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Re: [TowerTalk] thrust bearings

Subject: Re: [TowerTalk] thrust bearings
From: K8RI on TT <>
Date: Fri, 14 Oct 2011 23:51:37 -0400
List-post: <">>
On 10/14/2011 6:21 AM, Jim Thomson wrote:
> 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.
> 73
> Roger (K8RI)
> ##  Roger, if you want things to go smoothly, start with the mast.  Use 
> either a quality 87 ksi DOM mast...
That's what I'm using with the exception of lighter loads and there I'm 
using 2" 6061T6 with a 1/4" wall.
> 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.
Good place for roller bearings instead of ball bearings. <:-))
> 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.
Which I probably will in some instances.
> ## 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.
Good idea to prevent loading due to expansion and contraction due to 
temperature changes.
>    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.

I use two sections of DOM masting with a 16" long coupling that fits 
over the masting. Recesses are drilled into the masts, but only deep 
enough to prevent the bolts from slipping.
A sleeve large enough to take an intermediate size piece of DOM split 
length wise can be dropped into this. It holds the split piece in place 
with the bottom serving as a stop while the bottom of the coupling rests 
on the top of the split piece.  Normally the split pieces are in the 
shop, or would be if I had that back up. That "will be" the system that 
has the 3 or 4L 40 and 7L C3i 6-meter Yagi at 100 and 115 feet when it 
goes back up.  It goes in place of the array I've posted photos of.

> [ + 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,
Good except for composite or say Delrin sleeves where the rough surface 
of the galvanizing can cause abrasion.
>    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 have boxes of them (used to farm) of not only the different angles but 
different sizes as well.  I don't really like the ones with the tiny 
threads as they are quite fragile and can be broken off.
> I capped off the very top of the  2"  x .375"  wall   chromolly mast.  Then 
> no water coming down the inside of the mast.
I weld caps on both ends of the tubes, usually a minimum of 1/8" but 
prefer 1/4".  I then drill and tap a small hole in one end. Then dump in 
about a half cup of LPS2 for a 24' long by 2 or 3" tube and insert a 
plug.  The mast is rolled and tipped to coat the inside. Then the 
threaded hole is welded closed.  I do this with tower legs also. It's a 
good idea to save this operation for last, after the welding has been done.
>     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.

Unfortunately I have not found any place than can hot dip 24' tower 
sections that are 2 to 4 feet on a side.


Roger (K8RI)
> later....... Jim  VE7RF
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