Train with multiple axles on a spline?

Thats one idea, and could work but using any method of Physical restraint will take days/ weeks/ months of trial and error to get something to behave realistically…

My own project has and is still being adapted / tuned to get an ever increasing speed range for consistent behaviour ( I’m up to 50 mph ish ATM)

Try thinking Slot car

Good Luck with your project

Paul G