Hello everyone!
I have bought a wall mount for my TV. The TV weighs 19 kg, the wall mount maybe 2-3 kg. It's screwed into the wall with four holes. There is a 10 cm vertical distance between the holes. The outer edge of the TV ends up 5 cm from the wall.
How do I calculate the tensile load on the top two screws? The wall is porous light concrete, so I would like to over-dimension the plugs! I've googled but haven't found any information on the subject.
Help is greatly appreciated!
/Jens
I have bought a wall mount for my TV. The TV weighs 19 kg, the wall mount maybe 2-3 kg. It's screwed into the wall with four holes. There is a 10 cm vertical distance between the holes. The outer edge of the TV ends up 5 cm from the wall.
How do I calculate the tensile load on the top two screws? The wall is porous light concrete, so I would like to over-dimension the plugs! I've googled but haven't found any information on the subject.
Help is greatly appreciated!
/Jens
Take the strongest ones that fit. With such a short lever arm, there won't be much pulling power.
Count less, act more!
Count less, act more!
Ok thanks for the reply! 
Maybe this isn't a big problem but I'm a little worried! The wall is very porous. You can easily hammer in a wood screw without any issues.
But if I use these (Essve lättbetongplugg):
https://www.essve.se/wcsstore/CAS/PIM/ESSVE/docs/875640.pdf 10mm variant.
It has a tensile strength of 0.3 kN. Four of these on the upper row (up to eight screws can be used in the TV bracket). That becomes 1.2 kN. This should then be divided by two according to Essve. "For long-term load/permanent load, the above load values are multiplied by the reduction factor 0.5"
So 0.6 kN.
The TV weighs 19 kilos. 19x2.5=47.5 kilos. Then I have a margin of about 12.5 kilos.
Am I thinking correctly?
/Jens
Maybe this isn't a big problem but I'm a little worried! The wall is very porous. You can easily hammer in a wood screw without any issues.
But if I use these (Essve lättbetongplugg):
https://www.essve.se/wcsstore/CAS/PIM/ESSVE/docs/875640.pdf 10mm variant.
It has a tensile strength of 0.3 kN. Four of these on the upper row (up to eight screws can be used in the TV bracket). That becomes 1.2 kN. This should then be divided by two according to Essve. "For long-term load/permanent load, the above load values are multiplied by the reduction factor 0.5"
So 0.6 kN.
The TV weighs 19 kilos. 19x2.5=47.5 kilos. Then I have a margin of about 12.5 kilos.
Am I thinking correctly?
/Jens
Just for future reference, you are neglecting the counteracting moment.
With the not very standardized unit kgm, for your case, assuming that the center of gravity is 2.5 cm out.
Driving force 19 kg * 0.025 m = 0.475 kgm
Assume you have 10 cm height on the plate and the center screw hole is 2 cm down from the top edge, so it becomes 0.475 kgm / 0.08 m = 5.937 kg tensile force in the upper screw row. The screws are also subjected to a shear force which is 19 kg.
It is appropriate to dimension the upper screw row for 5.4 kg tensile force and the lower screw row for 19 kg shear force.
With the not very standardized unit kgm, for your case, assuming that the center of gravity is 2.5 cm out.
Driving force 19 kg * 0.025 m = 0.475 kgm
Assume you have 10 cm height on the plate and the center screw hole is 2 cm down from the top edge, so it becomes 0.475 kgm / 0.08 m = 5.937 kg tensile force in the upper screw row. The screws are also subjected to a shear force which is 19 kg.
It is appropriate to dimension the upper screw row for 5.4 kg tensile force and the lower screw row for 19 kg shear force.
Then one has probably assumed that the TV gets there without extra forces and that one never pulls it outwards (like when trying to plug in an HDMI cable with a hand that's far too thick)E Eavuy said:
Regardless, 5.4 kg is a good bit below 150N, which each screw above can be expected to withstand over a long time, so TS's suggestion seems reasonable, doesn't it?