Now the Theory of operation on the cars:
With the angle cock to the engine open and the last angle cock in the
train closed this provides the sealed train line for operation. For sake
of argument well focus on just one car.
First start of system:
The train line is set for max air Which in my case is 40 psi.
The check valve opens to allow air to charge the tank on the car and
apply pressure on the front of the cylinder, also the rear of the
cylinder has 40 psi on it.
Now when equalization occurs ie the tank on the car is charged and the
train line stablizes at 40 psi then a miracle of Physics occur. The
pressure on the front side of the cylinder is 2psi lower that the train line
"this is because the cracking pressure of the Clippard check valve
happens to be 2psi". So in this case the front of the cylider has 38psi
on it and the back has 40 psi. This in combination with the fact that
the front side of the cylinder is a smaller volume "because the piston
shaft is taking up space". The cylinder moves to the released position
"full extended".
Now when a reduction in the train line occurs the pressure on the back of the cylinder drops to below the front pressure and the cylinder begins to retract. The Air tank on the car cannot discharge to the main line because of the check valve. Therefore as the train line is reduced the more force is applied to the retracting rod. When the train line is fully reduced the full force is now placed on the front of the cylinder and the brake is full on.
Releasing the brakes is the same process as starting from scratch except this time you only have to charge the train line and any loss off the air tank on the car.
Emergency brakes happens just as in the real ones. You break an air line the loss of air on the back of the cylinder causes full brake on the car. Brakes will release when the line fault has been corrected.
Last Item moving the car in the yard.
Just like the real boys there is a valve on the car that when opened
will allow the tank to discharge into the train line. Thus to move the
car that has its brake set close both angle cocks then open the brake
release valve this will equalize the pressures and release the brake
cylinder. Once this occcures the release valve should be closed and the
car placed. then to set the brakes just open one of the angle cocks to
set the brakes again. I have found that this can be done about three
times on a single charge of the air tank on the car.
As far as mechanical advantages in the system the cylinder I chose gives 90% force to pressure. This coupled to the brake rigging from moutain car co. provides me with a shoe force far in excess of the rail holding capability of the wheel. In other words in a panic stop I SLIDE! Any more force is not needed.
The only springs I have in my system are the same as whats on Mountain Cars rigging This is only to guarantee that the shoes on the truck return to the off position when the cylinder lets off.