Wheels on

 

The running gear on these coaches is minimalistic, but it's simple and robust, just what you need in the garden. 

Bearing are fitted in the MDF sideframes, and I reamed them out a bit to give a touch of slop to help in less than perfect track. 

Other than that, glue one solebar in place, let it dry, then fit the other one, trapping the wheels in place. Check it rolls and if so, let the glue harden. 

One issue, there's no marks to show where the solebars go, so a bit of jiggery-pokery was requied to work out how far apart they should be, 55mm, and marking things out either side of a centre line.