# Gravity Yard?



## jackpresley (Dec 19, 2017)

Been under the weather so doing some reading. Read an interesting article on the Cotton Belt (SSW) gravity yard in Pine Bluff, Arkansas. 

Got me to thinking how this might be handy to have. I have yet to buy or try any automated uncouplers in H0 or N scale, but if these worked reliably, coupled with gravity (pardon the pun), it could make working a yard fun and entertaining.

I don't know if track braking would cause derails on lighter cars, but it would seem easy to bash some together out of old turnout parts.

I'll see if I can't draw this out for easier visualization.


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## DonR (Oct 18, 2012)

Jack

You are referring to the 'hump' yard employed by many
railroads. It has a rise in the tracks (hump). A switcher
pushes the cars to the top of the hump where they are i
uncoupled allowing it to roll down the hump to various tracks
determined by a code on the car. The computer throws
the turnout points and applies braking as needed to
control speed.

Unfortunately, hump yards are not too successful
on model railroads. The cars are not heavy enough to
build the gravity needed to keep them rolling...I'm not
aware of any model 'braking' that is available. This
is important to avoid crashing into other cars in the
destination track.

Don


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## J.C. (Dec 24, 2016)

knew some one that had a working hump yard (cars shoved up to top of hump and rolled down by gravity to sorting tracks) that used compressed air to slow cars down , hump was sharp enough that cars uncoupled at top by them selves . is this what you want to do ?


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## gregc (Apr 25, 2015)

i'm curious.

i have cars that roll on what looks like a flat grade. So I'm guessing that not much of a hump is actually needed.

i also recently read about a yard in europe that is built in a depression with each of the yard rising. cars are allowed to roll into the yard, start rolling up the opposite end of the yard, roll back and eventually settle at the bottom. Obviously they smack into cars already on the track. No need for retarders.

what i'm curious about is how to uncouple cars on the "hump". Can an uncoupler be located on a downslope so that the engine can be paused just as the coupler is above the uncoupler, with enough slack to uncouple and at the point where the car just starts rolling downslope?


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## jackpresley (Dec 19, 2017)

So the actual yard was all downhill. Of course there was a hump at the beginning to start the grade, but from what I read, you could uncouple anywhere and the cars would roll down the yard, through switches. They used what the author called track braking, which the photo made it look like they clamped against the inside of the wheels to slow the cars. But brakemen normally road on the cars and braked them manually and a lot of the "automation" of the time was not used. Because of where the tower was, it made it difficult to tell distance to go so someone had to be there to signal anyway.

I tinkered with it and the only quality built car I have rolls downhill easily. The beat up, not maintained, old Bachmann cars -- not so much. It would be doable with new rolling stock.

I'm more interested in finding a reliable uncoupler, but that will have to wait until a later date.

I think if a "hump" was sharp enough to uncouple a car, it would likely be a real issue for other operations. The prototype photos I saw, the hump was hardly perceptible.

An interesting side story. My dad would summon me whenever the Cotton Belt would drop off boxcars at his warehouse from the middle of the train. Our siding was right off the mainline, which they didn't like, so they were always very quick about it. They would decouple and brake the trains behind the boxcar being delivered. When there was enough separation, they would decouple the boxcar and brake it some. When the front of the train passed the turnout, they'd throw the switch diverting the boxcar onto the siding, and then throw the switch back. The back of the train would coast in to reconnect with the front of the train. Reconnect the air hoses, and off they went. I'd often jump on the boxcar and ride it into the siding. I'm sure these days that's all verboten, but it was fun to watch and fun to get a short ride hanging off the boxcar ladder. 

And yes, they did screw up once and sent a fully loaded boxcar off the end of the siding. As I recall, we unloaded it and used tractors, wench trucks and dock fork lifts to pull the thing back up onto the siding, but the truck that went off the end splayed the track open so we couldn't get it up on the tracks. When the Cotton Belt crew showed up, they jacked up the boxcar with about 4 huge simplex jacks and then used a big come-along to wench the rails together under that truck. They set it down on the track and rolled it up the siding a ways and then cut off that splayed section of track and laid new rails. It went through the end bumper like it wasn't there, so they replaced it with a few dump truck loads of ballast about 6' high. I don't think that was ever tested, luckily.

I later asked my dad why he went to so much trouble to get the boxcar back on the tracks when it wasn't his responsibility. He was worried they'd just close the siding and we'd have to unload in town and truck it to the warehouse. Luckily a feed mill moved in next door and branched off of our side, so the turnout on the main line became a lot more profitable for the railroad.

I will add that there was more than one occasion when we'd get a boxcar dropped off and we had boxcars already on the siding. Back then flour was in 100 pound sacks and they were stacked pretty damn high in the cars. The old guys would always grab me and say "let's get on the dock until that new boxcar gets here." One day I learned why. "Watch out boys, this one's coming in quick." A fully loaded boxcar doesn't have to be going very fast to deliver a huge jolt when it was stopped by the boxcars on the siding. About 3 or 4 rows of flower came tumbling over onto the floor and probably would have squashed me like a bug.


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## gregc (Apr 25, 2015)

jackpresley said:


> I'm more interested in finding a reliable uncoupler, but that will have to wait until a later date.
> 
> I think if a "hump" was sharp enough to uncouple a car, it would likely be a real issue for other operations. The prototype photos I saw, the hump was hardly perceptible.


i've read that someone "pulls the pin" on the coupler when the car crests the hump

if you plan on using Kadee uncouplers, the coupler can't be in tension such as it might be on the downslope. The car must separate before passing beyond the coupler. If the engine stops over the coupler, momentum can carry it.


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## DonR (Oct 18, 2012)

Jack


Kadee makes an electromagnetic uncoupler. You push a panel
button to energize it to uncouple.


Don


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## gregc (Apr 25, 2015)

typical uncoupling procedure is to 1) stop over the uncoupler, 2) back up, and then 3) go forward, pushing the car with the couplers open until the car is positioned.

i'm assuming that you would like to slowly push the car over a hump, just as the car starts going downslope, the couplers are over the uncoupler and if the engine stops, the car will continue to roll forward with the couplers uncoupled and continue downslope onto the yard track without the need to reverse the engine. Then repeat for the next car. i don't believe uncoupling will be reliable if there is tension (pull) in the couplers.


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## Old_Hobo (Feb 20, 2014)

It definitely won't work like it does in the real world.....hwell:

The cars will race down the grade....they don't have enough mass to look like the real thing rolling....


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## J.Albert1949 (Feb 3, 2018)

re jackpresley's post 5 above:

What you describe is "flat switching" by "kicking" cars to where you want them to go.

This is a common procedure, but really works best with a brakeman on the crew along with your conductor.

Engineer is on engine, brakeman is usually "at the switch", conductor may be pulling the pin (sometimes they switch positions).

On the signal (usually a "backup" made in fast motion, this _IS NOT_ in the rule book), engineer revs up and gives the cut of a cars a good shove backward.

Conductor "gets the pin" with the slack, gives a "STOP" to the engineer.
Engineer slams on the brake and shoves throttle back to idle.

Car (or cars) roll off on their own down the selected track (you want to have something there (another car with the hand brake on) to "catch them"!

Meanwhile, brakeman throws the next switch.
If necessary, engineer pulls ahead to get enough room for the next kick.

Repeat until the cut of cars is gone.
Then, go get some more cars, do it all over again, etc.

If a workable "hump yard" was possible in model railroading, I'm sure at least one club would have one up and running by now.

From the standpoint of being a model engineer, I would think flat switching (even without the "kicks") would be more interesting.


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## jackpresley (Dec 19, 2017)

*More ramblings*



J.Albert1949 said:


> re jackpresley's post 5 above:
> 
> What you describe is "flat switching" by "kicking" cars to where you want them to go.


Thank you for the explanation of flat switching. This was the common mode of delivery to our out of town siding.

What I was describing was the rare occasion of cutting one or two cars out of the middle of the mainline train. I called my Pop today to discuss it with him. For an 88 year old, he remembers older events with great clarity.

Pop never knew who was who -- except for the engineer in the locomotive-- so my choice of brakeman or conductor might not be accurate. 

A "railroad man" would show up in a truck (driving down the road, not the track) and park by the switch. They would leave the yard in town with a brakemen on the end of our boxcar(s) and the conductor on the front end of our boxcar(s). As they approached the airport road crossing, the engineer would brake to a stop and the brakeman would uncouple the back end of the train just shy of the airport road. Then the engineer would move the consist and remaining train forward and then brake to take the tension off the coupler. The conductor would pull the pin and decouple, and start braking the boxcar(s). After the end of the front section went by, the "railroad man" would throw the switch and divert the coasters onto the siding. Then he would straighten out the switch and leave in his truck.

After braking the boxcars to a stop on the siding, the conductor climbed up the berm and into the locomotive. They'd then backup and recouple at the airport road crossing and then press on forward to the next town.

The particular event I remembered was when the brakeman decoupled the rear of the train and gave them the signal to press on. Unfortunately, although moving slowly, the remaining train never came to a stop. The railroad man, cooly diverted the boxcars, straightened out the switch, and (I assume) radioed to the engineer to pull forward to match the speed of the train slowly coasting down the hill. Both sections of the train were way down the line before the coasters caught up and were stopped. "I didn't hear anything, so I assumed it went well."

It did, but the impact was enough for the brakeman to lose his grip so he chose to jump off rather than fall off. Unfortunately he landed in some thick briars and looked a bloody mess, but was actually just scratched up. The "railroad man" cleaned him up with his first-aid kit and off they went.

Other great stories ensued and it was a very enjoyable afternoon conversation. He could write a very thick book of war stories about planes, trains, trucks, tractors, and jeeps. Apparently a WW2 surplus jeep would have been called, using today's terms, "a chick magnet" in 1947. Apparently, the stories of "equipment I broke" would fill several chapters. (It is a miracle I'm alive.)


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## rogruth (Mar 6, 2012)

Many years ago, I don't remember when, Model Railroader had an article on building a working hump yard. I did not have any kind of layout at the time and thought it would be an interesting and difficult project to make work like the real thing.


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## mustangcobra94 (Apr 28, 2014)

there is a club using a hump yard. the nysme in Carlstadt n.j.has a ho scale hump yard and they use compressed air to slow the cars. I'm sure if you do a Google search someone probably has video of it.


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## gregc (Apr 25, 2015)

rogruth said:


> Many years ago, I don't remember when, Model Railroader had an article on building a working hump yard.


for those with access, the Trains Index lists several articles on hump yards


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## ebtnut (Mar 9, 2017)

The inertia physics of model railroad equipment vs. the prototype just don't mesh. I've seen a couple of model hump yards and most aren't that good. There is such a great disparity in ease of roll due to car weights, friction, lubrication, etc. that you really can't get much consistency. I've seen models using air, and also short lengths of monofilament fish line to help control the speed, but the results aren't consistent. The prototype humps have a series of car retarders that squeeze on the wheels, with the pressure based on the weight of the car and how far it has to travel into the yard before it bangs into what is already down there.


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## DonR (Oct 18, 2012)

Here is a video of a N scale hump yard under construction.

The actual hump operation starts at 6:06 in. 






It pretty well illustrates the problem of scale and
inertia...these are N cars racing down the hump at
breakneck speed. The actual proto cars on a proto
hump are auto braked to a snail pace.

Don


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