[TowerTalk] Mast slippage

[john at kk9a.com]

You made a good decision going with a 3" mast. It is stronger and you have
more surface area to clamp. I just looked at photos of ProSisTel mast clamps
and basically it looks like two formed plates are bolted together.  Either
these plates are bending or it is just not clamping enough surface area. I
think K7NV is the only one to figure out that using a round clamp on a round
mast has a lot of contact area.  From the photos it appears that there is a
center hole for pinning, just like Yaesu recommends. Two options that I see
are pin the mast or purchase a clamp from K7NV. In my opinion drilling 4130
is really not that difficult but you have to use quality drills, the right
speeds etc.  If I were doing it I would spot the center on each side with a
center locating punch and then drill a small hole though first and then
drill it larger.

GL,
John KK9A  

Les Brown VE3NNT

I have 2 large Yagis attached to a 3 inch OD ¼ inch wall thickness Chromoly
mast running down the tower to a ProSisTel PST-71D. On a windy day, I hear
creaking sounds from the tower. The mast is slipping slightly in the rotator
mast bracket. I’ve already tried to tighten the 6 bolts, but it still slips.
I don’t want to tighten them to the point where they might snap. I’m
thinking that what I need to do is to go up the tower, drill a hole through
the mast (the rotator mast bracket already has holes), and pin the mast and
bracket. I understand that it’s not easy drilling through Chromoly pipe, so
before I try this, I thought I would ask if any of you have any other
suggestions.

73, Les VE3NNT