# How to support a sign on our museum wall?

1. Apr 29, 2012

### agap015

Hi all,

I went to an engineering school 40 years ago but never finished, so I kind of know that this is easily solveable.

I have a triangular sign 12' long (attached to wall) that is 2 1/2' thick and sticks out from the wall 6'. If I use 2 guy wires anchored to the wall 12' apart, that meet the sign at a 45* angle at the point, how large should the wires (stainless steel cable) be in diameter?

The sign weighs 200# total.

The sign is to be attached to our local museum announcing an event.

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Thanks

George

2. Apr 29, 2012

### K^2

I'm a physicist, but pretty far removed from engineering, so take it for what it's worth. Hopefully, somebody better qualified will come along.

If I understand your setup correctly, each wire is under roughly 150lb of load. (A diagram would help to make sure.) You want this to be within yield strength for the wire, to give yourself a bit of an overhead. Of course, there are steel cables, and then there are steel cables. But you should be able to count on at least 200MPa. That means wire just a touch over 2mm in diameter. So you should go with at least 11 gauge (AWG) for this.

Keeping the load within yield strength should make the structure reliable enough, and if things go wrong, should be able to take nearly twice as much load for a short while. But if you expect adverse weather, such as winds or snows, you'd have to account for that separately.

3. Apr 29, 2012

### agap015

2MM isn't very large. I will probably use 3/16" cable or about 4MM. The sign is a half scale theater marque. It will showcase our town theater.

Thanks

George

4. Apr 29, 2012

### Bobbywhy

I am also an owner of a Museum.

I agree with K^2 that it is simply prudent to "overestimate" on the side of safety in supporting this marque. What's the difference in cost or difficulty of using a "stronger than you think is mimimally necessary cable"?

Bobbywhy

5. Apr 30, 2012

### K^2

4mm really ought to do it. I'd expect anchor points or welds on the marquee to go before a 4mm cable does.