Troubleshooting derailing rolling stock

troublehshooting derailingIf you’ve got rolling stock that always derail this may be the answer.

I’ve written before on how to troubleshoot derailing trains. That post covered the most common problems and solutions but I recently noticed a particular wagon derailed frequently and none of the usual suspects solved the problem.

No matter what I tried if this unit, a GWR wagon, was being pulled it would come unstuck.

It was only after some investigation with a magnifying glass and calipers that I identified the problem and it all came down to size.

Watching the wagon move, either as part of a rake or on its own, it would just slip off the rails.  Closer examination of its movement with Jewelers Loupe showed the front wheels to be at fault.

More out of hunch that for any other reason I measured the distance between the wheels on the axel.

It’s an N gauge wagon so this distance should have been 9mm. The LCD display on my digital calipers however showed the front wheels were fractionally closer together.

Digital Calipers?
Digital calipers measure internal, external and height and depth dimensions to great precision with the distances shown on an LCD display.

They’re a great tool for all manner of small jobs that crop up when railway modelling including not just for wagon troubleshooting but model making and checking clearance around track. I use these available from Amazon.

Something I wouldn’t have detected if not for precise measurement and digital display of the calipers, but big enough to cause problems.

This wagon was picked up a boot fair a while back and was found at in a box of other rolling stock so the wheels probably slipped when rattling around in the bottom of this box and getting knocked against other items.

I swapped wheels with a spare set I had to hand and sure enough the wagons ran perfectly.

Examining the original wheels set a second time again confirmed the wheels had moved on the axle. Very gently pushing them apart with pliers returned the wheels to their correct distance apart and on being swapped back my GWR wagon ran without further problem. Hurrah!

I’ve not seen wheels move on axles before but if you have rolling stock that regularly derails it’s certainly something to check.


> A final, personal, note: I spend a huge amount of time testing, photographing, writing and researching techniques for these articles and pay for all the running costs of MRE out of my own pocket. If you found this article useful you can support me by making a donation on my fund-raising page. Thanks and happy modelling, Andy.

Founder of ModelRailwayEngineer, Andy Leaning

Andy is a lifelong modeler, writer, and founder of He has been building model railways, dioramas, and miniatures for over 20 years. His passion for model making and railways began when he was a child, building his first layout at the age of seven.
Andy’s particular passion is making scenery and structures in 4mm scale, which he sells commercially. He is particularly interested in modelling the railways of South West England during the late Victorian/early Edwardian era, although he also enjoys making sci-fi and fantasy figures and dioramas. His website has won several awards, and he is a member of MERG (Model Railway Electronics Group) and the 009 Society.
When not making models, Andy lives in Surrey with his wife and teenage son. Other interests include history, science fiction, photography, and programming. Read more about Andy.

Afflliate disclosure:The links on this page may take you to carefully selected businesses, such as Hornby, Amazon, eBay and Scale Model Scenery, where you can purchase the product under affiliate programmes. This means I receive a small commission on any orders placed although the price you pay does not change. You can read my full affiliate policy here. I also sell my my own ready to use, pre-made and painted buildings and terrain features. browse the range.

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