[steamer_ctn]

In the current OR code when a locomotive with a BASIC configuration (ie no tractive force table) reaches the value stated in the MaxVelocity parameter the Tractive Force goes to zero, which implies that the Rail HP has also gone to zero.

I believe that this is not correct representation of the operation of a diesel locomotive. Looking at the graph that was posted by DarwinS the power certainly decreases once it reaches a certain point, but does not go to zero in a single step. As shown on the graph, there appears to be two different points, ie the Unloading Point, and the Maximum Design Speed.

When both of these points are reached it is apparent that whilst power is decreasing it has not gone to a zero value. Hence the locomotive is capable of producing some output rather then no output as is currently modeled in OR. In some literature that I have seen, it has been suggested that physical damage can occur to the locomotive if the Maximum Design Speed was exceeded.

To prevent this in later model diesels, I believe that a "power off" feature of the monitoring system would shut the locomotive traction motors down at a speed where there was concern about damage being done to the diesel. The speed set point wouldn't be related to the route speed or other similar limit, and would be purely the maximum design speed of the locomotive.

In early model diesels, I suspect that no monitoring of this speed was done, hence it was purely up to the driver to practice good driving practices.

Thus I am proposing to add extra parameters to diesel locomotives as follows:

i) ORTSUnloadingSpeed - Once this speed is reached it will initiate a decay in power, and hence a similar decay in tractive effort.

ii) ORTSMaxDesignSpeed - once this speed is reached a new TCS function (if required) will initiate a power down operation. This will simulate more modern diesels, whilst earlier models will not configure the TCS function.

The following should be noted -

i) Neither of these parameters will influence the speed limits of consists in activities, etc.

ii) The ORTSUnloadingSpeed parameter will not have any influence where a Tractive force table has been created, as it will be assumed that the user has plotted this unloading point into the table themselves.

iii) The TCS (ORTSUnloadingSpeed) trigger will apply to both the situation where a table has been configured, and where it hasn't.

[steamer_ctn]

Whilst reading a diesel locomotive operational manual (EMD SD18) I came across the following comment which I felt might be relevant and of interest to some in regard to the design speed of the locomotive.

"LOCOMOTIVE SPEED LIMIT
The maximum speed at which the locomotive may be safely operated is determined by the gear ratio. This ratio is expressed as a double number such as 62-15. The 62 indicates the number of teeth on the axle gear while the 15 represents the number of teeth on the traction motor pinion gear.

Since the two gears are meshed together, it can be seen that for this particular ratio, the motor armature turns approximately four times for every one revolution of the driving wheels. The locomotive speed limit is therefore determined by the maximum permissible rotation speed of the motor armature. Exceeding this maximum could result in serious damage to the traction motors.

Various gear ratios are available to suit specific locomotive operating requirements . For each gear ratio, there is a maximum operating speed. This information is given in the "General Data" section at the beginning of this manual.

Although not basically applied, overspeed protective equipment is available for installation on locomotives . This consists of an electro-pneumatic arrangement with many possible variations to suit specific requirements. In general however, an electrical microswitch in the speed recorder is used to detect the overspeed. This switch in turn causes certain air brake functions to occur to reduce the train speed."

As previously suggested the existing "OverspeedMonitor" is designed to monitor the track speed conditions rather then the overspeed limit of the locomotive. Therefore as proposed I was going to clone the existing OverspeedMonitor and rename it to something like LocomotiveOverspeedMonitor. It would be triggered (if needed) by the value in the MaxVelocity parameter.

Given the current changes in the TCS system, I am wondering if one of the developers already working in this area could implement this function on my behalf? As this would prevent any issues with code merges, etc in the Unstable version.

Thanks

[joe_star]

steamer_ctn, on 20 May 2020 - 09:16 PM, said:

Whilst reading a diesel locomotive operational manual (EMD SD18) I came across the following comment which I felt might be relevant and of interest to some in regard to the design speed of the locomotive.

"LOCOMOTIVE SPEED LIMIT
The maximum speed at which the locomotive may be safely operated is determined by the gear ratio. This ratio is expressed as a double number such as 62-15. The 62 indicates the number of teeth on the axle gear while the 15 represents the number of teeth on the traction motor pinion gear.

Since the two gears are meshed together, it can be seen that for this particular ratio, the motor armature turns approximately four times for every one revolution of the driving wheels. The locomotive speed limit is therefore determined by the maximum permissible rotation speed of the motor armature. Exceeding this maximum could result in serious damage to the traction motors.

Various gear ratios are available to suit specific locomotive operating requirements . For each gear ratio, there is a maximum operating speed. This information is given in the "General Data" section at the beginning of this manual.

Although not basically applied, overspeed protective equipment is available for installation on locomotives . This consists of an electro-pneumatic arrangement with many possible variations to suit specific requirements. In general however, an electrical microswitch in the speed recorder is used to detect the overspeed. This switch in turn causes certain air brake functions to occur to reduce the train speed."

As previously suggested the existing "OverspeedMonitor" is designed to monitor the track speed conditions rather then the overspeed limit of the locomotive. Therefore as proposed I was going to clone the existing OverspeedMonitor and rename it to something like LocomotiveOverspeedMonitor. It would be triggered (if needed) by the value in the MaxVelocity parameter.

Given the current changes in the TCS system, I am wondering if one of the developers already working in this area could implement this function on my behalf? As this would prevent any issues with code merges, etc in the Unstable version.

Thanks

This is correct. The gear ratios are vital in determining the actual top speed of the locomotives in question. The same powered and equipped locomotive may be geared differently to serve passenger or freight purposes, with the former having a higher top speed at the loss of lower range tractive effort, and vice versa. This distinction is clearly demonstrated by the Indian Railways passenger WDP-4, vs its freight counterpart WDG-4

[Weter]

There are multiple speed limits:
-for bogies (that centrifugal force, which can destroy traction motors)
(this is essential for transportation of "cold" stock as well)
-for diesel (limited by DGU's maximal available power output)
There is also limitation, caused by magnetic saturation of motor's core
(this can be somehow widened by field weakening)