Looking for very long ladder (or similar)

[Nick]

Rather odd task. I need to temporarily span a distance of 32ft (approx. 9.75m). Temporarily being about 6 months! Whatever I use has to be fairly lightweight, single span and minimal sag. It can only be supported by 2" at each end. A very long ladder would do the job but an extending ladder would be no use. Has to be single span. I suppose I could join 2 aluminium or wooden ladders together. Intended usage is to support a very lightweight item from end to end but

10ft above ground. It's important that this is kept as flat as poss. Item would fit nicely between the uprights of a ladder. Can't tell you the exact purpose as I don't know. Suffice to say that it's to do with a uni project that my kids are working on. Of course cost is a major consideration. Any ideas please? Thanks, Nick.

[Matty F]

How about pieces of timber with vertical sheet galvanised steel on each side?

[Dave Plowman (News)]

A ladder is designed to take its load in the direction intended - and will very likely flex if used for what you want. You need something like an I beam for minimum deflection.

[spuorgelgoog]

Running a model railway line between two separate halls of residence?

Stage lighting truss is light and rigid, but not sure if it will self-support over that distance.

Owain

[The Natural Philosopher]

without knowing what the load is, any suggestion is pretty impossible to make.

Suffice to say that when making up a simple stiff end supported beam, a truss is the lightest way to go at minimum height. Other classic designs are suspension and arch type structures for bridges - the roadway still stays flat on those..

[jkn]

I can't tell you where to obtain one (apart from d-i-y it!) but my thoughts would be turning to some sort of tensegrity/geodetic structure. A bit like the display stands you often see at exhibitions. I'd have thought that you could make something very light and rigid with this kind of construction.

J^n

[Tim+]

Timber I-beam? You could make your own up with sterling board web and strips of wood glued & screwed to both sides of both edges. Making one

10m long might be interesting though. I'm sure uni kids should be able to do the sums to work out the best dimension. ;-)

Tim

[Nightjar]

It seems a good time for them to learn about the properties of space frame girders - the things that are usually used for tower crane jibs.

For a lightweight, temporary, and relatively cheap structure you could build one from bamboo bean canes and string or cable ties. Use two or more canes for each 32 ft element; if the thing being supported is to be vertical, use four of those arranged in a square, viewed from the end. Stagger the joints and tie them well together. Then connect them into a girder with shorter diagonals, to create a structure that has triangles in every direction you look, including inside the square. However, it will need to be well secured at the ends to resist the wind loading from whatever it is holding up.

Colin Bignell

[Dave Liquorice]

Or a ladder on edge, rather than flat. B-) But be better if the bracing (rungs) were forming triangles, lighting trusses have already been mentioned.

32' is long though, if a single length it's going to be interesting transporting it. Lighting trusses come in shorter lengths that you bolt together.

[Chris Hogg]

James May's Meccano bridge? Although I suspect it would fail on your last consideration!

[fred]

In article , Nick writes

I would suggest some form of tensioned wire system, either at its simplest with just 2 tensioned wires or in a more complex suspension arrangement.

If it is a truly lightweight load then make any deck out of double skinned modelling board.

End result is simplicity and low risk of injury if something goes wrong and the whole lot comes down.

For that sort of span you're not going to be able to build a truly light structure from ladders or in timber so you have risks associated with collapse should the structure be damaged or dislodged and as it is only

10 feet off the deck then those risks are significant. Too easy for 2" supports to be popped under deflection on a span that size.

I'd expect the Uni to get a bit nervous of large, home made, suspended structures.

[harryagain]

A steel cable/rope + some sort of tensioning device is the cheapest way so long as the anchor points are adequate.

[Reentrant]

OT - ish ... I can thoroughly recommend going to a spaghetti-bridge competition if you get the chance -great fun and very educational. You can download blueprints of various standard truss designs scaled to standard spaghetti length, or come up with your own. Strands are joined with hot-melt glue which sticks very well to it.

I had no idea this was a well-established form of competition amongst engineering students, and it's surprising how realistic-looking (and strong) the finished article can be. Take a look at this:

[dennis]

There must be a better way to put a model train between the buildings.

[Michael Chare]

2nd hand scaffolding is not very expensive and would have a resale value. I think the normal maximum length of single pieces is 6m.

[Tim+]

Wow! Very impressive.

Tim

[newshound]

I think you have to define what "as flat as possible" means and suggest a budget. Is this indoors or outdoors? If outdoors, how exposed is it to wind, etc. Does "the thing" have to have a free view of the sky? If it involves something like "radio", are there restrictions on the use of metal?

[Tim Lamb]

In message , fred writes

Catenary supporting lengths of suspended ceiling *T* bar. Pop rivet assembly and adjust support hangers to level.

[Bill Wright]

If you do that you'll likely ruin the ladder.

Bill

[Grimly Curmudgeon]

Also an insane price.