kitemap
Immoderate
If they're anything like my Traby, the short dividers are just that, dividers, they are not made to be load bearing except in the vertical plane. The long bits are supported properly at the ends and by the dividers.
Ikea Kallax Shelving - Help with weight considerations
- Thread starter hockman
- Start date
If they're anything like my Traby, the short dividers are just that, dividers, they are not made to be load bearing except in the vertical plane. The long bits are supported properly at the ends and by the dividers.
The problem with the short dividers is that they're only fixed to the longer dividers by two short wooden dowels. Any weight on the shelf/divider has to be transferred across the dowels into the rest of the structure. Whereas, the other way round (long dividers horizontal), the weight is transferred along the full depth of the shelf which is significantly stronger.
Sean K
pfm Member
Kitemap and Simmey
Thanks for that. I get that the dividers are only connected by dowels into holes; this is obviously weaker than a continuous run of shelving. I can't get my head around why the structure , if loaded evenly and on a level and solid floor would be more vulnerable to shearing (?) when not oriented as recommended.
I'm not an engineer, so there may be something obvious I'm missing due to ignorance of factors influencing mechanical failure. I also realise my question is trivial from a practical point of view (Just orient them as recommended, brace the rear of the structure and secure to wall).
It's my pedantic curiosity; sometimes it's very helpful, but mostly it just annoys my wife...
Thanks for that. I get that the dividers are only connected by dowels into holes; this is obviously weaker than a continuous run of shelving. I can't get my head around why the structure , if loaded evenly and on a level and solid floor would be more vulnerable to shearing (?) when not oriented as recommended.
I'm not an engineer, so there may be something obvious I'm missing due to ignorance of factors influencing mechanical failure. I also realise my question is trivial from a practical point of view (Just orient them as recommended, brace the rear of the structure and secure to wall).
It's my pedantic curiosity; sometimes it's very helpful, but mostly it just annoys my wife...
Sean K
pfm Member
Earthquake straps would be a better solution or just a short piece of chain that lets stuff wobble but not tip over; mandatory around these parts as we're somewhat quake-prone.
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Sean K
This will be my undoing...
Assuming the short dividers are placed horiznotally and long dividers vertically...
If loaded evenly, on a level solid floor AND secured to a wall (to prevent movement), the liklihood of shearing failure will be low. However, the dowelled joints will not be capable of sustaining significant loads in same way as continuous dividers - the dowels may fail or the hole in which they're sited may fail.
If the structure is not secured to the wall then all bets are off. The dowelled joints become/behave like hinges with any sideways movement. If this is coupled with the dividers carrying load then the tendency will be to magnify the hinge effect and cause failure of the joint.
This will be my undoing...
Assuming the short dividers are placed horiznotally and long dividers vertically...
If loaded evenly, on a level solid floor AND secured to a wall (to prevent movement), the liklihood of shearing failure will be low. However, the dowelled joints will not be capable of sustaining significant loads in same way as continuous dividers - the dowels may fail or the hole in which they're sited may fail.
If the structure is not secured to the wall then all bets are off. The dowelled joints become/behave like hinges with any sideways movement. If this is coupled with the dividers carrying load then the tendency will be to magnify the hinge effect and cause failure of the joint.
You can visualise it if you draw a diagram. Without going into too much detail, there will be a failure mode where the dowels are being drawn out rather than bent, and in this they are weak. It's only the adhesive holding them in. The parallelogram failure mode will not happen at 45°, but will depend on the orientation of the dowels. As soon as the forces start to contain a substantial element that is drawing out the rods then the structure will start to move. As this happens it will get rapidly worse (think of a pack of cards being tilted until they start to move, then see how fast it all goes to hell in a handcart as soon as things start to slide) and go down with a bang.
formbypc
pfm Member
With the long sections horizontal, the weight of the long section and load above is distributed between end fixings (simple dowels) and the vertical short sections below. This is more important with a 4x4 or 5x5
With the short sections horizontal, all of the weight is taken by the end fixing dowels, and there's no support beneath.
If one shelf gives way, and/or if the records are loosely packed, a domino effect takes hold. this will be especially troublesome if only one end of dowels gives way. One end of the shelf will drop, and most of the weight of the vinyl above will be transferred to the side, as it slips down the shelf which is now at an angle.
In short, the short uprights are essential to support the long shelves.
I thought you assembled them with a drop of PVA on each dowel. I may be mistaken, I've assembled a lot of flat pack stuff, some gets glued together and some not. Obviously if you do, it's better, but you're never disassembling it again.
formbypc
pfm Member
The problem goes away if you add a solid back piece. Thin plywood, chipboard, MDF or similar, covering the whole of the back, and secured to the outer pieces and all internal shelves and uprights with many panel pins or similar ....
Or, for each 12.5 x 12.5 inch recess, a piece of plywood/chipboard of matching size, inserted at the back, and secured with plastic block fittings or glue to the shelves and uprights. This has the same supporting effect as the long shelf would do.
Both of these have the added bonus of keeping dust out at the back, and keeping your LPs from hitting the wall behind.
JensenHealey
pfm Member
I have never assembled anything from Ikea with adhesive, and have done quite a bit over the years.
If you are very sure of not wanting the change anything then assembling with adhesive will improve strength, but there is no question that a thin plywood back panel, pinned (or glued and pinned) all the way around will stop any chance of a shelf unit leaning sideways and shearing.
If you are very sure of not wanting the change anything then assembling with adhesive will improve strength, but there is no question that a thin plywood back panel, pinned (or glued and pinned) all the way around will stop any chance of a shelf unit leaning sideways and shearing.
Yank
Bulbous Also Tapered
I've never used anything that didn't come in the box. The instructions didn't say anything about glue.
The pegs are such a tight friction fit, with compression, that I didn't think glue would be necessary.
ToTo Man
the band not the dog
Sorry to dredge up an old thread but do you know where I can find max load bearing specs for Kallax units? I'm thinking about buying a 1x1 cube to sit my R2R tape deck on top of and store 10.5" tapes inside it. My deck weighs 25kg. Does the equation change if I raise the cube up on legs instead of sitting it directly on the floor?
I wouldn't worry so much about it sagging as collapsing sideways. They are pretty tough with heavy loads on top. The problem is shear -- it is very susceptible to nudges from the side and end up getting 'wiggly'. If it's a single cube it's probably good, but you could really strengthen it with some diagonal supports, e.g. eye bolts on the back corners with wire forming an X. And this is also the reason why flat pack cabinets and armoires often have a flimsy piece of MDF tacked on the back (with dozens of brads). A thin membrane can be extremely helpful for preventing shear!
ToTo Man
the band not the dog
I would like to keep the back open if possible. Would glueing the dowels in place help with the shearing risk?
Sean K
pfm Member
You wouldn't need to close the whole back, screwing a section of ply (or hardboard, or anything; I'll defer to the expertise of the engineers on here) covering only a third of the height would stiffen it very significantly. Not sure if that's any help, if you're after a certain aesthetic effect.