Alan, Graham and Mal
Thanks for your help, advice (and concern).
I was going to wait until I had got some results and a photo (to save complicated explanations) but in view of the responses some further explanation seems required.
My shack is inside a two storey heavy steel girder framed agricultural barn. The local blacksmith has welded some heavy duty brackets so that I can mount 2 x 21 ft steel scaffold poles about 18 inches apart to one of the upright girders. There are several horizontal bracing struts (2inch steel) between the vertical poles secured with scaffold clamps. From the top of each of the vertical scaffold poles there are two angled bracing struts (2inch steel) going down to the girders supporting the roof. This makes a very strong frame for the lower part of the mast and easily supports a ladder for work at the top. For the 2nd section, a thick walled 6m x 2in is supported by clamps on three of the horizontal bracing struts. This section can be pushed up through the clamps leaving some overlap. The third section is swaged 2in pole light aluminium and inside 1.75 swaged aluminium forming a double skinned but light 20ft section. The 1.75in pole inserts about 0.5m into the 6m Alloy and the 2inch section is clamped to the 6m alloy with a saddle joiner.
I tested this afternoon and the 2nd and 3rd sections pushed up to nearly full height (50+ feet) without guys and a strong wind without showing problems. I shall fit the guys ropes (top and middle) tomorrow and push up to full height.
Sorry for the mixture of metric and imperial measurements!!
I have 2 trees (60 – 70 ft) about 50 – 60 metres from the shack already rigged with rope to provide the other support for the Kevlar based antenna wire.
Terry GW0EZY
Hi Terry I have put up 60 ft masts with dural scaffold pole and sleeve joiners. The problem with the method is you need a lot of real estate and 12 guys. No trouble with "bendies" and a couple of 4m beams on top. An unguyed pole would need a lot of stiffening, and steel poles will bend just like dural( I have some bent bits to prove it ) and are much (much) heavier.
I have a 53 foot pole which is a 20ft joined to 16 ft. ( nominal 2in. dural) these are hinged at about 3ft above ground ( Barenco hinged, U-bolted plate ) to a 18 foot steel pole set in concrete. The top is 1.5 inch TV pole( slides nicely inside dural, bottom filled with garden split cane to stop it bending sharply over the dural end) very floppy and needs bracing to take sideways wire tension. The central join in the 1.5in TV pole is a 2ft length of 1.25in steel handrail. The bits were "to hand" :-)) It currently needs reguying since storms blew tree branches into the guys. Also 60 ft trees have spead across the wire run :-((.
----- Original Message -----
Sent: Monday, September 10, 2012 5:54 PM
Subject: LF: Antenna mast
Graham
I understand your surprise at 60ft with scaffold poles! In fact Mark1 was a disaster with single poles and joints – all bendy in the middle and no chance of getting it vertical – if you see what I mean!!
Mark2 is a different design combination steel and alloy. I’ll let you know if it works and post some photos. At the moment all is going to plan apart from the Welsh weather.
73 Terry
60 ft ! I have 2 x 20 alloy as insulated mast , with saddle joints , you using steel or alloy ?
