Locking a part in horizontal direction

Hi, I am trying to simulate a passive dynamic walking apperatus that walks down a slope driven only by potential energy in Simmecahnics. I finished the model and would like to play around with the parameters (length of the legs, position of the centers of gravity and so on) to make it work, but I have a problem with the slow simulation speed.

I assume that is because of the calculation of the horizontal force which is activated when the the foot hits the floor. For the vertivcl force I modeled a spring damper system which works fine. I also did that for the horizontal force but since I did that it became very slow.

Now I am looking for another solution. I actually don't need the spring damper system in horizontal direction. It would also be okay if it is just locked in that direction as soon as the foot hits the floor. Kinda like as if the contact point would become a revolute joint.

Any ideas how I could do that?

Thank you very much in advance!

[Philipp]

Is this forum the right place to ask questions regarding Simmechanics?

[Jan]

Yes, Philipp, Simmechanics is a part of Matlab.