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Thread: A question of strength
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22nd August 2007, 10:46 AM #1Futon Man
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A question of strength
Hi all budding structural engineers
I'm building a WI wardrobe with 2 hanging wardrobe rails one over the other. I can either purchase 30x15mm oval steel - welded wardrobe rail or aluminium both at 1.5mm thickness. The top one I can support in the centre but the bottom one has to span 1290mm unsupported in the centre.
Which do you think will be the least flexible / strongest to go that length.
Cheers
Darryl
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22nd August 2007 10:46 AM # ADSGoogle Adsense Advertisement
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22nd August 2007, 12:30 PM #2GOLD MEMBER
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the oval profile is the stronger of the two
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22nd August 2007, 01:43 PM #3
Steel is stiffer than ally, but I don't think either is big enough for 1290 span
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22nd August 2007, 02:16 PM #4Member
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I guess 25mm or 32 mm chrome tube (shower curtain rail ) is out of the question ? It can be purchased at most hardwares with the support fittings including a centre support bracket.
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22nd August 2007, 02:41 PM #5Futon Man
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Thanks. They are both the same profile (oval & 30x15 x1.5) and both available through Hafele at about $16 for 3.6m for al and less for steel
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22nd August 2007, 03:52 PM #6
Hi FlatOutBEn,
Steel is around 3 times the strength of Aluminium, but also around 3 times the mass. The trick that is normally used is to go the aluminium option, but make it 3 times thicker, which gives the same mass, but 3 times the stiffness.
Having said all of that, in your case (given no option of thickness), go the steel.A man who thinks that it can't be done shouldn't interrupt a man who's doing it........
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22nd August 2007, 04:41 PM #7
Steel is about 3 times the stiffness as aluminium (not necessarily the strength, though; depends on the alloys). Even so, the rule of thumb for preliminary bridge design is to make the span 24 times the depth of the girder. 24 x 30 is only 720mm. Why do you need to make the lower rail span the full length? Standard practice here is to use a triangular bracket at midpoint, attached to the back wall of the closet/wardrobe. If the back wall is too weak, you could suspend the lower rail from the upper one at its mid-span attachment.
Joe (retired SE)Of course truth is stranger than fiction.
Fiction has to make sense. - Mark Twain
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22nd August 2007, 05:58 PM #8Futon Man
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Thanks Joe
However it only has to hang shirts! I ordered the aluminium rail this arve. Maybe I can make up a wall bracket just in case. I will attach a photo when its complete. Darryl
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