Tracing path of jointed arm

[Jim K...]

With a very short pencil & a very long arm?

[Davidm]

Not even sure that's a good title - google didn't seem to find anything relevant. I've got a TV mounting bracket, with 3 pivot points:

- one on the plate that fixes to the back of the TV (it's horizontrally central on the TV)

- one on the wall mounting plate

- and one where the two arms meet. However the wall arm is twice the length of the TV arm, so when the TV is pushed against the wall it's offset from the centreline of the wall bracket. Since I'm mounting the TV in an alcove, with not much clerance either side, I want to plot out the "swing envelope" to check it will fit, and just where to mount the wall plate. Is there any bit of software (Windows) that will do this, or help in some way, or might I just as easily knock up a dummy frame, mount the bracket and add a piece of timber the width of the TV and trace the thing out on a table top?

I've always been fascinated by how people design complex hinge systems, when I can't even visualise a simple TV bracket's trajectory.

[nothanks]

I would knock-up a quick prototype, as you've described - you'll have an answer that you believe long before you will have found and learned how to use a piece of software.

[Andy Bennet]

Inverse kinematics. I use Autodesk Inventor for complex mechanisms. I am sure other software is available.

[Murmansk]

I had a similar situation - I just attached the bracket to the TV, folded the bracket into its closed position and put the TV in the middle of the alcove and marked the wall with the position of the attachment plate.

[harry]

The reason for it is that when the TV is pushed back to the wall, the wall mount and the TV mount don't collide so the TV goes back much further.

It's easier to think about if you imagine the TV and wall to be always parallel.

[Lee Nowell]

If I follow correctly, the centre of the bracket that goes into the TV would be the centre of the when the TV is against the wall. So if you position that in the centre you can mark the holes for the fixing bracket to the wall.

Given the 3 hinges, I think (you could validate by putting it on the floor) but you would be able to move the TV out perpendicular to the wall and whilst keeping the TV parallel to the wall. The 2 arms / TV bracket would pivot to a greater or lesser extent to accommodate.

I may be visualising your setup incorrectly?

[newshound]

A very interesting question. I once worked in a research group who were looking at this for generalised cases (and much more, in that they included friction and also the dynamic as well as static loading).

Since commercial TV brackets are *very* simple I would just knock up a full scale mock up using 18x38 batten and M6 coach screws as others have suggested.

Unless you are *already* using Autodesk, Inventor, or one of existing packages.

[Davidm]

With an offset bracket the TV is going to move sideways as you pull it out, and if there's only 1cm clearance each side....... I'd rather work out if it will fit before I go drilling fixing holes for masonry bolt.

[Davidm]

Yes, it's not the marking out that's my concern, it's if the TV can pull straight out from the wall for 25cm or so, and then far enough that it can be rotated about 35 degrees without one side of the screen getting obscured by the alcove.

I think I'll just mock something up, using the real bracket.

[Lee Nowell]

Would be interested in your findings but as I see it (also checked with a ruler and pencil mock up) because there are 2 arms independently rotating, you can pull the TV out straight with no sideways movement.

[Dave W]

That would be the best plan.

We could do with some more dimensions. It sounds as if with the TV against the wall, it fits with 1cm to spare either side in the parallel-sided alcove. Let's say the TV is width w and depth d, and the arms are b and 2b and short enough to be within the confines of w.

You say the TV is offset from the wall pivot when against the wall, so that means that b is greater than d/2, too long to allow the wall pivot to be immediately behind the centre of the TV.

You should make the wall pivot as near as possible to the centre of the TV when it's against the wall, to gain the maximum possible distance that the TV can be brought forward. That would be 3b if the wall pivot was in line, but less if not.

You say you don't want the TV to be obscured by the alcove when tilted, which means the depth of the alcove is too great for the TV to be swung in front of it?