I hope someone here can help me, I am trying to carry out an FEA on a chassis I have created, It features 3 or 4 different weldment profiles. However as i try to simulate the model it comes up with an error message saying "Model is unstable, Check that you have applied adequate fixtures to stabilize the model."

I have applied a "fixed constraint" at the rear or the model (four corners) and applied a force at the front.

Could someone please give some guidance to what i need to do. I can upload more pictures should it be required.

* Revised - I have a feeling the error is in the constraint (the fixture) i have selected "joint" fixtures, if i try to select a face it comes up saying "Load/Restraint cannot be applied to the beam face, edge or vertex

Many Thanks

Ryan