In a message dated 99-07-18 12:49:42 EDT, tacookfam@exotrope.net writes:
> I need to axially connect two pieces of 2"OD x 1/4" wall 6061-T6 (I know
> - chrome-moly is stronger) for a torque-tube drive.
Your aluminum mast of choice has about 35kpsi yield strength which is
suitable for modest loads and windspeeds.
For medium sized HF yagis or other mid-range mast torque stesses, the
mast coupling hardware (U-bolts, saddles, etc.) will tend to gall the
aluminum over time and the antenna(s) will start slipping on the mast. This
problem is eliminated with a carbon steel mast.
Mast selection is based on local windspeed conditions and antenna
system. There are several choices between 6061-T6 (low-end) and chromoly ($$
high-end).
>Seems my T-twister
> won't fit inside a 14" (face) tower section and I have to get it down to
> the 18". There will be ~34' inside the tower; there will be a lateral
> thrust bearing ~10-15' down inside the tower. I have considered using
> an internal tube for axial alignment and a flat plate with muffler
> clamps (four min.) to transfer the torque.
What kind of tower is it?
Your internal tube sounds like a good idea since you're going to have a
long mast and some sort of coupling in there somewhere.
>
> The antenna stack is a 2 wavelength 6m. beam + two 24 el. K1FO style 432
> beams - the top of the stack is ~10' above the top of the tower (50'
> tower) - not too bad.
>
Pretty modest windload-wise.
> QTH is in the Southern tier of NY on top of a decent hill.
>
Steuben County is only a 70 MPH windspeed zone - the lowest rating
they give - so no big deal wind-wise.
Anyone wishing to find out their local windspeed rating can go to
http://www.championradio.com and look under Tech Notes.
Cheers, Steve K7LXC
Tower Tech
Champion Radio Products
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