stopping racking?

[engineer one]

ok so i am planing for the future, but.
i kind of like the idea of making some drawer units and such like as open framed items, i.e four uprights, and cross members, with no side panel or rear infills, drawers maybe able to be opened from front and rear, not sure yet.

so question is if this is say 1220 high, and 600 square, how can i be sure it will not twist and rack. will a top and bottom be all that is necessary, or should i think about some other device to hold it square both static, and if i try to move it??
paul :wink:

 

[OLD]

When you think about the construction of say a kitchen table it doesn't rack because of the dimensions and stiffness of the materials and the strong jointing system used so you could apply this to your design with may be a 'test corner' made out of spare material to determine minimum sizes etc.

 

[Wanlock Dod]

Paul,

I would go for a fairly stiff wood and relatively large sections if I were to try such a thing myself, I think. That could lead to it being a bit heavy though.

Another option, which may not really be what you are after, might be to use reinforcements, perhaps at the corners or additional cross braces. Depending on the design these might work quite decoratively.

Cheers,

Dod

 

[Steve Maskery]

Hi EO,
I like open-framed carcases, and I think you shold not have a problem. The stiffness you desire will come from a large number of small joints.

I once made a display table. It had glass sides (so they were free to move and were not structural) and a lift-up top, so you could get inside. it meant that the only jonery was a set of four rails about 20mm square, 150mm from the top of the leg. It wob;;ed like crazy. But when I scewed o the top frame which held the glass in, the whole thing stiffened up beautifully.

Keep your joinery good, and your glue-ups square, and you should be fine.
All the best
Steve

 

[engineer one]

hi guys, thanks for the answers. i guess my concern comes from reading magazines, and then (horror) buying things from ikea.
if you buy a certain frame system from the swedes, it is a ladder system, and once you have added the shelves, they give you a metal cruciform that is supposed to stop racking. i know they have hse problems and lawyers, but it is a consideration.

then when you read the books and mags, they say if you make a solid material cabinet, you need a back to prevent racking, even if it is a loose fit piece of ply in rebates, without fixing.

so whilst i appreciate what you say steve, i am also thinking about the kitchen table mentioned. my personal thought is that this does not move for two reasons, the loads tend to be straight down, or cutting motions, and also the top and frame tend to be pretty substantial, generally with some kind of corner block.

however as you say if you make a four sided ladder, then how do you keep it rigid, since by design you want quite thin sections to look nice.
you kind of wonder, that if solid sides and back need anti-racking help,
then if you remove the sides and leave fresh air why not?

my feeling is that if i use the drawer slides as the supports from front to back, then mortise and tenon joints with pins across the back and front, then corner blocks at the top, and a good solid top it should work.
since it is drawers, the strains are less twisting than when you put a door on something.

anyway i will draw it out, and then see how it works, think i will make the first one in beech using 2x2's as the legs, and 1in sections for the other bits, plus probably an mdf veneered top, and maybe a bottom too.

still always nice to look outside the box.
paul :wink:

 

[Jake]

This sounds very like the cabinet that inspired Devonwoody's embroidery drawers.

 

[devonwoody]

Jake.

Could you re-phrase that please, My underwear is plain white.

My 5 drawer unit is now nearly 12 months since construction and I oddly enough checked out the drawers for the wife this morning and no problem, serious. The 13 drawer unit has no problems other than some of the sliders were not up to scratch,(cross grain) and are brittle and some have broken. Replacing with oak when required.
The top lid of each unit (around 7mm thick) does have a slight gap owing to shrinkage but this means that drawers are not to tight.