“Al and my fellow modellers,
Reading one of Al’s eMails today I noticed in the comments how many people were suffering from derailment issues.
Well, I thought, they are not alone! I have spent a lot of time over the last couple of weeks solving all of my own.
Various things cause derailments and I have done lots of research on why individual items choose to jump off the track and ruin my day.
I thought I should share the findings with you and hopefully point you in the right direction.
Firstly, they are all solvable! Even my most stubborn lightweight wagons have been solved. What you need to do is tackle the problem systematically.
Firstly, is it the track?
The track will only work well if it is in gauge. I foolishly assumed that my track (peco 100) would be in gauge at all times, after all it is made in a factory and the rail is inserted into sleeper chairs that are a fixed distance apart. WRONG!
Flexible track on curves has a tendency to slightly tighten up the gauge. Usually not a problem until you create a joint on a curve. These do tend to press inwards on the inside rail. I used a stout pair of pliers to bend the rail back outwards and re-checked with a track gauge. That was problem one solved.
Problem 2: almost everything struggled going into a particular point in the fiddle yard section. It was NOT the point (turnout/switch for the rest of the world) it was the 2 inch (50mm) section of track before it.
Once again the plastic sleepers had not proved sufficiently rigid to hold the track in gauge. The track had rotated inwards at the tops. You couldn’t see it, but you could measure it with a track gauge. Sure enough it was about .75mm too narrow.
Now for wheels:-
OK so if your wagons / rolling stock / locos cope perfectly well on a straight flat section of track why is it they fall off the track when going through a point?
Well first it is more common for a derailment to occur going into the point from the toe. Hence why certain railway companies insisted that there be no facing points on mainline track and where possible to avoid it altogether. Not bad advice for us modellers too! Apart from anything it increases the operating complexity and allows us to shunt more than we would otherwise.
However, having said that, at some point in time you have to approach a point from the toe end in order to choose between two (or even three) route alternatives.
The main requirement is that the wheels follow the desired route. Seems simple enough doesn’t it?
Well often they don’t bother and de-rail instead. So why? What stops them following the rails around the correct curve?
Well let’s look at the relationship between the two wheels. They need to be the correct distance apart between their inner faces. This is known as the back-to-back setting. Buy a gauge! Set the back to backs and you will be a lot better off.
Older wheel sets tend to be too narrow on their back-to-back settings for modern track. This worked well on the coarser track like Hornby and Tri-ang but often fail miserably on code 100 and probably won’t even entertain code 75 track!
The best option for this type of stock if you can’t adjust the back-to-backs is buy replacement wheels. A caution here too. Dapol wheelsets seem to have very small flanges that are designed for code 75 track. They do not resist sideways pressure at all and will pop off the track with the slightest sideways provocation.
The Hornby replacement wheels are slightly deeper flanged and work really well.
Anyway let’s look what happens if the back-to-back is too narrow.
If the wheels are too narrow you can see that the flange is likely to collide with the switch blade at point A or collide with the check rail at position B.
Either way you will see the loco/wagon jump up slightly as it does so. Push it through by hand with very light finger pressure and you can feel the collision. Bad enough on the straight through section but almost always disastrous on the curved route and don’t even think about a curved point where both routes are curved!
So you might think the wider I have the wheels the better! Wrong again I’m afraid. Let’s have a look at what happens if you spread the wheels out so they are a tighter fit between the rails. i.e. too wide.
So initially it looks like we have solved the problem. As both wheels are pushed towards the rails then the clearance past the switch blade at position A is increased and no collision occurs, likewise at Point B the flange is held far from the check rail… but there is always a BUT!
Look carefully at position B. The flange of the wheel is far away from the check rail, so as we said no collision! BUT masses of free-play. The option is there to slide inwards and move closer to the check rail. So what then happens to the wheel crossing the frog?
The free-play at position B between the check rail and the back of the flange has allowed this wheel to ride inwards pushing the far wheel outwards, often catching on the wrong side of the frog and riding up outside the rail. Derailing!
Again this is particularly a problem for the curved route as it is easier for the wheel at the frog to arrive out-of-gauge and slightly at an angle to the intended route further promoting riding up and out.
i) Ensure your track is in gauge everywhere. You can’t be too particular in going over every inch even if it looks correct it may very well not be.
ii) Ensure that the wheels you are running actually suit the track it is on. If not replace them.
iii) Set the correct back-to-back using a commercially available gauge on every set of wheels you have.
iv) If you still have problems then closing the gap at B will prevent the opposite wheel escaping over the Frog. The suggestion to glue in a small strip of brass or very thin plastic to the inside of the check rail will catch the sideways movement before it allows the far wheel to get outside the frog.
v) You can glue check rails into position on the inside rail of any curve to do the same trick. Why not? Real railways have them and exactly for this reason, they don’t do it for fun you know! I did this on my own curves where the tracks split over a baseboard join. Before, almost everything de-railed, now everything passes without problems.
I hope you have found this explanation helpful in trouble shooting your own problems.
Happy Railroading everyone!
And now on to Dangerous Dave:
“Just uploaded today, short session to show I’m still here!
That’s all for today folks, a big thanks to Dave, and especially to Mal for taking the time to put that excellent derailment ‘how to’ together.
Please do keep ’em coming.
And don’t forget the Beginner’s Guide is here if today is the day you make your start, on your layout.