Trouble Shooting Derailments

One thing that all model railroaders have to do, is trouble shoot problems on their layout. Believe me, no matter how advanced some of us might think we are, when it comes to trying to figure out why a derailment occurs in the same spot gets all of us going.

In this trouble shooting page, we will look into what can cause derailments, how to pinpoint the problems, and then how to fix them. We will look into several problems, and show how to find out what is causing the issue.

Derailment in the same place.
Nothing worse than running your trains around your layout, and having a derailment. And not every time, does a derailment mean anything is wrong. A car may have been placed incorrectly on the track, or maybe a switch was thrown while a train was in the switch, and then it was thrown back. If you have a derailment, best thing to do is place the cars or engines back on the track, and to keep running them. The first thing that needs to be understood, is to not trouble shoot something that happens once. No need to tear up half the track, and remove scenery for a car that jumped off the track.

But when a derailment happens in a certain place several times, then we need to start finding out what is causing this.

A few questions to ask, before we start trying to fix anything:

  1. Has any Scenery been done in the area, or remodeling?
  2. Is it the same cars or engines?
  3. Is it in a switch?

Where is the problem happening?
This is important, not only to trouble shoot, but to see WHERE to start trouble shooting. Just because a car is derailing in a switch, or a curve, doesn't mean THAT is where the problem is. The best way to find out is to watch your train, and the car that has been having the problems. Put it back on the track, and the let it run around, as you watch the wheels of the car. It might be jumping off in the straight away from a nail head, but it doesn't derail until it hits the switch. You can look into the switch as much as you would like, replace it, and take it out. If you don't find that nail, you will still have the same problem.

Your trains wont lie. If there is a problem, they will show you where it is if you just watch them.

Also, watch at what speed you run them at. Most model Railroad engines are best run at a slower, more realistic speed. If you run them too fast, you can just cause problems because of the speed they are traveling.

1. Has any scenery or remodeling been done in the area?
This is one that is usually over looked, and can save a lot of time in trouble shooting. More times than not, when you have been working in an area, things are dropped or forgotten. So when you see derailments happening at a certain place, look around to see if anything is between the rails, or around the tracks that could be causing it. If scenery has been dropped on the track, nails not pushed down all the way (or one has worked it's way back up), tools left on the layout by the tracks.

As stupid as this sounds, this does cause problems and lend itself to trouble shooting the wrong thing.

2. The same car or engine keeps derailing.
Rolling stock, The first thing you always want to check on any piece of rolling stock that has been derailing, is the wheels, and couplers. These are the items that cause derailments the most.

The coupler needs to be set to an NMRA height standard. This is so that it will match up with other couplers and the 'Glad Hand' (in HO, the curved metal part of a Kadee and other knuckle type couplers) will be high enough to clear rails, switch points, and other items in between the rails.

If a coupler is lower than it should be, the 'Glad Hand' can rub against certain things between the rails, and cause derailments. If you get a coupler height gauge such as Kadee's (for HO knuckle couplers), it will help get all of your couplers the correct height, and stop this problem. Another thing is that sometimes the magnetic part of the coupler (the 'Glad Hand' that is supposed to be the air hose) may be too low, or bent at a bad angle. This may be because either the wrong coupler was used, or the coupler itself needs to be shimmed.

To shim a coupler, is to add a thin piece of plastic or washer to adjust the height of the coupler, and usually take out an slack that causes the coupler to have up and down movement.

Kadee has 2 insulated washers (red at .015 thick, and gray at .010 thick.) that can be used to adjust the height of the coupler in the coupler pocket. Or you can use a small thin piece of styrene cut to the inside dimension of the coupler pocket. You can get pieces of styrene in various thicknesses, from .005 to .040. Place the washer (or styrene cut to fit) at the top (closest to the body of the car or engine.) to lower the height, and toward the bottom (closest to the rail) to raise the height in the pocket. Make sure that you test the coupler to make sure it moves smoothly back and forth, and does not hang up anywhere in its travels.

Never oil a coupler in its pocket. If you feel that lubrication is needed, a very small amount of powdered graphite may be blown into the coupler pocket.

Trucks, also need to be set to NMRA standards. This is usually NOT the problem. You should check the wheels to make sure they are the proper distance apart for the rails. But the main issue usually is the screw holding the trucks in place, is too tight. You should just be able to back the screw off (turn the screw counter clock wise, maybe a ΒΌ of a turn.) so that the trucks move freely, but are still held in place.

The wheels. These are the things that are being derailed. And sometimes are the cause as well. The biggest problem with wheels is dirt building up on the tread part of the wheels. usually a small screwdriver can rub off the dirt. Just use a finger to turn the wheel, while you hold the flat part of a screwdriver against the tread part (this is the part of the wheel that rides on top of the rail). Dirt can build up on the wheels of rolling stock until the flange can no longer do its job of keeping the wheels centered on the rails. Just taking a quick glance at the wheel sets can miss the buildup because it looks so much like the tread of the wheel. It isn't until you look closely and see that the wheel treads do not all look alike that you realize that it is time to clean.

Another thing to check, is the car in front or behind the derailing car. I do know that 86' cars (trailer, auto rack, Hi cube boxcars) can sometimes pull other cars off. Due to their long coupler housing attached to the wheel set. Where as most pieces of rolling stock, the coupler pocket is on the underside of the car itself. Keeping the coupler in the center of the rails. If there is a sharp turn or small switch (a number 4 turnout for example.), this can push the excess length cars coupler over the rail, and pull the trailing car off.

One last thing is to check that the car has been put together correctly. If the body of the car is not on the frame, this could be causing a problem. Also, if it was car built from a kit, check to make sure nothing is rubbing against the wheels and also nothing is stopping the couplers from moving side to side. All wheel sets and couplers should move back and forth easily. If the stick or stop then you may have just found your problem.

Engines also can derail. The first thing would be to follow the steps for rolling stock. Couplers and wheels can also cause derailments on engines.

You can check the engines for tight trucks also. Inspecting an engine is a lot like inspecting a piece of rolling stock. Turn it over in your hand, take your other hand and lightly turn the trucks side to side. they should move freely and easily. If not, you may need to take a small file and file the area where the diesel trucks travel on the frame. This is something that might be better done by a hobby shop or an experienced modeler. Taking off too much can cause more problems. But after someone shows you how to do this, it is an easy and valuable skill.

Also, check the wheels in curves. Many 6 axle engines will jump off the rails in a curve, if the curve is too tight. Most 6 axle engines need 22" radius curves or better. Again, watch where the derailment happens. And check to see if the wheels are off before that. If they are, then run the train and try to pick a place several feet up the track. Watch as the train goes by again. If the wheels are still off, then go back up the track further until you find the point where they jump off. Check to see if there is a rail joiner at the spot, or a gap in the rails between sections. Also look for nails that are not pushed all the way down. Next, you need to check for level track. if there is a dip, or bump in the track work, this can lead to many problems. Check under the rails and ties. With all the cutting, sawing, drilling, and other things done on a layout, there is a chance of pieces of debris being trapped under the track work or roadbed.

Checking for Bumps. Bumps will usually mean something is under the roadbed or track, or the track isn't nailed down securely. Check to see there are nails in the track around the area of the bump. If so, then check to see if there is anything under the rails or roadbed in the area. If this is at a spot where tables come together, then you may need to look at the tables to make sure they are level. (the same thing if this is the beginning of a grade).

The transition from one table to the next should be smooth and level. If not. Then either one side of the table needs to be filed down, or realigned, or the other side needs to be shimmed or realigned. This can usually be done with a level. Start by checking in the middle of the table, and then work your way toward the next table. It should be level all the way across. If it is not, then you might need to add a support across the table to keep it level, or perhaps a leg might be needed.

Checking for dips. This is almost the same as checking for bumps. You can still check the table to make sure it is level. But one other thing to look for is the track to be nailed down too tightly. The nails are suppose to go into the wood to hold the rails. There should not be any bowing of the ties. If any nail seems to be too far down. Just pull the nail out, and put it back in. You just want to make sure it is flush with the top of the tie. This will hold it in place and not cause a dip.

3. Is it in a switch?
Out of all the pieces of rail, the switch can cause the most problems. But if you look them over, and do a few checks, this can all be avoided.

One thing to keep in mind. The switch may be where you saw the derailment, but the wheels could have come off further back on the track. If you have found the switch to be the problem. then this should help you out.

First, make sure the frog and guide rails are free and clear of any debris. The smallest piece of dirt can cause many nights of derailments. A small paint brush works well for this. Just take a few brushes back and forth over the switch can remove most problems. Another good idea is keep a spare set of trucks off of a piece of rolling stock around. Put them on the rails, and place a finger over them. NOT HARD, just enough to move them back and forth. This way as you lightly push them through the switch, or other area that is having derailments, you can feel if the wheels run over or are affected by anything.

Another good thing to have is an NMRA track gauge. This is to see if the rails are the correct space apart, and also if you have good clearance for the switch points (the 2 pieces of rail that move on the switch, to change the routes of the train). Sometimes these may need to be bent to let the wheels go by. Again the trucks or the NMRA track gauge can show you if this is needed.

When you are having derailments and you can't find out where it is happening, just follow the train path backward until you find the point of error. This is not always easy. Sometimes it will be in a rail joiner not connected correctly, a gap in the rails, or a misaligned piece of track (a lot of times this is in a curve). One way of checking this is also with eyesight. You can usually see if the rails are not aligned. You may see a kink in the rail (Instead of the rails curving steadily, there will be a small kink), you can check this with a curve gauge. this a piece of metal that is set to a certain radius. It fits in between the rails, to make sure that the curve is steady all the way through. This only works with a continued radius, but will help. You can buy them in various radius sizes.

Also in a straight-a-way, the same thing can cause problems. You can look for kinks, pulled up nails, gaps in the rails, or rail joiners not on the rail properly.

Remember, trouble shooting may not always be fun. But it is oh so rewarding. Once you find the problem, and your trains run through the area without derailing, you will be on your way to enjoy this wonderful hobby even more.

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Page last updated February 17, 2001