Omaha, Nebr. - Tuesday, 24 March 2009.
Here’s a question that occurred to me today and it concerns an unusual piece of equipment that the Canadian Pacific Railway operated in the wintertime.
As the weather gets colder, many little microleaks develop within a train’s air brake system. These leaks happen where glad hand gaskets join, at slip joints, maybe around the angle cocks, and possibly within a car mounted control valve because some internal appurtenance didn’t seat properly. Under the most extreme conditions, keeping a train “pumped up” can be a real challenge.
Before the widespread adoption of distributed power, Canadian Pacific developed a unique solution to this cold weather challenge: Air Repeater Cars.
As I recall reading in Trains Magazine many decades ago, these Air Repeater Cars were recycled EMD 4-axle B-units that had their original prime movers, electrical systems, and traction motors removed. Inside each car body was a much smaller diesel engine that drove an air compressor that was hooked up to one or more main reservoir tanks, some control valves, and a branch pipe connected to the train line air. These cars also had blocks of concrete ballast to achieve the proper weight that their Blomberg trucks required.
So here’s my question: Did these Air Repeater Cars add and decrease train line air pressure by means of telemetry commands received by radio from the locomotive, or did they operate off of a “sense-and-react” technology? By “sense-and-react” technology, let me explain using the following ex
First let’s clear up one misconception, CP started using DPU, or as they called them Robots, in the late 1960’s and any radio dead spots have long since been corrected by the use of repeater stations.
But the real problem of brake pipe pressure loss didn’t occur in the mountains, With the arrival of SD-40’s and Robots, the pulling power of the engines and the train lengths between engines pretty well dealt with pressure loss. The real problem occurred on the prairies. Once SD-40’s came into use, they could pull far more tonnage than they could keep up brake pipe pressure in. My father was a dispatcher on the Laggan Sub west of Calgary and the Brooks and Maple Creek Sub’s to the east from 1965 to 1985. When it is -35 degrees F. with a west wind of say 10 MPH, a westbound train couldn’t keep up pressure in a train any longer than they ran in steam day’s. This created a lot of talk among many departments and no solution could ever really be found. It really looked like the only way they were going to get around it would have been to develop a system that would have involved long manifest trains coupled up using semi permanent joints and shop forces.
When I heard that CP was planning to run 15,000 foot trains in the future I really had to laugh because they are relying on cutting edge 19th century technology to pass the air from one car to the next. I really would like to know how they plan to do that, as I got the sense from the article you saw that the converted B unit plan was a failure.
AgentKid
[quote user=“Bob-Fryml”]
Omaha, Nebr. - Tuesday, 24 March 2009.
Here’s a question that occurred to me today and it concerns an unusual piece of equipment that the Canadian Pacific Railway operated in the wintertime.
As the weather gets colder, many little microleaks develop within a train’s air brake system. These leaks happen where glad hand gaskets join, at slip joints, maybe around the angle cocks, and possibly within a car mounted control valve because some internal appurtenance didn’t seat properly. Under the most extreme conditions, keeping a train “pumped up” can be a real challenge.
Before the widespread adoption of distributed power, Canadian Pacific developed a unique solution to this cold weather challenge: Air Repeater Cars.
As I recall reading in Trains Magazine many decades ago, these Air Repeater Cars were recycled EMD 4-axle B-units that had their original prime movers, electrical systems, and traction motors removed. Inside each car body was a much smaller diesel engine that drove an air compressor that was hooked up to one or more main reservoir tanks, some control valves, and a branch pipe connected to the train line air. These cars also had blocks of concrete ballast to achieve the proper weight that their Blomberg trucks required.
So here’s my question: Did these Air Repeater Cars add and decrease train line air pressure by means of telemetry commands received by radio from the locomotive, or did they operate off of a “sense-and-react” technology? By “sense-and-react” technology, let me explain using the following example.
Say a locomotive i