TV on long reach wall mount - max turning moment on wall?

[Tim Watts]

Engineering/physics folks:

Does this look reasonable? Partly an academic exercise...

Single skin internal solid brick wall Single storey, non load wall (so nothing sits on top - ceiling joists run parallel and either side)

TV mount 0.8m down from top of wall and about 0.6m from the corner, doorway 0.6m to the right of the TV mount mid position.

Cannot verify if this wall is tied to the main outside wall (left of diagram - probably is as both are brick and 1950s build??

Blue bricks take the fixing bolts. Green bricks show what I think are the bricks whose weight transfers onto those blue bricks.

There are 105 blue/green bricks at 2kg/brick and assuming 0.5kg mortar+plaster per brick.

So for the TV to be able to tip that wall over, even if it was dry stacked loose, would require 165Nm or turning moment assuming:

105 brick's worth of weight acts vertically downwards in the centre of the wall and the bracket is 1/2 brick+10mm plaster away from the centre.

TV is 11.4kg, soundbar is 4kg, 50% of the TV bracket is 5.5kg, so total load at 600mm (max reach of bracket arm) is 200N rounded, with a turning moment of 120Nm < 165Nm

In reality the limited adhesive effect of the mortar will add strength, the wall is probably (should be) tied to the outside wall on the left so that will resist toppling and there is a heavy wooden sliding door hung on the otherside of this wall (goes behind the TV when open) so that's counterbalancing too.

Thoughts on method and assumptions?

[Tim Watts]

Oh and I've assumed the fulcrum point is

a) At the plaster/tv mount interface;

b) At the bottom of the mounting bracket (lower set of bolts).

[The Natural Philosopher]

I mounted a CRT TV on a single brick wa'l back in te day iusoing ine of those cantlever things...

A brick - well a half brick - fell out during drilling, but after mortaring it back in place the thing took the weight no problems

[Andrew]

If there is a pitched roof then I would use some long galvanised straps at right angles to the wall, on top of wall and attached to the top of the wall and the joists on either side.

If it is a flat roof, then I would hackoff the internal corner plaster to make sure the internal wall is tied into the external wall.

[Jimbo ...]

sand lime mortar ? .....

[Jimbo ...]

get a samsung....they don't weigh much ....

[Tim Watts]

Already is and 11kg is not bad for 48" :)

[Tim Watts]

I'll check that one - it might be that wall has a wall plate (some internal walls do some don't).

Then I could add a noggin on top of that between the 2 ceiling joists which are 5" apart (literally at both front and back faces of the wall)

Easily accessible - it's upstairs in the dormer area (pitch roof over this bit)

[Tim+]

The maths is beyond me alas but personally, if I had any misgivings about the wall strength I would fix the TV bracket to a solid board mounted on the wall to extend the spread of the load both vertically and horizontally.

Thickish MDF maybe? As long as its a bit smaller than the screen and painted to match the wall it?s not going to be obtrusive.

Tim

[John Rumm]

My approach would be to assume absolute worst case - work out what would happen if the mount were fixed to just the bottom line of bricks.

On the other side of the 600mm leaver's fulcrum (i.e. the thickness of the single skin wall) you can assume say 100mm of leverage. That gives you a 6:1 mechanical advantage that would try to lift the higher bricks.

The 6:1 gives give you 1200N of lift - spread over 3 bricks. Ignoring the weight of mortar and plaster, and adhesive effect, and the restraint of the perpendicular wall, you have at least 2000N of load.

Needless to say the actual situation is far less pessimistic than the assumptions. So nothing to worry about.

[Rob Morley]

I'd be inclined to ignore the sums and just fix a bit of 4x2 between the floor and the ceiling, thus avoiding the bricks completely. :-) I might be biased because I have in the past knocked a brick out of a wall by trying to drill a small fixing hole in it with a regular hammer drill.

[Tim Watts]

That's interesting John - You've proposed that the leverage is effectively lifting the *far* edge of the brick and thus mechanical advantage should be applied to that point - whereas I assumed it should be applied the centre of gravity (centreline of the wall).

That makes sense as bricks are rigid - and doubles the advantage (I had

1:12 more-or-less)

Thanks - and this would make an excellent physics A Level question :)

[John Rumm]

I am also assuming that they will resist tipping (due to effects of the mortar and the perp wall) - that may not always be the case. A wall of smooth blocks resting in a stack would be easier to make "fall over".

Probably slight too many uncontrolled variables for that.

[Robin]

Belated thought: I wonder if the risk assessment needs to include child/idiot using the mount for pull-ups :(

[Tim Watts]

I usually try that with a good tug on the mount :) (Fitted one before, but to a load bearing wall with the building sitting on top of it)

[DerbyBorn]

Robin wrote in news:bb422416-fe6b-7889-85da-36b75cad2bc7 @hotmail.com:

...whilst being videoed for Facebook / Harry Hill !

[Johnny B Good]

That's only a couple of Kg lighter than my Lidl Parkside PGI 1200 B inverter genset![1] :-)

That's given me an idea for mounting the genset safely above the rear patio concreted area (not really - only joking :-)

[1] If you're quick off the mark, you just might be able to get your hands on a really cheap 1KW (1.2KW 5 seconds peak) inverter genset for a mere 99 quid; less than a third of the typical price of a Toolstation 900W version or just under 35% of the price of Screwfix's 1200W (1500Wpk) inverter genset offering (Impax IMDY1500LBI model) if you need a touch more 'grunt'.

Screwfix are currently better value than Toolstation for small inverter gensets right now even if it does mean paying just over four times as much for 2.2 times the grunt of a Lidl 'Special' (the Impax IMBY2200W inverter genset).

Apologies for the OT sub-thread. I'll post a seperate thread about my adventures with Lidl inverter gensets during the best part of this past fortnight shortly. :-)

[charles]

I bought one last summer - it refused to start. I wentb back to Germany and new one arrived - the spring on tehn recoil statrted failed on the 2nd use. So I went and got my money back.

[Johnny B Good]

There's a good chance that was due to a stuck oil level float switch. Easily remedied, apparently.

Just poor quality control. It was fourth time lucky for me. I didn't see any issues with the recoil starter until checking out my 'bulk buy' of the last two where the one selected for return seemed as though it may have been a refurbished return which had seen some service out of its starter cord.

Looking at pictures of alternative brands of inverter gensets in the

1000 to 1500 VA range costing two to three times as much, I got the distinct impression that they all used the same kit of parts assembled into differently styled casings. IMO, You could spend two or three times as much on any of these alternatives and still be no better off qualitywise.

BTW, I did post a seperate thread as threatened. It turned out a lot larger than even I anticipated. Hopefully, it'll prove useful to the more stoic of computer DIY enthusiasts prepared to at least skim through the article.