Curve Speed Testing
Aim - This page aims to describe how to test the operation of the curve speed limit within Open rails, and the setting of this within realistic bounds.
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The tests described on this page will confirm the correct setting of parameters that are used by Open Rails to determine the safe and most efficient speed that a train can travel around a curve. As described in more detail in the train resistance page, the optimal curve speed is determined by the track superlevation, cant deficiency (unbalanced superelevation), and track gauge.
The permissible speeds that a train can travel around a curve are as follows:
- Equilibrium Speed - maximum speed around a curve which ensures that the load of the wagon is balanced across all the wheels, and that the forces between the wheels and track are equal. Mainly influenced by track superelevation.
- Unbalanced Speed - maximum speed around a curve which allows a certain amount of load unbalance between the wheels and the track. Typically the amount of unbalance is determined by the of the amount of unbalanced superelevation (cant deficiency) is allowable.
- Critical Speed - the speed at which the rolling stock is likely to overturn. Mostly impacted by the Centre of Gravity.
The research information required to set appropriate performance benchmarks for these tests should include:
- Amount of super elevation applied to the curves on railway route that the player is operating on.
- Amount of unbalanced superelevation that is applicable to the rolling stock.
- Track gauge.
- Centre of Gravity.
In these tests, it is also important to use only 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 calculators at the bottom of this page can be used to calculate the relevant curve speeds that Open Rails calculates, and produces relevant warning messages. The useful references show some documentation from different railways to confirm the value of these speed values.
Establishing Performance Benchmark
The most accurate test outcome for curve speed performance will be achieved if information on the track super elevation for the route is available and the unbalanced super elevation is know for the rolling stock.
Curve Speed Test
For the curve speed test a section of track with a number of different known radius curves along the route is best. For the different curves we need to find the following information for the route being used as a test environment:
- Track gauge.
- Super elevation of various radius curves.
- Unbalanced superelevation (cant deficiency) applicable to the rolling stock being used.
- Rolling stock centre of gravity.
- Any other information that might be relevant.
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 examples shown on this page are merely a guide to demonstrate the approach that can be used to define the curve speed performance benchmark.
Typical Railway Track Design
In undertaking these tests it is important to understand the typical characteristics, or design principles used by different railway companys for setting curve radius.
Whilst different companies have in the past have adopted different values for the above design parameters, more modern railway designs have become reasonably standard across different companies or country systems. When reviewing different design approaches the following summary may assist the tester:
- Historical (low speed) railways - When railways were first introduced, speed was not an design criteria, and often the track was laid to achieve the cheapest construction costs. This often resulted in the railway track following the gradient of the surrounding land, and as a consequence, early railways could have steep gradients and sharp curves included in their right of way. The minimum curve radius would often determine the maximum speed that the train could travel in a particular section. Some companies adopted the practice of putting speed posts on different radius curves for the guidance of the driver, whilst others, especially on secondary or minor routes, advised driver of the locations of "sharp curves" and expected them to learn the route, and drive to appropriate safe speeds when traversing around a curve. Thus whilst a generic speed limit was imposed on the route, this was not necessarily a universal speed limit that could be adopted throughout the route by the driver.
- Modern (high speed) railways - As time has gone by, railways have been under pressure to increase their speed of operation in order to remain competitive. Most existing railways have had increased superelevation and unbalanced superelevation added to the curves in order to increase the speed that can be traveled, however there is a limit to the quantity that these values can be set to. So modern high speed routes have purpose built to allow a continouous speed of operation along the route, and the minimum curve radius has been set to ensure that this speed can be safely maintained. Thus for modern high speed railways, speed limits are more likely to be set as a route speed limit, or signposted as appropriate.
Open Rails Operation
The curve speed limits and associated warnings will only apply if the relevant option is selected in the Open Rails Option menu. Open Rails provides two warning messages if the relevant speed limits are exceeded:
- Unbalanced Speed - indicates that the train is operating above the optimal curve speed limit.
- Critical Speed - indicates that the train has overturned due to excessive speed.
In addition Open Rails will activate relevant penalties if the relevant speed limits are exceeded:
- Unbalanced Speed - will cause the a brake air hose to break, causing the emergency brakes to be applied. (Normally the brake air hoses will break at the same point as the warning message is applied. The brake air hose breakage can be set to break at higher levels if the "Durability ( 1.00 )" parameter in the consist (CON) file is set at a value higher then 1.0).
- Critical Speed - will cause a coupler to break.
Rolling Stock Definition
Refer to the setting page for more information on defining the basic resistance setup for various rolling stock.
Test Rolling Stock
Curve Speed test
Note: The following tests are done in the "Explore Route" mode of Open Rails.
This test is to see how the train curve speed limits train operation as it travels around various radius curves. A number of different consists have been provided to demonstrate the difference in settings. For our test we will use the "Curve Branch" in the the Coals to Newcastle test Route (v1.8 or greater), and use the standard freight test stock.
Based upon the curves radii included in the test route Open Rails currently defaults to the following superelevation values:
- 250 metre radius - 3"
- 500 metre radius - 4"
- 1000 metre radius - 2"
- 1500 metre radius - 1"
- 2000 metre radius - Calculated based upon route speed, or a default of 1".
Based upon these above values, the curve speed calculators below can be used to determine the speed at which Open Rails will issue one of the above warnings. These values can be compared to prototypical values shown in the useful references section, or alternatively researched from the Internet.
To run the first test select the following options:
- Locomotive: - "AU CTN Test - Atlantic"
- Consist: -"CTN OR Test Consist - Unbalanced Superelevation 0in"
- Starting at: - "Curve Branch Yard"
- Finishing at: - "Station - NE Corner"
In this test the train will traverse a number of different radius curves. Check speed thresholds through the different radius curves with the different unbalance settings.
This test can be repeated with the different consists in the test pack below which model different values of unbalance superelevation (cant deficiency) of 0in, 3in and 6in.
Try adjusting the "Durability" parameter in the CON file as well to note the impact of different values have.