Modeling Motorcycle Rider Stiffness

[HDFEA]

Hello,
I am trying to model the rider and passanger on a full-vehicle motorcycle FE model. I am representing them as lumped masses at their appropriate c.g.'s and want to hook them up to the vehicle so that during acceleration loading (braking), their masses will load the vehicle appropriatly. I am thinking of hooking the rider up to the handlebars (right and left side), as well as the footboards (right and left side). The passanger I will hook up to the passanger footboards (right and left side and the area of the seat that he/she touches). How do you model the stiffness of the person into the vehicle? I am currently using very soft 3-d springs so that I don't artificially stiffen the structure. Is this appropriate? I am just trying to distribute their masses into the vehicle properly. Any suggestions?

 

[toothroot]

I think, rigid bars or rigid elements could be more appropriar, since it can be assumed that the rider's stiffness does not contribute to the overall performance of the motorcycle. (Except when the rider changes his/her position dramatically during acceleration or breaking, which I hope he won't...) Rigid construction are frequently used to give an abstraction of structures that transmitt forces without adding to the overall stress or displacement behaviour. But careful! You should always check the connection between rigids and your model. Rigids have rotational dofs (like beams), if you connect them to solids in the wrong way, you may end up with an unconstrained model. Plus, if you look at stress results close to the connection, you get highly exaggerated peak values if you connect the rigid construction only to a few nodes. I'm not that sure about numerical effects, but if you use the sparse matrix solver, you should be able to get good results. In case of the iterative solver, be careful not to loose convergence!

 

[HDFEA]

Thanks for the reply toothroot, but I'm a little confused. In my experience, when you hook up a lumped mass with rigid bars from the handlebars to the footboards (a long span of distance) you artificially stiffen the structure unless you have soft springs between the rigids and whatever they are attaching to.