[steamer_ctn]

I am currently preparing to make some changes to accommodate a vacuum (steam) ejector.

In researching its operation I have come across this publication:

Dreadnought_Ejector

I am interested in the operation of the small ejector steam valve (labelled 'e' in the above publication). According to this publication it appears that this valve can be adjusted up and down to set the steam pressure applied to the small ejector.

I believe that MSTS uses the "J" key to just toggle this valve on/off.

Is anybody able to point to a publication or confirm whether the small ejector steam valve is and On/Off control or an Up/Down adjustable control to allow variance of steam pressure to the ejector?

Thanks

[copperpen]

According to an old book I have on locomotive management that valve is adjustable to vary steam pressure supplied to the ejector. The Dreadnought could work from as low as 90 psi. The J key in MSTS only turned the small ejector on or off, had nothing to do with steam pressure. I would make the operation of the steam pressure adjustment an eng file item with a limited range of adjustment, say 90 to 110 psi. That would then mean boiler pressure has to be maintained at least to that figure, or the brakes will start to apply. I think the Gresham & Craven Type C would operate at lower pressures, but used more steam than the Dreadnought or other later types.

[steamer_ctn]

copperpen, on 23 November 2016 - 03:12 AM, said:

According to an old book I have on locomotive management that valve is adjustable to vary steam pressure supplied to the ejector. The Dreadnought could work from as low as 90 psi. The J key in MSTS only turned the small ejector on or off, had nothing to do with steam pressure. I would make the operation of the steam pressure adjustment an eng file item with a limited range of adjustment, say 90 to 110 psi. That would then mean boiler pressure has to be maintained at least to that figure, or the brakes will start to apply. I think the Gresham & Craven Type C would operate at lower pressures, but used more steam than the Dreadnought or other later types.

The other alternative is to have it adjustable by the player, ie J to increase pressure, and perhaps Shift+J (if available) to decrease pressure. This would make it consistent with other adjustable steam devices, such as the injectors, steam heating, etc.

The other point is should this operation only be available in Manual firing mode, and not Auto Fireman mode?

What about diesel locomotives fitted with vacuum pumps, was this an on/off control?

[copperpen]

The ejector should be available in both modes because it is an essential part of the braking system. The item e is not the actual ejector, merely the valve that allows the admission of steam at a set pressure. The small ejector control itself regulates how much steam is used by virtue of being a variable control to maintain a required level of vacuum while the train is running. This is why I suggested an eng file setting for the item e which is not the actual ejector. When at a stop, the small ejector should in fact be off and if I am reading things right, is actually stopped by placing the brake handle in either the apply or lap positons. Moving the handle to the release position activates the large ejector to release the brakes and moving to the running position allows the small ejector to maintain the vacuum.

Diesel locomotives had a system driven from the main engine, this would be an automatic system to maintain the vacuum, and some steam engines, notably on the Great Western had a mechanical small ejector driven by the crosshead. In both steam and diesel the main braking had the facility for partial applications to slow the train, with brake release the small ejector would once again take over to maintain the required vacuum.

In operation the main brake handle of the Westinghouse vacuum brake had 5 positions, Full release, two running positions which regulated the vacuum, lap, and full application. Full application was in two stages, initial to make a set at which point the handle goes back to Lap. By successive use of the application and lap the brake force could be increased in increments. Full movement in the braking position gave full application. The two running positions would equate to the small ejector of the Dreadnought. I think that it is this Westinghouse system that the current system is trying unsuccessfully to model. Unsuccessful because there is no steam to drive it.

The Dreadnought would only have had 4 main handle positions, Release, Running, Lap and Apply, with the lap and apply working in a similar way to the Westinghouse version.

[steamer_ctn]

Thanks for the feedback.

For better clarity there is a colored diagram on page 156 of this publication, Operation Book for Locomotive Drivers. The labels on the diagram correspond to the lower case letters in the earlier reference document.

copperpen, on 23 November 2016 - 01:31 PM, said:

When at a stop, the small ejector should in fact be off and if I am reading things right, is actually stopped by placing the brake handle in either the apply or lap positons. Moving the handle to the release position activates the large ejector to release the brakes and moving to the running position allows the small ejector to maintain the vacuum.

Based upon my reading of the document - the small ejector is isolated from the train pipe by moving the brake control handle (2nd handle on the Dreadnought). So I agree that the small ejector will have no effect when the brake is in the "Brake On" position, however it will still have steam flowing through it.

I agree that the brake control handle controls whether the small or large or both ejectors are "connected" to the train pipe, and thus their impact upon braking.

As the small ejector is used to overcome train pipe leakage when in the RUNNING position, the small ejector steam valve would be set by the locomotive driver probably infrequently during the trip depending upon the train length, etc to match train pipe leakage requirements.

Thus the controls associated with vacuum braking appear to be as follows:
i) Brake Control Handle - controls the air and vacuum flows into and out of the train pipe. (Corresponds with existing OR Brake Controllers) - appears to be a three position controller - BRAKE ON / RUNNING / BRAKE OFF (What document references the LAP position?)
ii) Small Ejector Steam Valve - used to control the amount of steam flowing into the ejector, and hence the vacuum creation ability. Used typically to manage train pipe leakage - adjusted infrequently by the driver (Appears to correspond to the J key in MSTS)

I believe that the J key implementation allowed for a fixed on/off operation of the small ejector, through a fixed statement in the ENG file. Since train pipe leakage was not modeled in MSTS, this model was probably good enough for a "static" system. However given that OR has the ability to model train pipe leakage, this ideally will require the setting of the small ejector steam valve to an appropriate pressure setting to match train pipe leakage.

Thus I believe that a variable pressure setting arrangement for the Small Ejector would be more realistic, however I am happy to go with the consensus of vacuum brake users.

copperpen, on 23 November 2016 - 01:31 PM, said:

Diesel locomotives had a system driven from the main engine, this would be an automatic system to maintain the vacuum, and some steam engines, notably on the Great Western had a mechanical small ejector driven by the crosshead. In both steam and diesel the main braking had the facility for partial applications to slow the train, with brake release the small ejector would once again take over to maintain the required vacuum.

I agree that this was probably the case, and the brake controller would allow for partial applications. (OR brake controllers appear to allow for partial application and releases)

I assume that the vacuum pump (certainly in the case of the diesels) would turn on and off as required based upon the position of the brake controller.In the steam locomotive the pump would run continuously, but would be isolated as required from the train pipe.

[copperpen]

The Lap position was used by the Westinghouse Vacuum Brake. I assumed that the Dreadnought would have a similar arrangement, but looking at the diagram, it is slightly different in operation. There is a partial application position before the full brake application is applied, so where the Westinghouse could make a partial application and maintain it by placing the handle in the Lap position, the Dreadnought could make a partial application, and maintain it by keeping the handle in that position, returning to Running allowed the small ejector to release the brakes again, unless it was turned off or down low.

I will copy the relevant pages from my book and send to you so you will be able to study the Westinghouse Vacuum brake with its 5 position brake handle.

Once again, item e is not the small ejector, it is the steam admission valve for both large and small ejector and is set to control the steam pressure. In the release position the large ejector was in use to fast release the brakes, then moved to the running position. The small ejector was then used to maintain the vacuum by varying the amount of steam used at the pressure set by item e.

[steamer_ctn]

copperpen, on 24 November 2016 - 03:42 AM, said:

I will copy the relevant pages from my book and send to you so you will be able to study the Westinghouse Vacuum brake with its 5 position brake handle.

Thanks, that will provide some useful background information.

However as I understand it the Dreadnought ejector was one of the most commonly used, and therefore I will focus on it as the base model

copperpen, on 24 November 2016 - 03:42 AM, said:

Once again, item e is not the small ejector, it is the steam admission valve for both large and small ejector and is set to control the steam pressure.

On the diagram that I have of a Dreadnought, it shows the large and small ejector with independent steam feeds (through different "admission" valves).

I think that I now have sufficient detail to start implementing a form of ejector control based upon the Dreadnought vacuum ejector. I will use the J key to increase steam pressure applied to the small ejector, and SHFT-J to decrease steam pressure to the small ejector.

[copperpen]

Still not quite right as far as I can see. The small ejector controlled the amount of steam used in creating and holding a vacuum. The steam pressure was set using a different control, and looking at the diagram in the handbook you linked to, this is done with a spanner to set a pressure, which said manual suggests that 120psi was the optimum. So my initial response is correct in that we have three controls to consider. Main brake handle uses MSTS style tokens for actions. Small ejector where fitted which controls steam volume used. and the third control which adjusts steam pressure, usually a one time only setting, so can be controlled by an eng file data line. This means that if the boiler pressure falls below the set pressure, brakes begin to set, bringing the train to a stop.

Once the Dreadnought is done, can we also have the Great Western crosshead driven pump that was used instead of the small ejector.

[copperpen]

If J is to be used to control steam pressure, we will need some form of visual reference for this pressure, which is supposed to be 120psi for optimal performance.

Can we also have the Great Western crosshead driven vac pump when Dreadnought is finished. It is used in MSTS.

[steamer_ctn]

copperpen, on 25 November 2016 - 07:20 AM, said:

The steam pressure was set using a different control, and looking at the diagram in the handbook you linked to, this is done with a spanner to set a pressure, which said manual suggests that 120psi was the optimum. So my initial response is correct in that we have three controls to consider. Main brake handle uses MSTS style tokens for actions. Small ejector where fitted which controls steam volume used. and the third control which adjusts steam pressure, usually a one time only setting, so can be controlled by an eng file data line. This means that if the boiler pressure falls below the set pressure, brakes begin to set, bringing the train to a stop.

I can't see any reference to settings done by spanner, the supporting text in the Dreadnought document tends to suggest that there are only two controls and that the small ejector steam valve was set by hand to control the steam pressure.

Quoting from the document:

At the same time steam passes to the small cone (d) through the small ejector steam valve (e). This valve is set by hand so as to wire draw and reduce the steam pressure to about 120 lbs, which is the pressure at which this cone is designed to give its greatest
efficiency.

copperpen, on 25 November 2016 - 07:20 AM, said:

Once the Dreadnought is done, can we also have the Great Western crosshead driven pump that was used instead of the small ejector.

I will have a look at it, and see if it can be added.

copperpen, on 25 November 2016 - 07:27 AM, said:

If J is to be used to control steam pressure, we will need some form of visual reference for this pressure, which is supposed to be 120psi for optimal performance.

I can add this to the Brake Information HUD.

Though the pressure is probably not the critical parameter, instead it will be how the ejector balances the train pipe leakage, thus the pressure may not need to be set @ 120psi every time, it could vary depending upon the train conditions.