Over the many years that I have been building MR's I've found that when you make a grade to sharp or not enough transition from the flat to the grade your cars will uncouple by themselves w/out any kind of magnet. To make a car roll freely down a slight grade all you need is metal wheels on that car that turn effortlessly in the slighest down movement. To make it easier, cut the glad hand hose off of the engine & you can leave the rest on all the rolling stock. To test this, take a 3ft rail & add another 3 ft. rail sweeping down just a little to make the cars disconnect. The only problem you will have is going out of the downhill to the flat track. all the cars will try to disconnect. Solution; have a switcher at the bottom to push all of the cars back up to the flat track to connect to the pulling engine. The Hump Yard downhill track only has to be at a slight angle to get all of the cars to roll freely w/metal wheels & smooth journals.
We've been talking for years about how to slow a car down in a hump yard so it wouldn't crash into the rest & so far no one has figured it out. Some cars will always roll super easy & then you will have those that no matter how much you do, won't roll at all.
Larry
I had a train break loose on a crest at the club several weeks ago and over 40 cars that didn't belong to me started to scream down the hill. Luckily I was just a few feet away and quickly grabbed the train. That could have been some bad press right there.
Also, I would suggest constructing a hump yard breaking system the same way the big guys do. Pinch the wheels. A simple bent piece of thin metal between the rails pushing on the inside of both wheels should do nicely. The trick is regulation, which just like the big guys requires speed sensors and the ability to adjust the pressure of the breaking system.
The additional thing to consider is based on the track you're sending them to you'll want the cars to travel different distances. And different cars are going to carry speed differently - or put another way, decelerate less quickly. It all becomes very tricky very fast.
You end up needing a long run after the hump before the brakes, and then again before the turnout array, then likely another set of brakes either mixed into the turnouts or on each yard track. The speed sensor(s) need to be just prior to the breaks.
The time I spent watching the North Little Rock hump yard in action there was at least one switch engine at the far end of the hump yard that was constantly tidying up the cars when they'd stop short.
Then if you want to take it a step further! Your cars will need some kind of RFID mechanism, a scanner, and a computer system that will automatically flip turnouts based on the inbound car.
If you're going to do it you might as well go all out, right?
