Steam Locomotive Performance Testing
Aim - This page aims to describe how to define the performance of a steam locomotive, and then types of tests that can be undertaken to ensure that it is operating within realistic bounds.
Whilst this page has been developed specifically for steam locomotives, a lot of the performance setting and testing concepts will equally apply to other types of locomotives.
If you wish to provide any feedback on this page, please use the contact page. It would be great to have some feedback as this helps to ensure the accuracy of the information and models.
To accurately confirm the performance of a steam locomotive in Open Rails it is necessary to establish a performance benchmark to test the locomotive against. To ensure the accuracy of the tests the benchmark needs to have some measureable values that can be used for comparison. Thus it is necessary to do sufficient research to find as much relevant "real life" or prototypical information as possible. Typically a lot of information can be found on the Internet, or alternatively through steam locomotive preservation groups or historical societies.
The research information required for these tests should include:
- Steam locomotive design parameters which include cylinder sizes, strokes, boiler pressure, grate area, evaporation areas, etc.
- Steam train operational information such as the loads, speeds, sectional running times, etc.
In these tests, it is also important to only use passenger cars or freight wagons that comply with known prototypical operational and design standards. Incorrectly defined rolling stock can cause inaccurate results compared to the benchmark. The test stock on this page should be a good "known" starting point, though the brake systems on the wagons or the locomotive may need to be adjusted to be compatible.
The main two aspects that can be tested to measure the performance of a steam locomotive are the following:
- Load - the amount of load that the locomotive can haul under various operating conditions. For the load test it is recommended that a known long even prototypical gradient is used, as this will ensure consistent test results. For example, for English locomotives, the Lickey Incline might be a good choice. This gradient was 1 in 37 ( 2.65% ) and just over two miles (3.2km) long.
- Steaming properties - the ability of the locomotive to sustain sufficient steam to meet the expected operational benchmark. Steaming properties will be partially covered by the load test above, but also can be further tested by running over a section of line with a series of undulations, and possibly working to a passenger schedule if appropriate.
Thus a standard test is suggested to cover each one of the above items. The load test should always be conducted first as it will confirm the accuracy of the locomotive steam definition. To accurately perform the suggested tests above it will be necessary to find suitable sections of line in an accurate route. For the load test, it is highly recommended that the Coals to Newcastle Test Route is used, as this route has a number of "standard" grades included. For the steaming test, any route which has been accurately constructed to a known real life route can be used. Check the OR route gradients against the published gradient diagram.
"Remember, to ensure OPTIMAL REALISM of the steam locomotive performance, ACCURATE INPUTS are required."
To demonstrate the testing process an example locomotive based upon the British Rail Hall Class locomotive will be used. This locomotive has a very small grate area, and therefore as a consequence it will be more of a challenge to maintain steam generation.
Establishing Performance Benchmark
The most accurate test outcome for locomotive performance will be achieved if there are test reports available for setting and testing the locomotive under test, however these types of reports are not always available, so a reasonable alternative is to use railway publications which tend to be more readily available. These documents, such as Working Timetables (WTT), will have a lot of the information described below in them.
For the load test a long even gradient is best, and we need to find the following information:
- Gradient profile
- Starting location and reference mileage
- Finishing location and mileage
- Running time for the train over section
- Tabled load for train
- Calculate average speed up the gradient
- Any other information that might be relevant and support the above items
For our worked example we will use the Hall locomotive (49xx Class), which was designed for passenger duties, and operated over the Lickey Incline, which was located between Blackwell, and Bromsgrove. This locomotive is referenced in the Gloucester Passenger Working Timetable (WTT) - 1962
Based upon the information in the WTT on page K92 (part A) a view of the ruling gradients, the starting and finishing locations can be developed. The ruling gradient is the steepest gradient in the section, and as such will be the limiting gradient as far as train loading is concerned. Using the start and finish locations we can calculate the distance over which we will be running. The following diagram demonstrates the information that can be ascertained.
Next, as can be seen from page K5 (part A) of the WTT, the point to point running time allowed between Bromsgrove and Blackwell for the different types of locomotives, and was in the range of 6 - 7 minutes. Using this running time (6 mins) and the distance of travel calculated between Bromsgrove and Blackwell (in above diagram - 2.1875 miles) the average speed between the two locations can be found to be. The unassisted load for this section of line for a Hall Class locomotive is 190 tons, and can be found on K162 (part B).
Thus we have defined an expected performance benchmark for the locomotive, i.e., the Hall locomotive will unassisted haul a load of 190 tons up a 2 mile, 1 in 37 gradient at an average speed of between 18.75 and 21.88 mph depending upon the running time.
Other measureable information may also help to confirm and validate our benchmark. Such an example in the case of the Lickey Incline might be this page, which indicates that the above benchmark is the correct order of magnitude.
We can now test our performance benchmark for the load test withe the sample Hall locomotive on the bottom of this page and the Mk1 passenger cars on the test stock page can be used. The Coals to Newcastle test Route has a long section of 1 in 40 gradient, and can be used as an accurate test environment.
It should be noted that the location of the above type of information may be found in different railway publications, and in different formats, depending upon the country and company, thus the example above is purely shown as a guide to the process that can be used to define the performance benchmark.
Refer to the setting page for more information on defining the basic setup for a steam locomotive ENG file.
The steam locomotive is a heat engine, which in other words relies on the transfer of heat energy to mechanical energy. Therefore it is important to make sure that there is always more heat going into the locomotive boiler then out of it. The boiler heat values can be seen in the Extended HUD, by pressing ("Shft-F5"), and these figures should be monitored when running the tests.
By maintaining a high value of HEAT in the boiler the operational pressure of the locomotive will be maintained at suitable levels. If the HEAT OUT value is allowed to exceed the HEAT IN value for a long period of time, then the boiler pressure will drop, and the locomotive will not have sufficient power to pull the load.
Starting (assuming a full load on train)
Start with regulator and reverser at maximum values. And as soon as the train has started moving start to reduce the reverser to a value of around 25%. Keep an eye on the HEAT values, if sufficient heat is not being generated by the fire, and then reduce the throttle to a value where the HEAT IN value just exceeds the HEAT OUT value. Slowly increase the regulator as the steam HEAT IN increases, until the fire has built up sufficient heat to maintain the boiler pressure.
Remember that a steam locomotive is not like a car, and therefore it is unable to accelerate as quickly in a short distance. Depending upon the load and track conditions, it may take a several miles to achieve the desired operational speed.
As suggested the first test is to see how the locomotive performs against the load benchmark as it ascends a known grade. For our test we will ascend the 1 in 40 grade in the the Coals to Newcastle test Route, and use the standard test stock.
To run the first test select the following options:
- Locomotive: - "AU CTN Test - Hall Locomotive - MSTS (Modified)"
- Consist: -"CTN OR Test Consist - Steam Performance - Hall - 315 tons - MSTS (Modified)"
- Starting at: - "Bottom of Hill"
- Finishing at: - "Top Station - 1 in 40"
Using the driving technique described above, run the locomotive up the grade, and compare its performance against the defined benchmark.
The test can be repeated by varying some of the settings or conditions. The test locomotive has a number of different configurations in it that can be used to compare the MSTS settings against the OR basic and advanced settings. Also other MSTS defined carriages can be used to test and compare the results.
Similarly other benchmarks, and tests can be defined using the methodology described above.
Things to check if the benchmark is not achieved
One of the first points of interest to note for the Hall test locomotive is the difference between the OR and MSTS versions, for example compare the calculated tractive effort in the MSTS versions to the OR versions. This is due to the different way that MSTS and OR uses the physics parameters to calculate performance values. Thus it needs to be recognised that a direct comparision of MSTS versus OR is not possible, and hence the need to define performance benchmarks based upon prototypical information.
If the testing does not achieve the defined benchmark, then check the following items:
- ENG File: Firstly double check that the ENG file has correct values in it for the locomotive in question.
- Tractive Effort: What was the maximum tractive effort that the locomotive was able to achieve, and does this match with the locomotive specifications? Not producing enough tractive effort could be a result either of poor ENG file definition, or the inability to maintain boiler pressure.
- Stock rolling resistance: The "standard" resistance calculated by FCalc may not match the actual values for the rolling stock in question. For example, whilst FCalc has been used to calculate generic restance valuse for the test stock, the actual measured resisitance values for British passenger stock as shown in this graph from a locomotive test report. You may wish to try and adjust your wagons to match.
- Boiler Pressure: Is boiler pressure able to be maintained with careful economical driving?
To facilitate testing and comparison of different ENG file configurations, the test locomotive has been set up with the following varieties included:
- MSTS Original - this version has exactly the same ENG files as was originally provided with the locomotive download. NB: This version is not compatible with the braking system on the CTN test stock, so it can only be used with compatible stock. Only a light engine consist has been provided in the pack.
Locomotive name - "AU CTN Test - Hall Locomotive - MSTS (Original)"
- MSTS Modified - this version has an ENG files that has been modified such that the braking systems are compatible with the CTN test stock. All other aspects are as was originally provided with the locomotive download.
Locomotive name - "AU CTN Test - Hall Locomotive - MSTS (Modified)"
- OR Basic - this version has an ENG files that has been defined using the basic steam locomotive physics parameters for open Rails.
Locomotive name - "AU CTN Test - Hall Locomotive - OR (Basic)"
- OR Advanced - this version has an ENG files that uses the basic steam locomotive physics parameters, but also includes a customised boiler efficiency statement. This improves the combustion rate and makes it easier to maintain steam. This should only be included where known (see test report below) or where it is impossible to maintain steam pressure, despite economical driving.
Locomotive name - "AU CTN Test - Hall Locomotive - OR (Advanced)"
Appropriate consists are also included in the Hall test locomotive pack.