Scissor mechanism problems

rollinns

Thank you to the creators of Sketchup and SketchyPhysics, it's extremely helpful.
Through searching I found a few scissor related questions on this forum, but they did not discuss the problem I'm having. Right now I kind of feel stuck.

My setup:
Sketchup 2014, Sketchyphysics 3.5.5

Please see my attached file. I'm designing a scissor lift stand for my bandsaw.
Here's a general idea, but mine will be battery powered to raise and lower it.
https://www.youtube.com/watch?v=gWh3PMyWwpI
the power mechanism I'm working toward can be found by searching youtube for "stryker ambulance stretcher"

The yellow component has a hinge that's working correctly, I'd also like it to slide following the piston joint toward the center of the green component. The white component also hinges correctly.

If you run the SP simulation, the wheels of the yellow piece will fall, I'm trying to get the top of the yellow piece (the end furthest from the wheels) to slide.

Once I get the yellow piece hinging and sliding, then I'd like to add a third hinge where the center lines of the white and yellow pieces are on the same plane. I haven't gotten that far yet, so that hinge is not present yet.

This link may help, but I still couldn't figure out how to make it slide.
http://sketchucation.com/forums/viewtopic.php?f=61%26amp;t=6671

Any help is greatly appreciated.

bandsaw-stand with scissor legs 2014 B5.skp

rollinns

I made some progress, so I thought I'd share in case I can help someone, or in case I forget.

I made a piston along the inside green frame.
there is a small white dowel between the green frame and the end of the yellow component. I grouped the white dowel and the piston together.
the hinge and the yellow frame are grouped.
I used the "Joint Connector" tool to join the green frame to the dowel.
I used the "Joint Connector" tool to join the hinge to the dowel.
I set the sketchyphysics properties of the green frame to static.

bandsaw-stand with scissor legs 2014 B4-B.skp

Anton_S

Hello and welcome to the forums, rollinns!

I think I got your model working the way you requested:
bandsaw-stand with scissor legs 2014 B5.skp
Here is some description explaining of what I did to get it working:

To get a physics joint moving, it must have a parent body. In your example, to get the hinge joint moving along the piston, it should first be created or grouped within a parent body. Usually, parent body is a simple "temporary" box. Then, the parent body (grouped with the hinge joint) must be connected to a piston joint. There, now the parent body (grouped with hinge) can move along the piston and the yellow component can rotate along hinge and move along the piston.

One more thing. When playing simulation it's a common practice to add two scenes. One called "Play" and the other called "Edit". The Play scene should have all physics joints hidden, simply tweaked by turning off the "Physics Joints" layer and updating scene. And the "Edit" scene should have all joints visible, simply tweaked by enabling the "Physics Joints" layer. The reason off adding such scenes is to prevent the joints from being displayed in the view. Also, settings the parent body (grouped with hinge) joint to "Physics Joints" layer would be a good practice as well, as it's just a temporary box and it won't be present in real world... I have all these things done in your model. Applying this tip to your future models might come handy.

Anton

rollinns

Anton,
Thanks so much for your reply. I got it working on my own, but I really appreciate it. Could you tell me what you mean by two scenes?
and could you tell me what you mean by a "temporary" box?

I'll reupload my model on this thread as soon as I finish the other folding leg. My end plan is to use a modified trailer jack to power the scissors up and down. The trailer jack will be driven by a parts of a broken cordless drill.