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Translational/Sliding Joint Location

Translational/Sliding Joint Location

Translational/Sliding Joint Location

When a translational/Sliding is created, does the location of the joint matters. When a hydraulic cylinder is modelled, where the translation joint between cylinder rod and cylinder housing should be created and what determines the location of the joint.

Thanks for your input and help.

RE: Translational/Sliding Joint Location

That's a very basic model of a hydraulic ram, and the answer is that it doesn't matter. However in a more complex model you would put one constraint at the rod guide and the other at the piston ring, but you wouldn't use the same constraint type as that would be redundant, and ADAMS would ignore the unnecessary constraint(s).

Basically you are suppressing all motion except Z and RZ, at one point. A 2 constraint system would suppress X and Y at 2 points. Down the track this would simplify adding radial compliances and so on.


Greg Locock

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RE: Translational/Sliding Joint Location

Based on my experiences ~25 years ago...

The location of the joint shouldn't matter, but it does affect the solution. The solver sees a constraint like any other error term to be minimised. ADAMS doesn't create a logical model, where constraints are removed from the equations. Try building a model that has a translational joint between two parts that is long way from a large normal force between them that would "bend" the joint. I have a vague memory of doing this and being able to estimate the effective torsional stiffness of a translational joint.

But the answer to the question is to locate the joint so that the above effect is minimised.


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