Look up train or cart or roller coaster movement on the forums. Basically that’s what you are trying to create. Instead of using gravity to keep the car down you need a rail to stabilize the car and keep it on track.
I’ve posted a couple of my train models on a few train threads How to make a basic train - #12 by Scottifly and one with dual axle bogeys that tilt and rotate (more than what you need, but still fun) How to make a train bounce up and down? - #2 by Scottifly
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