[TowerTalk] [Bulk] Re: [Bulk] Re: Shorty Forty Hose Clamp thread

[Grant Saviers]

One other thought - if I understand correctly, metric tubing does not 
telescope as tightly as US 0.058/0.120" wall.  So squeezing the inner 
tube to the far side is a way to compensate for the extra slop.  A 
logical solution for Optibeam, but I think a bad idea if 0.058/0.120 
wall tubing is available.

Grant KZ1W

On 8/13/2015 8:42 AM, Grant Saviers wrote:
> An interesting experience, building so many antennas.  Thanks for the 
> support of the WRTC event.
>
> I need some help understanding why this works better than other means 
> (e.g. two cross bolts)
>
> 1. it requires an expensive, hard to find drill bit, which can only be 
> re-sharpened cnc
> 2. and a second longer drill to reach the other wall, unless custom 
> made step/counterbore drills are used with a long enough pilot size
> 3. the step drills you reference drill 0.250" vs the 0.226" head 
> diameter of the 18-8 SHCS 6-32 from McMaster.  What is the benefit of 
> the slop?  Or were custom major diameter step drills used?  I'd have 
> to do some deeper research, but suspect the standards don't tolerance 
> cap screw head diameters as tightly as screw diameters/threads.  Maybe 
> that is why, even with a drawer full of them, I never seem to have the 
> right size counterbore :-(
>
> And mechanically, what is the reasoning that it is better? (beating 
> rivets is easy!)  Cross bolts tighten the tubes against each other in 
> two planes.  Absolutely no wiggle.  Works on large antennas.
>
> OTOH, this may be a production manufacturer's tolerance shortcut - 
> drill a large hole in one side helps to insure interchange of 
> elements, since the outer tube holes don't need to go exactly thru the 
> tube center.  Or if the inner tube holes are slightly off center there 
> is enough slop for the bolt to pass through.  With a single screw, 
> there is no hole pitch tolerance requirement. Smaller, lighter beams 
> made for a price point, and limited wind - I get it.
>
> I use two 3" or 4" Chinese cast iron v-blocks (<$20) screwed to a 24" 
> long plywood base to drill press drill assembled element holes, drill 
> first one, insert screw, turn 90 deg (visually measured), drill 
> second.  No special drill, two steps. No hacksawing of slots for hose 
> clamps.  These aren't cnc'd tolerances so elements are not 
> interchangeable, but that isn't a requirement I have for homebuilt. A 
> volume manufacturer would likely develop tooling to enable interchange 
> of elements.
>
> http://www.shars.com/products/measuring/layout-setup-tools/4-x-1-5-8-x-2-5-8-high-quality-cast-iron-v-block 
>
>
> Grant KZ1W
>
> On 8/13/2015 7:20 AM, Jim Thomson wrote:
>> ##  I understand counter bore.... but how can you do a counter bore, 
>> when the tubing thickness is paper thin to begin with... like .058 
>> wall etc?
>>
>> Jim  VE7RF
>>
>>
>> -----Original Message----- From: Stan Stockton
>> Sent: Thursday, August 13, 2015 6:53 AM
>> To: Jim Thomson
>> Cc: <towertalk at contesting.com>
>> Subject: Re: [TowerTalk] Shorty Forty Hose Clamp thread
>>
>> After about 40 years of making my own antennas I learned something a 
>> few years ago when faced with assembling 65 tribanders (520 elements) 
>> we made for WRTC2014.
>>
>> I was introduced to the element joint attachment method I am told is 
>> used by Optibeam.  I was skeptical when I heard the verbal 
>> description, having settled on pop rivets after every other 
>> conceivable method about 20 years ago.
>>
>> I made one element with pop rivets and another with a single 
>> stainless steel socket head cap screw with a counterbore (head 
>> clearance on socket head screw) for one wall of the larger diameter 
>> tubing for each joint, then grabbed each one in the center and 
>> violently shook them back and forth.  The one with SHCS joints felt 
>> like one solid piece of tubing as compared to the pop riveted one.
>>
>> It is so easy and so solid, I will never mess with pop rivets again.
>>
>> A V block fixture with stops, drill press and some of these bits 
>> along with straight bits for the smaller diameter tube drilling are 
>> all that is needed.
>>
>> http://www.wttool.com/index/page/category/category_id/14686/
>>
>> make the job easy in comparison to many methods.  The counterbore is 
>> important.  Use stainless nylock nuts.
>>
>> YMMV but I'm sold on it.
>>
>> 73...Stan, K5GO
>>
>> Sent from Stan's IPhone
>>
>>
>>
>>> On Aug 13, 2015, at 7:42 AM, Jim Thomson <jim.thom at telus.net> wrote:
>>>
>>> The rest of the yagi should be using  3 x rivets
>>> at each joint.
>>>
>>> Jim  VE7RF 
>>
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