05-04-2019, 07:37 AM
I normally wouldn't touch this with a "ten foot pole", either round or square section, but since you haven't had a lot of responses, I will contribute a few thoughts.
Aluminium : tensile strength is the main criteria. As you elevate the tube from horizontal and particularly if you already have a head load attached to the top, it will bend - and as I have experienced previously - that happens most at about 40-50 degrees elevation. The issue is whether that will be a permanent or temporary bend.
I use 'scaffolding tube' for the pipes out of the top of the rotators here. It is rated T6061 and has dimensions 44.44 mm OD x 4.47 mm wall thickness. It comes in 6.1 metre lengths and weighs 1.67 Kg per metre. That would probably be the best tensile strength readily available - and is fairly cheap too.
You could use it as the flagpole-style base as well as the pivoting arm. If you plan to use a rotator on top, buy an extra length plus some thick aluminium checkerplate to make the rotator support L-bracket and a second L-bracket for the top thrust bearing support. Clamp them on to the scaffold tube using 50mm muffler clamps allowing more than a metre between the two L-brackets. The further down the tube the rotator weight is, the lower the top load so if you used almost the whole 6.1M as a rotator tube, that places the load right towards the bottom as well as giving you virtually a double-strength tube during the lift.
Now about that temporary/permanent bend. You can use a permanent gin pole off the upper side of the tube to take the pressure off the tube as you elevate or you can do the cross-over spars that are used on yacht masts to also protect it when vertical. https://en.wikipedia.org/wiki/Spar_(sailing), bottom picture on https://en.wikipedia.org/wiki/Mast_(sailing)
The cross spars should probably be galv'd steel angle ( and for a single gin pole arm if used) as aluminium angle doesn't have the tensile strength. So that requires two steel cross bars, slotted or drilled at each end, clamped around mid-way up the available tube plus a set of 4 stainless wires through the holes/slots, clamped near the top and bottom and then properly tensioned with turnbuckles. That provides the extra mechanical strength that the T6061 tube can't provide by itself during the lift process.
I suspect part of the lack of replies was that you didn't provide enough raw information in your post. Expected height, sizing, loading, antennas,.... Better to provide plenty of your initial thoughts and allow others to provide suggestions to alter them..
73 Doug
Aluminium : tensile strength is the main criteria. As you elevate the tube from horizontal and particularly if you already have a head load attached to the top, it will bend - and as I have experienced previously - that happens most at about 40-50 degrees elevation. The issue is whether that will be a permanent or temporary bend.
I use 'scaffolding tube' for the pipes out of the top of the rotators here. It is rated T6061 and has dimensions 44.44 mm OD x 4.47 mm wall thickness. It comes in 6.1 metre lengths and weighs 1.67 Kg per metre. That would probably be the best tensile strength readily available - and is fairly cheap too.
You could use it as the flagpole-style base as well as the pivoting arm. If you plan to use a rotator on top, buy an extra length plus some thick aluminium checkerplate to make the rotator support L-bracket and a second L-bracket for the top thrust bearing support. Clamp them on to the scaffold tube using 50mm muffler clamps allowing more than a metre between the two L-brackets. The further down the tube the rotator weight is, the lower the top load so if you used almost the whole 6.1M as a rotator tube, that places the load right towards the bottom as well as giving you virtually a double-strength tube during the lift.
Now about that temporary/permanent bend. You can use a permanent gin pole off the upper side of the tube to take the pressure off the tube as you elevate or you can do the cross-over spars that are used on yacht masts to also protect it when vertical. https://en.wikipedia.org/wiki/Spar_(sailing), bottom picture on https://en.wikipedia.org/wiki/Mast_(sailing)
The cross spars should probably be galv'd steel angle ( and for a single gin pole arm if used) as aluminium angle doesn't have the tensile strength. So that requires two steel cross bars, slotted or drilled at each end, clamped around mid-way up the available tube plus a set of 4 stainless wires through the holes/slots, clamped near the top and bottom and then properly tensioned with turnbuckles. That provides the extra mechanical strength that the T6061 tube can't provide by itself during the lift process.
I suspect part of the lack of replies was that you didn't provide enough raw information in your post. Expected height, sizing, loading, antennas,.... Better to provide plenty of your initial thoughts and allow others to provide suggestions to alter them..
73 Doug
Doug VK4ADC @ QG62LG51
http://www.vk4adc.com
This Forum is only going to be as interesting as the posts it contains.
If you have a comment or question, post it as it may trigger or answer the query in someone else's mind.
http://www.vk4adc.com
This Forum is only going to be as interesting as the posts it contains.
If you have a comment or question, post it as it may trigger or answer the query in someone else's mind.