Verical Bearing ...Maybe?

[WB4AM]

Hello,

I have had an antenna project in mind for a good while for an adjustable vertical antenna for 40 through 160.

I am including a picture of a bearing that I had come across some time ago.  I am not sure what this particular bearing was designed for, but I was searching for such a bearing or something similar.

I would like to experiment with this type of bearing by inserting it into the top of an aluminum tubing, and then inserting a smaller diameter tubing into this type of bearing.  I might want to have several sections in a telescopic fashion depending which way I decide to erect an antenna for 40 through 160.

Of course I need this bearing to be stainless for the outdoor elements.

So my question is, does anyone know where I can purchase such bearings?  I happen to find this one and this one only at a metal scrap hardware store called Fazzios in New Jersey.

I understand I could find aluminum telescopic tubing where I might not need such a bearing, but I would like to go the route that I am seeking after for better structure and better stability. 

I have also taken in account for ice build up that can occur.  I haven't put a lot of thought into the ice build up as of yet, but I was thinking in the order of some type of flexible rubber boots for now.  I'll cross that bridge later.

Anyway any help on the bearing would be appreciated.

Thank you,
Ken

[KA2DZT]

I've built a number of telescoping aluminum masts, not as easy as it looks.  A lot of things to consider.  First thing you'll need is a lathe.  Not sure what that bearing is, never saw one like it.

Fred

[WB4AM]

I've built a number of telescoping aluminum masts, not as easy as it looks.  A lot of things to consider.  First thing you'll need is a lathe.  Not sure what that bearing is, never saw one like it.

Fred

Hello Fred,

Thanks for the response, I wasn't sure if this was a good place to post this or not.

I bought telescoping tubing before up to 1/4 wall schedule 80 for my 160 meter vertical antenna at a height of 57 feet total.  But it was all pinned at each sections and not used to be adjustable.  I just added a wire at the top of the mast horizontally for an inverted V antenna.

This particular telescopic tubing be it schedule 40 or 80 will be connected to the bottom of a non-insulated 20 foot tubing coming out of the top of a 55 foot crank up tower. 

As the tower is crank upwards, this telescopic mast will rise along with it at its side.  The telescopic mast will rise to 60 feet when the tower reaches 55 feet.  The mast will be connected to the bottom of the non-insulated tubing coming from the top of the tower by means of two horizontal support arms that are conductive.  These arms are what will be used to lift the telescopic tubing and also making the electrical connections.

The total length electrically speaking will be roughly 70 to 85 feet depending if I decide to place a longer mast coming out of the top of the tower.  Some serious thinking and calculations will have to be done to determine if it will be worth the extra 15 feet which I am doubting, so probably a total of 70 feet.

Very good on the Lathe which I do have two of, but the largest one will only accommodate about 3 1/2 feet I believe.  But collars could be made if needed.

Most important thing for me right now would be finding the bearings that I would like to experiment with.

Again thanks for responding Fred.

Ken

[KA2DZT]

I've built a number of telescoping aluminum masts, not as easy as it looks.  A lot of things to consider.  First thing you'll need is a lathe.  Not sure what that bearing is, never saw one like it.

Fred

Hello Fred,

Thanks for the response, I wasn't sure if this was a good place to post this or not.

I bought telescoping tubing before up to 1/4 wall schedule 80 for my 160 meter vertical antenna at a height of 57 feet total.  But it was all pinned at each sections and not used to be adjustable.  I just added a wire at the top of the mast horizontally for an inverted V antenna.

This particular telescopic tubing be it schedule 40 or 80 will be connected to the bottom of a non-insulated 20 foot tubing coming out of the top of a 55 foot crank up tower. 

As the tower is crank upwards, this telescopic mast will rise along with it at its side.  The telescopic mast will rise to 60 feet when the tower reaches 55 feet.  The mast will be connected to the bottom of the non-insulated tubing coming from the top of the tower by means of two horizontal support arms that are conductive.  These arms are what will be used to lift the telescopic tubing and also making the electrical connections.

The total length electrically speaking will be roughly 70 to 85 feet depending if I decide to place a longer mast coming out of the top of the tower.  Some serious thinking and calculations will have to be done to determine if it will be worth the extra 15 feet which I am doubting, so probably a total of 70 feet.

Very good on the Lathe which I do have two of, but the largest one will only accommodate about 3 1/2 feet I believe.  But collars could be made if needed.

Most important thing for me right now would be finding the bearings that I would like to experiment with.

Again thanks for responding Fred.

Ken

Ken,

OK FB, sounds like you don't need any help from me.  Your work reaching heights above fifty feet is more than I've ever been able to do.  OK on the two lathes, you're right they come in handy making collars.  Schedule 40 pipe is heavy enough to handle, schedule 80 and you're getting into crane work.

Can't help much with the bearing, never saw one before.  You might try searching the Granger catalog,  if anyone would have such a bearing it would be Granger.

Fred

[Pete, WA2CWA]

McMaster Carr carries a wide range of linear/sleeve bearings:
http://www.mcmaster.com/#standard-linear-bearings/=110hf36

[wb3eii]

MSC Direct has them as well.
http://www.mscdirect.com/browse/tn/?searchAheadTerm=linear+bearing&searchAhead=true&hdrsrh=true&typahddsp=Linear+Bearings&navid=12104446

[K7LYF]

What is the part number that is on the end of the bearing? With that one can research what the bearing is intended for.

[WB4AM]

Ken,

OK FB, sounds like you don't need any help from me.  Your work reaching heights above fifty feet is more than I've ever been able to do.  OK on the two lathes, you're right they come in handy making collars.  Schedule 40 pipe is heavy enough to handle, schedule 80 and you're getting into crane work.

Can't help much with the bearing, never saw one before.  You might try searching the Granger catalog,  if anyone would have such a bearing it would be Granger.

Fred

Hello Fred,

Looks like I have my answer from what I am seeing below.  I agree Schedule 80 may be to heavy, especially if I was to start out using a large diameter tubing at the base, which I was intended to do.   Also looks like those bearings are very expensive.  I only paid 6 or 7 dollars for mine at Fazzios.

Thanks for the heads up on the schedule 80.

Ken

McMaster Carr carries a wide range of linear/sleeve bearings:
http://www.mcmaster.com/#standard-linear-bearings/=110hf36

Hello Pete,

Thank you for the link.  Wow I couldn't believe I saw one like the one I have here.  I did a Google search and I could find anything like it.

Funny thing is I have been to this site looking for stainless U-Bolts, but at the time I was not looking for these bearings or had even seen one like this.

You guys here are awesome!

Seriously...Thank you.

MSC Direct has them as well.
http://www.mscdirect.com/browse/tn/?searchAheadTerm=linear+bearing&searchAhead=true&hdrsrh=true&typahddsp=Linear+Bearings&navid=12104446

Nothing like being Direct...Link that is!  Okay bad joke line.  It looks like I might be able to experiment in the way I was thinking after all.  But looking at the prices of those bearings and their sizes, I will be force to use the smaller tubing anyway.  But that will make it easier to handle and easier for the tower to do the lifting.

By the way I heard you on 3.705 calling CQ yesterday while I was working down in my basement.  I didn't walk over to the rig to check the signal, but you were coming across just fine.  My transmitter had not been turned on.  I see you are in Pa. as well.

Thank you Ed for the link.  

Ken

What is the part number that is on the end of the bearing? With that one can research what the bearing is intended for.

Hello Michael,

I have to be honest here, I never even thought of looking for it for any reason.  I guess "Stupid IS AS Stupid Does" !

I just looked and its stamped Thompson Ball Bushing and there are a series of numbers stamped on it as well.

Thank you Michael for your help.

Ken
  

[WBear2GCR]

these linear bearings are usually designed for precision work - so the average pipe will be a bad fit, and likely not get much benefit from trying to ride loosely (which would be required) inside the bearing cage. Ground rod is the usual thing that rides in them.

not quite clear to me anyhow, from your description of the way this thing will work, and the part with arms off the top of the tower, etc.

not sure but it might be better to use a cable system like those used on the typical concentric pipe type "tower".
Linear bearings not required.

If bearings are needed to ride inside or outside a tube/pipe, it's probably better to make a 3 or 4 roller assembly to ride on the outside surface, or inside surface depending on if it is going inside a pipe or holding a pipe from the outside. Sealed ball bearings might be an option - probably best if they were stainless though. Simple steel rollers with bronze bearings on a stainless shaft could be ok, or just stainless rollers on a stainless shaft - since it is moving occasionally and at slow speed, ball bearings are rather overkill, imo.

another issue with these linear bearings is that they are not designed to handle wet conditions at all. Also I would expect that large diameters are rather pricey.

Also the bearings will not do a good job of being an electrical connection, ground or hot, regardless.

if the aim is to make a "whip" to lengthen the tower for use as a vertical, I'd think that running an appropriate length of metal through a tube in the top section and then pulling it up from the bottom with a cable & pulley would be simpler, less troublesome and more reliable? I suppose the same sort of assembly could be used off the side of the top section as well.

                    _-_-

[PA0NVD]

These bearings for big diametrs will be indeed very expensive. Than it is a lot cheaper and easier to mount three or more normal small bearing vertically in a ring. A normal bearing can take a whole lot of force, so with 1 - 2 inch OT bearings you can support very heavy masts and the fit is no problem. You can even mount one bearing with a slightly excentered shaft to adjust the fit. Below a sketch.
I think that can save you a lot of trouble and money

[WBear2GCR]

exactly - agree with the basic principle.

there are a number of mechanical methods to accomplish the same basic idea.

ps. by "ground rod" I mean "precision ground rod" as opposed to the thing driven into the earth to
make an electrical ground

[WB4AM]

not quite clear to me anyhow, from your description of the way this thing will work, and the part with arms off the top of the tower, etc.

not sure but it might be better to use a cable system like those used on the typical concentric pipe type "tower".

Hello Bear,

Here is a drawing that I did in MS Paint.  I hope it comes out.  This might give a better picture of what I am trying to describe.

I understand the cable systems used on "pipe Towers" and how they work.  They are quite simple really.

I have thought of this in the past, but it would be difficult to incorporate it with the tower itself while cranking up the tower.  At lease that is what I think!  (I can't see a visual on how it could work)
I would like to use the tower and the tower mast to achieve the flexible desired lengths.

Also the bearings will not do a good job of being an electrical connection, ground or hot, regardless.

I was not aware of this, as I thought if I used stainless it would not rust but also the stainless would also transfer the "RF" from the aluminum to the stainless and then back to the next aluminum section and so forth.

These bearings for big diametrs will be indeed very expensive. Than it is a lot cheaper and easier to mount three or more normal small bearing vertically in a ring. A normal bearing can take a whole lot of force, so with 1 - 2 inch OT bearings you can support very heavy masts and the fit is no problem. You can even mount one bearing with a slightly excentered shaft to adjust the fit. Below a sketch.
I think that can save you a lot of trouble and money

I hear what you are saying, but I am not sure how to incorporate these with the size of aluminum tubing that I was originally going to use.  I would need to see the bearings either in person or at lease a picture of them so I could see how they would be mounted and such.

But I agree the linear bearings are expensive and would be difficult to match the size of aluminum tubing that I would like to use.

You guys are defiantly jogging my mind with ideas and perhaps thoughts on how to approach this differently.

Ken


 

[Pete, WA2CWA]

Is the plan to shunt feed the tower or is the plan to just feed the telescoping sections?

[WB4AM]

Hello Pete,

No on the shunt feeding the tower.  I wanted to insulate the aluminum tubing coming from the top of the tower and make the connections from this tubing at the bottom to the tubing to the right of the tower.

The coax and maybe a series variable capacitor would connect at the bottom of the tubing that's to the right of the tower.

And of course I would be installing many ground radials.

The idea is to make the tower motorized and remote the functions to the shack so that I could adjust the length of the tower/tubing for best SWR for the desired bands.

I feel confident that I can make it work, but an easier way and a cheaper way would make the best sense.

When I say easier, I mean the way I am intending to do it by means of using the tower and such for more length/height.  Its a little extreme, but life needs to be interested!

Ken


 

[Pete, WA2CWA]

Well, unless the tower is made out of non-conducting metal, the close proximity of the metal tower to your vertical will degrade the performance of the vertical. That's why verticals are generally mounted out in the open with very little, if any, metal structures nearby to screw up the performance and matching.

Shunt feeding of a tower has been done by amateurs over the years but if it's a crank up tower you have the additional problem of electrical conductivity between each tower section. Grease, rust, and other contaminants all act as insulators where the crank up sections come in contact with each other.

[KA2DZT]

Well, unless the tower is made out of non-conducting metal, the close proximity of the metal tower to your vertical will degrade the performance of the vertical. That's why verticals are generally mounted out in the open with very little, if any, metal structures nearby to screw up the performance and matching.

Shunt feeding of a tower has been done by amateurs over the years but if it's a crank up tower you have the additional problem of electrical conductivity between each tower section. Grease, rust, and other contaminants all act as insulators where the crank up sections come in contact with each other.

I agree,  I think this whole idea needs to be scrapped.  The close proximity of the tower and it's poor contact surfaces will create diode affect points that will generate harmonic radiation.

Fred

[WB4AM]

I think the idea of using different bearings as suggested is probably the better idea due to the expense and the transfer of the RF to the Aluminum.

As for the proximity of the two, I suppose there would be some capacitance effects going on there.

But I have had close verticals/yagis near by before on both of my towers and they always seem to play well enough for me not to notice or to think I was not having an issue because of the proximity.

I have a 1/4 wave 75 meter vertical now that might be 25 feet away from the one tower and it always played well.  At the moment I am using it as a Mast for a 10-20 meter vertical.  Its horizontal at the moment but that is for another story!

Although this particular installation would be quite closer.  But the main radiator would be 15 feet above everything. 

I guess I will find out one way or another if it will work or not.  Experimenting is also what makes life interested. 

I have never shunt fed a tower, but like you say Pete about the tower being a crank up, it would not be a good idea.

I won't be experimenting with this antenna setup anytime soon.  I am just trying to get some answers before I dig in to deep.  I still think I can get it to work.  But the bearings does have me concern.  So with what has been said, I will have to look into those other bearings that were mentioned and go from there.

Ken


 

 

[Pete, WA2CWA]

Having 15 feet of pole above the tower really doesn't make much difference as far as the close proximity to the tower is concerned. Why would you think that's the main radiator? Also, some sleeve bearings have a lubricant/grease embedded within the structure which should be considered when trying to use this as part of an RF radiator. The lubricant/grease can add act as an insulator, or as Fred stated, poor contact area. But, hey, it's your dollar, you can do whatever perks your desire and interest.

[VE3LYX]

Just finished my 40m 80M vertical last week. Inspired by Neil W0VLZ who has been using his for sometime in vintage events. I used surplus fiberglass army tent poles and Neil said to make sure you only buy the ones with the extra ring at the bottom. Now I didn't make mine full length as I bought a 11 meter marine fiberglass whip for the top at the same surplus store for $20.
I tested it successfully over the weekend on 80M and am using it every night 3561kcs. 7pm and 9 pm. I am only running 5 watts on it so you will need to be within 300 to 400 miles to hear.
The bearing will make it WEAKER not stronger. Give it to someone you dont like.
donVe3LYX
Just added up my cost. About $70 Canadian and current since this was built and all bought in the last three weeks.
Mine is bottom fed and approx centre loaded although the loading coil is in the bottom third and reachable just above my head for moving the clip. On 80M clip is hung free.
Also have a 20M vertical which has been a wonderful antenna for many years here. I have worked the world on it  and that is no exaggeration (and without an AMP)

[WBear2GCR]

My immediate reaction is that you'd likely do better with a simple "J-pole" vertical hung off the side, and tuned at the bottom. Will save a boatload of work too, and $$.

You can always put a "spur" out the top, even with a "capacitance hat".

Another idea that could be played with is to use something like a "Gamma Match" but you'd be feeding the tower, or perhaps an outrigger wire that runs parallel to the tower - maybe a coil spring loaded affair.

[WB4AM]

Having 15 feet of pole above the tower really doesn't make much difference as far as the close proximity to the tower is concerned. Why would you think that's the main radiator? Also, some sleeve bearings have a lubricant/grease embedded within the structure which should be considered when trying to use this as part of an RF radiator. The lubricant/grease can add act as an insulator, or as Fred stated, poor contact area. But, hey, it's your dollar, you can do whatever perks your desire and interest.

Thanks Pete for reminding here on the radiator.  I do recall somewhere in an antenna hand book showing a slight curved line drawn from the top to the bottom of a vertical representing the signal/voltage I don't remember exactly.  I understand the the vertical section radiates, but I always think of all the energy going out to the end of the vertical leaving me to state what I had stated.  Thanks for the correction.

I now understand too about the bearings as far as not a good transfer of RF.  Maybe a type of finger stock as some use on those screwdriver antennas but something much beefier.

Well my confidence on this antenna is loosing steam as I look forward.  But that's okay you guys are saving me money and time and maybe a better idea will come out of all of this.  

I have to say, I like to be a little extreme, or do things differently.  I get bored with the same old same old.

Thanks again Pete.

Ken

My immediate reaction is that you'd likely do better with a simple "J-pole" vertical hung off the side, and tuned at the bottom. Will save a boatload of work too, and $$.

You can always put a "spur" out the top, even with a "capacitance hat".

Another idea that could be played with is to use something like a "Gamma Match" but you'd be feeding the tower, or perhaps an outrigger wire that runs parallel to the tower - maybe a coil spring loaded affair.

Good possibility Bear, I'm not sure what I will end up doing, but sounds like a good idea.

The bearing will make it WEAKER not stronger. Give it to someone you dont like.

Thanks...I think?...No that was funny! LOL

Have fun with your new Vertical.

Ken

[KA2DZT]

Most of the energy leaves the antenna at the highest current area, usually this the low impedance feed point.  Least energy at the end of the radiator (top end). This is why some loading coils are up somewhere along the length of a vertical rather then at the base.   Same is true for simple dipoles.

Fred

[PA0NVD]

Hello Ken
Have you thougt of using a reel with copper wire at ground level that rolls off when you raise the antenna instead of the aluminimum tubing??
It will give no contact problems and is very simple. I use a reel with silver plated stainless steel tape for variable inductors in tuners. But there the Q is very important and it is only 1 meter. If you use the old fashioned bronze antenna wire at a reel, I am sure it will perform at least the same as the mast, only the induction will be higher due to the smaller diameter. But no mechanical and contact problems at all.