overhead swing arm query

[gunner]

Ok local garage is looking for me to build him an over head arm to swing out that will have power cable and airhose hanging from it at the end. For less cables on the floor. He wants it to swing out 7 meteres from wall. I need to know what size material i should use for it to not be all sagging all advice ideas welcomed. I know it will need angle brace where it mounts at wall is this best suited over or under the actual arm. thanks

 

[Spark plug]

For a length like 7m I think you will need to to build a triangulated frame along the lines of a gantry crane job using the lightest materials possible.

Many use 25 mm box for the first 3 meters then 20mm for the remaining 4.

 

[madkayaker]

lad i know uses a bit of dexian racking with a rope and chain mid and end point. if you can extend above the arm use steel wire with tentioner in to take the sag out. the brilliant thing then is more can be added if needed and there not going to add weight to the arm

 

[Coo]

You could maybe use hollow scaffold bar hinged ...
... or look to F1 pit lane air hose lines for inspiration

 

[Luke]

7 meters will need a fair bit of support. How much height do you have? I'd have thought you'd want 2-3m minimum above the arm to run either solid or wire supports. With the supports in tension, wire would make sense.

How much mass do you need to support? It's not too hard to work out what tension will be on the wall plate the wires fix to.