My son really likes trains, so we wound up accumulating a lot of Thomas the Tank Engine train sets.
If this sounds familiar to you, then maybe these things can be of help to you as well:
It turns out that there are many different kinds of Thomas the Tank Engine train sets, each with different kinds of tracks, that are all incompatible with each other. Even though the train engines for these sets are basically the same, different sets use different kinds of track connectors.
We didn't have enough of any one kind of train track to make a very long course, so my son would use up one set of track until he ran out, and then continue with another kind by simply butting the ends of the different tracks together. The problem was, when the train came along and tried to cross this transition, it would invariably push the tracks apart and derail, unless someone was there to hold the tracks together and guide it over the gap. Take it from someone who knows: this gets old fast.
To remedy this, I modeled various track adapters to allow different kinds of tracks to connect and 3D printed them.
I made adapters to interconnect Trackmaster, Tomy, and Thomas Wooden Railway train tracks. You can purchase these adapters from my shop on Shapeways, or if you have access to your own 3D printer you can download the model files from there and print them yourself.
Sometimes, trains break. The most common pieces that break are the connectors that link the trains and train cars together. We had a number of trains that were out of service for want of these small parts, so I made models of these connectors and 3D printed replacements. Replacing the connectors is a simple operation that just requires a screwdriver.
If you find yourself in need of some spare Thomas train connectors, you can purchase them from my shop on Shapeways. The model files are also available there if you wish to print them yourself.