Hi gang.
I was watching the Bailey yard web cam and noticed that when they are humping cuts there are at most a pair of cars or singles. Why not more than two cars coupled? Even if they are destined to the same bowl track there are not more than two.
http://www.visitnorthplatte.com/Golden-Spike-Live-Web-Cam.html
Thanks.
Pete
Here’s an assumption; take note of the first 3 letters…of the subject…
Retarders have an amount of retarding force and the obligation to reduce the humped cut’s speed to produce a coupling impact within boundaries.
Say that the retarders were able to release at 2 to 4 mph 3 131 ton cars which on a speed-sustaining .2 % downgrade would make an acceptable damage free joint.
Now say that the world has rotated and now coming off the hump are 3 cars, each weighing 143 tons, which is now pretty near universally accepted as the proper max. 4-axle car weight.
Just blew right by the retarder’s ability by 36 tons to slow the cars.
The release speed being unacceptably high, would dictate…2 cars not 3.
It probably has to do with the number of decisions the computer controlling retardation has to make. These decisions are controlled by weight, rollability of the cars, weather conditions, curvature of the bowl track, wind direction and speed, you name it. I’m not sure why it makes a difference in the quantity of cars cut off, but that’s the way it was done.
It also has to do with how far the pin-puller has to walk back to make the cut. The more cars that are on the down side of the hump crest before the cars are cut off, the further back the pin-puller has to go to get the pin before the slack runs out. Two, or maybe three, loads is not much of a problem in most cases, but many more than that, and the slack has to be controlled, often by the same retarders that are responsible for slowing the cars down.
The two-car edict was forced down our throats at Proviso (which, many people don’t realize, is the only modern hump yard where switches and retarders are individually and manually controlled). As a practitioner of the art of retarder operation in this yard for many, many years (and as a pin-puller for more than a few years), I speak with a bit of experience on this. We handled all of the same considerations that a computer could, and did it all the time, with a faster reaction time when unexpected things (such as tracks filling up) would happen. And I would much prefer to handle a large cut of cars going to one destination as a single cut. I could slow them down to a speed at which downhill motion was barely perceptible, and the momentum of all that weight would take them off the lead, into the track, and against the cars already down there without moving them more than a matter of feet.
No more retarded conductors?[:)]Aren’t you glad you retired?
Good thing you’re on the other side of the continental divide there bubba.
Perhaps because of the sudden slack run-in action and the dynamics of the weight of the trailing cars suddenly shoving against the leading cars in the retarder as they’re being slowed (or vice-versa if the retarder is applied to the trailing cars). Someone with Carl’s experience could "feather’ / gradually apply the retarder force for the right amount for each car, but a computer might not know how to do that . . . [swg] [:-^]
Computers don’t count here as there were hump yards before computers controlled them. So, weight of the cars going down has to be a consideration as well as the length of the retarders themselves which would of course control the speed of the cars. And remember, too, cars were once a standard 40 ft. but grew to 60 feet in some cases, so…the reasons are several based on date of the pictures, size and weight of the cars, length of the retarders, and the speed of the cars Another factor I just thought of is the apex of the hump…perhaps no more than two cars could be over the hump when cut or something like that. And I believe I have seen more than two cars in a string going down certain larger, later hump yards.
Computers don’t count here as there were hump yards before computers controlled them. So, weight of the cars going down has to be a consideration as well as the length of the retarders themselves which would of course control the speed of the cars. And remember, too, cars were once a standard 40 ft. but grew to 60 feet in some cases, so…the reasons are several based on date of the pictures, size and weight of the cars, speed, and the hump itself. I believe I’ve seen pics of newer, modern hump work with more than two cars…
Carl.
Thank you. It is great to have the answers from someone who has been there and done that. I can see tonnage playing some part but not all cars being humped are full to capacity. Bailey is a relatively modern yard and I would figure that there had to be a reason why you see several pairs of cars going to the same bowl track instead of a cut of four or six. Computers are great machines but I guess they have no idea what slack is. Reminds me of the old saying, “Computers. What used to take days to screw up now only takes seconds.”
Thanks again.
Pete
Under ‘normal’ humping operations cars are shoved over the crest at a constant speed and will thus decend down the hump within a predicable speed range and require X amount of time to clear the leads for conflicting routes.
There is a defined amount of space between the crest of the hump and the master retarder. Cars are expected to be free rolling when they enter the master retarder. In most cases, cuts longer than 2 cars would not be free rolling when entering the master - they would still be being shoved by the hump engine waiting for the pin puller to make the cut on the longer cut. If the lead car(s) of the cut are being braked by the retarder before they have become ‘free rolling’ you will end up with a cut that has ‘stalled’ on the hump. That cut will then have to be shoved to it’s destination track and then the remainder of the train pulled back over the hump to resume humping operations. Shoving a cut over the hump to it’s destination track and then pulling the remainder of the train back over the hump to restart humping operations wastes time and decreases the efficiency of the hump.