[darwins]

The final part (errors and omissions excepted) deals with dual braked locomotives.

During the change over from Direct Vacuum Brakes to Automatic Vacuum Brakes in Austria, some locos were fitted with an automatic vacuum brake for the train, but retained a direct brake on the locomotive (and/or tender).
The two different systems were completely independent with no connection.

https://i.imgur.com/T2Pjk6h.jpg

Another case where the two brake systems were separate was the Highland Railway Castle class.
The locos were built with vacuum brakes, but some were also fitted with air brake equipment for working air braked trains.

Working vacuum braked trains was normal:

https://i.imgur.com/IJg90Bk.jpg

Working air braked trains, the driver had to use two different brake valves:

https://i.imgur.com/xeleypJ.jpg

Some dual braked locomotives used proportional valves so that one brake system could control the other.

LBSCR locos were normally air braked:

https://i.imgur.com/llHzyPC.jpg

The vacuum brake valve when used could control the air brakes by means of a "Jackson valve":

https://i.imgur.com/800FFcp.jpg

Some companies used the opposite system, where an air train brake could control a vacuum brake.

Where the locomotive brakes were steam brakes they might be controlled either by air:

https://i.imgur.com/IldE2CI.jpg

or by vacuum:

https://i.imgur.com/wDb88Ia.jpg

In modern times UK, India, Spain and Portugal have changed from vacuum brakes to air brakes.

For modern dual braked diesel and electric locomotives the air brake system is the principal system:

https://i.imgur.com/fEsreYq.jpg

The air brake valve controls the vacuum brakes when these are being used:

https://i.imgur.com/v0utxHI.jpg

[darwins]

Missed out above are the locomotives that had two complete braking systems.

The Metropolitan Railway Electric Locomotives used either Air or Vacuum brakes.

https://i.imgur.com/ksPNRny.jpg

The District Railway Electric Locomotives were similar, except...
...like an old "suck" / "blow" vacuum cleaner they ran the compressor in reverse for vacuum braking!

https://i.imgur.com/GmlO6BC.jpg

[Weter]

Are You about LT's lines? As Sarah Siddons?

[darwins]

Yes, as built Sarah Siddons was like that. (Not any more as she now has twin pipe air brakes only.)

[Traindude]

Just wanted to share some Trello Cards for ideas that I have pitched on this thread in the past:

Variable Main Reservoir Charging Rates (Diesel)
Adjustable Air Compressor Steam Usage Rates (Steam)

[Weter]

Good point, thanks.
Maybe some more later...

[darwins]

Traindude, on 16 February 2023 - 08:34 AM, said:

Just wanted to share some Trello Cards for ideas that I have pitched on this thread in the past:

Variable Main Reservoir Charging Rates (Diesel)
Adjustable Air Compressor Steam Usage Rates (Steam)

I believe there are four possible options for compressors:

1. Rolling stock without compressors
Some early electric trains on short routes were built without compressors.
The main reservoirs were recharged at terminal stations.
We would need to add a fuel pick up type ( Air ) into OR to model these.

2. Steam Pump compressors
Steam compressors are generally On/Off controlled by governors depending on Main Reservoir pressure.
We can model the on/off operation and adjust the charging rates.
We may need to find a way to vary steam consumption.
I am not sure if there were ever manually controlled compressors, but there is a compressor on/off control inherited from MSTS.

3. Electric compressors
Also On/Off controlled by governors depending on Main Reservoir pressure.
We can model the on/off operation and adjust the charging rates.
These seem to be modelled reasonably well for diesel and electric locos.
It should be possible to add these to trailer cars in multiple unit trains though.

4. Mechanical Rotary compressors
For these the charging rate depends on the diesel engine rpm.

[darwins]

For vacuum brakes, devices that suck are a bit more diverse.

In most cases they suck air directly from the brake pipe via the driver's brake valve, although a few examples do include a reservoir which is then connected to the brake pipe via the driver's brake valve.

The different types of device are:

Ejectors - steam is used to create a vacuum, most steam locomotives had a 'large ejector' for 'quick release' plus a 'small ejector' for 'maintaining' the vacuum and release. (Some locomotives had only a single ejector.)

1. Separate Ejectors - the driver controls the steam flow to the large ejector with a valve that is separate from the brake valve.

2. Combination Ejectors - steam is automatically supplied to the large ejector when the brake valve is moved to the 'Release' position.

3. Vacuum Pumps - to 'maintain' vacuum - driven from crosshead, dependent on velocity of locomotive.

4. Electrical Exhausters ( fast/slow type )
These are the only exhausters currently available in OR. They run at 'fast speed' for 'quick release' and at 'slow speed' or 'maintaining' the vacuum and release. They may be controlled either by the driver's brake valve or by a separate 'Exhauster Fast Speed' button.

5. Electrical Exhausters ( on/off type )
These were found on some older electric trains and worked in a similar way to on/off compressors, except that where no reservoir was present they would be activated by the vacuum in the train pipe.

6. Mechanical Exhausters
The rate of evacuation depending on the speed of the engine crankshaft. These would normally be connected to a reservoir.

[Laci1959]

https://kephost.net/p/ODY4NjYz.png

Hello.

The brake release pedal of the locomotive. If it is held down when braking with the train brake, the locomotive does not brake. If used while braking, it will dissolve.
Push the locomotive brake, i.e. the locomotive.
I think this is the Bail on off function, which was mentioned earlier

Sincerely, Laci 1959

[Traindude]

darwins, on 16 February 2023 - 11:54 PM, said:

2. Steam Pump compressors
Steam compressors are generally On/Off controlled by governors depending on Main Reservoir pressure.
We can model the on/off operation and adjust the charging rates.
We may need to find a way to vary steam consumption.
I am not sure if there were ever manually controlled compressors, but there is a compressor on/off control inherited from MSTS.

Oh, and by the way, I forgot to mention it, but when the maximum reservoir pressure is reached, a steam-driven air compressor doesn't shut off 100%. Instead, the governor allows a small trickle of steam to flow to the compressor in a sort of "idle" state. This allows the compressor pistons to slowly creep up and down until the reservoir pressure once again drops. This was mainly to prevent condensation from accumulating in the compressor steam cylinders, but it also ensured the compressor was still receiving lubrication, prevented the pistons from seizing up (especially in colder weather), and to provide some compensation for main reservoir leakage. The "idle" speed was not enough to increase the main reservoir pressure significantly, so it stands to reason that, depending on the size of the orifice in the governor body that the steam must pass through in the "idle" state, the usage rate would be no more than maybe 2-4 lbs/hr.