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7th Mar 2019, 01:14 PM #1Intermediate Member
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What type of steel would they use for this
hi. What type of steel do you think they used for the legs of the sideboard in the attached image. Obviously it’s not just mild steel rod because the item is top heavy and it would wobble pretty seriously if it wasn’t something more rigid.
Would it be some type of hardened steel tube?
This furniture item is from a Spanish designer and sells in various forms in Europe for about $3k, so I assume it’s fit for purpose and not inclined to wobble.
And how would the bits of steel be joined together. What type of welding?
If you are going to answer, I know next to nothing about metal so please make it simple.
Cheers
arronBE5936C5-8FE0-4D97-AC0F-5F49C6AC28ED.jpeg
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7th Mar 2019, 01:49 PM #2Senior Member
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For long slender legs like that, failure would be by buckling, so there is no point in going to anything stronger than mild steel. The load where buckling failure occurs depends on the stiffness of the material and it's cross sectional shape only, and not on the ultimate strength of the material. All steels have very similar stiffness, and it does not improve with heat treatment, so no gain is to be had from using stronger steels. Using solid bar would be better than tube because the cross sectional area is increased.
Exotic materials such as tungsten carbide have greater stiffness, but would not be practical on a piece of furniture. Laminated epoxy/carbon fibre has lower stiffness than steel, so that's no better either.
My guess is that the item pictured is made using thick walled mild steel tube, or solid mild steel bar, welded by any old process. Cheap and quick.
Graham.
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7th Mar 2019, 02:13 PM #3Most Valued Member
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Also it's probably just as flimsy as you are imagining.
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7th Mar 2019, 02:17 PM #4Senior Member
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Yes, I agree. It's a classic case of form winning over function.
The engineer in me is offended by designs like this. One diagonal member would make all the difference. But engineering is not everything in life.
Graham.
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7th Mar 2019, 05:00 PM #5Member
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I'd say this will be flimsy regardless of the material
Structurally it would hold up weight, but it would rock around like crazy under sideways loads
Fun fact about steel: All cabon steels have a modulus of elasticity of 200 GPa give or take a small amount (this is fancy engineer talk for how stiff something is under a load)
Mild steel is just as rigid as high carbon steel, and even hardening does not alter this stiffness.
This is going outside of my knowledge area now, but I would suspect that more exotic steel alloys could potentially be made somewhat more rigid (higher modulus of elasticity) with the inclusion of say tungsten and similar elements
Overall though, short of maybe carbon fibre which is hella rigid, this table will wobble. For the price it would want to be made from something like that!
Cheapo mild steel with diagonal braces would be the best solution...
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7th Mar 2019, 05:29 PM #6Senior Member
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Do you have a reference for a steel/tungsten alloy of higher stiffness? I've never heard of such an alloy. For all practical steels, you're stuck with the ~200 GPa, and even lower for stainless steel alloys.
Unfortunately carbon fibre in any practical matrix is not "hella rigid". At best it has a modulus of elasticity no better than steel, and that is for a very high fibre to resin ratio - only attainable with advanced manufacturing techniques. The raw fibres have a much higher modulus of elasticity, up to ~1000 GPa, but they are not usable on their own except in a few very specialised circumstances. What makes a carbon fibre laminate stand out from metals is its stiffness to weight ratio, but it is not stiffer than steel on a size for size basis.
Tungsten carbide is the outlier in practical materials, with a modulus of elasticity of ~500 GPa, which is one reason it makes great cutting tools, but those legs are certainly not made of this material!
Graham.
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7th Mar 2019, 06:35 PM #7Most Valued Member
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Assuming something like this? https://www.scp.co.uk/products/aura-console-1
I'd say it would be 20mm or slightly larger tube, and IIRC from my school days they wouldn't be THAT much longer than the tube legs on the old wooden desks which had similar diameter.
The legs on the desks were pretty stiff, and were only really wobbly if the fixings to the desk part were loose. Don't think I ever saw one failed from the legs buckling, it was usually from the screws being ripped out of the wood or the brazing/welds breaking.
If the legs were solidly mounted in the timber part so it was only the tube itself that could flex (ie not a poorly fitting joint between leg and box) then I'd say it would be pretty reasonable.
Steve
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7th Mar 2019, 07:20 PM #8Gear expert in training
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Don't bet on that.
I have had to fix sideboards that are made in Denmark and retail here for north of $10k that are most definitely NOT fit for purpose; a reasonable assumption of purpose being to store crockery, which can get rather heavy.
I have also been involved in the manufacture of furniture that we expressly excluded from warranty cover because the design they insisted on was prone to failure.
So yeah...form over function. Don't let architects design furniture
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7th Mar 2019, 07:27 PM #9Mechanical Butcher
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Unless it needs to be able to be walked around, there is a way to get plenty of rigidity with the elegance of seemingly-too-slender legs.
Assuming it can be placed against a wall, construct the cupboard to be wall-mounted.
The legs are then just garnish, made to look as if they are holding up the cupboard, but actually doing nothing.
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7th Mar 2019, 07:37 PM #10Most Valued Member
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Anything top heavy is prone to toppling. Type of steel is not the real problem here providing the steel frame can support the weight.
Anchoring so it cant tip over is the main concern!...or making the support so it cant tip over.
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7th Mar 2019, 08:58 PM #11Philomath in training
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From the look of it, those legs are not round but rectangular. By using the orientation correctly, fore-aft would be pretty stiff and by having the cross member so that the larger dimension is vertical it can be welded to the between leg pieces in a way that will stiffen it up (if it was round it could flex around the joint, but with depth it will not - as much )
Michael
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7th Mar 2019, 10:29 PM #12Member
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7th Mar 2019, 10:32 PM #13Most Valued Member
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According to this website the legs are round: https://www.treku.es/en/portfolio/high-sideboard-aura/
And according to this website it has to be fixed to the wall (click on Details): https://shop.mohd.it/en/aura-madia-alta-s8.htmlChris
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8th Mar 2019, 10:16 AM #14Banned
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Simple mild steel rod welded by either stick or MIG. Not particularly strong as it doesn't need to be, it's a piece of furniture where form beats function.
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8th Mar 2019, 10:52 AM #15Intermediate Member
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Yep, you’re right. I saw that but assumed the maker was covering themselves from legal issues if a child pulled the cabinet over on themselves. I didn’t think it meant it had to be fixed to stop it wobbling about. The former might require just a discrete chain. The latter would require a couple of fairly meaty screws, and raises problems with skirting boards etc. Now I’m not certain, but maybe it means both?
It would be a hard sell, I think, persuading someone to buy a cabinet that looks freestanding but needs to be fixed, with the subsequent wall damage and limited ability to rearrange your furniture. On the other hand, selling a cabinet that wobbled around every time you touched it wouldn’t be an easy sell either.
Also, I magnified the 8mage and used a scale rule to measure the legs and they look to be 12mm rod, or maybe a bit more.
These are sold everywhere too.
I’m still mystified about how this works.
Thanks for the input anyway.
Arron
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