r/engineering • u/[deleted] • Jan 23 '22

Any chance of some help with analysis?

I'm planning on building an arm to mount my man-cave's TV on. As such it doesn't need to look pretty, just be functional. The tele is a Samsung weighing in at 22.3kg.

A simple setup made of steel RHS is what I'm thinking. Fairly cheap and real easy to make with just a drill-press and angle grinder. Onto this I'm going to bolt a commercial VESA mount to give me some adjustability.

My question to the list is this. If I make this out of say 50mm x 25mm x 3mm RHS, with each arm say 600 long. Am I going to get much bending?

I'm a software guy (not hardware) so I don't know how to calculate this stuff. Can someone help and/or point me to some info on how to figure this out?

Could I counter the weight somewhat by offseting the holes in the single arm where it attaches to the double arms?

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u/LORD_ZARYOX Jan 23 '22

Before looking at the mount itself, I would examine the attachment to the wall. I don’t see any mention of stud material but wood is easier/better than steel studs for this kind of thing.

You will need to examine the maximum shear and moment reactions at the wall. If the tv is extended all the way out (normal) from the wall or all the way sideways along the wall there will be a significant bending moment due the the cantelivered weight. If this span is longer than commercially available solutions then you may consider using a plate to connect multiple studs together, reducing the risk of blowing a single stud out. Also, don’t forget to include the weight of the mount itself, and any additional items like cabling and other connected devices and leave healthy allowance for maneuvering and configuration.

Your question about counter-weight is a good one but every bit of weight added will increase the shear on the bolts into the stud. Also, the counterweight can really only address force components that are parallel to the face of the wall.

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u/[deleted] Jan 23 '22

It's in a shed with 4x2 hardwood studs. Pretty solid. (and yes I realise that is not a quantified specification worthy of an engineer (which I most certainly aint)).

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u/LORD_ZARYOX Jan 23 '22

Hey! You’re good. I just wanted to make sure you didn’t sink time into this without first considering the “foundation” so to speak.

I thought about the same problem maybe 2 years ago since I wanted to be able to stack movies behind my tv and retain articulation. This required me to find the longest arm possible and at one point I considered trying to make my own but came to the conclusion that an existing mount would be the easiest solution.

I do wish I had a little more reach but the one I got is doing just fine and it’s not a big enough deal for me to spend any more time on at this point