Building a "floating" desk

[allanmartin]

Hi All

I would like to put a desk in this space. Its quite long (3meters) and i really would like to avoid a let to support it.

I went to a steel shop and angle iron is still bendy at that length unless I go very thick, but wondered if anyone could suggest or advise if a box length of steel would hold up the desk?

I could put a piece of 2x4 wood, and I know that is strong, but the 4" length would either make the desk low or high...

Anyone got advise? Is the strongest thing length of box steel or T Piece perhaps?

Thanks a lot

Al View media item 92990 View media item 92990

 

[Burnerman]

With a 3m length, the desk top must be supported at the back and sides......timber bearers will be fine.
However, you still need a peg leg at the front really. ....anything is sure to sag in the middle, but square tubing (heavy gauge) is probably your best bet - but even that is flexible.
John

 

[allanmartin]

With a 3m length, the desk top must be supported at the back and sides......timber bearers will be fine.
However, you still need a peg leg at the front really. ....anything is sure to sag in the middle, but square tubing (heavy gauge) is probably your best bet - but even that is flexible.
John

Thanks John for that. Yeah, I will have wooden support along all sides and back. Its just the front. So you think that even a 40mm x 40mm box would bend?

Al

 

[freddiemercurystwin]

What size angle did you try, I can't imagine something like a 50x50 angle would flex?

 

[Burnerman]

For me Al, I'd maybe consider 50x25 rectangular section tubing, (minimal) with the 50mm side vertical.......obviously the wall thickness would play a part and typically this would be 3mm.
There would certainly be some 'bounce' with this, and I wouldn't recommend anyone to put their full weight on it in case of it bending. It would give you a work surface, of course!
What do you intend the work surface to be made from?
John

 

[big-all]

why not go for say 3 gallows brackets stopping say 200mm from the front edge giving the appearence off a floating front edge but with support every 750mm

 

[foxhole]

You could make the desk in box section which will prevent sagging , give you somewhere for nick naks or even draws.

 

[endecotp]

How good is your maths? If you know:

The length of the beam L
The width and height of the square box section w
The thickness of the walls of the box section t
The mass to be supported m
Gravity g = 9.8
The strength of steel E = 200x10^9

Then you can compute the deflection d =

5/384 m g L^3 / E 12 / ( w^4 - (w-t)^4 )

So if L = 3m, w = 0.04m, t = 0.004m, m = 30kg,
Then the expected deflection would be 7mm

I recently made a desk much like this, about 2.5m wide. I ran 3 square box section steels from left to right; two larger ones (40mm) and one smaller one (25mm) at the front (for better knee clearance). It is rock solid. But beware that the deflection increases rapidly with increasing span (see the L cubed term), so yours would deflect almost twice as much as mine under the same load.

 

[SFK]

I would second a gallows bracket for a hidden support effect.
Something like this attached to the wall where the studs are.

www.ebay.co.uk/itm/STEEL-GALLOWS-BRACKETS-PORCH-SUPPORT-SHELVING-WORKTOPS-COUNTERS-/141618085275

SFK