Thrust bearing on a tapered top tower

[Cesar N7BUS]

Just got a 33ft tower with a  tapered top, is there a way to install a thrust bearing on top? maybe a yaesu g-050? any ideas out there?

Thanks everyone

Cesar / n7bus 

cn-87

[kd7ts]

http://www.3starinc.com/manuals/25G_buyers_guide.pdf

Thrust bearing ?? no, maybe you mean a bushing ??

Generally, the rotator supports the axial load, (the weight) and the bushing takes care of lateral forces.

Mike KD7TS

[Stephen Hanselman]

What kind of tower?  I cut off the taper section and put a second rotor plate at the top.  Ifs there is room then you could put a plate very close to the top.

The folks at Rhom used to have a thrust bearing that fit the top of their taper section.

Mike,  that's why they call it a thrust bearing.  The idea is to take all, or at least most of the load off of the rotor and transfer it to the tower. If you have a long enough space you put the rotor 6 feet below the thrust bearing and you end up with a lot of lateral support for the array

Regards,

 

Stephen Hanselman, KC4SW

Datagate Systems, LLC

3107 North Deer Run Road #24

Carson City, Nevada, 89701

(775) 882-5117 office

(775) 720-6020 mobile

s.han...@datagatesystems.com

www.datagatesystems.com

a Service Disabled, Veteran Owned Small Business

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[Stephen Kangas]

Actually, Mike, a thrust bearing is primarily for taking the downward weight of the antenna array so that the rotator is relieved of that weight, thus extending the life and fine control of the rotator.  The antenna mast then goes does a short distance to the rotator, and then between the two you have lateral support.

 

Stephen W9SK

[kd7ts]

On Sun, 15 May 2016 21:12:05 -0700, Stephen Hanselman <goo...@kc4sw.com> wrote:

> Mike, that's why they call it a thrust bearing. The idea is to take all, or at least most of the load off of the rotor and transfer it to the tower. If you have a long enough space you put the rotor 6 feet below the thrust bearing and you end up with a lot of lateral support for the array

> Actually, Mike, a thrust bearing is primarily for taking the downward weight of the antenna array >so that the rotator is relieved of that weight, thus extending the life and fine control of the >rotator. The antenna mast then goes does a short distance to the rotator, and then between the two >you have lateral support.
> Stephen W9SK

Hi Stephen and Stephen,

Although I did not ask, I do appreciate your enlightening me on the reason for the name, and the purpose of a thrust bearing.

Maybe I was too literal in thinking of a bearing on the top. In a "rocket" top section the nomenclature for the insert is "bushing". These are #TB50 and#TB75 for a 25AG2 top section. TB means tower bushing in this case. You could certainly put a bushing in the top.

Thrust bearings are also "TB", but this time it refers to thrust bearing ! And these are are TB3 and TB4.

Thrust Bearings mount directly to the pre-drilled ROHN "Flat-Top" Tower Section models 25AG4 and 45AG4. These Thrust Bearings are also used on Bearing Plate models BPL25G, BPL45G, or BPL55G which may be added to straight 25G, 45G or 55G Tower Sections, respectively. They may also be used on the combination model BAS25G Bearing Accessory Shelf for straight 25G Tower Sections. Note that none of these are tapered tops, and thrust bearings do not mount in tapered tops.

Cesar asked ...

Just got a 33ft tower with a tapered top, is there a way to install a
thrust bearing on top? maybe a yaesu g-050? any ideas out there?
Thanks everyone
Cesar / n7bus
cn-87

My answer was no. Specifically, there is no Rohn thrust bearing made to work with a 25AG2 (tapered) top section. I don't know about the Yaesu thrust bearing. My question was "Do you mean bushing?"

Read the manual

http://www.3starinc.com/manuals/25G_buyers_guide.pdf

I cut off the tapered top of my tower and replaced it with an accessory shelf. It was not a Rohn part, but fit OK. The rotor sits down about 10 feet inside the tower on another accessory shelf, AS25G.

Now if someone could just explain about these pesky bushings ...

KD7TS

[Stephen Kangas]

Good question re the "bushing".  I've not used one, but here's some guesses: (1) light-weight antenna where the rotator supports the entire weight of the mast/antenna assembly, and the rotator is mounted on a shelf inside the tower, and perhaps the bushing inserted in place of a thrust bearing.  But, given that a thrust bearing is inexpensive, I don't see significant cost saving using just a bushing in a bearing's place.  Or (2) it may have some use in a tower that has a thrust bearing mounting plate at the top with a thrust bearing installed, and two rotator shelves inside the tower, the lower one for mounting the rotator and then the middle one with that bushing, all for supporting an extra long mast going another 10-15 ft out the top in high winds where extra lateral support may be needed for that mast.  Or (3) the OD of the bushing looks like it must might fit into the ID of the 25AG2 model taper top (per the catalog spec'd dimenstons), perhaps for the mast to have lateral support there and then the rotator shelf inside the tower which rotator would then bear the entire weight of the mast & hopefully lightweight antenna.  My best guesses, but maybe someone else here knows better.

 

I agree that removing the top taper section and replacing it with a bearing plate would be needed to put in a thrust bearing.  I've used the Yaesu bearing, it fits in that shelf. 

 

Stephen

[Edward R Cole]

Let me weigh into this discussion:

I have two 50-foot Rohn-25G towers both of which I installed the BPL25G bearing top plate.  As I recall back 15 years ago they then sold for $96.  I use the Rohn TB4 thrust bearing bought in 2008 from Texas Towers for $204.  At that time Texas Towers sold the std 10-foot tower section for $73.  $300 to put a top bearing is not what I would call "cheap".  I placed the Ham-IV rotator ten foot below at the junction of the standard 10-foot tower sections and use a 20-foot mast, ten foot of which extends above the bearing to hold a HF beam, 432 yagi and two 222 yagis.
http://www.kl7uw.com/Tower2-Feb2009.jpg
I had two 6m yagis when this photo was taken which since have been removed.

One of my Rohn towers uses a Hazer Lift and I bought their thrust bearing.

In my Rohn catalog they show two Tower bushings TB50 for 1-1/4 inch ID and TB75 for 1-1/2 inch ID.  I believe they are made of bronze so that they wear instead of the mast.  Not sure how one mounts them; I decided to get the TH4.

I have one short tower using just the 8-foot section with tapered top that has a pipe stub thru which one can run 1-1/4 inch mast.  I have a mast holding a Yaesu B5400 az-el rotator on a short mast which is clamped inside the tower about 2-foot below the top.  This tower hold small yagis for 2m and 70cm satellite tracking.  I use no bearing or bushing and the pipe stub limits horizontal movement of the mast when moved by wind.

When I put up my 16-foot dish I needed a strong thrust bearing which would fit the 2-1/2 inch ID sched-80 rotating mast.  I found it on e-bay for $16.  It has a four hole square mounting flange and permanently sealed ball bearings.  I had a 1/4-inch steel plate welded onto the 3-inch ID azimuth support mast that is set into concrete.  The bearing is bolted to that plate (that has 3-inch hole in center).  The moral of this story is you can find better deals on bearing if you look around.  Tower bearings appear to be overly expensive and not to the quality of good high speed bearings.
http://www.kl7uw.com/Azimuth_Drive_New_1.jpg
http://www.kl7uw.com/Azimuth_Drive_New_2.jpg

My masts are all sched-80 steel and never had one bend or break - but they are heavy.

73, Ed - KL7UW

73, Ed - KL7UW
http://www.kl7uw.com
    "Kits made by KL7UW"
Dubus Mag business:
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[Marc Lacy]

"Now if someone could just explain about these pesky bushings ...

KD7TS"

IIRC, a bushing would be used when a mast section was smaller than the opening in the top of the tower.

Usually this would have been done in an installation for a lighter weight antenna, such as a TV antenna, and using a rotator that was much lighter.

Just my $0.02.


73 de KD7RYY

Marc

[Paul Drahn]

I just have to add my nickle's worth to the discussion.  If your rotator is of the Ham-m, Ham II, series of rotators then the thrust bearing carrying some of the weight of the antenna is valid. My Japanese made worm gear rotator documentation specifically states the rotator is designed to carry all the weight of the antenna system. It has a very large ball in the base that rotates with the antenna. The thrust bearing is there for side thrust, only and the documentation states there should be a small gap between the set screws and the mast.

I bought the rotator many years ago at the Seaside ham fest. Spent so much money, I have never been back! I think it was also sold by Yeasu.

Paul, KD7HB

[n7au]

In all the towers I have run across, the smallest tube in the tapered top sections has the bushing in it. I am thinking that is because of light weight antennas such as TV antennas used a very thin wall mass and the bushing keeps the mast from rubbing on the hard steel of the top section of tower. The bushing cushioned the mast as it twisted and turned and kept it from bending and breaking. It anyone used an aluminum mast on any of the tapered top section you might have seen a grove in the mast right where it comes out of the tower. I didn’t know about a bushing for the larger tubes so I always cut a soup can and slid it down inside between the tube and the mast. Tape it or use a hose clamp above the top of the tube. Always worked for me to keep the grove out of the mast. You really don’t need a bushing if you are NOT using an aluminum or thin wall mast. It has not weight bearing on the rotor or mast. Just sideways motion from turning or wind just rocking the antenna. I have not had any trouble with steel masts and the grove.

 

The bearing in my opinion has two functions. One is to take some load off the rotor if needed. Either at the top or in the middle. At the middle if you are using a flat plate at the top it helps to keep the mast in a vertical position when you rise the mast (and lock it in the bearing) to remove the rotor. Using a flat plat at the top you should always use a bearing there just to keep the thin metal plate from wearing on the mast not matter what mast you are using.

 

I have several antennas on a 2 inch aluminum mast and (no bearing and bushing with a tapered top section) with a can around the mast I have had no trouble for years.

 

Bob

N7AU

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~The Voice of the Pacific NorthWest VHF Society~

[Edward R Cole]

Bob,

I've never seen bushing used up here.  Mostly either use nothing or a flat top plate with bearing.  BTW those Rohn bearings appear to have no rollers or balls in them, just stamped or cast metal rubbing on metal.  Way too expensive for what they are.  I can get NIB genuine roller or ball bearing flange bearings from e-bay for a tenth the cost.

I do not see bearings carrying any of the weight of the mast.  Their purpose is to take lateral stress from wind.  I have a Ham-IV supporting my 4-yagi eme array for over 15 years.  The Ham-IV is mounted in a Hazer-4 Lift with about 7-foot steel mast with half extending above the Martin-Tower Bearing.

I believe I've read that the bushings are made of bronze or other soft metal to preclude wear on masts.  I long ago stopped using aluminum masts and only use steel.  Last time I 'cheaped out' with a 1-1/2 inch alum mast this happened:
before: http://www.kl7uw.com/SATtower_1.jpg
after: http://www.kl7uw.com/Wind-damage12-15-10.jpg

I removed the dish and shortened the mast:
http://www.kl7uw.com/sattower_001.jpg

Weight of Yaesu B5400 az-el rotor plus 33-inch dish with 60mph winds what did it.  BTW tower was pushed out of plumb by 20-30 degrees.  Now has guy wires.  Base is hinge-over plate and not enough concrete.

73, Ed - KL7UW

At 10:29 AM 5/16/2016, n7au wrote:

In all the towers I have run across, the smallest tube in the tapered top sections has the bushing in it. I am thinking that is because of light weight antennas such as TV antennas used a very thin wall mass and the bushing keeps the mast from rubbing on the hard steel of the top section of tower. The bushing cushioned the mast as it twisted and turned and kept it from bending and breaking. It anyone used an aluminum mast on any of the tapered top section you might have seen a grove in the mast right where it comes out of the tower. I didn’t know about a bushing for the larger tubes so I always cut a soup can and slid it down inside between the tube and the mast. Tape it or use a hose clamp above the top of the tube. Always worked for me to keep the grove out of the mast. You really don’t need a bushing if you are NOT using an aluminum or thin wall mast. It has not weight bearing on the rotor or mast. Just sideways motion from turning or wind just rocking the antenna. I have not had any trouble with steel masts and the grove.

73, Ed - KL7UW

[James C]

On Mon, May 16, 2016 at 1:19 PM, Edward R Cole <kl...@acsalaska.net> wrote:

I believe I've read that the bushings are made of bronze or other soft metal to preclude wear on masts.  I long ago stopped using aluminum masts and only use steel.  Last time I 'cheaped out' with a 1-1/2 inch alum mast this happened:
before: http://www.kl7uw.com/SATtower_1.jpg
after: http://www.kl7uw.com/Wind-damage12-15-10.jpg

A little 'OT' but 'cheaped out' with aluminum? I'm not sure what you had there Ed.  I've got 2" 6061 T-6 and there's no two ways about it. It's light and extremely durable, The trade off is the cost I suppose. They sure don't give it away. I built my entire 144mhz H frame out of it. I've read nothing but good things and looks forward to many years of service from it.

Sorry to see that what you used failed but I'm moving away from steel as best as I can.  For example, I also have a Glenn Martin H-4 Hazer, it's Aluminum too but is a solid piece of kit (you'd agree?)  .-James KE7KQA

 

[Steve Toth]

I believe 6061 T-6 is aircraft hardened aluminum.  BIG difference from regular aluminum.  IIRC used small 6061 T-6 tubing, internally threaded on the ends, with ball joint assemblies for tie rods in quarter midget cars for my girls.  Very stout stuff.

Based on my experience I would agree that 2" 6061 T-6 would work fine.  But like the man said, it is not cheap.

- Steve  W7SJT

"Always look for a positive solution then Improvise, Adapt, and Overcome"

"Sometimes it is the people who no one imagines doing anything, who do the things that no one can imagine".....

 

---

From: James C <jab...@gmail.com>
To: Edward R Cole <kl...@acsalaska.net>
Cc: n7...@usa.com; PNWVHFS <pnw...@googlegroups.com>
Sent: Monday, May 16, 2016 1:57 PM
Subject: Re: [PNWVHFS] Thrust bearing on a tapered top tower

[Loren Moline WA7SKT]

I have used some 1/2" thick UHMW drilled for the mast on a plate with a larger hole where the mast goes thru the plate. Then used a set collar to ride on the UHMW as a thrust bearing. Kinda like a self lubricated bearing..lasts a long time

Loren Moline  WA7SKT

Member: Pacific Northwest VHF Society and ARRL

Member: Hearsat Satellite Monitoring Group.  www.uhf-satcom.com
Member: CVARS-Chehalis Valley Amateur Radio Society

Starchat IRC: Channel = #hearsat
RF Electronics: Starchat IRC: Channel = #rfelectronics
Grid: CN86mr

---

Date: Mon, 16 May 2016 22:17:12 +0000
From: pnw...@googlegroups.com
To: jab...@gmail.com; kl...@acsalaska.net
CC: n7...@usa.com; pnw...@googlegroups.com

[Loren Moline WA7SKT]

Not sure how you would use such a setup on a tapered tower unless you mounted a piece with angle iron clamps

Loren Moline  WA7SKT

Member: Pacific Northwest VHF Society and ARRL

Member: Hearsat Satellite Monitoring Group.  www.uhf-satcom.com
Member: CVARS-Chehalis Valley Amateur Radio Society

Starchat IRC: Channel = #hearsat
RF Electronics: Starchat IRC: Channel = #rfelectronics
Grid: CN86mr

---

From: lmo...@hotmail.com
To: pnw...@googlegroups.com
Subject: RE: [PNWVHFS] Thrust bearing on a tapered top tower
Date: Mon, 16 May 2016 15:34:48 -0700

[Mark Spencer]

Re aluminium vs steel mast pricing.

Over the years I have viewed using aluminium for masts as a less expensive and less desireable alternative to buying structural steel tubing and having it galvanized.

(The minimum charges for having steel galvanized tend to offset the extra price of aluminum in my experience. I went down the galvanizing road during my last antenna project and ended up getting several extra prices of steel galvanized as I had already paid for the galvanizing.)

I've also used alumimum masts over the years and would generally rather use galvanized structural steel.

Your experiences may vary from mine.

If anyone can point me to local source of galvanized structural steel tubing suitable for antenna masts that is cheaper than aluminum, or knows of a cheap place to get steel galvanized I'd love to hear about it.

All the best
Mark S
VE7AFZ

[Edward R Cole]

What all you assume is that one only has to drive down to the local metal supplier to pick up some.

I inquired and they told me that they stock no aluminum tubing, but they could order it delivered from the lower-48 (2400miles minimum by truck) if I would pay shipping. 

So would you pay $12/foot for minimum of 2,000 foot?

BTW my last local RS is closing end of June...that mean's nearest electronic supply is 180mi by road (Anchorage) $7 min chg UPS ground (1-day delivery).  I can order a lot of components from Mouser for $6.60 min shipping. Takes 3-5 days.

DX Engineering sells 6061-T6 but by 5 or 6-foot lengths.

Hint: Alaska is not like "down there"! 

73, Ed - KL7UW

At 02:17 PM 5/16/2016, Steve Toth wrote:

I believe 6061 T-6 is aircraft hardened aluminum.  BIG difference from regular aluminum.  IIRC used small 6061 T-6 tubing, internally threaded on the ends, with ball joint assemblies for tie rods in quarter midget cars for my girls.  Very stout stuff.

Based on my experience I would agree that 2" 6061 T-6 would work fine.  But like the man said, it is not cheap.

- Steve  W7SJT
"Always look for a positive solution then Improvise, Adapt, and Overcome"

"Sometimes it is the people who no one imagines doing anything, who do the things that no one can imagine".....

 

From: James C <jab...@gmail.com>
To: Edward R Cole <kl...@acsalaska.net>
Cc: n7...@usa.com; PNWVHFS <pnw...@googlegroups.com>
Sent: Monday, May 16, 2016 1:57 PM
Subject: Re: [PNWVHFS] Thrust bearing on a tapered top tower



On Mon, May 16, 2016 at 1:19 PM, Edward R Cole <kl...@acsalaska.net> wrote:

I believe I've read that the bushings are made of bronze or other soft metal to preclude wear on masts.  I long ago stopped using aluminum masts and only use steel.  Last time I 'cheaped out' with a 1-1/2 inch alum mast this happened:

before: http://www.kl7uw.com/SATtower_1.jpg

after: http://www.kl7uw.com/Wind-damage12-15-10.jpg

A little 'OT' but 'cheaped out' with aluminum? I'm not sure what you had there Ed.  I've got 2" 6061 T-6 and there's no two ways about it. It's light and extremely durable, The trade off is the cost I suppose. They sure don't give it away. I built my entire 144mhz H frame out of it. I've read nothing but good things and looks forward to many years of service from it.

Sorry to see that what you used failed but I'm moving away from steel as best as I can.  For example, I also have a Glenn Martin H-4 Hazer, it's Aluminum too but is a solid piece of kit (you'd agree?)  .-James KE7KQA


 

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[Edward R Cole]

Or weld a flat steel plate to the tower center tube (if it is like Rohn-26G).  Probably what I will do on my Rohn-45G tower  top later this summer when I extend the tower 20-feet and install an additional 6m yagi with elevation.  At present I just run the mast loose up thru the top pipe.  But with antenna at 20-feet its not as susceptible to wind load.

Innovation goes with ham radio!

73, Ed

73, Ed - KL7UW

[WB6FFC]

UHMW is wonderful stuff, easy to cut on a band saw, easy to machine in a Lathe

but impossible to shape with a file or belt sander, really good for a wearing surface!

 

Mike

WB6FFC

____________________________________________________________
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[Edward R Cole]

At 04:12 PM 5/16/2016, Edward R Cole wrote:

At 03:45 PM 5/16/2016, WB6FFC wrote:

UHMW is wonderful stuff, easy to cut on a band saw, easy to machine in a Lathe
but impossible to shape with a file or belt sander, really good for a wearing surface!
 
Mike
WB6FFC

1/2-inch black UHMW used as dog sled runner up here.  Pulls easy in -30F snow which acts like sandpaper on bare steel.

Good idea though, and cheaper than a bearing.  Might use that for my 6m eme tower.  Mast will be steel.

[Cesar N7BUS]

Thanks everyone for your feedback, I  ended up with a yaesu G-050 mounted on top of  a 1 1/2 in. flange with a 1 1/2 inch pipe going inside the taperd tower pole. I'll be using a 10ft 1 1/4 in. pole  to support my 6 , 2  and 440 antennas.Now I'm just trying to figure out how to mount my radioshack rotor inside the tower.  

[Cesar N7BUS]

This is the finalized project..

[Stephen Hanselman]

Very nice job, congrats!!!

Regards,

 

Stephen Hanselman, KC4SW

Datagate Systems, LLC

3107 North Deer Run Road #24

Carson City, Nevada, 89701

(775) 882-5117 office

(775) 720-6020 mobile

s.han...@datagatesystems.com

www.datagatesystems.com

a Service Disabled, Veteran Owned Small Business

DISCLAIMER:

This e-mail and any attachments are intended only for use by the addressee(s) named herein and may contain legally privileged and/or proprietary information. If you are not the intended recipient, any dissemination, distribution or copying of this e-mail and any attachments is strictly prohibited. If you have received this e-mail in error, please immediately notify me and permanently delete the original and all copies and printouts of this e-mail and any attachments.

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