Thread: Barristers Bookcase Type Door

Originally Posted by echnidna

When its up out of the way the timber frame will have a tendency to sag over the 3 meter span.

Looking for suggestions to prevent it sagging.

Without stating the obvious - by not making it sooooooooooo wide...

Its the front door to my cnc router and must be that wide.
I dont want to steel frame it/

My timber garage door (5m wide) has light weight steel sections screwed to it, I'll take a pic later.

Cheers,

P

Bob

Consider making the main members (the ones that span 3 metres) as lattice trusses. Have a look at these two links. They refer mainly to the use of lattice trusses in bridge design but the principles work equally well for any long-spanning timber structure where the aim is to reduce the size of the members without sacrificing spanning capacity.

http://www.coveredbridgesite.com/ny/truss.html

http://en.wikipedia.org/wiki/Lattice_truss_bridge

Col

Thanks BM and Driver.
I might go for the truss idea at the front and supports on the back wall so I can keep the cross sectional area minimal. That way the door won't interfere with my DC duct which I'll hang below the door space.

Torsion Box was my first thought but inserting a truss rod throught the long members and adjusting with a slight bias opposite to the desire of the member to sag should do it. If you dont get what I mean the look at the way an electric guitar is made.
However I would use a metal frame and hide it with some timber if needs be.

Ross

I am going to use clear polycarbonate for the panels so I can observe the machine while running.

So the torsion box is unfortuately impractical.

You could make the whole door from clear polycarbonate in the torsion box style... wont be cheap but!
What if you just made the outer frame a torsion box with say 6mm mdf, after all you could use the cnc to cut all the parts



Just noticed Ross is back, welcome back!

Bob,

All of that seems like hard work!

My timber garage door "trusses" are simple top-hat sections that you could have made at any sheet metal work (or they may be available off the shelf!).

Note that three simple bits are enough to keep the whole door (5.4m) wide quite straight. Panelling and framing is WRC, so reasonably light (for a solid door).

The basic dimensions are - chord(depth) 70mm,
"top" flange (actually the bottom one in this photo, but I thought I'd make it as confusing as possible.... 15mm,
"bottom" flange (see note above)...70mm overall including the flat bits each of 20mm, ie the structural "web" is 30mm wide at that point.

If that's not clear, let me know and I'll try again!

Cheers,

P

Thanks BM, A pictures worth a thousand words.

Originally Posted by Harry72

You could make the whole door from clear polycarbonate in the torsion box style... wont be cheap but!
What if you just made the outer frame a torsion box with say 6mm mdf, after all you could use the cnc to cut all the parts



Just noticed Ross is back, welcome back!

Mate not realy back more just passing through. I dont have much time anymore what with work and hobbies and such. But thanks anyhow!!!

Ross