Lone Sentry: The German Class 52 Locomotive (WWII Tactical and Technical Trends, No. 24, May 6, 1943)

a. General

This is a summary of information and conclusions regarding the much publicized German class "52" locomotive recently adopted as standard to replace the class "50" locomotive. The information has been sifted from various German sources, some of which conflict and many of which are of a propaganda nature. Questionable statements have been eliminated as far as possible.

The evidence points to the conclusion that the earlier class "50" locomotive, for which a program of 7,500 locomotives per year was announced by the Germans in March 1942, was a transition model of a class introduced shortly before the war and was only intended as a stop-gap to tide over a critical period. As proof of this, in the accounts of the class "52" locomotive there are several references to a "transition" model, and the photographs which have appeared in the German press are believed to have been of this simplified class "50" locomotive. Furthermore, technical experts severely criticized the older design from available photographs, particularly on the ground that the frame was light and the cylinder saddle weak. The class "52" locomotive is apparently stronger in these respects. In further evidence that the class "50" locomotive, which was light, was constructed as a temporary expedient to provide means for rapidly increasing production, the German press announced that the first of the class "52" locomotives left the factory early in September--although the design and subsequent production of the model class "52" locomotive is estimated to have required 15 months. Evidently considerable progress had already been made on class "52" at the time that the simplified class "50" was temporarily adopted as a standard model.

b. The Design of the Class "52"

A comparison of photographs of the classes "50" and "52" shows that, contrary to German press accounts, they are lighter models of the class "44," and have the same basic design. In comparison with transition class "50" the new class "52" has a deeper frame, stiffer cylinder saddle, and a welded tender of the modified Vanderbilt, frameless type in place of the riveted type carried on a frame. The bracket for the valve motion has been stiffened by a bridge girder between the bracket and cylinder. A snow plough has been fitted to the locomotive. The smoke deflector plates, the forward steam dome which contained the preheater, the feed pump, and the feed water heater have been eliminated. It is evident that the side and main rods have been redesigned; the brake rigging and similar apparatus are simplified; the locking device on the smoke box has been replaced by a ring of cleats; and the cylinder-exhaust branches are rectangular instead of circular in cross section.

[German WWII Class 52 Locomotive]

The class "52" locomotive is claimed to be more effectively protected against freezing than the class "50," by thicker lagging, steam jackets around exposed piping, and transfer of exposed parts to a position nearer the boiler. Although it is difficult to verify all these claims from photographs, it appears that the boiler, cylinders, and exhaust branches are well insulated. The photographs do not indicate which pipes were brought nearer the boiler or which pipes have been steam-jacketed. However, contrary to normal practice the air-compressor valve mechanism at the top of the compressor has been covered by a casing and insulated. It has been reported that a closer fit has been made on class "50" locomotive journal-box covers in order to prevent snow from entering, and, no doubt, this has been done on the class "52" locomotive also. The precautions taken against freezing would adapt the locomotive for service on the Eastern Front. Minor differences noted are the mounting of the headlight generator above the firebox instead of on the smoke box; the replacing of two oil lubricators by a single lubricator above the boiler; and the fact that the sand dome, instead of being separate, is inclosed by the rear steam-dome casing.

c. Data on Locomotives of Class "44," "50," and "52"

Class "44" "50" "52"

Wheel arrangement 2-10-0 2-10-0 2-10-0

Weight of locomotive, empty (long tons) 99.5 80 82

Weight of tender, empty (long tons) 28.6 26 18

Water capacity of tender (gal) 7,930 6,870 8,980

Fuel capacity of tender (long tons) 10 8 10

No. of cylinders 3 2 2

Diameter of cylinders (in) 23 5/8 23 5/8 23 5/8

Piston stroke (in) 26 26 26

Driving-wheel diameter (in) 55 1/8 55 1/8 55 1/8

Leading-wheel diameter (in) 33 1/2 33 1/2 33 1/2

Wheel base, incl. tender (ft and in) 62' 11 1/2" 61' 11 3/4" 61' 11 3/4"

Boiler pressure (kg per sq cm*) 233 227 227

Grate area (sq ft) 50 1/2 42 42

Total heating surface** (sq ft) 2,551 1,912 1,912

Superheater heating surface (sq ft) 1,076 685 685

Maximum speed (mph) 50 50 50

*Information as received. This converts to 3,314 and 3,229 pounds per square inch, which is much too high. Probably should be pounds per square inch instead of kilograms per square centimeters.

**This is probably evaporative heating surface.

d. Comments on Data and Weights

As shown in the table, the locomotive class "52" without water in the boiler is 2 tons heavier than class "50," contrary to some accounts that both are of same weight. The class "52" tender is lighter, but has a larger fuel and water capacity.

The main reduction in weight obtained in class "52" is effected by adopting the frameless tender of welded construction, mounted on two trucks with roller bearing axles. The lower portion of the tender is of half-round cross section; the upper portion is flat sided with a curved roof plate. The elimination of the feed water heater effects a reduction in weight of 2,100 pounds, while a further reduction is obtained by simplified rods, substituting cleats for the lock on the smoke-box door, reducing the number of parts in the locomotive, and probably by substituting welding for rivets and bolts.

Although the class "52" locomotive is believed to be actually heavier than the class "50" without the tender, press accounts refer to marked savings in the weight of semi-finished parts required to produce finished parts. The following intermediate (semi-finished) and net (finished) weights can be deduced from the information given:

Weight in Tons (2,240 lbs) of Semi-Finished Parts
to Construct the Locomotives

Locomotive
Tender    Locomotive
and Tender

Int.   Net   Diff. Int.   Net   Diff. Int.   Net   Diff.

Class "50"   123   80   43   42   26   16 165 106   59

Class "52" 114   82   32   26   18    8 140 100   40

If the expected output of 7,500 locomotives per year is attained, 187,500 tons of material would be saved at the 25 tons per locomotive shown in the table. A reduction of 16 tons of the total of 25 is accounted for in the tender. Part of the economy in weight of the locomotive is achieved by the use of drop forgings instead of hand forgings for the whole of the valve-motion gear and side rods, and throughout the brake rigging. Reference is also made in German accounts to economy of material by using plain instead of forked ends in the motion gear, and by the adoption of a "gas tube in place of the firebox wrapper plate" (probably an arched, firebox crown sheet).

According to German accounts, a reduction has been secured in the quantity of non-ferrous metals by using 495 pounds of copper in the class "52" as against 1,600 pounds in the class "50" locomotive. It is claimed that 840 pounds of this reduction has been accomplished by the substitution of steel-backed for bronze-backed bearings for the 2 big-ends of the main rod and for the 10 axle bearings, and that a further saving of 55 pounds of copper is obtained by substituting a steel casing for the former bronze steam-whistle casing.

It is further claimed that 138 pounds of tin were saved in the steel-backed bearings, and 2 pounds of tin in using the steel whistle casing, although the main economy in tin as compared with the class "44" is the result of the replacement of plain by ball bearings for the tender axles.

e. Reduction in Labor Requirements

Careful consideration has been given in the design of the class "52" locomotive to economy in man-hours required for its construction. After comparing various reports, it is estimated that a class "52" locomotive can be built in 24,000 man-hours, representing a building period of about 10 weeks, as against 30,000 man-hours for class "50" and 60,000 man-hours for class "44." The economy of 6,000 man-hours is an estimate based on the prototype model, and not a figure based on actual experience. The 24,000 man-hour figure might possibly be attained in the largest and best-equipped plants, but it is practically certain that well over 30.000 man-hours will be required in many of the smaller European plants.

There is no doubt that a welded tender of the frameless type could be built in about half the time required for the framed type. The wide adoption of drop forgings and changes of design to reduce machining would lead to economy in labor. The following table compiled from data in the German press shows certain features in class "44" and "50" locomotives which have been changed in the "52" class, with the resultant saving in intermediate weight and man-hours.

Class with
which the
"52" is
compared Part    Remarks Intermediate
Weight
saved Man-hours
saved

Class "44" 2 safety couplings Eliminated     128 lb   40

Class "44" Smoke-box door lock Replaced by cleats     181 lb    3

Class "50" Hand rails or running boards Nine eliminated     234 lb   12.5

Class "44" Bell Eliminated      33 lb   10

Class "50" Eight coupling rods Drop-forged instead of hand-forged 10,400 lb 632

Class "50" Steam dome with feed water heater Eliminated   2,100 lb 174

Class "50"   Two smoke deflector plates Eliminated   1,950 lb 110

Class "50"   Two connecting rods Built up from two drop forgings and rolled section, instead of hand-forged   2,600 lb   79

Reports claim a reduction in machining time of a cylinder block of from 28 to 4 hours, and it is claimed that a further reduction to 1 hour will be attained upon completion of a special machine. A highly specialized tool for machining locomotive cylinders would be very costly to build, and it is doubtful whether the German machine-tool industry is now in a position to accept orders for such a machine. If such tools were manufactured, only a limited number of plants could be equipped with them. Due to the transport difficulties involved, the machined cylinders would hardly be shipped to factories distributed throughout Europe. Too much weight need not be attached to actual figures given; however, they show that every attempt is being made to economize in labor and speed up production.

It is stated in one report that by limiting the finish to one coat of paint, 235 man-hours have been saved.

f. Production of Class "52" Locomotive

A paper entitled "Estimated Main-Line Steam Locomotive Output in Axis Europe," based on the class "50" design, gave an annual output of 3,400 locomotives by the end of 1942, 4,040 by July 1943, and 6,040 by the end of 1943, on the assumption that all class "44" locomotives under construction when the plan was announced would be completed, and that all future locomotives would be of the simplified class "50" design. However, the adoption of class "52" as standard modifies these estimates.

Although the tender or class "52" could be built in about half the time of the class "50" tender, this would not appreciably affect the relative production rates of the locomotives proper. The following points should be considered: (a) modifications in design for greater output, (b) modifications in methods of production, and (c) extension of subcontracting.

The conclusion already stated on the first two points is that through these modifications, the class "52" engine can possibly be built in 24,000 man-hours as against 30,000 man-hours for the class "50" by the largest and best-equipped works, providing drop forgings are used in place of hand forgings and that they can be obtained without delay. If the locomotives are built in a number of scattered minor works, as appears likely, such forgings will have to be obtained from outside shops in a great many cases. Due to difficulties of regular supply, the economy in man-hours resulting from use of drop forgings will be a maximum of 10 percent and will most probably average about 5 percent. The production of the necessary dies for the drop forgings will lead to some delays resulting in a small drop of the estimated locomotive output in first half of 1943, followed by a rise to about 6,400 instead of 6,040 by the end of the year. If the above assumptions are correct, the chief advantage of the new class "52" design over the class "50" will not be an increase in production, but the substitution of a sound for a defective design as a standard production model.

Considering the last point, there is very little reliable information on which to base an answer to the question whether the Germans can increase locomotive output by subcontracting beyond the present estimated 10 percent. Reports have been received of proposals to convert the leading European locomotive works to assembly plants, with all components made either in other locomotive works or in plants not hitherto engaged on locomotive production. If this is done, the machine capacity of selected plants would be lost or used for purposes for which the plants were not laid out. Also, a carefully synchronized plan would have to be worked out to cover movement of parts over a transport system that is already heavily taxed. Considering that the delivery of locomotives from some leading French works is months overdue owing to various unexpected difficulties, the required degree of synchronization would be nearly impossible to obtain.

Press accounts, apparently referring to the class "50" locomotive, refer to 18 percent of the total man-hours being performed by subcontractors at the present time. Such component parts of locomotives as air compressors, feed pumps, injectors, and parts of the braking apparatus have usually been obtained from an outside firm. Some of the smaller firms obtained even the boiler from an outside source, and it is difficult to deduce whether the figure of 18 percent includes these parts or only parts normally manufactured by the locomotive builder. Some European works have always made a practice of subcontracting locomotive tenders, and a few have subcontracted boilers.

Until it is established that the 18 percent is in fact over and above the figure accounted for by subcontracting before the war, the figure of 10 percent additional output obtained by subcontracting should be used when estimating total output.

g. Utility Value of the Class "52" Locomotive

The conclusion drawn from published data and photographs is that the class "52" locomotive appears to be of sound design throughout, and should have a useful life comparable with prewar engines.

The elimination of the feed water heater at a sacrifice of approximately 7 percent in thermal efficiency will increase fuel costs but reduce maintenance. The elimination of safety couplings and bell, and the use of thin tires, are justifiable in wartime, and there will be no difficulty in changing these parts at a later date. There is no evidence that the class "52" ;ocomotive has been designed for a short working life. The retention of extension piston rods to reduce cylinder wear on class "52" is direct evidence to the contrary.

From the viewpoint of normal continental practice the class "52" is a light model of moderate power, suitable for operating branch lines and local services, but not suitable for heavy, main-line post-war traffic in the Reich.

From German accounts, the construction of the class "42" is to be initiated in 1944 for heavy service. This class has never previously been built in quantity but it is thought to be comparable in performance to the class "44." It is thought probable that if the class "42" is built, the class "52" locomotives will also be continued in construction.