I want to construct a simple cabinet for holding a 25'' TV set. I'm planning
to construct the surfaces of MDF and make some structure of pine to give it
the strength to hold the TV height. The structure will resemble a table:
four legs joined by four rails to support the upper panel (table top). Three
sides will be covered by panels (one will stay opened for shelves/drwawers)
and also will be a bottom panel. Panels will be secured to legs so it will
give the cabinet more strenght. The question is which width I need for the
pine beans that will conform the structure? The cabinet will be about 80
inches long by 20 inches height and width. The holding "legs" will be 20
inches apart from each side. I wonder if I'll need another central rail.
Any other idea for giving the cabinet strength? There are any existing
tables on the net for estimating material withstanding?
Any suggestion will be appreciated
Thanks in advance
--
Faustino Dina
--------------------------------------------------------
If my email address starts with two 'f'
drop the first 'f' when mailing me.
Great structural information site Greg, I for one thank you.
--
Chipper Wood
useours, yours won't work
"Greg Ostrom" <[email protected]> wrote in message
news:[email protected]...
> You can find information on elasticity modulus on the net also. This
will
> tell you how much sag you will get with a weight application. Lots of
neat
> stuff out there.
> http://www.engineersedge.com/beam_defl_even.htm
>
>
"Faustino Dina" <[email protected]> wrote in message
news:[email protected]...
> > If you ask an engineering question, you get an engineering answer.
> I'm not an engineer but I think engineers doesn't recalculates structural
> ressistence for each project... I believe they REUSE some design patterns
> already calculated by someone else and tested an validated for many others
> in practice...
Sometimes you can. More often you can't. In almost all of my designs, I
had to do my own stress analysis because there wasn't anything else around
similar enough with published data.
todd
On 21-Apr-2004, "Faustino Dina" <[email protected]> wrote:
> I suppose you guys when plans your furniture doesn't relies on such pretty
> formulae, but on experience. I was expecting some response like " 2 x 2 pine
> beam will be ok"....
If you ask an engineering question, you get an engineering answer.
Mike
You can find MOE, density and other properties of MDF here
http://www.lungster.com/l/speakers/mdffaq/mdf.html#Q3
"Faustino Dina" <[email protected]> wrote in message
news:[email protected]...
> > http://www.engineersedge.com/beam_defl_even.htm
> Nice formulae BUT...
> - I dont know the Modulus of Elasticity (E) for 1/2 MDF edge banded by a
> pine beam
> - I dont know the Moment of Inertia (I) of the same arrangement
>
> I suppose you guys when plans your furniture doesn't relies on such pretty
> formulae, but on experience. I was expecting some response like " 2 x 2
pine
> beam will be ok"....
>
>
>
On Wed, 21 Apr 2004 13:09:26 -0700, Chipper Wood <[email protected]> wrote:
> Great structural information site Greg, I for one thank you.
Wow, that is a fantastic site. Yes, thank you, Greg.
Dave Hinz
> http://www.engineersedge.com/beam_defl_even.htm
Nice formulae BUT...
- I dont know the Modulus of Elasticity (E) for 1/2 MDF edge banded by a
pine beam
- I dont know the Moment of Inertia (I) of the same arrangement
I suppose you guys when plans your furniture doesn't relies on such pretty
formulae, but on experience. I was expecting some response like " 2 x 2 pine
beam will be ok"....
> If you ask an engineering question, you get an engineering answer.
I'm not an engineer but I think engineers doesn't recalculates structural
ressistence for each project... I believe they REUSE some design patterns
already calculated by someone else and tested an validated for many others
in practice...
Faustino Dina wrote:
>> If you ask an engineering question, you get an engineering answer.
> I'm not an engineer but I think engineers doesn't recalculates structural
> ressistence for each project... I believe they REUSE some design patterns
> already calculated by someone else and tested an validated for many others
> in practice...
Depends on what you're doing. For some things there are codes and standard
analytical procedures, for others there aren't. But it's rare that a full
stress analysis of a subassembly can be lifted from one project and dropped
into another--there's usually enough difference in some aspect of the
loading or attachment to merit recalculation even if the assembly itself is
unchanged.
--
--John
Reply to jclarke at ae tee tee global dot net
(was jclarke at eye bee em dot net)
"todd" <[email protected]> wrote in message
news:[email protected]...
> "Faustino Dina" <[email protected]> wrote in message
> news:[email protected]...
> > > If you ask an engineering question, you get an engineering answer.
> > I'm not an engineer but I think engineers doesn't recalculates
structural
> > ressistence for each project... I believe they REUSE some design
patterns
> > already calculated by someone else and tested an validated for many
others
> > in practice...
>
> Sometimes you can. More often you can't. In almost all of my designs, I
> had to do my own stress analysis because there wasn't anything else around
> similar enough with published data.
>
> todd
of course nobody else has enough data to satisfy the todd.... not in
politics OR woodworking.
randy
It's hard to see exactly what you mean without seeing a plan.
I have built entertainment centers before and the TV's are very heavy and
must be accounted for carefully.
What I would do is cut your MDF to size, attach some pine as you say
underneath it to give it extra strength and place the MDF on two sawhorses
at the same distance as you plan to install your legs and put your TV on it
and see if it sags at all. That will tell you how many legs you need. Be
conservative. If in doubt, add strength.
I assume you are planning on painting it so if you have to add another leg,
you can cover any mistakes with paint.
Or, you could just add another leg anyway. Not a bad idea in my mind.
"Faustino Dina" <[email protected]> wrote in message
news:[email protected]...
> I want to construct a simple cabinet for holding a 25'' TV set. I'm
planning
> to construct the surfaces of MDF and make some structure of pine to give
it
> the strength to hold the TV height. The structure will resemble a table:
> four legs joined by four rails to support the upper panel (table top).
Three
> sides will be covered by panels (one will stay opened for
shelves/drwawers)
> and also will be a bottom panel. Panels will be secured to legs so it will
> give the cabinet more strenght. The question is which width I need for the
> pine beans that will conform the structure? The cabinet will be about 80
> inches long by 20 inches height and width. The holding "legs" will be 20
> inches apart from each side. I wonder if I'll need another central rail.
> Any other idea for giving the cabinet strength? There are any existing
> tables on the net for estimating material withstanding?
>
> Any suggestion will be appreciated
> Thanks in advance
>
> --
> Faustino Dina
> --------------------------------------------------------
> If my email address starts with two 'f'
> drop the first 'f' when mailing me.
>
>
Being a graduate structural engineer, I surely love the site
referenced, but alas as you may of seen or pointed out, how do you find
the values to plug into the deflection calculations. Instead of running
the numbers, set up a experiment. Figure out the span that you want to
start with, support it on the ends and place a like load + 20% (ye ole
fudge factor, which is MOST important) with bricks, blocks, stones, etc
in the middle of this span (creates the most deflection). Since the
supports at the end of the span, for your test will be simple supports,
then your deflection will be greater than the supports you will create
(fixed or moment supports). Observe and measure the deflection. Remember
the weight of the material will generate some deflection, though you may
not see it with your eye. If you are uncomfortable with the deflection,
then move the supports in and retest. If the span length is too short
for your comfort, then add stifiners and retest. I suspect that you will
quickly come up with a suitable design. How do you think the
engineers/architects of old did this type of work ? Through testing and
trial and error (though the errors some times resulted in loss of life).
HTH
JAW
Faustino Dina wrote:
> I want to construct a simple cabinet for holding a 25'' TV set. I'm planning
> to construct the surfaces of MDF and make some structure of pine to give it
> the strength to hold the TV height. The structure will resemble a table:
> four legs joined by four rails to support the upper panel (table top). Three
> sides will be covered by panels (one will stay opened for shelves/drwawers)
> and also will be a bottom panel. Panels will be secured to legs so it will
> give the cabinet more strenght. The question is which width I need for the
> pine beans that will conform the structure? The cabinet will be about 80
> inches long by 20 inches height and width. The holding "legs" will be 20
> inches apart from each side. I wonder if I'll need another central rail.
> Any other idea for giving the cabinet strength? There are any existing
> tables on the net for estimating material withstanding?
>
> Any suggestion will be appreciated
> Thanks in advance
>