[Traindude]

In researrching how to fine tune the air brakes on the rolling stock I download, I discovered something that I am not sure is implemented in OR.

In addition to the Auxiliary and Emergency reservoirs, many passenger cars with the "UC" type brake system had a "service reservoir." This was used in conjunction with the auxiliary reservoir to provide the necessary braking force in service applications.

More info can be found here:

https://heritagerail...ve%20manual.pdf

Is this feature implemented in OR at this time? If not, I am more than willing to create a Trello card for this to be implemented at a later date.

[darwins]

I am trying to understand what a service reservoir is. Does the following description make some sense:
UC brake system

Passenger Operation = Graduated_Release_Triple_Valve

Auxiliary Reservoir is recharged from Emergency Reservoir (rather than brake pipe)

When releasing brakes
( i ) The auxiliary reservoir is first recharged (from Emergency reservoir) until Aux Res pressure is 7psi less than brake pipe pressure.
( ii ) When Aux Res pressure is 7 psi less than brake pipe pressure then Service Reservoir is recharged from emergency reservoir.

( iii ) If a re-application is required after a partial release, all of the air comes from the Auxiliary reservoir, as it has a higher pressure than the Service Reservoir at that time.
During service brake application if Aux Res pressure > Service Res pressure than Aux Res will transfer air to brake cylinder, but if Aux Res pressure is less than or equal to Service Res pressure then air from both with transfer to brake cylinder.


Freight Operation = Triple_Valve

Auxiliary Reservoir is recharged from the brake pipe (train line)

Service Reservoir is recharged from Emergency Reservoir (at the same time).
During application then Auxiliary and Service reservoir always act together.


With 70psi in brake pipe then at equalisation 50psi in BC and 50psi in Aux Res and Service Res.

BC has safety valve set to max 60 psi.

With 110psi in brake pipe then drop of 24 psi in brake pipe produces 60 psi in BC.
Further reductions in brake pipe do not give higher pressure in BC.
Is that correct?

Have I missed anything important?
Would you be able to help with figures for charging rates for the various reservoirs by the various methods? (Also brake application and release rates)
Do I presume that in either case the emergency reservoir would only begin to recharge after the auxiliary and service reservoirs had reached the same pressure as the emergency reservoir? Some Westinghouse documents also mention a "supplementary reservoir". What is that?

[dajones]

It been a while since I've looked at this, but I think the main purpose of the service reservoir is to increase the range a brake cylinder sizes that a given value works with. To increase the brake force for a given pressure in the real world requires increasing the brake cylinder area. So you need to increase the brake cylinder diameter or the number of brake cylinders. And that would normally require an increase in the aux. res. volume to keep it at 2.5 times the brake cylinders. But that in turn would require a different valve in order to get the same response to brake pipe changes. So, instead of using a different value for each brake cylinder size, they keep the aux. res. size about the same and add the service res. so that the combination of aux. plus service reservoirs equals 2.5 times the brake cylinder volume. So the aux. res. supplies the air to operate the brake valve, but both operate the brake cylinder.

You'll notice that the document also lists different chokes that a installed in the pipe bracket for different brake cylinder sizes. These adjust the air flow rate so the response times are about the same.

Doug