[TowerTalk] XM-240 Shorty-Forty: X-Hat Modification- Update

[Joe Subich, W4TV]

Dick, 

> I just went out and inspected the X-Hat assembly on my 1 year 
> old  XM-240.  It is constructed as Joe said the original X-Hats 
> were constructed: "The original X-hat elements were solid rod 
> 3/16" in  diameter with a 1.25" long by 3/8" OD sleeve crimped 
> over the  center of he rod before drilling for the #8-32 x 1.75" 
> mounting  bolt."

When you inspected your rods, how "tight" was the sleeve - what 
was the wall thickness?  

If the center of the sleeve is too large, there will be no 
support in spite of the crimp.  On the old antennas, there  
is very little clearance between the sleeve and the rod ... 

The other possibility is that the material was changed.  I have 
an old rod that is bent into an "S" shape but shows no ill 
effects.  The aluminum is obviously very soft.  If the new rods 
are a stiff and brittle they will break much more easily. 

73, 

   ... Joe, W4TV 
 



> -----Original Message-----
> From: towertalk-bounces at contesting.com 
> [mailto:towertalk-bounces at contesting.com] On Behalf Of RLVZ at aol.com
> Sent: Tuesday, February 09, 2010 4:55 PM
> To: towertalk at contesting.com
> Subject: [TowerTalk] XM-240 Shorty-Forty: X-Hat Modification- Update
> 
> 
>  
> Hi Guys,
>  
> Thank You for the input regarding my XM-240 Shorty-Forty X-Hat rods  
> breaking and falling off.
>  
> For those who asked, the X-Hat Rods are 34-1/2" in length.
>  
> I just went out and inspected the X-Hat assembly on my 1 year 
> old  XM-240.  
> It is constructed as Joe said the original X-Hats were  
> constructed: "The 
> original X-hat elements were solid rod 3/16" in  diameter  
> with a 1.25" long 
> by 3/8" OD sleeve crimped over the  center of he rod before 
> drilling for the 
> #8-32 x 1.75" mounting  bolt."
>  
> Therefore, the "1.25" long by 3/8" sleeve crimped over the 
> center of the  
> rod" is a part of my X-Hat.  I am very happy that most people 
> have not had  a 
> problem with their X-Hat rods breaking and falling off!  But 
> if you think  
> about it, the strength of the small 3/16" rod is almost entirely  
> compromised when it was drilled thru to accomadate the #8-32  
> mounting bolt which is 
> 1/8" in diameter.  Therefore, about the only  thing holding 
> the rod together 
> is the 1.25" long by 3/8" OD sleeve  crimped over the 
> center... which only 
> provides 1/2" of support on each  side of the hole!  (and how 
> strong is a 
> crimped sleeve)
>  
> I think we discovered why the "on the tower" life of my new 
> XM-240 has not  
> exceeded 1 month either time it was up.  Either vibration 
> from the  wind 
> and/or birds landing on the weakened 3/16" rods... cause them 
> to  break apart. 
>  By the way, when the 2 different 3/16" rods fell to the  
> ground the 3/8" x 
> 1.25" sleeve was no longer attached to any part of the 4  
> remaining rods 
> pieces.  I believe this indicates that the crimped sleeves  
> probably failed.
>  
> As an option to replacing the X-Hat with extended elements, 
> perhaps I  
> might consider using 3/8" aluminum rod with a 2nd sleeve over 
> the  center where 
> drilled.
>  
> 73,
> Dick- K9OM
>  
>      
>  
>  
>  
>  
>  
>  
>  
> In a message dated 2/9/2010 4:12:52 PM Eastern Standard Time,  
> na8w at hotmail.com writes:
> 
> That's  exactly what happened to mine.
> 
> Darl   NA8W
> 
> --------------------------------------------------
> From: "Joe  Subich, W4TV" <lists at subich.com>
> Sent: Tuesday, February 09, 2010  3:22 PM
> To: "'Tower and HF antenna construction topics.'"  
> <towertalk at contesting.com>
> Subject: Re: [TowerTalk] XM-240  Shorty-Forty: X-Hat Modification
> 
> >
> >> I wonder why they  fall off?
> >
> > The original X-hat elements were solid rod 3/16" in  
> diameter with a 
> > 1.25" long by 3/8" OD sleeve crimped over the  center of he 
> rod before 
> > drilling for the #8-32 x 1.75" mounting  bolt.
> >
> > Newer antennas - or at least some production runs -  appear to lack 
> > the crimped sleeve as they fracture through the  mounting 
> hole due to 
> > vibration.  My guess is that the sleeve  was eliminated as a cost 
> > cutting measure <G>.
> >
> >  73,
> >
> >   ... Joe,  W4TV
> >
> >
> >
> >
> >
> >
> >> -----Original  Message-----
> >> From: towertalk-bounces at contesting.com  
> >> [mailto:towertalk-bounces at contesting.com] On Behalf Of Gregg Seidl
> >>  Sent: Tuesday, February 09, 2010 1:57 PM
> >> To: Tower and HF antenna  construction topics.
> >> Subject: Re: [TowerTalk] XM-240 Shorty-Forty:  X-Hat Modification
> >>
> >>
> >> I wonder why they fall  off?  I've never heard of that. Mine have 
> >> been up  for 6 years now.  Gregg  K9KL
> >> ----- Original  Message ----- 
> >> From: <RLVZ at aol.com>
> >> To:  <towertalk at contesting.com>
> >> Sent: Monday, February 08, 2010  4:43 PM
> >> Subject: [TowerTalk] XM-240 Shorty-Forty: X-Hat  Modification
> >>
> >>
> >> > Hi Guys,
> >>  >
> >> > I've had problems with the X-Hat Rods falling off of my  XM-240. 
> >> > Therefore, I would like to eliminate the X-Hat by  
> lengthening the 
> >> > elements.  I'm wondering if anyone has  done this
> >> successfully and how
> >> > much length must  be
> >> > added to the elements?
> >> >
> >> >  Or if anyone has modeled the removal the XM-240 X-Hat by
> >>  lengthening
> >> > the elements... please share what element lengths  you came up 
> >> > with.
> >> >
> >> > Thanks!
> >>  >
> >> > Dick- K9OM
> >> >  _______________________________________________
> >> >
> >>  >
> >> >
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> >>  >
> >> >
> >>
> >>
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