Table Design, Meeting Maximum Sag/Deflection Standards

[custard]

The brief is a table with a top that's 2400mm x 700mm. I'd envisioned hardwood rails under the top that are 75mm x 25mm, and a top that's 18mm veneered plywood (I understand ply is a lot stiffer than MDF).

However here's the challenge, the load on the table will be two printers that each weigh 24kg, they're pretty wide pso I could assume that equates to 48Kg evenly distributed. The requirement is for sag/deflection to be 3mm or less.

Anyone any idea how I can design to this brief?

 

[marcros]

Could you make it a torsion box, with 2 thin veneered skins of ply, and a series of beams in the middle?

 

[custard]

Thanks marcros, but there's other restrictions on room beneath the rails and maximum height of table that make a torsion box difficult (as well as a budget!).

In any event, my instinct is that a normal table should easily meet the brief, but I was hoping for a second opinion.

I've seen in the past tables giving the maximum deflection for shelves using different spans, loads, and materials; so was wondering if some well informed forumite had ever come across something similar when rails are introduced into the equation?

 

[9fingers]

For a quick heads up, I'd assume the top is just dead weight plus printers and then look at beams on the sagulator with 2 or maybe 3 end to end.

hth

Bob

 

[custard]

Bingo! Thanks 9fingers, about 2mm of sag.

 

[houtslager]

seconded,

I made two board room tables 3m x 1m as a torsion box of 10cm deep. I walked on them both and had 1mm deflection then I was 100kg.

So a smaller torsion box say 4cm will give you sufficient strength to size imho

hth

K