By G. H. Nickerson, C. E., Merced, Cal.

The sugar pine timber belt In the Sierra Nevada Mountains of Central California 13 located at an altitude of 5000 to 7500 feet above the sea level. The principal rivers are only 2000 to 3000 feet elevation, flowing through deep and very precipitous canons. Above the cliffs, or rims of these canons, the slopes flatten and, where there Is sufficient soil, sugar and California white pine grow to perfection. In these timbered areas there are steep rocky blurts of granite, high ridges with deep ravines. There Is practically no flat land. The lumber is of large diameter - five and six-foot trees being plentiful, while some seven and eight - foot trees are scattered about. There is one 10 - foot tree which is believed to be the record sugar pine. Owing to the large amount of young timber, I think the trees will average three and a half to four feet at the stump.

During 1910 an option was taken on some 7000 acres of this timber, situated on the slopes of a high ridge between Merced River and the South Fork, along the western boundary line of the Yosemite National Park, located from 5000 to 8000 feet above sea level.

The Yosemite Valley Railroad starts at Merced, Cal., where it connects with the Southern Pacific and the Santa Fe Railroads. It strikes easterly across the San Joaquin Valley 24 miles to Merced Falls, at the mouth of the Merced canyon at an elevation of 350 feet above the sea. It follows the river 54 miles to El Portal, elevation 1925 feet. The hills on each side are low and rolling at Merced Falls, but, as you go up the river, the hills begin to get higher and more precipitous until you reach the Yosemite Valley, the "Wonderland of the World." At El Portal, the terminus of the railroad, and the "Portal" or gateway to the Yosemite Valley - the hills have become steep mountains rising 3000 feet to 5000 feet above the railway.

Owing to the great number of waterfalls and rapids In the narrow crooked canyon of the Merced and the Summer heat in this latitude, the humidity of the canyon was not considered favorable for a drying yard for lumber. The narrowness or the canyon at the same time, did not give sufficient room for operation on the scale contemplated, This will be better understood when It is known that, in the 30 miles of the upper end of the Yosemite Valley Railroad, there was only one place where a "Y" could be constructed so as to turn an engine. These conditions necessitated the location of the mill in the San Joaquin Valley, or up in the mountains. There is no site in the timber, except on a steep ridge where water is scarce and it would cost $30,000 to $35,000 for a six-mile wagon road to connect with the stage road in the Yosemite National Park, or by building a direct road ten miles long out of the Merced canyon, which would cost between $80,000 and $100,000. It would be difficult and very expensive to get the machinery over this road. The problem of getting the lumber out from a mill in the woods, was considered nearly as difficult as to bring out the logs, and would necessitate locating the planing mill, box factory and general plant in the valley and re-handle all the lumber going to these mills.

A site for the mill was selected at Merced Falls, where there existed a railroad station, a few old buildings, level bed rock close to the surface, and a pond of some thirty to fifty acres of back water above a concrete power dam.

Late in 1910, F. M. Fenwick, who had become interested in the options on this timber, asked the writer two questions as follows:

  • First: How would you get this timber down to the railroad?
  • Second: How much would it cost per thousand feet to operate?

The first was immediately answered: the second question necessitated a survey to see what would be the construction expense, and the cost of operation including the upkeep. The answer to the first question contemplated an incline up the mountain, so as to gain as much height in as short a distance as practical; then locate a logging railroad on a practical grade through the lumber so that standard gauge flat cars could be loaded in the woods, then hauled in trains, one at a time while an empty is hosted up the incline. The cars were to be assembled at the foot of the incline and sent in trains over the Y. V. R. R. 54 miles to the mill at Merced Falls.

The survey developed the full magnitude of the undertaking. The incline was 8000 feet long measured on the slope of the track and 3100 feet in height, starting at an altitude of 1900 feet and ending at 5000 feet above the sea level.

From the top of the incline all the timber can be reached from a main line, using 4 per cent grade and not to exceed 40 degree curves.

The incline is located from the highest point of the ridge. direct into the middle of the railroad yard at El Portal. It is located on a straight line, that is, without horizontal curves, and has gravity switching tracks both at the top and at the bottom. The Merced river is crossed with a trestle using inclined bents to form a span of 76 feet over the main channel. There are two other trestles over ravines, and a half trestle where one side is out over a cliff. The lower half of the incline is single track, the upper half is double track laid on 6 - foot, 8 1/2 inches center to center. The ties are 6 - inch by 8-inch by 14-foot redwood. In the middle is a passing track where the two tracks are 12-foot centers.

The grades fit the ground as near as possible and utilize the balancing effect of the empty car. The grades run all the way from 10 per cent to 78 per cent, which is the maximum; the average grade being practically 45 per cent. The 10 per cent grade is opposite a saddle in the ridge and comes at the foot of about 700 feet of 78 per cent grade, so that the cable would go about 250 feet in the air. This is on the double track. To hold the cable down, two frames were erected; one on each side anchored with rock and concrete. Across the top was placed sufficient timber to stand the stress as calculated and a system of 10 sheaves was installed for each cable, set in the arc of a circle, so that each sheave would take about 1500 pounds of load. These sheaves are about 16 feet above the track and the cars pass under them like going into the portal of a tunnel. At one other point below the switch it was necessary to build one of these holding down structures.

A double incline, using only one track on the lower end, requires something to take the side thrusts of the cable at both ends of the passing track. To do this two humps were graded in the road bed, one at each end of the passing track, so that the cable is laid down in the sheaves in the center of the track by the down going car before it takes the turn out of the switch.

Owing to the location of two small cross ridges, these humps would seem to be accidental or made to save grading. Many persons, including some visiting engineers, and even officials of the company, have asked why these slight humps were not graded off.

The cables are carried in the center of the track on cast steel sheaves placed on the humps in the grade so as to give a load of about 1200 pounds to each sheave. They span over the sags in long catenary curves. Eight of these humps or vertical curves and the two holding down structures divide the cable into eleven principal catenary curves. The cable is well lubricated daily to prevent rapid wear, or abrasion, and is carried on steel rollers in the straight way grades, or wooden rollers in the sags, so it will not drag in the ballast and pick up grit. This cable is built especially for this incline to specifications furnished by the writer. The outside wires of each strand have a uniform strength in tension within certain limits, and the several inside wires having a uniform strength in tension but within considerable higher limits, so that the cable as a whole, under ultimate stress, would develop the full strength of the inner wires when passing around the drum, without breaking the outer wires due to the additional bending stress. The construction is Warrington, 6 x 19 plow steel, regular lay. This year I have had a wire rope made to new specifications, the tension being raised in the outside wires and a wire core of 6 x 19 plow steel provided. We are now using this rope, but will not be able to judge of its merits until next year. All rope makers in their catalogues recommend lang lay rope for inclines. While this may be best where the endless system is used, or where it is not necessary to unhook from the cars, in the lumber business where the incline is a lowering proposition and the cars are hooked on and off at each end of the cable the regular lay has proven to be the cheapest and most suitable and safe, and where it is to be used afterwards in the woods, it is the only lay to use. Our cable is 1 1/2 inches in diameter and is worn to about 1 3/8 inches when sent to the woods.

The engine for the top of the incline was built especially to suit the conditions of this incline. The main features were specified by the writer as follows: Ample braking power at 12 pounds pressure per square inch, cooled indirectly by water on the inside of the brake drum. Brakes to be in duplicate, one to control the speed and one for emergency. Both to be set with springs and releases by steam pressure, so that the cars could not start without steam, any failure of steam would automatically set the brakes. The brake blocks and the brake drum to be oiled with valve oil to give smooth action in arresting the motion of the cars and to make it entirely noiseless when in use. The main axle to be in shear stress only, and relieved of any torsion due to the gears or brakes and the cable. This was accomplished by casting the brake drum and the cable drum In one piece and bolting the gear wheel to the rim of the cable drum so as to cause the power from the gear wheel to be transmitted from the rim directly to the rim of the cable drum.

Both of the brakes would act directly on the extension of the cable drum without torsion in the axle. The cable drum has manganese cast steel segments bolted to it so that it makes a large eight-foot diameter gypsy. The cable makes three and one half turns around this gypsy. The engine is geared twelve to one, and has 14 x 14 inch cylinders, so that with a car speed of 500 feet per minute, the piston speed was 600 feet per minute. The details and general arrangements were designed and the engine constructed by the Willamette Iron & Steel Works of Portland, Oregon.

The cars are a steel underframe type, standard gauge and especially designed to meet my specifications and the unusual conditions due to the three separate systems of transportation. They have special center plates and long side bearings, with the brakes hung to the trucks, so that the cars can go around curves of 100 foot radius, the centers and side bearings also allow a large rolling motion of the trucks so as to go over the vertical curves on the incline. The center backbone of the car had to take care of 12 tons extra stress downward over the trucks, due to the down pull of the cable on the vertical curves of the incline; this when the car goes down across a flat grade then changes to a very steep grade. This was provided for by allowing the angles of this center construction to run through over the trucks close to the draft gear and by increasing the thickness of the top cover plate. A 40,000 - pound load on this incline produces more severe stress in the car than a 60,000-pound load on an ordinary railroad. It requires 70,000-pound capacity car springs in these trucks.

A bulkhead is built at one end, five feet above the line of the bunks, and riveted to the steel construction of the car body. This is utilized to prevent any logs sliding off on the 78 per cent grade. The cable is attached to a cast steel draw bar, riveted to the car above the draft gear. An eye splice in the cable with a close fit, puts the pin in double shear, this being a very dangerous point in incline operation. The cars operate the switch automatically by trailing through. A spring in the body of the stand holds the switch where thrown and until operated by the next down car.

The capacity necessary to supply the mill with 125,000 feet of logs was estimated at 25 cars carrying 5,000 feet each, or practically one train a day on the Yosemite Valley Railroad. The incline was designed for a speed of 500 feet per minute, traveling 8,000 feet - the length of the incline - in 16 minutes and allowing four minutes for hooking on new cars. This would deliver a car every 20 minutes or 30 cars in ten hours.

The next point of interest to logging engineers is to know what success has been attained in operation. In order to show what this has been I will state that usually the cable is put on and one car lowered or pulled up to observe the action of the cable, then the rollers or sheaves are installed, switch put in, and track adjusted, taking from two days to a week, according to the force at hand. In this case the rollers were located and placed in accordance with their calculated position; the switch installed as the track was laid; and automatic stand connected up. The first car was lowered July 27, 1912, and 17 were lowered that day, which was all that it was possible to get loaded in the woods. Every day afterwards, all the cars loaded have been lowered on the same day, without changing a sheave or a roller. The cable bears equally on all the sheaves. In the holding down structures, the cables come up gradually against the middle sheave. Then as the tension increases it comes against sheaves on each side until, at maximum stress, the cable is working equally against all the sheaves. As soon as the company saw that the incline was a success and would supply the mill, it wanted to double the crew at the mill and get out more lumber. This necessitated faster work on the incline. It was then found that, by increasing the speed, a dangerous whip to the cable developed, so that the speed could not be much increased over the speed first intended. The cable being suspended from point to point in catenary curves of varying lengths, with a certain sag due to a given tension in the cable, when the cars would enter on a flatter gradečand the changes in grades are too numerous to mentiončthe cable would sag. Then as the car entered on a steep grade the cable would whip up. Twice the speed would make four times the whip. Observations were taken to see how much allowance should be made to make up for the possibly careless handling of the engine. I know the tendency is for all men to get more or less careless after they have run awhile. I soon found that considerable margin was necessary to insure safety at all times, and safety is essential, since it is impossible to keep men from riding on the cars.

It was deemed unsafe to run at night, as rocks on a new grade were liable to loosen and fall on the track at any time.

Plans were made to make changes after the operations for the season were over. During the winter of 1912-13 another gear was installed on the engine to give two speeds; the first speed of 500 feet per minute was retained for pulling up fuel oil; the second speed of 960 feet for a piston speed of 600 feet being used for lowering logs. As the piston speed can safely exceed 600 feet by 25 or 30 per cent, we could safely get from 1,000 to 1,250 feet a minute, while doubling the speed would increase the cable whipping four times. This action of the cables was studied; the stresses being all recalculated so as to make this increase of speed with safety. The vertical curves were changed to a longer radius so as to give more time for this change, at the increased speed, to take place in passing from one grade to the other. It was necessary to deliver a car every 12 minutes to supply the mill. To make up for delays it was calculated to deliver a car every ten minutes.

When we started this season we found that we could lower a car safely in seven minutes and do the switching and hooking on in one minute. The operation was smooth and without any noticeable whip. We can stop the car by electric signal to the engineer and have done so repeatedly when the cars are on the steepest grades. The capacity now is ample, for it was simply a question of getting the cars loaded in the woods, as they can not load only an average of 50 cars a day or less. We are now lowering a car in from nine to 10 minutes and taking about two minutes to hook so that the incline will not have to wait on the trains. The trains simply set the carloads of logs on a siding at the top and pick up a train of empties on a second track, while the incline does the rest.

The distance we are now operating is four and one-half miles by logging train; one and one-half miles by incline and 54 miles by shipment over the Yosemite Valley Railroad, making 60 miles on three systems of transportation, without moving, adjusting or touching the original load. The operation cost per thousand feet is safely within my estimate.

In a large, long and heavy incline the problem of properly handling the cable and controlling its action so as to protect it, is a most difficult problem. In order to study what the probable action would be, I calculated the stress in the cable at the engine and at the cars, for each separate grade, on the whole incline, together with the stresses due to the loaded car, the empty car, the length of cable on each grade above the cars, the friction of the engine, rolling friction of the car and the friction of each cable from the engine to the car at each position. These stresses were tabulated and plotted on a diagram for different loads for study and comparison in adjusting grades. All stresses due to proposed changes of grades were plotted on this diagram for comparison, with a view to securing a certain effect, rather than saving a few yards of material in grading the roadbed.

I want to mention the friction on the incline, because this factor has not been definitely determined so that any rule can be given by cable makers or hoisting machinery companies' engineers. They all use some percentage of the maximum stress on the cable for friction's without regard for the angle of its inclination. This may be true for that part due to weight on the journals of the main drum, but in incline cables the greater part of the friction may be due to friction on rollers and sheaves, which carry only the weight of the cable and no part of its tension. A cable running vertically would have very little friction, while on running on a level would have the maximum friction, both with the same tension. By observation and calculation, I have determined the friction so close as to find the cars running without steam, or changing to steam at points calculated. The following will show the carelessness of an engineer of a large machinery house, which is interested only in sales: The friction of the cables was added in both sides of the incline; one having a tendency to help hold back the empty. This was correct, but the friction on the other side was added to the load to help shove the cable down the hill. Another machinery concern reported that, as the cable was so long and heavy, it would take steam all the time to run this incline and that brakes were not needed; that their design had brakes shown because I had specified them and for safety in case of accidents. This company must have used a very high percentage of friction. In work of this kind a competent engineer should be engaged by the lumber company to solve these questions, rather than having the owners accept the results of men only interested in the sale of their machinery.

The engine at the top of the incline works steam at three separate points on each car lowered; the balance of the time using brake power. At the time it is using steam, it uses about 250 horsepower for one minute or less at a time, then the brakes consume from 0 up to 500 horsepower during the balance of the trip. Both brakes could handle one thousand horsepower and turn it into heat. As a result we have had no serious accidents. The successful handling or the lowering of logs to the railroad is reflected in the first question asked, namely, "How would you get that timber down to the railroad?" The scheme from start to finish, is my answer to the question.

Several photographs accompanied this article with the following captions.

  • Top View - General Plan.
  • Bottom View - Figures designate relative distances from the bottom of the incline.
The above article was published in the October 1913 issue of THE TIMBERMAN.

G. H. Nickerson was chief engineer for the Yosemite Valley Railroad Company before he was employed by the Yosemite Lumber Company. He returned to work for the YVRR later.