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[TowerTalk] US Tower bearings ?

To: <>
Subject: [TowerTalk] US Tower bearings ?
From: "Jim Thomson" <>
Reply-to: "Tower and HF antenna construction topics." <>
Date: Tue, 27 Apr 2010 05:38:59 -0700
List-post: <">>
I just took possession of a used US Tower Corp HDX-689 yesterday.  What's the 
deal on the
2 x thrust bearings?   Mine are both for a 2" mast.   What I DON'T see is.. any 
set screws, etc
for either of the bearings.  [these are US-tower corp bearings].    I slid a 
piece of 2" OD AL 
tubing I had handy.. and it slides right through the bearings.. then into the 
K7NV prop pitch
clamp... also made for a 2" mast. 

The ID  of BOTH  bearings appears to be 2  1/16".     So there is a 1/32"  
[.03125"]  gap between 
mast ..and ID of bearings.    So there is a little ..'play'  in it.   Why no  
set screws ?? 
I was thinking of stuffing a  .030"   or a .027"  thick shim in there.. to take 
out the play.  

The K7NV 2" mast clamp  [ minus the 5 x bolts]  is a snug fit for 2" OD AL tube 
I stuffed into 
it for my test.   No play at all !!     Just barely tighten those 5 x bolts.. 
and the mast is not gonna
slip any time soon.  It's a mech marvel, and very well made.  

OK,  with NO set screws on either thrust bearing... the ENTIRE weight of mast + 
yagi's, is,
will  be sitting on the prop pitch. 

As a side note... when my local trucking outfit was heading north... I had him 
stop by the US Tower corp
factory... and pick up a new  galvanized,  20' chromolloy mast.    2"  OD  x 
.375" wall.....  107 ksi.  [140 lbs] 
Talk abt built like a tank !    It's the real deal.   Well it has to be, cuz I 
have to be able to climb the mast.

Of course the Ferry  from Vancouver bc.. to Victoria was running 40 mins 
late.... so I had to delay my crane guy
till  4PM.   Then this windstorm comes up outa nowhere, meanwhile we are 
sitting there with one truck, one
flat bed  trailer, and a crane.. orange safety cones every where... on my side 
street  [I'm on a corner lot] .  Of course
the power lines just have to be on my side of the street !   Plus tree's in my 
side  yard in the way.  Ended up having
to double park the truck/trailer  beside the crane.... and allowed just enough 
room  for single lane traffic to
just squeak  through.   It's all sitting in my 20' wide driveway right now... 
so I can still park one vehicle..[wife's
of course]... while I'm relegated to the street. 

I thought the base plate for these towers  was like a giant letter T.... this 
one is not.... it's a huge triangle, 1" thick
and at least 250 lbs...and 4'  on a side.   The crane guy put the weight scale 
on the hook... which will record the reading
so when it was lowered down onto 4x4's [sitting on 2x6's]  it said exactly 5000 
lbs !!   And that was without the base plate,
no mast either... just the 45 lb prop pitch.. and one thrust bearing.    So 
much for the 3250 lbs the spec sheet sez.  The
trucking guy was right... since he had driven over the scales a few days 
before... and did the maths.  Crane guy sez the reading
on that weight scale can't be trusted, since the slightest jerk.. and you add a 
dynamic load to the scale... sorta like jumping 
on a bathroom scale. They both said it's well > 4000 lbs.   It's a BIG mother. 

sri for the diatribe.

later... Jim   VE7RF     

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