[TowerTalk] Mast slippage

[tony.kaz at verizon.net]

I had slippage with my 2" mast. Changed the Prosistel mast clamp bolts to #8
hardness and added a Slipp-Nott by Teledyne. I cranked down really hard on
all the bolts. The mast hasn't slipped in at least 14 years, when I
installed the Slipp-Nott. Don't know if they are still available.
I had drilled 4130. That was to add an extension so that I had a 32' 4130
mast. I used a taper drill and taper pin. Below John has good advice on
drilling.
GL
N2TK, Tony

-----Original Message-----
From: TowerTalk <towertalk-bounces at contesting.com> On Behalf Of
john at kk9a.com
Sent: Tuesday, July 28, 2020 9:53 PM
To: towertalk at contesting.com
Subject: Re: [TowerTalk] Mast slippage

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

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