[Moon-Net] metric bolts for RAK

Edward R Cole kl7uw at acsalaska.net
Mon Apr 5 00:25:14 CEST 2021


Had several replies so will answer all here:

Sorry Alfa-Spid RAK nor Alpha-Spid (got it)

The RAK has just a round housing (call it a pipe).  No nuts welded to 
it.  Thread is only the depth of the pipe (maybe 1/8 inch or metric 

Therefore was concerned that over tightening would strip out the thread.

Mast is what we call black-pipe; mild steel.  1.25inch I.D. 
schedule-80.  Used same on my other antennas with no bends or failures.

I have learned thru experience not to trust pipe bolts from slipping 
so have been using a 5/16-inch bolt thru rotator pipe and mast to 
help hold the pipe but small enough to shear if something binds 
up.  Well the rotator was installed in Sept. 2020 (six months ago).

I did maintenance on antennas and cables last weekend and found at 
least five loose set bolts.  Also the head of the 5/16 inch bolt had 
been sheared off and weight of the array caused mast to drop slightly 
(nut end of shear bolt was intact and bolt had bent downward making 
removal impossible).  So I re-tightened the set bolts figuring that 
would be OK for a couple months as I had plans to do more work in 
warmer wx (still winter here).

This was a Sunday and only Home Depot open.  The good bolt outlet is 
closed weekends.  Rented Man-lift returned on Monday morning.  So 
unlikely to find eight longer metric bolts on Sunday.

Guess I could have used lock-tight (never occurred to me as other 
rotators never had this issue).  I use an identical RAK on my 2m-eme 
system and it free-fell 50-feet in a high wind storm yet rotator was 
secure and undamaged; set bolts tight.

Well I will use lock nuts and longer M10 bolts, plus lock-tight.  I 
will replace shear bolt with at least 3/8 inch diameter.

6m-eme array is very large:  25-foot long cross boom with 32-foot 
long yagi booms.  That catches a lot of wind force.
Rotator may still turn the array in calm wx (??), but will require re 
calibration, frequently.  Maybe, I  can delay until May wx when 
easier to work without winter coats/gloves.  I have to replace my 
elevation actuator and repair my digital encoder (which will require 
dismantling).  Actuator arm is 40-inch long and weighs probably 
35-lbs or more; awkward to handle at 45-feet.  So I had planned to 
rent the man-lift for this work.

73, Ed

At 01:15 PM 4/4/2021, Don Hawbaker wrote:

>My SPID has nuts welded onto the pipe. It's an RAS.  Different 
>model.   You have to be careful.  I have stripped the threads on at 
>least one of the nuts.  Someday I will cut it off and weld on a new nut.
>73  WA3RGQ
>Sent from <https://go.microsoft.com/fwlink/?LinkId=550986>Mail for Windows 10
>From: <mailto:moon-net at mailman.pe1itr.com>Edward R Cole via Moon-net
>Sent: Sunday, April 4, 2021 4:50 PM
>To: <mailto:sp2fry at gmail.com>Andrzej Hoffmann
>Cc: <mailto:ak-vhf at mailman.qth.net>ak-vhf at mailman.qth.net; 
><mailto:moon-net at mailman.pe1itr.com>moon-net at mailman.pe1itr.com
>Subject: Re: [Moon-Net] metric bolts for RAK
>Well we got as windy day, today.  Only been a week since I discovered
>the Alpha-SPID set screws loose and tightened all eight of them.
>My 6m-eme array is free-rotating in the wind.  Apparently the set
>bolts loosened up in only a few hours of wind, and the remains of the
>shear bolt has fully sheared off.  And all because the mfr was too
>cheap to supply stop-nuts (or lock-nuts) to keep the set bolts
>tight.  I actually tried adding a stop nut but that left too little
>thread to tighten the set bolts (nut needs to be thinner or bolt longer).
>So either try to find longer metric bolts in America or quit and
>smash everything to H and take up stamp collecting.
>Was considering trying eme with the new array pretty soon, but it
>will cost me another $233 to rent a man-lift just to tighten the 
>bolts (again).
>Well, I will use a 1/2-inch shear bolt this time (equivalent diam to 10mm).
>I did test the RAK and its rotating ((evidenced by the change in
>direction on the indicator) so apparently not a gear failure -just
>not attached to the antenna.
>Hopefully array will not over-rotate and destroy coax lines in the process.
>73, Ed
>At 02:37 PM 3/31/2021, Andrzej Hoffmann wrote:
> >Hi Ed.
> >
> >If you have a problem with the metric screws I can send you some.
> >Write down the length of the bolt you need. The original ones are
> >probably 25 mm. As far as I know, they are M10 threaded screws.
> >
> >Vy 73
> >
> >Andrzej SP2FRY
>73, Ed - KL7UW
>    <http://www.kl7uw.com>http://www.kl7uw.com
>Dubus-NA Business mail:
>    dubususa at gmail.com
>Moon-Net posting and subscription instructions are at 

73, Ed - KL7UW
Dubus-NA Business mail:
   dubususa at gmail.com 
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