Battleship Gons! Cool. I think F&C offer them in Resin for HO modelers.
That is a very intriguing brake arrangement on the brass model...never seen anything quite like it before.
The brake levers closest to the trucks would usually have two functions: activate the brake beams on the trucks and to allow the hand brakes to be set. Let's go to the left one to explain...
Ok, the brakes are off and the brakeman turns the wheel on the left end. It causes the lever to engage the brakes on the left truck...and pulls all of the brake rigging to the left which causes the right truck to have its brakes applied as well...but this isn't the case in your model...as the the brake wheel attaches elsewhere.
If the brakes are off and the engineer applies the automatic air brakes, it causes the pistons in the brake cylinders to be pushed out, pulling the levers and applying the brakes. If they are on, it causes the air in the brake cylinders to be released and gravity causes the brake shoes to fall of the wheels and push the levers back. Yes, gravity is what keeps the shoes off the wheels (and from causing trouble) when the brakes aren't being applied.
Although it isn't really needed to build the rigging...here is the basics of how Westinghouse designed his brakes...
Initially, they were straight air brakes. When the engineer applied the brakes, air was pumped from the engine into the brake line and into the brake cylinders applying the brakes. Its direct competitor (or at least most capable competitor) was Eames Vacuum brakes which did the same thing, but pumped the air out of the train line and cylinders...using atmospheric pressure to power the system. Atmospheric pressure is 13.7psi. Therefore, Eames could only get a force equivalent to around 10psi*the size of the brake cylinder. Westinghouse's originally was 70psi...70psi-13.7 is close to 60psi* the size of the brake cylinder. Still, there was one major problem...the train would lose braking power if anything happened to the line!
So, Westinghouse invented automatic airbrakes. Instead of pumping air into the line to brake...air pressure in the line is always maintained, and the brakes are applied when the pressure drops! The air used to apply the brakes rests in a reservoir beneath each car. The brains of this system was the triple valve. A slight drop in pressure caused light braking (such as going down a slight hill). A moderate drop caused normal braking power. A huge drop, such as an air hose being broken or a car becoming detached from the train, caused emergency braking. Obviously, the greatest weakness in this design was that a train can't brake continually...or else the reservoir will be drained and it will have NO braking power. For this reason, Eames brakes remained (and may still remain) common on elevated railroads and subways. Locomotives have straight airbrakes...for it would be silly to use automatic on them. The first railroads to adopt airbrakes were mostly mountain roads...since Eames system lost power at altitude (less atmospheric pressure).
Of the years, Westinghouse development many improvements...newer triple valves, higher pressure, and bigger air lines. It is also worth noting that not everyone used Westinghouse. Eames company eventually became the New York Airbrake Company and managed to grab, I believe, 25% of the market or so. The K style brakes, IIRC, were from around 1910 or so.
A few oddities about your brass car:
One, the brake wheel is on the right end...the top lever is clearly the brake wheel lever...which makes the two rods under the trucks quite odd...only one would usually be needed...perhaps it is due to the buckeye trucks.
Two, two brake cylinders and reservoirs is quite odd. I suspect it was to save money on more powerful, individual brake cylinders. The D&RGW did this on engines...two smaller airpumps rather than a newer, bigger, single pump. The VGN may have done that in house...using older cylinders...saving on $$$...and it may not have been standard on every car.
Three, the triple valve is the round thing on the side of that thing on the top, left of center. I suppose that it is some sort of aux reservoir or something (passenger cars sometimes had 3 reservoirs). Note that the piping has recharge lines going to each of the reservoirs...plus the triple valve...and the activating lines coming out of the triple valve and to one of the cylinders (but not both!?)
The reservoirs are also dinky! Very odd! Typically, freight car reservoirs, triple valves, and cylinders were single, integrated units. Passenger cars typically had them broken up.
My advice would be to use just a single K brake cylinder. Full brake rigging isn't very noticable unless you layout is 66" above the floor. Just adding the cylinder implies that more is there than in reality. Of course, I am hypocritical for suggesting this, for I can't allow my models not to receive full rigging...I love it whether anyone else appreciates it or not!
Michael