tan z respectively, which, added together, equal U in Fig. 5. U has its lateral component which is U1 U cos u. The reaction of the leading truck radius bar pin causes the wheels to follow the curve radially. In order to do this the reaction of the pin must be sufficient to cause the slipping of one of the wheels, at least when the coning is not precisely right, as is generally the case, all because the outer and inner rails of the curve are not the same length. Because the outer wheel carries the lesser weight, it is the one to slip and the force required to slip it is fO. If d is the distance from center to center of the rails, as in Fig. 6, and a the distance from the pivot pin to the center of the truck as in Fig. 5, then by taking moments about the inside wheel, the reaction fod

The reaction of the trailing truck radius bar pin is due to the same cause as the reaction of the leading truck radius bar pin and may be found in a similar manner. Thus let d again be the distance from the center of rail head and a' the distance from the pivot pin to the center of the truck. Then by taking moments as in the case of the leading truck, the dfO value of the side thrust is R = and its lateral coma'

ponent is R1 = R cos r. The reaction of the leading driver will be considered as the unknown and when once determined, it will enable us to tell whether or not that wheel will stay on the rail. Thus by using the moment arms given in Fig. 5, in a manner similar to that used for the resistances, the combined moments of the rotating reactions are zU1 + yS+xR1 + pV1, in which S is unknown.

The Vertical Reaction

This horizontal thrust S has a vertical reaction S, which is opposed by the weight on the driving wheel. If the

to hold it down against this friction. This can be better understood by recalling that the wheel bears against the rail at an angle, causing it to nose into the rail and tending to make it roll up the inclined plane and go over the rail. This friction, due to the binding action, high bearing pressure and small area of contact, is very high, and its cofficient, f', S

may safely be put at .35. The normal force s sin i and the friction is then f's. This friction then has the vertical component S1 f's sin i. Therefore the vertical reaction which must be overcome by the weight on the wheel while rotating is S1 + $1.

The Factor of Wheel Bearing

The ratio of the weight on the wheel to the vertical thrust which tends to lift the wheel may be called the factor of wheel bearing. When this factor is equal to or greater than 1.00, the wheel will stay on the rail and when it is less than 1.00, the wheel will climb the rail. As soon as the flange gets on top of the rail, the factor of wheel bearing increases, but it is too late and the longitudinal rolling carries the wheel over. Sometimes after the leading driver has left the rail, the factor of wheel bearing of the second driver becomes sufficiently low to cause it also to climb over the rail, but such cases, while reported occasionally, are not nearly as common as derailments of the leading driver only. One would naturally suppose that when the first driver left the rail, the additional weight thrown upon the second driver would give it the necessary factor of wheel bearing to keep it on the track, which it does in most cases.

[This discussion will be continued in the January issue, in which a practical application of the factor of wheel bearing will be given.-EDITOR.]

ment will result. The relation of the wheel and rail is shown in Fig. 8, in which the rail is curve-worn, as that is usually the condition in which the rail is found when a derailment takes place. The relation is similar to that of an inclined plane, the thrust S producing the normal reaction s and the vertical reaction S1. If the angle of incline is i, then S1

S cot i. When the wheel is at rest, then the reaction S1 is the only one which the weight of the wheel must overcome. But when the wheel is rotating, there is an additional vertical reaction to be overcome, which arises out of the friction between the flange and rail due to the normal pressure s. The contact point being at the distance q ahead of the center of the wheel, the friction at this point would cause the wheel to tend to rotate about the bearing point, rising off the tread, so that some of the weight of the wheel is required

and

respectively.

The following correction should also be made in the three formulas for boiler efficiency on page 525 where the quan

tity
formula shown on this page which reads

is given. This should read.

The last

17.

Feed pump.

18.

Feedwater heater.

20. Turbine for driving the furnace fan.

21. Oil pump for main turbines.

22. Stand-by oil pump.

23. Oil cooler.

24. Atmospheric exhaust.

25. Air storage for automatic air brake.. 26. Live steam for turbine on recooler.

Reduction gear.

Circulating water pump.

E

SCHER WYSS & CO., Zurich, Switzerland, in conjunction with the Swiss Locomotive Works, Winterthur, has successfully converted a mogul type reciprocating locomotive into a turbine driven condensing locomotive. The principal change, in general appearance, as compared with the original locomotive has been the replacement of the cylinders by a turbine. The original boiler, equipped with a Schmidt superheater, has been provided with a turbine-driven fan arranged in the front part of the smokebox as a substitute for the draft produced by the exhaust steam of the reciprocating engine.

The Main Turbines

The new locomotive was constructed for the same performance as the old one, so that the six-stage impulse Zoelly turbine for running ahead was designed to give 1,000 hp. at the crankpin. The back-up turbine consists of a simple compound wheel and is contained in the same casing as the ahead turbine. The turbine rotor, comprising both the ahead and back-up wheels, is made out of a solid block, the blades being inserted in slots in the wheel rims. The turbine drives through a double-reduction gear (the first reduction 1:7 and the second 1:4.1), a jack-shaft carrying the crank-pins and the drive to the wheels being obtained by connecting rods.

The turbine casing with the reduction gear, intermediate shaft, jackshaft, and all bearings are mounted on a onepiece steel casing which is riveted to the locomotive frames. The turbine is placed in front of the boiler, its axis parallel to the locomotive axles.

Steam admission to the ahead or back-up turbines is controlled by valves which are operated from the enginemen's cab. For running ahead two groups of nozzles have been provided in the first guide wheel, one allowing the passage of about 11,000 lb. of steam when fully open, and the other for 4,400 lb. One or the other of the valves, or both, is fully open, according to the load. Intermediate quantities are obtained by throttling with the main governing valve. Abstract of paper presented before the annual meeting of the Railroad Division of the American Society of Mechanical Engineers. The paper also appeared in the November issue of Mechanical Engineering, published by the society.

Only one valve which allows a total of 15,500 lb. of steam to pass, has been provided for running backwards. Smaller quantities are likewise obtained by throttling down with the main governing valve. The efficiency of the back-up turbine is lower than that of the ahead turbine for a locomotive usually runs ahead. Backing up is only provided for switching maneuvering, or for use in cases of emergency where a smaller amount of power is required.

The maximum traveling speed of the locomotive is 47 miles per hour and is limited by the type of locomotive. The driving wheels have a diameter of 60 in. At 47 m.p.h. the turbine makes 7,500 r.p.m. The turbine speed is of course, proportional to the traveling speed. When running ahead the back-up wheel rotates in a vacuum, as is common pracback-up turbine is small, and the losses are therefore intice in marine propulsion. The wheel friction for the simple significant.

The Condensers and Auxiliaries

The steam passes in about equal quantities from the exhaust end of the turbine, in both the ahead and the back-up turbines, to condensers placed longitudinally on each side of the boiler. These condensers are water cooled and are of the surface type.

All auxiliaries of the condensing plant are driven by one small turbine which revolves at 9,000 r.p.m. This speed is reduced to 1,200 r.p.m. through a reduction and bevel gearing and drives a vertical shaft carrying the circulatingwater, air, and condensate pumps. The circulating pump takes water from the tender and forces it through the condensers and back again to the recooler. The air pump discharges at a pressure of about 75 lb. to a water-jet air ejector which communicates with the two condensers. It is designed so that the air in the air separator can escape into the atmosphere and the water return to the suction side of the circulating pump.

The condensate from the condensers is led to the condensate pump, which latter discharges at about atmospheric pressure into the feed pump. The latter is placed on the side platform of the locomotive. It is a reciprocating pump running at 59 r.p.m. and is driven through a second reduction

from the auxiliary turbine. The feed pump discharges directly through a heater into the boiler.

The auxiliary turbine is a three-stage Zoelly impulse turbine connected to the condenser and receives steam at 11 lb. gage pressure. Exhaust steam is used in this turbine from a back-pressure turbine which drives the ventilator of the recooler.

The Forced Draft Fan

Special means had to be provided for producing the firebox draft, as the exhaust steam was no longer available. The locomotive was first equipped with a forced draft for producing pressure under the grate. After a long series of tests, however, it was found necessary to change over to the suction principle.

The fan is of the centrifugal type, provided with a spiral casing, and is capable of producing a vacuum in the smokebox of 8.2 in. of water. A maximum of 280 cu. ft. of flue

gases can be discharged per second when running at 1,500 r.p.m. The fan is driven by a small turbine through a gear

The Turbine Casing and Balanced Crank

with a transmission ratio of 1 to 6. The turbine receives live steam and exhausts with a back pressure of about 7 lb. gage to the feedwater heater. The admission of steam to the turbine is regulated by a valve which is also operated from the enginemen's cab. The exhaust steam from the turbine which drives the fan is passed into the heater as there is a certain ratio between the quantity of feedwater and the exhaust steam from that turbine. If for some reason there should be no water in the heater and the steam could not condense, a safety valve opens a connection from the heater to the condenser. The condensate of the heater steam always escapes directly to the condenser and thus goes to the boiler along with the condensate of the main circuit.

This design lacks the advantage of the usual draft producer, i.e., the proportioning of the draft to the quantity of steam required in the main turbine. This, however, can be realized on condensing locomotives by bleeding steam from the main turbine.

The design of the Westinghouse air pump does not quite suit the different operating conditions of the turbine locomotive as the exhaust steam is lost and cannot be used on account of the oil it contains. In future designs the natural course will be to employ a rotary pump, which can be driven by the same auxiliary turbine that drives the condensing auxiliaries, thus returning all steam to the boiler.

The Boiler Feedwater

Theoretically the condensing locomotive does not need any additional water for boiler feeding, as the water in the boiler is working on a closed circuit. It is practically impossible,

however, to eliminate leakage losses, loss through the steam whistle, and last but not least, loss through train heating. In order to obtain full advantage from the condensing locomotive it is essential that none other than clean soft water gets to the boiler. This can be assured in two different ways. It is possible to have a special tank for boiler feedwater on the tender, the feeding being effected by an injector as in the case of the ordinary locomotive, or water from the coolingwater tank may be used, which should be treated before be ing sent to the boiler. The Krupp Company, Essen, Germany, which holds a Zoelly license, cleans the make-up water by sending it to a small evaporator. The feedwater evaporated in the evaporator escapes into the condenser, where it condenses and it is then sent to the boiler along with the condensate of the main circuit. Instead of leading the steam from the evaporator direct to the condenser, it is also possible to send it to a low-pressure turbine, or to a certain stage of the machine, thus doing useful work.

Neither of these two solutions has been resorted to on the experimental locomotive. The cooling water is used direct for boiler feeding, and is fed by the steam injector when necessary.

System of Lubrication and Recooling

Each turbine has its own lubricating system, comprising an oil tank and a geared pump driven from a shaft of the reduction gear. Gears and bearings are under forced lubrication, the oil for the main turbines passing through an oil cooler which is connected with the cooling-water circuit of the condensers.

The most vital part of the condensing locomotive, working with water as a refrigerating medium in the condenser, is the recooler. All the heat units taken from the steam in the condenser go to the cooling water, which of course, has to be recooled in order that it may be used in a cyclic process. The recooler is a separate vehicle, taking the place of the usual tender, and it provides room for coal and make-up water for boiler feeding. It works on the vaporization principle, air being brought into intimate contact with the water to be cooled, which heats it and saturates it with water vapor. The heat to be absorbed in such manner is enormous, amounting in the case of the 1,000-h.p. experimental locomotive to about 5,760,000 B.t.u. per hour, and increasing in proportion for larger locomotives.

The recooler comprises a certain number of water and air elements working in parallel. Each element consists of a wrought-iron channel of rectangular cross-section. This channel is divided diagonally into two halves in the longitudinal direction by means of perforated trays containing Raschig rings; i.e., small tubes of about equal length and diameter. The water to be cooled is led to these trays by tubes which act as sprayers, the air passing in counterflow. The cooling elements are so disposed that the natural current of air produced by the traveling train can enter the cooling element direct. A fan produces a sufficient current of air when the train is stationary or traveling at a very slow speed. and also augments the normal current when traveling at ordinary speeds. It is driven through a gear by a small backpressure turbine, as previously mentioned. Admission of steam to the turbine is controlled by means of a valve from the enginemen's cab.

The cooled water flows from the cooling element back into a tank, whence it is again drawn into the circulating pump. As a certain amount of water is evaporated in the process it becomes necessary to add a corresponding amount in order to keep the circulating quantity constant. There is provided. for this purpose, a large storage tank on the tender, which communicates with a suction tank by means of floaters. The water in the tender need not necessarily be pure as it does not enter the boiler nor come into contact with such parts as could seriously affect the working of the plant.