[TowerTalk] 2 in. or 3 in. O.D. thrust bearings found a good supplier
Kevin Adam
n9iww at live.com
Thu Feb 28 17:00:56 EST 2013
I found a good thrust bearing from www.WB0W.com he had one on display that
was CNC out of stainlees steel with a good radial bearing to take the load
bearing was out of stainless to.
Con tact him since he is a ham to he designed this for hams.
Just a customer N9IWW
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Sent: Thursday, February 28, 2013 4:41 PM
To: towertalk at contesting.com
Subject: TowerTalk Digest, Vol 122, Issue 65
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Today's Topics:
1. Re: Thrust bearings (Grant Saviers)
2. Re: TowerTalk Digest, Vol 122, Issue 58 (K8RI)
3. Re: Thrust bearings (K8RI)
4. Thrust bearings (John E. Cleeve)
5. Re: Thrust bearings (K8RI)
6. Re: Thrust bearings (John E. Cleeve)
----------------------------------------------------------------------
Message: 1
Date: Thu, 28 Feb 2013 09:54:07 -0800
From: Grant Saviers <grants2 at pacbell.net>
To: Larry Loen <lwloen at gmail.com>
Cc: Michael Goins <wmgoins at gmail.com>, towertalk
<TowerTalk at contesting.com>
Subject: Re: [TowerTalk] Thrust bearings
Message-ID: <512F99BF.6020101 at pacbell.net>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed
Lot's of confusion because commercial "thrust" bearings are really some
combination of thrust and radial load bearings. What most hams need
with tower installations is a bearing for radial loads, something that
will take the side load of the mast above the top of the rotator when
mounted in a tower. If the rotator is mast mounted then the rotator
bearings have to do all of the work, both thrust and radial and that is
why the antenna height above the rotator and wind load is so limited.
Many stock towers have sleeves at the top to handle the radial loads or
a tapered top section can be used that ends in a sleeve. Usually, these
are all that is needed as a bearing. If the tower has a flat top plate
with a hole for a "thrust" bearing then a radial bearing needs to be
installed to handle the side loads.
Let's apply logic to the situation with the commercial thrust bearing
and rotator in a tower and compare them. I don't have either apart in
front of me so this is a bit from memory, please respond with the
accurate numbers if you have them.
Products that I have used have similar load/stress/wear/corrosion
limitations - (not stainless) steel ball bearings in aluminum races
(Rohn & Yaesu thrust bearings and HyGain, Yaesu rotators).
The number of bearing balls (they are all about the same diameter) ratio
thrust bearing to rotator in simply the ratio of pi * Diameter of the
bearing. That ratio varies between 1:2 and 1:4 and probably averages
1:3. Therefore the load is less per ball by that ratio in the rotator,
and at first order approximation the rotator life will be greater by the
inverse of same ratio. Could you split the loads thrust bearing and
rotator? Highly unlikely given this requires a few thousands of an inch
accuracy and thermal changes would exceed that amount even if attained once.
Then there is the method of clamping the thrust bearing to the mast. If
you are concerned about the stock Orion mast clamp (I have one rotating
40m beam and 86' long 80m dipole, no problems). then surely you view the
3 or 4 grub screws used in a thrust bearing to hold the mast thrust load
as a joke. Plus the castings have tapped threads in aluminum for those
screws or the castings crack (my Rohn did) if the screws don't strip as
tightened. The Orion and Yaesu use grade 8 bolts and nuts to provide
mast clamping force - quite a difference. No doubt the K7LXC Orion
clamp is better than the stock one, but compare either of these to a
stock thrust bearing clamp system.
Could a commercial thrust bearing be used as a radial only bearing?
Perhaps not tightening the grub screws onto the mast would work? Not
considering the designs I've seen, they require some sort of thrust load
to stay together and/or preload the bearing. A plain radial ball
bearing would work much better with a loose fit to the mast. If water
can be kept out this is an alternative, and be bought as a pillow block
assembly, but be prepared to grease it periodically. The plastic radial
support bearing ideas presented on the forum are a better alternative
IMO. Stacking up 2 or 3 pieces of plastic cutting board with mast sized
holes or bore a hole into a 1 to 2" thick chunk of nylon plate (black or
MDS filled for UV resistance), will last a long time and be maintenance
free.
If that logic isn't convincing, than plan out what it takes to replace a
thrust bearing on a multi-antenna mast vs removing a rotator that will
last 2 to 4 times longer. It either case it makes good sense to replace
the grease every 5 years or so to maximize the life of the bearings. I
replace the balls with stainless ones when rebuilding them.
Its clear to me, the standard commercial "thrust" bearing is to be avoided.
Grant KZ1W
On 2/28/2013 7:39 AM, Larry Loen wrote:
> To me, it's a no brainer. 150 dollars to almost certainly lengthen the
> life of a much more costly rotor?
>
> Let's suppose the rotor's specs will take that compressive weight.
> Wouldn't logic indicate that, regardless, it will last longer if we don't
> press all that weight on the rotor 24 by 7, forever?
>
> Moreover, the clamp that comes with even my M2 Orion rotor is not rated
> the
> best by many on this list. There's a better replacement but (so far) out
> of stock. Until I can get it replaced, it seems likely to last longer if
> _it_ doesn't have to deal with the compressive load, at least, especially
> as it seems plausible to me that ordinary physics will transfer some of
> that downward load from side to side (e.g. a strong wind) sometimes.
>
> I'm sure it's not a perfect solution, but it seems quite likely that it is
> at least worth the money.
>
>
> Larry Wo0Z
>
> On Tue, Feb 26, 2013 at 8:24 PM, Michael Goins <wmgoins at gmail.com> wrote:
>
>> Thrust bearings (like baluns) seem to be one of those things that create
>> a
>> lot of confusion in the ham community. They are used to keep the antenna
>> centered on the rotor to eliminate side strain, or to take compressive
>> strain off the rotor, or both, depending on who one talks to about them.
>>
>> I'm putting a T-8 on a HG-52-SS that does not have a thrust bearing on it
>> at the moment. Everything I read about CDE rotors indicate that there is
>> no
>> need because the rotor can handle the weight if a short mast is used
>> minimizing the leverage effect. Other readings say to use one because
>> it's
>> important to hold the antenna weight off the rotor. Many thrust bearings
>> do
>> not have any way to hold the antenna off the rotor seemingly to be only
>> for
>> keeping the mast centered in the rotor. That appears to me the purpose -
>> to
>> minimize any lever-like lateral pressure on the rotor generated by the
>> antenna and mast induced by wind.
>>
>> There are lots of HG-52-SS towers in ham service and apparently no
>> factory
>> thrust bearing available, and while the Rohn TB-3 and Array Solutions
>> version (and others) are adaptable, they require a few holes to be
>> drilled,
>> not necessarily an easy project 20+ feet off the ground.
>>
>> Is a thrust bearing really needed or is it something that most of us do
>> just because?
>>
>> Mike, k5wmg
>> Fast cars, slow boats, good dogs, and summers off to write
>> _______________________________________________
>>
>>
>>
>> _______________________________________________
>> TowerTalk mailing list
>> TowerTalk at contesting.com
>> http://lists.contesting.com/mailman/listinfo/towertalk
>>
> _______________________________________________
>
>
>
> _______________________________________________
> TowerTalk mailing list
> TowerTalk at contesting.com
> http://lists.contesting.com/mailman/listinfo/towertalk
>
------------------------------
Message: 2
Date: Thu, 28 Feb 2013 12:55:52 -0500
From: K8RI <K8RI-on-TowerTalk at tm.net>
To: towertalk at contesting.com
Subject: Re: [TowerTalk] TowerTalk Digest, Vol 122, Issue 58
Message-ID: <512F9A28.1010808 at tm.net>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed
On 2/28/2013 10:38 AM, Patrick Greenlee wrote:
> Lots of opinions and no consensus. Typical.
>
> I didn't have nary a drop of water in my 3 inch conduit 6 months ago but
> I will check again because of all the folks who think all buried
> conduits have water.
It's not that all buried conduit will have water, it's just most any
buried conduit is likely to get water at times.
Presently mine which is shallow enough to be in frozen earth and open on
both ends with none of the joints glues doesn't have ant water standing
in it, T%here are NEMA BOXES on each end, There is about a 6" stub
through the end plate into the basement. As on end is into the fairly
warm basement, this is a prime location for condensation and frozen
droplets. There is none at present and pulling out 4 or 5 feet of pull
line shoes no moisture. Due to the heating system in the house this
tends to have a negative pressure causing a slight flow into the basement.
The pull rope will show moisture in the spring when the relative
humidity is high, but "so far I've never found liquid water.
Very cold air enters through the fittings in the large box at the base
of the tower.. even in the frozen ground it is warmed a little above the
outside air temp. which reduces the relative humidity. In the spring
warm, humid air enters at the tower and is cooled which raises the
relative humidity which will cause condensation. As the ground warms
with the onset of warm weather this condensation will evaporate. The
typical time for there to be condensation in the conduit is 4 to 6 weeks
although there a few times in late spring, early Summer, or fall when
conditions may be right for a few days.
It'd be interesting as to how much cross flow there is between the
basement and shop as the conduits have the box at the base of the tower
in common.
A dry air purge through the conduit dry but is it worth the effort?
http://www.rogerhalstead.com/ham_files/cablebox.htm shows the history
and what I have from the basement to the tower as well as from the shop
to the tower.
Originally I had a 5" sewer pipe from the tower to the basement with a
"Y" just before entering the basement. One leg of the "Y" was down and
capped. The cap had some small holes for drainage if necessary. Almost
the entire run is in the sand back fill around the basement. There is a
weep tile at the bottom so the sand is always dru excep when it's
raining and then the water just drains down through the sand.
The run from the shop to the tower is basically below the watwe table in
the spring, but it's open on each end. I've not had problems with water
in it, but I don't think it'd be a problem were it to be filled with water.
I can see where water can be a big problem with direct burial coax, but
not with coax in conduit unless it's there when you wish to pull cables
in or out.
73
Roger (K8RI)
------------------------------
Message: 3
Date: Thu, 28 Feb 2013 13:54:14 -0500
From: K8RI <K8RI-on-TowerTalk at tm.net>
To: towertalk at contesting.com
Subject: Re: [TowerTalk] Thrust bearings
Message-ID: <512FA7D6.6050009 at tm.net>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed
On 2/26/2013 10:24 PM, Michael Goins wrote:
> Thrust bearings (like baluns) seem to be one of those things that create a
> lot of confusion in the ham community. They are used to keep the antenna
> centered on the rotor to eliminate side strain, or to take compressive
> strain off the rotor, or both, depending on who one talks to about them.
Look at the bearings and races usually tells you whether it's designed
for a lateral (side) load, or end load. Beyond that, read the manual or
call the manufacturer. Hy-Gain has always been very helpful.
But as to bearings. Look at the Ham series of rotators. The bottom race
is a simple half circle, or "U" looking up with the mating race an
identical "U" facing down. It's a typical, low RPM, load supporting
bearing. I believe most og them are good fo 500#, give or take.
If you put a side load on this bearing, where is the force applied?
Directly on the gap between the two races which is where you don't want it.
As the bearing is a large diameter, "leverage will cause one side to
lift and the other to have a corresponding increase in pressure, so
these rotators can handle "some" leverage, but not a lot.
A thrust bearing used with these does not need to support weight, but it
does need to eliminate lateral force. A good example is the "pointy
tube top on some towers. In typical cases, it es more than enough
These rotators are not good at handling negative loads
BUT, "call HY-Gain" to get their take on what to use. It takes but a few
minutes, they are very helpful, and you have information, right from
"the horses mouth"
BTW if you are putting enough weight on a Ham series rotator to need a
weight supporting thrust bearing, you are probably turning more mass
than the rotator was designed to handle.
Look at the ROHN TB series of thrust bearings. They do use that "U"
shaped race BUT the inner and outer edges are offset meaning a side
force does not have the bearings pushing directly on the gap.
Typically, ball and roller bearings are designed for lateral loads.
Taper bearings (like wheel bearings are designed to take considerable
loads in both axes. Some rotators us them, but lateral force can put
loads on rotator housings they were not designed to handle
There is one ball bearing designed to take linear lloads and that is the
throwout bearing in a clutch.
>
> I'm putting a T-8 on a HG-52-SS that does not have a thrust bearing on it
> at the moment. Everything I read about CDE rotors indicate that there is
> no
> need because the rotor can handle the weight if a short mast is used
> minimizing the leverage effect. Other readings say to use one because it's
> important to hold the antenna weight off the rotor.
The only rotators I know of that are not designed to support vertical
loads art inexpensive TV antenna rotators.
As the old CD rotators were beefed up to handle larger ham antennas, a
wedge brake was added with better direction indication and they evolved
into thr rotators Hy-Gain now sells..
I think you will find this design is created to support considerable
weight and should not be operated without a load, but again, ask Hy-gain.
Many thrust bearings do
> not have any way to hold the antenna off the rotor seemingly to be only
> for
> keeping the mast centered in the rotor. That appears to me the purpose -
> to
> minimize any lever-like lateral pressure on the rotor generated by the
> antenna and mast induced by wind.
Isnt there a pipe or sleeve at the top? This is usually more than suficient.
73
Roger (K8RI)
>
> There are lots of HG-52-SS towers in ham service and apparently no factory
> thrust bearing available, and while the Rohn TB-3 and Array Solutions
> version (and others) are adaptable, they require a few holes to be
> drilled,
> not necessarily an easy project 20+ feet off the ground.
>
> Is a thrust bearing really needed or is it something that most of us do
> just because?
>
> Mike, k5wmg
> Fast cars, slow boats, good dogs, and summers off to write
> _______________________________________________
>
>
>
> _______________________________________________
> TowerTalk mailing list
> TowerTalk at contesting.com
> http://lists.contesting.com/mailman/listinfo/towertalk
>
------------------------------
Message: 4
Date: Thu, 28 Feb 2013 20:17:14 -0000
From: "John E. Cleeve" <g3jvc at jcleeve.idps.co.uk>
To: towertalk at contesting.com
Subject: [TowerTalk] Thrust bearings
Message-ID:
<19c3635b369cac5ec553cfe7f58f2423.squirrel at webmail.plus.net>
Content-Type: text/plain;charset=iso-8859-1
Gentlemen,
I have read the thread with interest, and here is my solution. Back in
1978, and in order to cope with the likely forces applied to a tower top
thrust race, I looked at the commercial products available but chose to
"engineer" my own, making use of roller bearings to provide a more
effective solution.
I looked for taper roller bearings with a centre bore of 2 inches or more,
and by using a commercially available two part metal collar, clamped
around the antenna support shaft, with the lower edge of the collar
resting on the edge of the inner ring of the taper roller bearing, as the
antenna shaft passed down through the bearing, the weight of the antenna
is transferred to the inner ring of the bearing. The taper aspect of the
roller bearing performance will cope with any radial forces applied to the
bearing.
New, taper roller bearings are quite expensive, but a metal scrap/vehicle
breakers yard will provide a very cheap source, especially if you are
prepared and able to remove them yourself. The taper roller bearings I
used, came from the rear wheel hubs of scrapped heavy goods vehicles, and
they are more than capable of handling the largest antenna related stress,
and better still, cheap, they cost about $1 each!
Of course, the bearing unit requires a "housing" in order to be fitted to
the tower top plate, but again, the same scrap source provided short
lengths of suitably sized, thick walled aluminium tube, in the form of
scrap "offcuts" sold by weight. I was able to fabricate a very acceptable
"product", and fitted with a suitable weather protection "hat", i.e a
scrap aluminium container lid, and the bearing well packed with grease,
one such unit has been in position since 1979.
Sincerely, John. G3JVC/GM3JVC.
------------------------------
Message: 5
Date: Thu, 28 Feb 2013 15:46:42 -0500
From: K8RI <K8RI-on-TowerTalk at tm.net>
To: towertalk at contesting.com
Subject: Re: [TowerTalk] Thrust bearings
Message-ID: <512FC232.9010802 at tm.net>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed
On 2/28/2013 3:17 PM, John E. Cleeve wrote:
> Gentlemen,
>
> I have read the thread with interest, and here is my solution. Back in
> 1978, and in order to cope with the likely forces applied to a tower top
> thrust race, I looked at the commercial products available but chose to
> "engineer" my own, making use of roller bearings to provide a more
> effective solution.
>
> I looked for taper roller bearings with a centre bore of 2 inches or more,
> and by using a commercially available two part metal collar, clamped
> around the antenna support shaft, with the lower edge of the collar
> resting on the edge of the inner ring of the taper roller bearing, as the
> antenna shaft passed down through the bearing, the weight of the antenna
> is transferred to the inner ring of the bearing. The taper aspect of the
> roller bearing performance will cope with any radial forces applied to the
> bearing.
>
> New, taper roller bearings are quite expensive,
I agree but, I've found wheel bearings to be relatively inexpensive new.
but a metal scrap/vehicle
> breakers yard will provide a very cheap source, especially if you are
> prepared and able to remove them yourself. The taper roller bearings I
> used, came from the rear wheel hubs of scrapped heavy goods vehicles, and
> they are more than capable of handling the largest antenna related stress,
> and better still, cheap, they cost about $1 each!
>
> Of course, the bearing unit requires a "housing" in order to be fitted to
> the tower top plate, but again, the same scrap source provided short
> lengths of suitably sized, thick walled aluminium tube,
Depends on what you mean by thick walled. I prefer a substantial
retainer with the bearing pressed in. I also prefer an over sixe ID
with an adapter that has a shoulder, that is a slip fit on the shaft,
but pressed into the bearing. If the shoulder is large enough I can
drill and tap it, allowing me to lock to the mast to support it for
rotator removal.
My rotator, a PST-61 has wheel bearings top and bottom so it can
tolerate long masts through thrust bearings that might pull o the
rotator due to unequal expansion and contraction with temperature.
73
Roger (K8RI)
in the form of
> scrap "offcuts" sold by weight. I was able to fabricate a very acceptable
> "product", and fitted with a suitable weather protection "hat", i.e a
> scrap aluminium container lid, and the bearing well packed with grease,
> one such unit has been in position since 1979.
>
>
> Sincerely, John. G3JVC/GM3JVC.
>
>
>
>
>
>
> _______________________________________________
>
>
>
> _______________________________________________
> TowerTalk mailing list
> TowerTalk at contesting.com
> http://lists.contesting.com/mailman/listinfo/towertalk
>
------------------------------
Message: 6
Date: Thu, 28 Feb 2013 21:41:33 -0000
From: "John E. Cleeve" <g3jvc at jcleeve.idps.co.uk>
To: "K8RI" <K8RI-on-TowerTalk at tm.net>
Cc: Towertalk at contesting.com
Subject: Re: [TowerTalk] Thrust bearings
Message-ID:
<8a25533406a23712e2943dd34fa8f1da.squirrel at webmail.plus.net>
Content-Type: text/plain;charset=iso-8859-1
Hello Roger
The scrap aluminium tube I used has a wall thickness of about 0.75 inches,
the object being try and find bearings/materials that I could fairly
easily fit together in order to fabricate the housing with minimal machine
shop access. Having done the bench metal cutting etc. I did get the edges
etc. cleaned up by asking for help from a local machine shop, otherwise,
the original 1979 bearing assembly was a true amateur radio "kitchen
table" product.
73, John. G3JVC/GM3JVC.
> On 2/28/2013 3:17 PM, John E. Cleeve wrote:
>> Gentlemen,
>>
>> I have read the thread with interest, and here is my solution. Back in
>> 1978, and in order to cope with the likely forces applied to a tower top
>> thrust race, I looked at the commercial products available but chose to
>> "engineer" my own, making use of roller bearings to provide a more
>> effective solution.
>>
>> I looked for taper roller bearings with a centre bore of 2 inches or
>> more,
>> and by using a commercially available two part metal collar, clamped
>> around the antenna support shaft, with the lower edge of the collar
>> resting on the edge of the inner ring of the taper roller bearing, as
>> the
>> antenna shaft passed down through the bearing, the weight of the antenna
>> is transferred to the inner ring of the bearing. The taper aspect of the
>> roller bearing performance will cope with any radial forces applied to
>> the
>> bearing.
>>
>> New, taper roller bearings are quite expensive,
>
> I agree but, I've found wheel bearings to be relatively inexpensive new.
>
>
> but a metal scrap/vehicle
>> breakers yard will provide a very cheap source, especially if you are
>> prepared and able to remove them yourself. The taper roller bearings I
>> used, came from the rear wheel hubs of scrapped heavy goods vehicles,
>> and
>> they are more than capable of handling the largest antenna related
>> stress,
>> and better still, cheap, they cost about $1 each!
>>
>> Of course, the bearing unit requires a "housing" in order to be fitted
>> to
>> the tower top plate, but again, the same scrap source provided short
>> lengths of suitably sized, thick walled aluminium tube,
>
> Depends on what you mean by thick walled. I prefer a substantial
> retainer with the bearing pressed in. I also prefer an over sixe ID
> with an adapter that has a shoulder, that is a slip fit on the shaft,
> but pressed into the bearing. If the shoulder is large enough I can
> drill and tap it, allowing me to lock to the mast to support it for
> rotator removal.
>
> My rotator, a PST-61 has wheel bearings top and bottom so it can
> tolerate long masts through thrust bearings that might pull o the
> rotator due to unequal expansion and contraction with temperature.
>
> 73
>
> Roger (K8RI)
>
> in the form of
>> scrap "offcuts" sold by weight. I was able to fabricate a very
>> acceptable
>> "product", and fitted with a suitable weather protection "hat", i.e a
>> scrap aluminium container lid, and the bearing well packed with grease,
>> one such unit has been in position since 1979.
>>
>>
>> Sincerely, John. G3JVC/GM3JVC.
>>
>>
>>
>>
>>
>>
>> _______________________________________________
>>
>>
>>
>> _______________________________________________
>> TowerTalk mailing list
>> TowerTalk at contesting.com
>> http://lists.contesting.com/mailman/listinfo/towertalk
>>
>
>
> _______________________________________________
>
>
>
> _______________________________________________
> TowerTalk mailing list
> TowerTalk at contesting.com
> http://lists.contesting.com/mailman/listinfo/towertalk
>
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