Let’s continue on the East Job.
But before we set out, a little more explanation on how air brakes work is in order than I gave in the last post. An alert reader pointed out that I left out some details. A more detailed explanation is offered at the end of this post.
The conductor lines the engine over to the main line to pick up the two empty box cars. Besides coupling into the box cars, connecting the air hose between the engine and the first box car, turning both the angle cock on the engine and the box car (it was closed when the cars were brought into Sanderson as it was the last car then), the conductor has to go back to the end of the second box car and close its angle cock and lift the pin lifter to uncouple it from the covered hopper. Never reach over the coupler to close or open an angle cock, cross over the end of the car to get to the side the angle cock is on and prevent body parts from getting caught in the coupler should the car move.
The engine pulls the two empty box cars clear of the switch to the passing track. The rest of the train from Pecos waits on the main line. We’ve been switching for some time now so it’s good we didn’t block any road crossings with those cars.
Shoving the empty box cars into the Lazy W Ranch spur. Yeah, the angle cock on this end of the box car should be closed, but don’t those scale width wheels under the box car look good. Plastic ones that came with a car kit from a long gone manufacturer back in the 1980’s. The LCN wishes it could have obtained more– never had derailment problems with them. (However, Exactrail and Athearn do make pretty good scale .088″ wheels today.)
The conductor sets the hand brakes on the empty box cars before cutting away. Those high brakes wheels tell you how old you are getting. Can’t believe all box cars and hoppers had them back in the good old days. Close the angle cock on the engine, lift the pin lifter, and lets go pick up a couple of loads of volcanic rock down at the other end of Sanderson.
The volcanic rock loads were shoved in from this end so the angle cock needs to be closed, might as well do that as we go by on our way to the other end.
We back into the loads from the other end. If there is any doubt about the coupler pins dropping we’ll tell the engineer to stretch them to verify a good joint.
Once the cars are laced up (air hoses connected, angle cocks checked for being open) and the hand brakes knocked off, we pump the brakes up on the cars, then do a brake set to verify the brakes on the cars are working before pulling them out to the main track.
In Part III, we will finish the run. However, before I finish this post, below is a chance to learn a bit more on air brake operations. Spotting a car and making up trains is hard work in the real world! (I haven’t even mentioned about lugging on couplers when they aren’t lined up. Talk about hard work! Those things are heavy.)
How do air brakes work? (A more technical primer)
The brakes on a railcar apply when there is a reduction in the train line air pressure, a break in the train line occurs, or the car is being uncoupled from because air in the air reservoir on the car is directed into the brake cylinder by the triple valve and pushes out the brake piston.
If you bleed all the air out of the air reservoir on the car, the brakes release and cannot be reset until the air reservoir is charged up again. So if you want to kick cars (the engine shoves them up to a speed judged fast enough and someone running along side the car lifts the pin lifter, the engine slows, the cars will continue to roll into what ever track the switches are lined for, stopping either when they hit cars already standing on that track, or someone on the rolling car sets the hand brake, a very common technique in a flat rail yard) you have to bleed the cars off so they will roll. A good switch crew can have three or four groups of cars rolling simultaneously into different yard tracks when kicking cars. Before radios the hand signals for signaling how many cars in the cut and into which track they were to go was pretty elaborate.
A car spotted on a siding can bleed itself off gradually as air seeps around the brake system seals. If the seals are in poor condition or there is a lot of dirt around the seals the brakes can release in a matter of days, or hours, or even minutes. The hand brake is an independent mechanical system from the air system. Setting the car’s hand brake will keep the brake shoes on one axle from releasing even if the air brake system bleeds off.
Pumping up the air when a car or cars have been coupled into is filling the air reservoirs on all the cars and the triple valve releasing any air pressure in the brake cylinder.
The triple valve is described as being so named as it performs three functions: Charging air into an air tank ready to be used, applying the brakes, and releasing them.
- If the pressure in the train line is lower than that of the reservoir, the brake cylinder exhaust portal is closed and air from the car’s reservoir is fed into the brake cylinder to apply the brakes. This action continues until equilibrium between the brake pipe pressure and reservoir pressure is achieved. At that point, the airflow from the reservoir to the brake cylinder is lapped off and the cylinder is maintained at a constant pressure.
- If the pressure in the train line is higher than that of the reservoir, the triple valve connects the train line to the reservoir feed, causing the air pressure in the reservoir to increase. The triple valve also causes the brake cylinder to be exhausted to the atmosphere, releasing the brakes.
- As the pressure in the train line and that of the reservoir equalize, the triple valve closes, causing the air pressure in the reservoir and brake cylinder to be maintained at the current level.