Westinghouse Air Brake Pressures World Wide

Hey all,

I've been collecting books of Ebay based on Australian Locomotive Brake Specs for Victoria over the past 2 years, these books cover up to 100 years and have been putting that data into the trainz physics based on the rollingstock era, I've been googling around for British and U.S.A Brake Pressures as I'd like to learn more about the operation other counties and the pressures they use, however Google has put me into a dead end, here's a quote from one of the pages I looked at

The compressor on the locomotive charges the main reservoir with air at 125–140 psi (8.6–9.7 bar; 860–970 kPa). The train brakes are released by admitting air to the train pipe through the engineer's brake valve. A fully charged brake pipe is typically 70–90 psi (4.8–6.2 bar; 480–620 kPa) for freight trains and 110 psi (7.6 bar; 760 kPa) for passenger trains.

Click to expand...

But that's all the stuff that keeps popping up and doesn't say the likely pressures used in other Counties, for an example: The Victorian Railways in Australia was fitting the Westinghouse system to all locomotives from 1886 and on rollingstock from 1890 we had a 60 PSI (Goods) 72 PSI (Passenger) Brake Pipe and a 90-100 PSI Main Res, the reduction is 22 PSI (150kpa Metric), by 1900s 72PSI was the Max Brake Pipe Pressure, when the EP brake came out the pressure was increased to 77PSI, from 1950 the Main Res Pressure was increased to 110-116 PSI, then from 1980s the Main Res was 116-120PSI (800-825kpa Metric) while brake pipe remained 72PSI (500kpa Metric).

As I'm a person who also develops rollingstock physics for trainz I've had some requests from people asking me to build a steam physic or a diesel physic and I'd like to use the real brake pressures from that era and country the physic is for to make it a little more realistic.

The default trainz brake specs are

Main Res: 119-120PSI
Brake Pipe: 69-70PSI
Brake Cylinder: 55-56PSI
Reduction Amount: 26PSI

Their's also some physics out there that can get you from 40mph to 10mph in just a few seconds of putting the brake on which is very unrealistic, however this is caused by the brake-ratio being too high, brake ratio is a braking effort percentage over the overall mass, so 120ton for 60% nominal brake ratio is a value of 73155.377448, brake-ratio is also calculated based on adhesion the wheels have to the rails so they don't skid at full brake cylinder pressure, so a freight car or passenger car with good adhesion can get up to a 92% brake ratio Unloaded Tare, some of the physics I've seen for trainz puts the brake ratio from 110% to 200% which is what causes the sudden speed loss when you tap the independent brake when running light engine.

Anyways,

Hopefully some people will be able to attack my post and give some corrections if I error'ed somewhere, my mind isn't 100% today so what I wrote probably didn't make any sense either, lol.

Cheers.

Depends what you mean by a few seconds of putting on the brake

Are we talking a self lapping brake system or a non self lapping brake system.

Non self lapping systems are common in steam locomotives (the engine at work uses 6ET for example) and unless you put it into lap, it will continue to drain pressure from the brake pipe until all the air is gone, locking up the brakes.

A self lapping system (like the 26L we have in 21 and 1203) will only reduce the pressure in the brake pipe a predetermined amount, depending on how far you move the brake handle, to a max of 20 PSI reduction, there is also a position to zero the air, and emergency of course.

Main reservoir pressure will vary depending on the locomotive, for example Shay 9 is set at 115 PSI, while the 1203 is set to 120. Depends on the condition of the air tanks, the type of service (lots of hills and need for lots of brakes) length of train, and so on. Typically Freight trains would run the brake pipe anywhere from 70 up to 90 PSI, passenger would run 90-110, depending on the rules of the subdivision.

But remember, with your brake pipe at 110 PSI, you need a higher Main reservoir pressure to charge the line back up when you release. A good example was the IRM used to run their main reservoir of the 1630 at 90 PSI, and the brake pipe at 90 PSI, requiring the air compressor to change the brake pipe back up, not a very good practice, thankfully, 1630 has better air tanks now.

Also, remember that the brake application pressure on the cars via the triple valve is 3x the reduction in brake pipe pressure. For example a 5 PSI reduction (or set as its known) will result in a 15 PSI application on the brake cylinder on the car. This is why its important to recharge the train line quickly, so that you can recharge the Aux reservoir on the cars themselves, and bring them back up to brake pipe pressure fast.