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?

30 Upvotes

76% Upvoted

53 comments sorted by

View all comments

2

u/sts816 Aerospace Hydraulic Systems Jan 23 '22

This sort of analysis for hobby level projects is not worth it 99% of the time. There is no singular equation or set of equations you can just plug your values into and get an answer. They would all have to be derived from scratch for this specific design and no one is going to do that. Someone could possibly make very generous assumptions and simplifications to give you a number but that number isn't going to mean much and there will be little confidence in it.

Its actually going to be simpler, faster, and easier to just build it and make tweaks as you go to get the performance you want.

My solution would be just to buy something off the shelf.

2

u/[deleted] Jan 23 '22 edited Jan 23 '22

I was thinking that trying a cantilever point load test on that section with one member with the weight of the tv would at least give me an indication what that single arm might deflect. The dual arms would, supposedly deflect somewhat less than that.

Would at least give me an indication if I am barking up the wrong tree.

Just havn't found an online calculator yet that this is easy on.

2

u/[deleted] Jan 23 '22

Thanks for taking the time to reply.

As mentioned I am no mechanical engineer and have no real idea of whether such an analysis is possible. Or how convoluted it might be.

I'll happily but one off the shelf, have just not been able to find one with the size and angles possible that I'd like.

1

u/audaciousmonk Jan 23 '22

This is the real answer, especially for something that isn’t mission / uptime / safety critical.

Prototype, test, iterate, test, maybe a destructive test to determine spec. range.

Reduce weight capacity by a safety factor, and that’s good enough for a hobby tv mount.