Nick I've been thinking about this and there is one way I was thinking why not fill the wagon with ballast and the easiest way to create a natural settling would be to say bang your hand firmly but not too much on the frame of the layout near to where the wagon goes but you would only be able to do a small area at a time.
If you ever had a playstation they had a rumble system in the controllers that gave the effect of say going on the grass or gravel when you use it on a driving game. I think the idea is based on something spinning in the handle on a spindle. But with the layout being in N gauge it is going to be very hard to get the desired vibration to pass through to the wagon.
the other way would be to get a small motor and imbalance the shaft and put some weight on 1 side to make it vibrate.
If you ever had a playstation they had a rumble system in the controllers that gave the effect of say going on the grass or gravel when you use it on a driving game. I think the idea is based on something spinning in the handle on a spindle. But with the layout being in N gauge it is going to be very hard to get the desired vibration to pass through to the wagon.
the other way would be to get a small motor and imbalance the shaft and put some weight on 1 side to make it vibrate.