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Has anyone built a good working hump yard?

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Has anyone built a good working hump yard?
Posted by roundstick3@gmail.com on Thursday, June 9, 2022 2:12 PM

With track retarders and automactic uncoupling?

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Posted by ndbprr on Thursday, June 9, 2022 4:51 PM

Had a friend who had one in O scale.  He tested each car and had a chart for how much retarding to do.  He used a manual system of reducing speed.  as I remember it was based on bringing the cars to a dead stop on the hill before releasing them.

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Posted by Pruitt on Thursday, June 9, 2022 4:56 PM

Ed Ravenscroft did back in the 1970's. MR had a detailed article about it, but I don't know the particular issue. It was early to mid-70's, as I recall.

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Posted by dknelson on Friday, June 10, 2022 11:03 AM

Yes Ed Ravenscroft, and I think he built two of them -- one at his layout (the Skokie Valley) when he lived in Illinois, and the second when he retired to Arizona.  So there was more than one Model Railroader article about it.  He also had innovative car forwarding methods involving small holes in the rolling stock and thumbtacks of various colors and perhaps letters.  It was sufficiently well known that someone made big discs with colors and letters and put them on some prototype freight cars, submitting the pictures as the supposed "prototype" for Ed's idea.  

If I recall right, Ed R's retarder used puffs of air to approximate the job of the retarders. 

Actual working retarders would be rather remarkable in HO, although I could imagine a very sensitively designed servo being used to ever so slightly narrow the guage of the track and effectively do the same job as a retarder.   Whether it could be triggered by the speed and weight of the car like the prototype would be an additional challenge.

Dave Nelson   

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Posted by MisterBeasley on Friday, June 10, 2022 6:01 PM

All my rolling stock has metal wheels, mostly with Intermountain wheelsets with metal axles, so to first order I would try electromagnets as retarders.  Typically, though, I "plant" tall field grass in between the ties of my sidings to keep my cars from rolling freely.

It takes an iron man to play with a toy iron horse. 

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Posted by dehusman on Friday, June 10, 2022 7:07 PM

There have been several hump yards built.

Whether they are "good working" facilities are a matter of your perspective.

Since model cars have VERY little mass, they need a higher speed to have enough energy to roll into the bowl tracks on their own.  That usually destroys the effect. In addiion to get the model cars rolling at the speeds necessary to work, it requires a pretty tall hump.

Automatic uncoupling is pretty easy, just put uncoupling magnets on the approach to the top of the hump and shove slow enough that as the car crests the hump it will roll away from the rest of the cut. 

I have worked around real hump yards and haven't seen a model one that didn't look like it was operating at 5-10 times actual speed as far as the cars rolling down the hump.

Dave H. Painted side goes up. My website : wnbranch.com

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Posted by NScale4x8 on Friday, June 10, 2022 10:29 PM

I was misremembering

https://nscale4by8.github.io/nscale4x8/

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Posted by BEAUSABRE on Saturday, June 11, 2022 6:13 AM

 The physics (momentum) doesn't scale. You can build one that will work, but because of that, it won't look realistic

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Posted by wrench567 on Saturday, June 11, 2022 9:19 AM

 While not a hump yard. I did try to build an elevated caboose track for an industry. The caboose would be spotted on the incline and uncoupled using super magnets under the track. The magnets were attached to a bell crank and operated by a knob. After switching the industry the magnets would release the caboose so it could roll to the departing train. Sometimes it would work but most times not. The caboose would either stop short or roll too fast and slam into the train. Sometimes it would derail. The rolling characteristics of the different cabooses made it hard to judge the right speed.

  This idea was from an article I read about prototype caboose operations. The brakeman would use the hand brakes to control the speed coming down the grade through a spring switch to couple onto the departure track.

     Pete.

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Posted by caldreamer on Saturday, June 11, 2022 2:34 PM

Controlling the retarding of a car can easily be acomplished with a computer program.  If I was to write it I would do so in Java since Java is universal and is available for Unix, Windows and Mac operating systems.

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Posted by maxman on Saturday, June 11, 2022 5:04 PM

caldreamer

Controlling the retarding of a car can easily be acomplished with a computer program.  If I was to write it I would do so in Java since Java is universal and is available for Unix, Windows and Mac operating systems.

 

In theory, maybe.  In reality, probably not.  The problem is translating the electronic theory into the mechanical reality.

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Posted by dehusman on Saturday, June 11, 2022 5:21 PM

caldreamer
Controlling the retarding of a car can easily be acomplished with a computer program.  If I was to write it I would do so in Java since Java is universal and is available for Unix, Windows and Mac operating systems.

Writing a program wouldn't be that hard. That's the easy part.

It still requires the cars to be able to roll a considerable distance on their own.  That's the first challenge.  The second challenge is actually being able to control the speed of the car.  How do you slow the car enough to affect it's speed without derailing it.  Ravenscroft used air jets to slow the cars.

Dave H. Painted side goes up. My website : wnbranch.com

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Posted by John-NYBW on Saturday, June 11, 2022 6:19 PM

There are many things in model railroading that don't scale down well. Gravity is one of them.

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Posted by maxman on Saturday, June 11, 2022 7:48 PM

Sometimes it is difficult to grasp the gravity of the situation.

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Posted by John-NYBW on Saturday, June 11, 2022 10:08 PM

It was proven a long time ago that gravity has the same pull on objects of different weights. A 100 pound object will fall at the same rate as a 1 pound object. When it comes to cars coasting down a hump yard, friction will partially offset the effects of gravity but since the scale model car has less friction than the full size car, there will be less offset. The result is a model freight car is going to coast down the hump at a much faster scale speed than the full sized car. 

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Posted by gregc on Sunday, June 12, 2022 5:06 AM

John-NYBW
but since the scale model car has less friction than the full size car, there will be less offset.

after noticing some of my cars rolling on very flat grades i made an effort to measure and correct my trucks with lubricant and a truck turner.   some rolled very well, others rolled better after some work and others had a hard time rolling freely down a 2% grade

i believe model trucks have more friction, not less than full scale cars and the friction varies more between truck.  a resistance of  2 lb/ton from Armstrong's chart is a ratio of 0.001, while the equivalent of a 2% grade is 0.02.

a hump yard might need to use air pressure to push rather than retard the speed of a car

greg - Philadelphia & Reading / Reading

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Posted by John-NYBW on Sunday, June 12, 2022 7:25 AM

Whenever I put a new piece of rolling stock on the layout, I use a truck tuner to improve the free rolling of the axles. To test it out, I give them a nudge down a 1.75% grade of about 12 feet to see how well they roll. If they are properly tuned, they pickup a lot of speed and go around a curve to a flat spot on the layout. Well tuned trucks will allow the cars to roll at least another 12 feet once it reaches the flat. I've seen the hump at Bailey Yard in North Platte in action and the cars roll down the hump at nowhere near the speeds my cars coast down my incline. 

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Posted by richhotrain on Sunday, June 12, 2022 7:33 AM

John-NYBW

I've seen the hump at Bailey Yard in North Platte in action and the cars roll down the hump at nowhere near the speeds my cars coast down my incline.  

That is the purpose of retarders in the hump yard - - to slow down the rolling cars.

Rich

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Posted by wrench567 on Sunday, June 12, 2022 7:38 AM

   Gravety and friction is part of it. The mass and weight is not scalable. Our freight cars would have to weigh an ungodly amount to scale up to the weight of a prototype car. I'm sure someone can overcome such problems using blasts of air or even under track electro magnets run by computer and location sensors, maybe even radar. Propelling cars forward like a maglev train. Would it be worth it? Perhaps.

     Pete.

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Posted by gregc on Sunday, June 12, 2022 8:40 AM

wrench567
The mass and weight is not scalable.

acceleration due to gravity doesn't depend on mass/weight.   Alan Sheperd demonstrated that on the moon

greg - Philadelphia & Reading / Reading

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Posted by wrench567 on Sunday, June 12, 2022 9:15 AM

gregc

 

 
wrench567
The mass and weight is not scalable.

 

acceleration due to gravity doesn't depend on mass/weight.   Alan Sheperd demonstrated that on the moon

 

  That may be for a free falling weight. But we try to avoid our trains from free falling. Put two cars on a grade. One heavy and one light and let them both roll and see which one goes farther and faster. Then get back to me with the results. Just like the Hot wheel cars of our youth. The heavier car always went faster and further. Neither hit terminal velocity like a free falling object.

     Pete.

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Posted by dehusman on Sunday, June 12, 2022 9:27 AM

gregc
acceleration due to gravity doesn't depend on mass/weight.   Alan Sheperd demonstrated that on the moon

But kinetic energy (KE=m*Vsquared) and momentum (M=m*V) does.

Our models have very little mass and very little velocity, they have very little kinetic energy and very little momentum.

A quarter pound model boxcar isn't going to perform the same as a 260,000 lb. prototype boxcar, a prototype car moving at the same velocity as a model boxcar has a million times more momentum and kinetic energy.

Dave H. Painted side goes up. My website : wnbranch.com

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Posted by gregc on Sunday, June 12, 2022 9:31 AM

wrench567
One heavy and one light and let them both roll and see which one goes farther and faster.

dehusman
Our models have very little mass and very little velocity, they have very little kinetic energy and very little momentum.

friction, including with air as Shepard demonstrated, is resisting the acceleration due to gravity and the buildup of speed

greg - Philadelphia & Reading / Reading

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Posted by wrench567 on Sunday, June 12, 2022 9:52 AM

  I built a pair of 30 foot gun flats from F&C. I used trucks and wheels from a pair of H21 hoppers. The hoppers would roll away on any slight grade. The flats without load will sit still on a 1 in 12 grade. Once the load is installed and the spacer flat in the center it rolls a lot easier once started. Getting over the initial starting friction the mass overcomes the friction by momentum. It's the added mass that keeps it going.

      Pete.

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Posted by gregc on Sunday, June 12, 2022 11:28 AM

wrench567
The hoppers would roll away on any slight grade. The flats without load will sit still on a 1 in 12 grade.

acceleration is inversely proportional to the mass, a = F / m, but friction is proportional to weight

wrench567
Getting over the initial starting friction the mass overcomes the friction by momentum

force needs to overcome friction, not mass.  (you can argue symantics, but why not use the correct terms)?

did you notice how the rolling resistance in Armstrong's Chart is higher for MTs (of course loaded cars have more weight)

greg - Philadelphia & Reading / Reading

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Posted by roundstick3@gmail.com on Tuesday, June 14, 2022 8:28 PM

Having rode over cars in a hump one must factor in the damage to payload and car if going to quickly.I think O scale with metal wheels might work out better 

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