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Old 29th July 2009, 09:43 PM   #1
Bengali is offline Bengali  United States
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Hi,

My goal is to mount two 1" x 1.5" Aluminum Tubes to
the back of my tv stand. A lcd wall mount would then
mount to the tubes. the tubes would act like the studs
in the wall.

the wall thickness of the standard aluminum tube is
0.125". the bolts would go through both sides of the tube.

My tv is about 45lbs. My question is if the aluminum is strong
enough to hold this weight. It does not seem like a lot of
weight for the aluminum but I could be seriously under
estimating. I'm trying to avoid steel since it costs drastically
more and much harder to work with.

thanks!
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Old 1st August 2009, 01:27 PM   #2
AndrewT is online now AndrewT  Scotland
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Have you tried to bend 1/8inch wall rectangular aluminium tube of that size?
Without any maths, just put a 3foot length across your knee and see what gets damaged first.

BTW,
M/I=E/R=Sigma/y if you want/need confirmation.
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Old 1st August 2009, 01:48 PM   #3
infinia is offline infinia  United States
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Default Re: Question for Metal Experts

Quote:
My goal is to mount two 1" x 1.5" Aluminum Tubes to
the back of my tv stand. A lcd wall mount would then
mount to the tubes. the tubes would act like the studs
in the wall.
How long are the tubes? maybe best to show a quicky sketch.
If they are longer, then sg steel would be advised. They are not that expensive unfinished, if you have a metal supply house nearby.
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Old 1st August 2009, 02:41 PM   #4
AndrewT is online now AndrewT  Scotland
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Hi,
if the tubes are vertical then the length of the tubes is irrelevant to strength.

Long tubes will deflect more due to the eccentric load and once they deflect they are no longer vertical. This will increase the eccentricity of the load.
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Old 1st August 2009, 02:44 PM   #5
infinia is offline infinia  United States
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Quote:
Originally posted by AndrewT
Hi,
if the tubes are vertical then the length of the tubes is irrelevant to strength.

Long tubes will deflect more due to the eccentric load and once they deflect they are no longer vertical. This will increase the eccentricity of the load.

That's the theory but unless he balances a top heavy load (under all conditions) there will be a bending force. As for conditions using only 2 vertical poles is not too stable to begin with. So use a tripod structure or get more strength to bending.
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Old 1st August 2009, 02:51 PM   #6
AndrewT is online now AndrewT  Scotland
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of course there is a bending moment on the vertical tubes.
It's eccentrcity * load.

The length of the tubes does not enter that equation.
Eccentricity does.
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Old 1st August 2009, 03:04 PM   #7
infinia is offline infinia  United States
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Quote:
Originally posted by AndrewT
of course there is a bending moment on the vertical tubes.
It's eccentrcity * load.

The length of the tubes does not enter that equation.
Eccentricity does.

since your civil I'll defer, but I'll bet the radius or length will be a factor.
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Old 1st August 2009, 03:05 PM   #8
Bengali is offline Bengali  United States
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thanks!

I think the aluminum will work since the bolts will
go through both sides of the tube. I bought some .75" sq.
I'll be using steel washers on both ends so that should
re-inforce it some more. bottom end will be bolted down to the metal frame of my tv stand.

Now I'm wondering how many inches I can extend the mount forward since the tv is now towards the back of the stand.
I'm going to look for 6' spacers if there is such and use long
1/4" bolts.

I bought a flat lcd tv mount on ebay for $30shipping
and the tubes were $22. It sure beats the $700 TV floor stand.
The prices for those this are nuts!

It will be nice to have the center channel higher up. Much better sound
Attached Files
File Type: pdf center mount.pdf (8.8 KB, 23 views)
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Old 1st August 2009, 03:37 PM   #9
infinia is offline infinia  United States
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If you are set on aluminium rods then use eyebolts for the 2 top mounts in the rear and then use heavier picture frame cable (pre loaded) to secure against the back wall for stability. Check for plumb.
IMO I would still check for steel sq stock.
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Old 1st August 2009, 07:46 PM   #10
Ron E is offline Ron E  United States
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Mountain bikes have wall thicknesses less than 1/32 inch in some cases and can withstand hundreds of pounds of rider jumping off an obstacle - the secret, very little bending moment.

As others have alluded to, it all depends on geometry. Sketch your design and someone can answer your question.
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