Mechanical problems, oscillation on a trailer

[Matt77]

So I built a rover prototype using some ideas I saw on the Scrap Mechanic forums.  It drives really well compared to some of my earlier designs, despite my current low-tech - some of my worst disasters have been rover-related...

The problem is the trailer on this contraption which is connected using two hinges, unpowered and free.  The original model had one wheel on the trailer and oscillated above about 7m/s.  The current version oscillates above about 25m/s.

Any hints to stabilise it?

https://drive.google.com/file/d/1yQu3icSVBrY1tk5VrmQvyc6LV5rK2u6Y/view?usp=sharing

https://drive.google.com/file/d/1RDuCtEdozOFaCB5sOvzxJpuoeRu8ONQU/view?usp=sharing

[Wizard Kerbal]

59 minutes ago, Matt77 said:

The problem is the trailer on this contraption which is connected using two hinges, unpowered and free.  The original model had one wheel on the trailer and oscillated above about 7m/s.  The current version oscillates above about 25m/s.

Mess with the steering/traction control and a few other buttons I don't remember. Generally, those work.

And my other guess other than it just being a rover in KSP is that it's not aligned with the CoM.

[Matt77]

I think I have it.  I tweaked the hinges a bit.  It's fairly stable up to about 25m/s on Kerbin, which as a prototype was it's only real job.  I like it so much I'm going to send one to the Mun when I have better wheels.  The tiny rover wheels explode if you hit an incline at that speed.

I did try moving the trailer to a central point (blocking the exit hatch, which was why it was off-centre to start with).  It makes no difference.  It does pull to the left slightly but I think that's the drag from the extra wheels as the CoG is good.

I tried all the tweakables but it seems like a limitation of the physics engine.  I can live with a 20m/s speed limit.  I just tapped that into Google and it's 45mph :-)