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Author Topic: Thrust bearing question  (Read 1901 times)
K2TTM
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Posts: 51




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« on: November 14, 2013, 12:39:55 PM »

I am using an Alliance HD-73-1 rotor, sitting about 3-4 feet inside the top of my 8' tower to turn a K4KIO Hexbeam. The hex is sitting at the top of a 10' aluminum mast. The antenna & mast weighs about 30-40lbs max.  I believe the rotor is rated at 10 s.f. so it's more than strong enough, but I'm wondering if I need a thrust bearing or is the HD-73 strong enough not to need it?

Thanks
Mike
K2TTM
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KB4QAA
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Posts: 2245




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« Reply #1 on: November 14, 2013, 01:25:43 PM »

It never hurts to have a thrust bearing!

[edit]  manual
http://bama.edebris.com/manuals/alliance/hd-73
« Last Edit: November 14, 2013, 01:33:37 PM by KB4QAA » Logged
KH2G
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Posts: 229




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« Reply #2 on: November 14, 2013, 03:17:40 PM »

You will find things last linger and run smoother with the thrust bearing. You can live without but it is highly recommended to use one..
Regards,
Dick KH2G
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K2TTM
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Posts: 51




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« Reply #3 on: November 14, 2013, 04:56:52 PM »

Thanks for the input.  Here's an additional wrinkle.  This is a homebrew tower and it is very slightly out of plumb so getting the rotor and a thrust bearing exactly inline may be difficult if not impossible.  That being the case there will be an issue with binding as the rotor attempts to turn the antenna.  Are these rotors strong enough to handle that type of added stress? I was thinking that a universal joint of some type would solve that particular issue, but I haven't found one that fits the bill so far. 

Thanks
Mike
K2TTM
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WA8UEG
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« Reply #4 on: November 14, 2013, 05:31:50 PM »

You really need to do whatever it takes to get everything in line. Over loading the rotor with weight won't hurt it near as much as not having everything plumb. If everything is not plumb you can expect to have problems with bearings and gears down the line. This is true for any rotor.
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K2TTM
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« Reply #5 on: November 14, 2013, 06:25:13 PM »

Thanks, that's what I am thinking too.  I guess for now I'll just let the rotor handle the weight and when I can, I'll try to remount the rotor more precisely.

Thanks
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KB4QAA
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« Reply #6 on: November 14, 2013, 11:18:35 PM »

Shims are a useful invention.  Smiley
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NV2A
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Posts: 102




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« Reply #7 on: November 18, 2013, 07:13:49 PM »

Thrust bearings are really nice to have but not absolutely necessary for all installations.   If I had one Ii would use it but I wouldn't be popping big money for one.  From looking at your owners manual it looks like it has two races of 100 bearings each.  My guess is it will handle your mast and light weight antenna with ease.  Now having said that...

I have a Tail Twister 2X and it's rated at 1200 pounds sitting on that is a 20 foot piece of 2" x .200 wall steel pipe, a M2 KT36xa 6 elements on 32 foot boom, 8 feet of fiberglass mast and a M2 1 element linear loaded 40 meter dipole.  I am using a bearing but not a thrust bearing.

Don't get caught up in the quest for perfection or you'll never get on the air.

here's you manual if you don't all ready have it.
http://pdf.textfiles.com/manuals/SCANNERS-A-E/Alliance-HD-73%20Rotor.pdf
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