Torsion box design

[Aidex]

Hi Everybody!

Quick question. If making a torsion box for a shelf is it best to use:
1. Strips the length of the shelf width with shorter ones in between them running depth wise to form the grid pattern;
2. Strips the length of the shelf depth with shorter strips running across the width of the shelf; or
3. A mixture of the above eg if have a "grid" with 5 rows from front to back of shelf rows 1,2,4,5 are strips that span the width of the shelf and row 3 uses shorter strips (so you have longer strips running along the depth between rows 2 &

I'm sorry if the above's a bit confusing I wish I knew how to sketch it out on my phone!

I'm just wondering if any of the above offers an advantage over the other.

Many thanks (as always)!!!
Aidex

 

[Beau]

Foam core? Lot easier than building up the lattice I just saw when googling torsion box.

 

[Noel]

Hi Aidex.
Go for number 1. Long strips the length of the shelf with shorter cross strips will be the most rigid. Think, if you want to fix a sagging shelf, would you use long batons the length of the shelf or short batons front to back? Use plenty of glue, no need for any mechanical fixings other that to the wall/walls although you can pin it all together if you want to be extra careful, . The shelf gets it's rigidity from good monocoque construction (like a F1 car etc), the top and bottom skins are the key to the overall strength.

 

[Jacob]

I wouldn't bother with cross pieces or a grid . Just two sheets of ply with battens between going the full length and closing/lipping pieces to finish off the edges.

 

[petermillard]

Is this a floating shelf or an alcove shelf? If the latter, then agree with Noel and Jacob, shorter battens running the depth of the shelf (front to back) would do little; full width (side to side) batten against the back wall, short battens at either end, and a full-width front batten attached to the short ones. Skin it top & bottom in 12/6mm and lip the front with 6mm to hide the edges.

But if it's a floating shelf bolted to a single wall, different story.

Also, how big are these shelves - width (side to side), depth (front to back) and thickness (top to bottom) would all affect the way you construct...

P

 

[Aidex]

Hi Guys
Thank you all for your help!

This is for floating shelves in a cabinet resting on shelf pins (I can get a few in the back ad which elk as 2 either side. Seth approx 300mm length 1000-1200. 6mm oak veneer mdf top/bottom. Either oak strip on front or 2mm oak edgbanding.

Out of curiosity Peter, what would be the difference in an alcove bolted to the wall scenario (will have a couple of those to do over summer)v

Many thanks again!
Aidex

 

[petermillard]

This is for floating shelves in a cabinet resting on shelf pins (I can get a few in the back ad which elk as 2 either side. Seth approx 300mm length 1000-1200. 6mm oak veneer mdf top/bottom. Either oak strip on front or 2mm oak edgbanding.

Ah, OK. In that case, over that span, I think I'd consider glueing in some steel angle / ally box section behind the front batten, if it were me.

Out of curiosity Peter, what would be the difference in an alcove bolted to the wall scenario (will have a couple of those to do over summer)

If it's an alcove shelf, then as above - batten the width of the back wall, short battens at the sides etc... If it's a heavier-duty floating shelf on a single wall (i.e.unsupported at either end) then I usually fix lengths of studding in with resin, and have short battens running front to back either side of the studding so I can bolt the shelf on; the short battens stop the shelf from collapsing in on itself when you nip it up tight.

Cheers, P

 

[Aidex]

Thanks again Peter!

Will go with some angle/box section. Would you bother with short perpendicular lengths or just have 4 battens each with a metal section glued to it?

Fortunately the ones I'll need to do are in an alcove and the spans not massive (maybe 12-1300mm). However the long shelf along the wall process sounds interesting (and involved). I'm bit confused with the studs. Do you have any pics you could post? Definite sounds like a good one to have knowledge of!

Thanks again!!!
Aidex

 

[petermillard]

Thanks again Peter!

Will go with some angle/box section. Would you bother with short perpendicular lengths or just have 4 battens each with a metal section glued to it?

Not personally, no - just the full-width battens.

However the long shelf along the wall process sounds interesting (and involved). I'm bit confused with the studs. Do you have any pics you could post? Definite sounds like a good one to have knowledge of!

Sorry, don't do many of these so no photos I can lay my hands on. The 'studding' i.e. threaded rod; is drilled into and bonded to the wall with resin anchor fixing, and the shelf is constructed in a way so it slides onto these. I like to nip the shelf into the wall with nuts on the studding as well.

HTH P

 

[Aidex]

Perfect. Totally get it now!

Many thanks.
Aidex