[TowerTalk] Rohn HDBX 40 - mast length

[RShirbroun at newportlabs.com]

I have just erected a new HDBX 40 in place of my 30 year old HBX 48, sacrificing 8' of height to gain some strength and load capacity (and peace of mind!).  The stock rotator plate allows 2' of mast below the top plate and I will be using the heavy duty Yaesu thrust bearing (along with the Yaesu heavy duty 2800 rotator plus the absorber plate).   I have added steel angle braces to reinforce the rotator plate.

I'm looking at using a 15' chrome/steel 2" mast (in place of my previous 9' mast), so 13' of the mast would extend above the tower.  The mast would support a TX38 tribander just above the top plate, a 6 m beam half-way up, and a 40m rotatable dipole near the top, 12' above the top tower plate and the thrust bearing.  The mast, of course, is very heavy, weighing around 75lbs.  The tribander weighs 40lbs and with 5 ft2 surface area; the 6 m. beam weighs 10lbs with 1.5 ft2; the dipole weighs 10lbs and is 0.5 ft2.

Is this too much mast for this tower?   (BTW - I'm aware the boom length exceeds the 10' maximum for this tower, but the HBX 48 handled a similar tribander for 30 years, with occasional severe ice-loading, without any problems.)

Thanks and 73,
Randy, ND0C



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