Wire moves relative to part sliding

gerald_kreissig

I am trying to design a telescoping boom of a mobile crane, where the boom extension is controlled by a wire and I would like to simulate the telescope behavior of all participating parts in relationship to the movement.

I can simulate the telescope behaviour of the two components with the slide mate connector and a linear relationship between them:

When the 2 part of the boom are moved, the overall wire length remains the same, but the distance between the anchor points in the back (read arrows) and the guide pulley in the front (green arrow) should change, which I cannot currently achieve.

Is this something, which can be designed and simulated with Onshape?

If this is the case, can someone point me to a tutorial or description, how this can be achieved?

I appreciate any advise or help to address this design challenge!

Best regards

Gerald Kreissig

wayne_sauder

I have not played with wire or rope, but I did spend a long time trying to get a conveyor chain to simulate for me. Never did get it, from what I understand such things would require a type of contact and release mate, which Onshape does not currently have. However, if you can figure out how to make it work I would be interested in knowing how it is done.

john_mcclary

You won't be able to show the wire being wound up in real time. But you can configure the part's lengths and show the positions you need. 

gerald_kreissig

I came up with this idea too and had already implemented it:

It works as expected, but it is missing the thrill of realtime movement!

john_mcclary

Well, because your wire is straight, you can take advantage of overlapping wires if you really want an animate-able model.

it won't work for a festoon or spring though.

https://cad.onshape.com/documents/6efff366880bd253f50599eb/w/e7b1f1f81ef075732a4a3af8/e/4e6e1a11dfe47771a8af7099

 

gerald_kreissig

That's neat!
Thank you for the idea - I will try it!

gerald_kreissig

Hello John,
I tried your idea of using the linear movement of wire segments as you have shown it with the light sabre:

It works just as I had envisioned it!
Thank you, Gerald

john_mcclary

Sweet