Anyone know about construction? How much support am I losing? (TV riser)

[55katest55]

So...i messed up my measurements. I'm building a TV riser to put my TV on top of and my huge center speaker underneath of. How much structural integrity/strength/support/whatever would i lose (if any) by going from TV riser A to TV riser B? The TV + stand weighs 76.5 lbs.

A:

B:

Sorry for the weird view, I havent built them yet and I was just trying to see what it would look like (I flipped the images).

THANKS!

 

[its phillip]

no idea. if you go with riser B, maybe add some bracing on the back of it?

 

[55katest55]

no idea. if you go with riser B, maybe add some bracing on the back of it?

I was suggested this and also thought i might do this myself, but i think the Polk CS2 has a rear-firing port and this would maybe not be the best idea.

 

[Adam]

It's been a loooong time since I took this in school, but there's some good information out there on the web these days. I believe that what you need to consider here are bending moments. If you research beams and loads, you'll find some stuff that might help you (here is a simple explanation on Wikipedia). Here is a beam calculator to get the ball rolling. By moving the legs further apart, you increased the span.

Alrighty, time for the younger or practicing engineers to join in.

 

[sawzalot]

I would brace the back and cut out for the rear port and maybe your conection as well, that set up definitely needs some lateral support if you will rely on it to safely support your TV panel. I feel as if it could fail as is.

 

[55katest55]

I would brace the back and cut out for the rear port and maybe your conection as well, that set up definitely needs some lateral support if you will rely on it to safely support your TV panel. I feel as if it could fail as is.

Any suggestions as to which is better though, A or B?

I will be attaching 4 L-brackets, glue, and screws going down. Is that not enough?

If i want the new, revised stand to look like TV riser A, i will have to make it like this:

stands 22" apart (so there is some wiggle room)
factor in the extra 3/4" for each board width so thats 1.5" more
and i guess have about 3" going past each foot on each side=6" more

so about 29.5-30" total for the top, where the feet will be about 22" apart and the TV stand will probably be about 22" wide as well.

 

[Swerd]

You can hide the front edge of ¾" thick MDF or plywood shelf by attaching hardwood trim to the entire front edge. If you use hardwood trim that is 1×2" or 1×3" instead just ¾", it will stiffen the shelf and hide the front edge.

The only decent illustration I could find is this. Look at the circle on the top right.

 

[55katest55]

Thanks swerd. Any suggestions on what type of wood to use? Apparently MDF is not suggested for this type of stand.

 

[Swerd]

Thanks swerd. Any suggestions on what type of wood to use? Apparently MDF is not suggested for this type of stand.

Home Depot, Lowes, or other lumber stores should have hardwood sized 1×3 in various lengths. You should be able to find at least oak or maple in those stores. Cherry, mahogany or other hardwoods might require a woodworker specialty store.

Plywood might be a little stronger than MDF, but if you already have those boards in your photo ready to use, they can work with stiffening strips across the front (and back too if you want). If your TV base is 22" wide, same as the legs of your riser, I don't think it will sag.

 

[55katest55]

Well, the only problem is that the legs need 22" of space BETWEEN them so they will actually be a bit further apart, so there won't be an overlap. It'll be close though.

Do you think there will be a big difference in strength between structure A and B?

 

[Swerd]

Well, the only problem is that the legs need 22" of space BETWEEN them so they will actually be a bit further apart, so there won't be an overlap. It'll be close though.

Do you think there will be a big difference in strength between structure A and B?

I would use structure A with the support legs wide enough to fit your center speaker plus about 1" on each side. That would be 24" between the legs. With the added hardwood stiffening trim, I don't think it would sag across the middle.

Another idea is to build a box instead of one shelf on two support legs. Add another board, the same size as the shelf, and attach it underneath the support legs. That should prevent the legs from splaying apart. I don't know if you have enough vertical space for that.

 

[55katest55]

Hmm alright. I will have to go buy more wood then. Should I:

A)buy more MDF for the new top part
B)buy a different kind of wood for the new top part
C)buy a different kind of wood for ALL of it

?

I may not go 24" wide since that would require me to get a gigantic slab of wood for the top part if I want overhang. How much overhang should I have on either side?

 

[Swerd]

Hmm alright. I will have to go buy more wood then. Should I:

A)buy more MDF for the new top part
B)buy a different kind of wood for the new top part
C)buy a different kind of wood for ALL of it

?

I may not go 24" wide since that would require me to get a gigantic slab of wood for the top part if I want overhang. How much overhang should I have on either side?

MDF or plywood. ¾" MDF is not that weak. The choice is yours. The amount of overhang won't affect the strength.

I guess I don't understand what your concern is about. If the weight of the TV is centered over the support legs, if you add the trim to stiffen the front & rear edge of the shelf holding the TV, and if there is enough room for your center speaker, it should work.

 

[55katest55]

Well my concern was that I was originally gonna do structure A but didn't measure correctly so I had to move to structure B. So I was wondering how bad that would be if I used structure B. Then people started saying don't use MDF board.

If I can, I'd like to use the MDF and structure B so that I don't have to spend more money. I'd of course add glue, screws, L-brackets, and maybe a horizontal or vertical brace(s).

 

[Swerd]

Well my concern was that I was originally gonna do structure A but didn't measure correctly so I had to move to structure B. So I was wondering how bad that would be if I used structure B. Then people started saying don't use MDF board.

If I can, I'd like to use the MDF and structure B so that I don't have to spend more money. I'd of course add glue, screws, L-brackets, and maybe a horizontal or vertical brace(s).

OK, I think I finally get it now . Go ahead with structure B. If your MDF is ¾" thick, it's probably stronger than what you think.

• I still recommend adding the hardwood 1×3 trim to the front edge of the shelf. It won't cost much.
  
• How far apart will the support legs be?
  
• Please describe the L-brackets you mentioned. If you plan to use them to strengthen the joints between the shelf and the support legs, that should help.

After looking at your photos, I wonder what the dimensions of your shelf board are. If your TV is a thin panel plasma or LCD set, why is the front-to-back dimension of your shelf board so large?

 

[u2generator]

If you use screws through the top into the two "legs" with glue and then use the four inside L brackets, the only other thing I would recommend would the the use of two outside L's on the back. If the "riser" is going to be covered (or you don't mind the look) I would also add the outside backets to the front. These outside L brackets would attach to the corners of the top/leg interface and give a little more lateral support.

I don't think you'll have any problems with MDF.

JMHO,

TW

 

[55katest55]

I can add a vertical brace on either side of the back or a horizontal one with a hole in it for the speaker port. MDF is 3/4" thick indeed.

Support legs will be about 22-23" apart (not counting the boards themselves obviously) since the speaker is 21.3" long.

L-brackets are 3" long on either side and have 2 #8-5/8" screws on either side.

The shelf is 14x24 because the TV stand is 21.5"x12" and I wanted about an inch on either side of it. Also the speaker itself is 11.1" deep anyway so it's about the same.

How many screws would you guys have going down vertically on either side? 4? 6?

 

[u2generator]

I can add a vertical brace on either side of the back or a horizontal one with a hole in it for the speaker port. MDF is 3/4" thick indeed.

Support legs will be about 22-23" apart (not counting the boards themselves obviously) since the speaker is 21.3" long.

L-brackets are 3" long on either side and have 2 #8-5/8" screws on either side.

The shelf is 14x24 because the TV stand is 21.5"x12" and I wanted about an inch on either side of it. Also the speaker itself is 11.1" deep anyway so it's about the same.

If you have enough material to make a solid back (but still cut a hole or holes in it) your riser will be pretty strong with out any L brackets.

 

[Swerd]

I can add a vertical brace on either side of the back or a horizontal one with a hole in it for the speaker port. MDF is 3/4" thick indeed.

Support legs will be about 22-23" apart (not counting the boards themselves obviously) since the speaker is 21.3" long.

L-brackets are 3" long on either side and have 2 #8-5/8" screws on either side.

The shelf is 14x24 because the TV stand is 21.5"x12" and I wanted about an inch on either side of it. Also the speaker itself is 11.1" deep anyway so it's about the same.

That should work fine. Those L-brackets look like this?

And not this?

 

[55katest55]

Nay my friend, they are the second kind.