construction of the line, whereas formerly they were macadamised. The cars themselves in passing and repassing were very noisy. If that objection could be obviated it would be a marked improvement. He considered that the system would be still more convenient for underground haulage than for ordinary tramwork. He could not but think that in many parts of London the system would be very dangerous, and that it was more suitable for thinly populated neighbourhoods than for streets where there was much traffic. He understood that it had been proposed to extend the line from Highgate to Finchley, but he could not understand hew a dividend could be earned upon such an extension, as there would be very few people to travel. He believed that the bill for the Finchley extension was lost.
Mr. W. Booth Scott, alluding to the noise which had been spoken of by the last speaker, said that at the points on the Highgate tramway where the line changed from single to double and vice versa, there certainly was a considerable noise occasioned by the passage of the gripping apparatus. The Highgate line combined, in its very short length, all the difficulties which would be met with in lines of any length. It commenced at the bottom of a steep hill with a double line, and before the top of the hill was reached the road narrowed, and the line had to become single. Again it changed to double, and then once more to single. Horizontally the line was far from straight, and vertically there were several changes of gradient. He had seen the cable tramway in operation in Chicago, and he knew no reason why it should not be applied to many of the streets of the metropolis.
Mr. Schonheyder said that it was interesting to see in the diagrams exhibited by the author the various ideas which engineers had had in dealing with the problem of cable tramways. He criticised some of the San Francisco tube-frames as being loose and flexible in construction, and considered that the slot would be liable to be closed up in consequence of the pressure on the sides. The Chicago system seemed to be, on the other hand, a stiff and substantial arrangement, although, perhaps, rather expensive. He wondered that such a section of rail as was shown in that system was tolerated in a street with much traffic. It was likely to wrench off the wheels of a lightly constructed carriage. In the section adopted for the Highgate tramway it was quite impossible for the slot to become closed by any amount of pressure. He did not see how the wrought-iron rails at the slot were fastened. In describing the pulleys for guiding the rope, the author said that they were mounted on pins, these pins being stationary. He did not know whether the work upon them was heavy, but they were intended to last a long time, and he considered that in such a construction the working would in time become very unsatisfactory, the pins, of course, wearing smaller and the pulleys larger. As to the grip pulley shown by the author, he (Mr. Schonheyder) should have fought shy of such an apparatus. It might bend the rope sharply by holding it too tightly, and then it would be very difficult to get the rope straight again. The pulley appeared to be too small for its work. It would be better to have larger pulleys with some kind of grip arrangement, like the well-known Fowler grip pulley, where the jaws opened of themselves directly the pressure was taken off. In describing the engines the author had said, no doubt rightly, that it was necessary to have a very good automatic expansion gear, and he had not the least doubt that the gear adopted fulfilled its purpose very well, and he admired the ingenuity of the designer, but he should be very sorry to adopt such a thing. It would, he thought, be impossible to construct a greater conglomeration of excentrics and levers and rods to effect automatic expansion. The same thing could be done at about one-tenth of the cost, and it would work satisfactorily. He should have thought, also, that it would be much more economical to adopt condensing engines. It was well known that condensing engines could be worked with as little water as the high-pressure noncondensing engines, or, in fact, with less. He believed that the slipper brake was tried some years ago on railways, and was condemned on account of its being dangerous. Of course it might answer at lower speeds, though not at high ones. It was a very old invention.
Mr. K. W. P. Birch said that it would be interesting if the author would tell the meeting how fast he had known the cars to travel on the cable principle. As he understood, the speeds mentioned by him had not been more than four to six miles an hour. It had, however, been said that the system would be suitable for working the underground railways; but on those lines the trains travelled from twenty to thirty miles an hour between stations. He (Mr. Birch) would like to know upon what experience the opinion that the cable method would answer for this work was based.
Mr. Kincaid congratulated the author and the Society upon the very interesting paper they had heard. He said that even if the system of cable traction was the most admirable that could be adopted, there were legal difficulties in the way of adopting any system of mechanical traction in this country without a sanction which it was very difficult to obtain. Cable traction was most valuable where the traffic was very large, and that was just the condition under which the Legislature was very jealous of allowing mechanical traction to be used at all. The existing prejudices were chiefly due to the perfections and annoyances which had shown themselves in the various forms of locomotive hitherto used. Cable traction was free from those objections. In this system of traction it was very necessary to have powerful brakes. Slipper brakes had been used on the Highgate tramway, and the Board of Trade, seeing that they were successful there, had brought them before several other tramway companies. His own opinion was rather in favour of the ordinary system of applying brakes to the wheels. The slipper brake, as applied at Highgate, was fixed under the centre of the carriage, and, in his own opinion, was neither so safe nor so reliable as the ordinary brakes which were applied to the periphery of the wheels.
It was curious to note how many different systems of laying the lines had been adopted in connection with cable tramways. Although the cable system could be used under any circumstances, yet great variations of details had to be made in almost every case. Although, as Mr. Scott had said, almost every form of difficulty appeared at Highgate, yet a great deal of ingenuity would still have to be shown in applying the cable system to other roads, in consequence of the existence of sewers and pipes and mains of various kinds. He hoped that the last reason which Mr. Colam stated in favour of cable tramways would be one which would induce the authorities to allow the system to be extended, and that was the great cruelty inflicted upon horses by employing them to draw tramcars up gradients for which they were quite unsuitable.
Mr. P. W. Morison said that he had been practically connected with the cable system of tramroads. There was no insurmountable engineering difficulty in designing them, although, as the last speaker had stated, some ingenuity was called for in particular cases. The cable system had a very great advantage over other mechanical traction systems in being able to work in such foul rails as tramways generally had. The foulness of the rails produced a friction exceeding, he believed, 15 Ib. per ton of load. Locomotive engines on tramways also laboured under the disadvantage of having their comparatively delicate machinery exposed to dust and dirt, which made it necessary to keep spare engines in the yard to provide for repairs. Another advantage possessed by cable tramways was that the cars could be taken up steep inclines without any necessity for extra weight to secure adhesion, as in the case of a locomotive engine, and therefore light rails could be employed on cable lines. He believed that in the locomotive tramway in Sydney the weight of the rails had reached 92 Ib. per yard, found necessary to carry the locomotives required for the work under their unfavourable conditions.
Mr. Arthur Rigg said that he spent about two hours last autumn in examining the tramways in Chicago. He observed that the grippers used there were about a yard long and were covered with wood, and the cables were extremely well greased. He should have thought that iron grippers, as described by the author, would be more likely to wear the cable than the wooden grippers used at Chicago. The machinery there seemed to work very successfully, and the cars were easily stopped when running at an unusually fast speed for road tramways, a speed which seemed to be more than six miles an hour, or at all events it was much faster than he had ever ridden in any London traincar. There were double pairs of horizontal engines for driving the cables, and the necessary grip was obtained by leading the cables a succession of times round two driving pulleys, and then, far away behind, there was a loaded pulley which kept up the needful strain. He should regard that as better than a single pulley where there would be a great tension upon the cable. All strains would be greater at Highgate than at Chicago, because, at the latter place, the line was absolutely a dead level. The cable used at Highgate was 1 inch in diameter. It looked a little light compared with the one which he saw at Chicago.
Mr. C. E. Audain said that he was sorry the author had not given information with regard to that great point which engineers had always to consider before they adopted any scheme, namely, £ s. d. Mr. Walmisley had remarked that the prime cost in the cable system was greatly in excess of ordinary systems. There could be no doubt that, in a case like that of the Highgate incline, the cable system was the best one which could be used, but in London there were very few gradients like those at Highgate; and if there was any considerable difference of first cost between the cable and the horse systems, he thought the horse system would have the preference in ordinary cases. With regard to the effect of snow, he had himself seen the Highgate tramway working satisfactorily on the occasion referred to by a former speaker.
But they did not have snow often enough in London to necessitate a special system of traction to meet its difficulties.
The President, referring to the effect produced by cable tramcars on horses drawing other vehicles, said that his experience was that unless a horse was well trained he did not like to see a vehicle moving along without any visible means of propulsion. He believed this would be a practical difficulty in crowded thoroughfares.
Mr. Booth Scott, alluding to the same point, said that at first the horses were startled by the tramcars at Highgate and pricked up their ears, but now not one horse in fifty took the slightest notice of them. He resided near Highgate, and had frequently observed them ; it would almost seem that they had means of communicating with one another.
Mr. Colam, in reply, dealing first with the question put by M. Manier as to how cable tramways could cross one another at right angles, said that the crossing might be effected in a variety of ways. The Geary Street line, to which he had alluded, crossed one of the other lines. (The speaker then sketched on the blackboard the arrangement adopted in this case.) The method here employed had been working with great success for the last six years. He owned that, as Mr. Scott had said, he had not stated quite exactly the figures in reference to coal consumption, for he was afraid the actual figures would hardly have been credited. On the 6th of last month there were 7048 passengers carried on the Highgate tramway, and on the 2nd of April there were 4090, and yet the consumption of coal was about 36 cwt. in each case, and what little difference there was in the rate of consumption was due, he believed, to the fact that different men were firing on these two occasions. A question had been asked as to the length of the longest cable line. The longest line was 44,200 feet, of a double track, and tho cables used in working it were 90,610 feet long. As to the splicing of the cables, the question was a rather difficult one to answer, because the process of splicing was a very complicated one; but he could say that the part spliced was, if anything, stronger than the other portion of the rope. A splice extended over a length of about 40 feet.
It had been suggested that on the Highgate line, when the cars reached the termini, the conductors had to fish with hooks for the cable, but that was not the case; indeed it would be dangerous to attempt to lift the cable direct in such a manner, for either the hook would be suddenly jerked out of the man's hand, or he would be himself pulled to the ground. On some cars, however, it is necessary for the conductor, when starting the car on a particular spot, to pull up with a hook the strap of a pulley, hinged at the other end, by which the cable was raised into the open jaw of the gripper.
The place referred to in the paper, as that at which the cable automatically leaves and returns to the gripper, is the spot where the cars gravitate in front of the engine-house. As to the section of the pulley at the bottom of the hill, it was really the V shape.
Two gentlemen had inquired as to the cost of constructing cable lines. In the case of the Highgate line, the promoters had to make two sewers. going from the top to the bottom of the hill through two different parishes. Apart from all the superfluous work of this sort, the cost of the Highgate line, equipped with machinery and everything ready for working, was 18,OOO£ for a mile and a half of single track. Under other circumstances tramways could be constructed more cheaply than that, namely, at the rate of 10,OOO£ a mile. With regard to the noise which had been alluded to, he believed that what little there was attracted notice only because there were no horses' feet to drown the sounds of the cars. If they could hear the ordinary horse-cars running along the line and crossing from one line to another without the sound of the horses' feet, quite as much noise would be observed as in the case of the cable line.
Mr. Schonheyder had alluded to the construction of the Chicago road. He (Mr. Colam) considered that that construction was intended to get rid of a great deal of money, and the line was certainly neither the most economical nor the strongest which could be made. A very heavy traffic upon a line of that construction would most decidedly tend to close the slot. The rail shown was a very common section in America, but he did not like it. The construction of the pulleys, upon which Mr. Schonheyder had commented, was found practically to work well at Highgate. As to the arrangement of grip-pulley jaws, he knew (as he had stated in the paper) that its action was rather severe on the cable, but others had been tried with nothing like such good results as were obtained at Highgate. It was well known that a grip pulley which would release a cable very well under some circumstances, would occasionally fail to do so when working cable tramways, because the outgoing strains were not uniform. In many cases where cables have not been freely released, permanent kinks have been the result, thus seriously lessening the life of the cable. As a practical illustration of the effect these pulleys had on the cable, he was glad to say he had with him a specimen of cable which had hauled 300,000 tons of coal 35,000 miles and which was still in fair condition. He agreed with Mr. Schonheyder that the model of the valve gear looked very complicated, and as an English engineer he was very much opposed to complicated valve gear ; but he had found at Highgate that there was very little wear indeed upon the different parts, and the cut-off had been most efficient. As to the mending of the cable, it could be very readily and quickly done; but he was glad to say it had not often been required hitherto on the Highgate line.
Mr. Birch had asked what was the greatest speed at which the cable travelled. The greatest speed of which he (Mr. Colam) had ever heard was 12 miles an hour; but they were going every day in Chicago at 10 1/2 miles an hour. In that city the speed was suited to the street through which the car was passing, being reduced where the traffic was more dense. The driver could go as slowly as he liked.
As to the slipper brake which Mr. Kincaid had criticised, he (Mr. Colam) was certainly very proud of it, for it had proved quite successful at Highgate, where the line could not be safely worked, trusting to a wheel-brake alone. Experience had shown that it was, as Mr. Kincaid said, wrong to place the slipper brake in the centre of the car. At Bradford he had seen it applied to one of Kitson's locomotive engines, and it was placed between the bogie wheels where it was undoubtedly more effectual. Mr. Higg had remarked that the grippers used at Chicago were different from those described in the paper. In the latter the motion was sent through a series of screw levers and wedge, and was very gently applied. The Chicago grippers were worked by a long lever which, in the hands of a new driver, gave a little trouble because the power was applied too rapidly, and the cars were jerked ahead. This could not happen where there was a screw and wedge. He found that there was nothing better than soft cast iron for the lining of the jaws of the gripper. Wood had been abandoned in Chicago because when wetted by the rain it was rapidly cut away.
As to the effect of the cable cars upon the horses running on the roads, his experience was much the same as that of Mr. Scott. The horses all round the district had become familiar with the cars, and they were now tolerably good friends. He could not say the same with regard to the tramways worked by steam at Leeds and Bradford. So long as the engines behaved themselves, the horses treated them pretty much as they treated the cable cars at Highgate ; but every now and then the engine gave a sniff or a snort, to which noises and the steam the horses decidedly objected. He thought that the cable tramways certainly had again the advantage in this respect. With regard to the cost of the construction and equipping of cable tramways generally, it was found that with a minimum length of three miles the outlay was about the same for cables as for horses; but in the case of cable lines of greater length, the comparison of cost was even more favourable.
The President, in closing the discussion, said that the cable tramways recalled the days of his youth when the Blackwall Railway, which was about the first railway in London, was worked by means of ropes. That system was very well so long as the ropes held, but occasionally there was a breakage, and consequent delay while the ropes were being mended. He did not suppose that anything of that sort was to be feared in the cable tramways. He had some little doubt as to the general applicability of the cable system, but it appeared suitable for steep gradients and short distances. They were very much indebted to the author for bringing the subject before the meeting.
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