Can NxN post hold Y weight?
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There have been a number of post in mags on differnt joints and load capability . If you are interested I'll try and run them down.
However based on some experience of work with graphic epoxy joints the bond joint thickness must be controlled. I will use bonding beads or wires in joints where I want to make sure I get max strength. Of course you still must make sure you control the bonding load. The idea is then you have a controlled bond thickness around the joint. I think I bought the bonding beads at Wood Craft?
BTW wood is some what like Graphic. You can a very large variation in load testing based on moisture content , joint termination, lot variation so one sample test will not be very good unless you make sure you have lot control also. I think the Forrest service has a hand book that gives info on design loads and then on top of that one usually adds muff factors to account for design changes as you go form concept to final build. Of curse how you calculate the loads is always a question.
I think you should not get too technical and just use some common sense and good wood working principles to build your project. At the end if you have concerns just do "proof" loads on the assembly to put your mind at ease.Oops just stepped on Dave's post. Epoxy is excellent and is one of the few that has good gap fill capability vs strength retention. The only down side it is not repairable andset up time and keeping alignment when clamping. I have tried heating some what and it then hardens to quickly.
I usually try to build items that can be repaired but that is designers choice. -
What kind of mounting will you be using to secure the TV to the post?
What about torsion? Even a ceiling fan could generate enough airflow to cause the large screen/ surface area to wobble on a spindly post. Won't necessarily fall down but you could get seasick.
Something like this will need a stable base and will probably have to be a heavy base, unless you are going to glue, screw and tattoo it to the floor, which is made of what? Wood? Concrete? -
@dave r said:
Most of the weight will be in compression and won't be a big deal. I don't think you'll need to worry about the column breaking. The bigger concern is how do you plan to keep the thing from tipping over? What do you intend to make the base out of and how?
To convince yourself of the strength of your wood, get a piece of 1x4 oak maybe 6' long. Clamp it securely to the work bench so it is sticking out of the end by 4 feet. Hang a 5 gallon pail at the end. Put a small clamp on the end of the board to prevent the bail on the bucket from sliding off. Now start putting weight into it. Test to destruction if your bucket is big enough.
Which will be fine for testing a cantilever beam... does the OP need to test a column?
Most likely if the post is short, even small dimensions can work - so long as the post doesn't buckle.
And you'll need to either have a moment connection to the floor, or some sort of bracing, as noted by others. -
My point in suggesting the testing was for him to prove to himself than the post will support the weight. He was talking about gluing up 3/4" thick oak. With the small amount of weight he proposes to put on it, there's no way it would buckle.
Assuming the post is securely anchored to some sort of base so that it can't tip over, there will be no problem with the post supporting the TV. There are boats with unstayed masts around 3" diameter. Those masts can support much more than 50 lbs of load laterally with no problem.
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My suggestion is that you persuade your girlfriend NOT to buy a TV, and that you find other ways to amuse yourselves in the evenings.
I would wait until you find somewhere to live and as the TV is likeley to be a flat screen, why not bolt it to the wall and free up some floor space.
You might also find some help here http://www.engineering-international.com/#WoodDesign
Regards, Bob
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Dear Bob,
You always have the best ideas and this one is excellent. there's nothing worth watching on TV anyway. Thank you for the link, too.
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@dave r said:
My point in suggesting the testing was for him to prove to himself than the post will support the weight. He was talking about gluing up 3/4" thick oak. With the small amount of weight he proposes to put on it, there's no way it would buckle.
Assuming the post is securely anchored to some sort of base so that it can't tip over, there will be no problem with the post supporting the TV. There are boats with unstayed masts around 3" diameter. Those masts can support much more than 50 lbs of load laterally with no problem.
ahh.
got it.+1 on no TV.
been TV free for 12? years now. -
if you're fed up with TV your cat could enjoy!
I played with the idea of James Owen
http://www.dexigner.com/news/9849
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In Bruce Hoadley's book, "Understanding Wood" there is an examination of the compression strength of wood along various load axes. It is ridiculously strong. You can load a very narrow column that would break the floor before it would fail. Of course slight bending stresses change it from "pure" compression. But have you ever noticed how well trees do? They're pretty heavy
Good luck, Michael -
Good information in the couple days I've been out.
As for not having a TV, trust me when I say I agree. I haven't watched TV on my own (without her begging me to "spend time with her" after work or something in years.
However, I won't complain about a big screen I can hook my PS3/Xbox360 up to. Currently I use my two computer monitors for them.
As for the base of this thing, it will be your typical TV stand. 18-20 inches deep and probably 50+ inches wide. Her current tv stand is a dresser that is 18x54x30 ish. Has enough room for her 32", and the various video devies stacked up next to it. That fills up 100% of the width of it.
A typical 55 inch (the biggest she said she would ever buy, and I agree) is about 52 inches wide I think. But having the bottom 30 inches up is way too high for a screen that big.
So what I was thinking was something about 20-24 inches high, with a post to mount the TV on just because it looks better like that.
Something with similar dimensions to this:
Except it won't be 600 dollars... Those things are pretty darn stable, the only way it can fall is backwards.
I might actually look into having something fabricated out of steel. I don't know how to weld, but my uncle does and has the tools to do it. We also know companies that can cut the pieces for low cost to me. That might actually be easier to do.
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masta
Some tid bits of info for you. I pulled my spec for the Sony 46 XBR Bravia I have;- Weight 84 lbs
- Size w/o its supplied stand 49 3/4 x 29 x 4 7/8 in
- For wall mounting using their separately supplied wall mount bracket they recommend the load carrying capability be 4x the weight
BTW I designed a small stand like you are thinking and it failed proof load. I still have it setting on the floor
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Failed proof load? I assume that means your stand wasn't up to snuff then.
Perhaps I should invest in some steel for this.... The only "important" reason for the post design is to be able to mount any size TV I want at the proper height. If I was just designing it for a specific TV I would simply build something to set it on top of with its included stand.
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That is the reason for proof loads and the bonding beads / wires I was discussing above. If you do the joints correctly then the wood will fail before the glue joint does provided you get the correct bond line thickness. If you do a search in mags like Fine Wood Working they have presented testing showing various joints and the load carrying capability. The results will probably surprise you. I usually build a test model first to work out problem areas and that is what failed so no big loss except some time .
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