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[TowerTalk] thrust bearings

To: <>
Subject: [TowerTalk] thrust bearings
From: "Jim Thomson" <>
Date: Fri, 14 Oct 2011 03:21:31 -0700
List-post: <">>
I think a Sleeve bearing would have been better still. <:-))
> ##  so far, on the new HDX-689 tower, the PEER brand   thrust bearings, with 
> their locking collars  works good.
> The set screw  for the locking collar  has to be slopped with never seize 
> goop  though....and also more goop to be
> applied to the female thread.
> ## Thrust bearings are not  easy to replace..after the fact.

That's what makes the wood and other split blocks so nice.

> The Rohn bearing's are not only expensive, they are poor value
> for the money, and poorly designed.   If u do use the TB3/4's... add a zerk 
> fitting, so at least u can pump it with grease
> once or twice per year.

I'm not sure if that will make them last any longer, but it will make 
them run smoother.


Roger (K8RI)

##  Roger, if you want things to go smoothly, start with the mast.  Use either 
a quality 87 ksi DOM mast... or
a  heat treated  4130 chromolly mast [ 107-120 ksi].     Either way, make sure 
they are hot dipped  galvanized. 
Ok, no rusting masts.   On my HDX-689... they not only use a PEER  brand thrust 
bearing at the very top,  I also have 
a 2nd identical  thrust bearing  down aprx 4'.  On the UST 689 tower, they also 
use a.. 'sleeve bearing', just below the
top plate/bearing.  This  2nd plate is aprx  6" below the top of the tower. A 
section of pipe with an ID that's a tiny bit bigger
than 2"  is welded into place..and  runs between thrust bearing plate at top of 
tower..and down 6"  to 2nd plate .   Both the top thrust
bearing plate and the 2nd plate are welded to the tower legs.   [ the lower 
thrust bearing + prop pitch plates  are bolted into
place, so 4 x plates in all].    That  short 6"  sleeve pipe  has nuts welded 
to it, and 3/8"  bolts.    Their purpose is to pin the mast,
when working on the rotor.   IE:   mast  is  temp elevated 12"-18"...and  3/8"  
set bolt  through the sleeve bearing stops the mast
from free wheeling about. 

##  although  both  PEER  brand  bearings spun smooth, I replaced em both on 
spec with new ones, since the tower is old, and the
bearings  were not too expensive.   I had no problem getting the locking 
collars off either thrust bearing either.   They provide  an
indented hole on the locking collar  to tighten the collar...with a few smacks 
CW  with a drift punch.   The 2nd hole on the locking collar
is for the big set screw.    As  long as the set screw and mating female thread 
on the collar are glopped with plenty of never seize
[ marine grade is the best version],  you will never have a problem with em. 

##  I did have to replace the bad bearing on the end of the big rotor drum 
though.  the bearing was just fine, but the base had 2 x cracks
in it, right  where the 5/8"  bolt  pass's  through one end.  [  both drum 
bearings and thrust bearing are 2 x hole mount].   The bad bearing
had to be cut off, since it seized on the 2" solid shaft.   After it was cut 
off.... I could see the insides of those things  are built like a tank !     

##  both drum bearings are the self aligning type, they  will swivel a bit, and 
factor in any mis-alignment.   Now you think the thrust bearings
have some kinda big side load on em  in a high wind, wait till  you see the 
side load  on a 2"  drum bearing !    Yikes, the entire weight of the
tower + mast/rotor/ants  is on that lift cable [ with a 4:1  mech advantage]... 
and the drum bearings  are  taking all the load.  

Note, the very bottom tower section  is sitting on concrete, so is not part of 
the drum bearing load.     Note, the ID  of the drum bearings is a hair
less than 2"..while  both thrust bearings  have an ID that is  a hair bigger  
than 2".    The drum bearings  have a thicker base and are self aligning.
I checked peer's  website..and no reason why u can't use their standard  2"  
self aligning bearing for a thrust bearing, at top of the tower, or
their normal bearing [ no self aligning]..but with a thicker base. 

## in the case of the UST towers,  it's  sorta  a moot point,  since that huge 
6"  sleeve that's welded between two plates is the ultimate ticket. 
[ Plus both those plates  are welded to tower legs. ]  Between the sleeve and 
the top thrust bearing,  it will handle a massive side load. 

##  On the bottom thrust bearing  [just above the prop pitch]    I don't use 
the locking collar per se.  I slide the locking collar up the mast 2", then 
lock it.
This allows the mast to free float  in the lower thrust bearing.   I feel  more 
confident [ and safer]  when working on the PP, that the mast is supported
by the top thrust bearing/sleeve/then the lower thrust bearing. [ + the mast is 
pinned  via the bolt through the sleeve, only used when mast is elevated
a bit, and PP is  worked on.   I ended up buying the UST  mast raising fixture, 
which bolts to the 2nd plate [ 6"  down from top].    That 2nd plate has
the big hole in it so the cable  for the mast raising fixture just passes 
through it.   A  special  2 x piece clamp, clamps  to the mast, and terminates 
on the
mast lift cable.   

##  Everything is galvanized, nothing rusts,  bearings are built really good, 
everything has zerk grease  fittings, and the small K7NV  PP  runs like a 
swiss watch, globs of TQ.   BTW, you can also get grease fittings  that have 90 
deg bends in em..and also 45 deg and also 65 deg..and also straight.
I capped off the very top of the  2"  x .375"  wall   chromolly mast.  Then no 
water coming down the inside of the mast.    The mast is also climbable.
I gave up years ago with painting masts.   On the galvanized chromolly mast.... 
I gave it a couple of coats of cold galvanize spray.   That stuff is
cheap, and works good.  I have enough zinc  on everything so nothing should 
rust.   The cold galvanize spray sticks to the hot dipped  galvanized
parts  very well. 

later....... Jim  VE7RF 

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