In tables A to D particulars are given of some performance data of locomotives using superheated steam on Dr. Schmidt’s system. It may be noted that these data, which were of a very satisfactory nature, were made under varying conditions in Europe and America. Most tests were not specially arranged, experimental trips of short duration, but practical comparative tests over long periods of ordinary running.

The marked economy of the Schmidt system is very striking, and the percentage of coal and water saved varied according to the surface of the superheater, the size of the cylinders, and the amount (if any) to which the engine was forced. The following figures may be taken as a safe average of the economy effected:

• A simple engine using superheated steam shows a better economy in coal of 25 to 30 %, as compared with that of a simple engine using saturated steam.

• A simple engine using superheated steam shows a better economy in coal of 15 to 20 %, as compared with that of a compound engine using saturated steam.

Apart from the reduced steam consumption, another very important advantage accrued from the use of highly superheated steam in locomotives, which is the considerable increase in haulage capacity. This detail has been discussed under a previous section.

In the following summary data are shown, which were collected by various railway companies:

	Configuration and No. of Carriages	Consumption of Coal		Consumption of Water		Economy in Coal
Engine	-	lb.	kg	Gallons	Litres	%
Borries’ Compound Schmidt Simple Borries’ Compound Schmidt Simple Borries’ Compound Schmidt Simple	(4-4-2)   9 (4-4-0)   9 (4-4-2)   11 (4-4-0)   11 (4-4-2)   13 (4-4-0)   13	260.2 195.0 238.2 171.9 233.2 155.7	118.0 88.5 108.0 78.0 105.8 70.6	161.0 95.0 151.9 90.4 138.2 87.5	732.0 432.0 690.5 411.0 628.0 398.0	- 25 - 27.8 - 33.3

1) Test data by Prussian State Railway within the Berlin District, in June 1905

The table shows that each increase in the train load brought about a proportional greater economy in coal consumption, which is proof that the superheated steam locomotive had a larger haulage capacity than the compound.

The time it took for the Schmidt Simple engine to complete the test run with 13 carriages was 42.75 minutes shorter than the time for the Borries’ Compound engine. Thus the four-coupled superheater engine, which had two 21-1/4 inch (540 mm) cylinders and 170 psig (11.7 bar gauge) boiler pressure, showed itself to be vastly more powerful and far more economical than the four cylinder compound "Atlantic" locomotive. The latter had 200 psig (13.8 bar gauge) steam pressure and 14-13/16 inch (376 mm) respectively 22-inch (589-mm) cylinder diameter.

2. Test data by Prussian State Railway within the Berlin District, in February 1906

A series of comparable tests were conducted to identify the working of a superheated steam tank engine with that of an ordinary saturated steam tank locomotive. These engines had the dimensions as listed below:

As a maximum, the saturated steam-tank engine could only haul a train of 84 axles (654 British tons or 664.500 kg) in the scheduled time. The much lighter superheater steam locomotive however was able to take a train of 104 axles (816 British tons or 820.060 kg) and that in ten minutes less than the scheduled time.

3. Test data by Prussian State Railway within the Breslau District

The railway authority carefully tested a 10-coupled (0-10-0) superheated steam tank engine, fitted with a Schmidt smoke-box superheater against a ten-coupled saturated steam tank engine of the "Hagan" type. Both locomotives were practically of the same weight. The trial consisted in working the heavy goods service between Hirschberg via Petersdorf and Gruenthal, the section of which had a grade of 1:40 to 1:45 over a distance of 15 miles (24 km). The following table gives details of the test:

From the above rating it can be seen, that the superheated steam locomotive has an excess of haulage power of from 33 to 54 % over that of the saturated steam tank engine.

4. Test data by Prussian State Railway within the Berlin District, in February 1905

Two comparative trials were carried out between an ordinary "Mogul" (2-6-0) tank engine and another locomotive of the same type, but fitted with a Schmidt smoke-box superheater. Below refer to the technical data:

The trials were instituted with a view of ascertaining the maximum haulage capacity of each engine, within economical limits. The tests took place on the Grunewald-Nedlitz section. The summarized results were:

• 41.6 % larger haulage power of the Schmidt superheated steam engine

• 51 axles maximum load of the superheater engine versus 36 axles of the saturated steam engine

• 16.6 % less coal consumption for the Schmidt engine

• 37 % less water usage for the Schmidt engine

5. Test data by Prussian State Railway within the Berlin District, in August 1906

One of the six-coupled superheated steam engines, shown in Fig.1, underwent a number of trials. These trials took place on the Grunewald-Sangershausen section with a distance of 245.6 miles (395 km). The line was a very hilly one, with steep gradients of 1:100.

The chief dimensions of the engine were:

The load behind the tender was 464 tons. The maximum weight of the train during that trial was 581 tons with 14 carriages and 56 axles.

The chart shows the speed, indicated horsepower, steam pressure and temperature curves. On a gradient of 1:100, a maximum of 1845 to 1890 H.P. was maintained for more than six minutes at a variable speed from 46.6 miles/h (75 km/h) to 43.5 miles/h (70 km/h). This performance was without dispute a most remarkable one, and one the excellence of which can only be attributed to the reduced consumption of steam, wholly due to steam superheating.

These experiments also proved that the 4-6-0 superheater express locomotive required no banking engine to assist it over the steeper portions of the line when hauling ordinary express trains. At a subsequent test, made with the same engine between Koenigsberg and Grunewald, the 370 miles (595 km) were covered at the scheduled express speed without change of engines. When, however, saturated steam locomotives were employed over the same line, it was necessary to change the engines no less than three times.

The Belgian State Railway in 1907 had 140 Schmidt superheated steam locomotives either in use or under construction. The authorities have obtained splendid results in the course of elaborate tests carried out with a large number of Schmidt engines. According to Inspector J.B.Flamme’s report, the latest trials of these engines showed a saving in coal of 32 %.

7. Trials by the Canadian State Railway, prior to 1905

Schmidt superheated steam locomotives were subjected to careful and exhaustive tests. The Superintendent of Motive Power, Mr Vaughan reported to the American Railway Master Mechanics Association in 1905:

The records from engine 548 extended over a period of 17 months, during which time this engine was compared with similar simple and "Vauclain" compounds in freight service, and with simple and two-cylinder "Pittsburg" compounds in passenger service. This engine consumed about 75 % of the coal required by a simple engine, and 82 % of that required by a compound engine in similar service. The superheat obtained in this engine is high however, running from 550 ° F (278 ° C) to 650 ° F (343 ° C), according to conditions, and it may be considered as representing the extreme limit to which superheating can be conveniently carried. There is no doubt that the results, which have been obtained are exceptionally economical, and the engine has been a favourite with the men handling it in any service. The valve and cylinder design have given entire satisfaction, although, when the superheat was raised above 700 ° F (371 ° C) a certain amount of trouble was experienced with the lubrication and packings.

8. Operation by the Aussig-Teplitzer Railway Company, prior to 1907

The company reported that on their lines between Aussig and Komotau as well as between Berlin and Karlsbad not the slightest ground of complaint could be raised using superheated steam engines. Considerable delays on the Karlsbad section caused by irregularities on the connections were to a great extent made good when using superheated steam engines. In 1906 there was one case where an overloaded train ( 408 tons behind the second tender) needed assistance on a 1:100 uphill section. The engine employed could manage 23 other overloaded trains. With regard to economy the superheated steam locomotives showed an economy of 20 % in coal in comparison with the 4-6-0 saturated steam locomotives.

9. Trials by the Swedish State Railway, prior to March 1907

The director of the Swedish Railway, Mr. Ivor Virgin published a report in 1907, which in specific terms confirmed the coal and water savings as well as the traction power and haulage. Mr. Ivan Virgin praised the capacity of the superheated engine to cover long distances without changing the engine. This trial was run between Malmoe and Katherineholm and covered a distance of 300 miles (483 km). Up to May 1908 the Swedish State Railways have ordered a total of 71 Schmidt superheater engines.

10. Trials by the Bohemian Northern Railway, prior to April 1907

The Board of Directors of the Bohemian Northern Railway reported that in 1905, inexperienced personnel commissioned the first two (2-6-0) simple, smoke tube superheater steam engines without the slightest hitch.

Trial also confirmed the savings of coal and water as well as the tractive power on 1:90 gradients. The tests were carried out between Prague and Turnau, with the short and steep stretch between Wysocan and Satalic. Attention is particularly called to the fact that, on the up-grades, the saturated steam locomotive had to be pressed hard, thus causing incomplete combustion and the ejection from the smoke stack of a large quantity of cinders and partly burnt gases.