[TowerTalk] Best Grease for Rotor bearings ?

Thu Oct 13 19:01:50 PDT 2011

On 10/13/2011 9:18 PM, Bill Aycock wrote:
> We have some major confusion in this thread. Some are commenting on
> Rotor bearings, while some are commenting on thrust bearings. Different
> loads, different environment.

Amen!

I had a TB-4 at the top of the tower with the big array.  Now the small 
antennas were well above the top of the tower.  The tribander (TH-5) was 
just above the top of the tower at 100' while the 7L C3i 6-meter Yagi 
was at 115' and the cross boom for the vertically polarized 2 X 11 on 
440 and 2 X 12 for 144 was just under 130 feet, or just about 30 feet 
above the top of the tower.  The thrust bearing was used only to support 
the mast from side to side. It had no vertical load.  The mast consisted 
of 2" structural steel tube with the rotator about 20 feet below the top 
of the tower. There was also a thrust bearing to keep the mast centered 
half way between the rotator and top of the tower.  This also helped 
keep the mast straight at the top of the tower instead of pivoting.

Again, none of the bearings supported any vertical load. That was 
entirely on the rotator and well within its specs.

Yes, I knew that was one whale of a load (due to the leverage) even if 
it was well within the wind area rating for the system.  In roughly 6 
years (I've forgotten the actual time now) the TB-4 was shot. The races 
were worn to badly the top of the bearing was setting down on the base 
and would not turn.  The edges of the bearing races were razor sharp.

After the first wind of 40 MPH this was pretty much what I had expected 
to eventually find although I expected it to last longer than it did.  
Those 144 and 440 antennas were whipping around like a bluegill fly rod 
that had just tied into a record keeping Bass. Depending on the gusts 
I've seen them move from 3 to 5 feet although the mast took it in stride.

I do still have the TB-4 out in the shop so I could provide some photos 
for those interested.

By the time I took them down the 144 Yagi on the right side had rotated 
to about 30 degrees nose up.  Every thing else was still not only there, 
but straight.
> Then-- the REAL difference-- Real thrust bearings and TB3s.  In truth,
> in most service at the top of a tower, used to steady a shaft, almost
> anything will work, except those that, like the TB3, have a failure
A TB-3 or 4 used to hold a mast straight with only a tribander or small 
VHF array would probably last a very long time, but put much load on 
them, particularly when it isn't turned often, and they will not last.

I have TB-3, and TB-4 bearings as well as the Yaesu thrust bearings. 
None make provisions for lubrication without disassembly.  It has been 
my experience that any bearing installation that is to be lubed has 
provisions to do so and if they are to be difficult to reach they have 
zerks to allow greasing in place.

It is my opinion and it's just that, an opinion, that typically we'd be 
better off with most ham installations using a sleeve bearing at the top 
of the tower instead of the typical "thrust bearing".  I do believe the 
wood block and "cutting board" are superior for the way "most of us" use 
them.  Ideally I'd choose a graphite impregnated Delrin lined sleeve of 
6" to a foot long with a smooth shaft/mast through it. I'd also install 
several zerks to grease the mast in the bearing, but more for rust 
prevention than actual lube as the bearing would be more than adequate 
for that.  The mast would also need to be a snug slip fit, but not tight 
enough to show much resistance to turning.  As long as you could turn it 
by hand should be sufficient.

The mast needs to be protected because if it's steel it will rust and 
rust will destroy the wood and other bearing blocks (including sleeve 
bearings) in a hurry

The problem with this approach as the bearings are custom made, is you 
either need to have a machine shop or access to one unless you are lucky 
enough to find tubing of just the right sizes.   A machinist who is a 
good friend would help<:-))

As to rotators, I have used white lithium grease for years.

73

Roger (K8RI)

> built in.
> Steel balls in an aluminum race WILL pit, due to vibration. This is
> actually worse when the shaft is not rotated very often, because the
> pits just get worse. Failure comes, not from use, but from non-use.
> Ask me how I know.
> I have seen several saying they had lubed bearings on an XX brand for yy
> years, when the different brands present vastly different circumstances
> and types of bearing.
>
> Bill--W4BSG
>
>
> On 10/13/2011 6:41 PM, Bob K6UJ wrote:
>> I also use wheel bearing grease to lube my thrust bearing.  25 years of service, no problems.
>>
>> Bob
>> K6UJ
>>
>>
>>
>>
>>
>> On Oct 13, 2011, at 4:34 PM, Tom Anderson wrote:
>>
>>> The thrust bearing that came with my W51 TriEx tower in the early 90s came with a grease fitting installed.  I've always used wheel bearing grease in my grease gun to lube it.  From what I've read, mechanics advise NOT to mix grease types, so I stick with wheel bearing grease which is usually available in both sizes of tubes to fit a hand pumped grease gun and a lever action one.  I've also redone the front wheel bearings in my car with the same grease.
>>>
>>> FYI: Mechanics advise not to use gasoline to clean wheel bearings for some reason.
>>>
>>> Tom, WW5L
>>>
>>> --- On Thu, 10/13/11, W3YY<w3yy at cox.net>   wrote:
>>>
>>>> From: W3YY<w3yy at cox.net>
>>>> Subject: Re: [TowerTalk] Best Grease for Rotor bearings ?
>>>> To: towertalk at contesting.com, jcjacobsen at q.com
>>>> Date: Thursday, October 13, 2011, 5:37 PM
>>>> I confess to not having read this
>>>> whole thread.  So at the risk of repeating
>>>> others experience or making statements that conflict with
>>>> real experts, let
>>>> me say I have 4 TB-3's that were lubricated with Lithium
>>>> grease 33 years ago
>>>> and they have worked perfectly ever since without any need
>>>> for service.  I'm
>>>> a EE, not an ME, so maybe dry is better.  I'm just
>>>> reporting what worked for
>>>> me.
>>>>
>>>> 73, Bob - W3YY
>>>>
>>>> -----Original Message-----
>>>> From: towertalk-bounces at contesting.com
>>>> [mailto:towertalk-bounces at contesting.com]
>>>> On Behalf Of K7LXC at aol.com
>>>> Sent: Thursday, October 13, 2011 3:17 PM
>>>> To: towertalk at contesting.com;
>>>> jcjacobsen at q.com
>>>> Subject: Re: [TowerTalk] Best Grease for Rotor bearings ?
>>>>
>>>>
>>>> In a message dated 10/12/2011 8:33:14 P.M. Pacific Daylight
>>>> Time,
>>>> towertalk-request at contesting.com
>>>> writes:
>>>>
>>>>>     Would either of you gentlemen please provide for
>>>> me the  instructions
>>>> from Rohn that states that their TB-3 thrust bearings are
>>>> to be  run dry. I
>>>> know that they are sold dry. I am looking for facts from
>>>> Rohn that  say that
>>>> these bearings should not be lubricated. I am not
>>>> interested in any
>>>> information except from Rohn.
>>>>
>>>>
>>>> Then I suggest you contact Rohn since  you're not
>>>> interested on our input
>>>> anyway.
>>>>
>>>>
>>>> Cheers,
>>>> Steve    K7LXC
>>>> TOWER TECH
>>>>
>>>>
>>>>
>>>>
>>>>
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