[TowerTalk] TEK screws

[K7GCO@aol.com]

In a message dated 17.03.00 10:50:33 Pacific Standard Time, 
dave_pomeroy@yahoo.com writes:

<< 
 Gang,
   when you take out the tek screws to rebuild can you
 still get the pieces apart?  
 
 
 --- K7LXC@aol.com wrote:
 > 
 >       A bunch of people have asked me about TEK
 > screws. Here it is again.
 > 
 >       A TEK screw is a chisel-tipped, self-tapping
 > sheet metal screw. TEK is 
 > just one manufacturer - there are others. Most any
 > hardware store will have 
 > them; my country True Value down the street has
 > them. 
 > 
 >      Get the ones with Phillips heads; the
 > quarter-inch long ones should be 
 > plenty for drilling thru two layers of aluminum
 > elements. They install in a 
 > couple of seconds with your cordless drill. I
 > haven't seen one of those come 
 > loose.
 > 
 >      I'll bet you a nickel that riveted joints
 > backed up with a TEK screw 
 > installed off-axis (per N4KG) will eliminate
 > 'loosening rivet' syndrome. The TEK screw
     will also provide a redundant electrical
 > connection.
 > Cheers,   Steve    K7LXC Tower Tech
 
Yes the TEC screws work.  But again it is a dissimilar metal--1 of the three 
corrosion creators along with air and moisture.  I coat the hole and screw.  
Make sure the inside hole drilled is the right size for the self taping 
screw.  Insofar as a 1/4" TEC being long enough for 2 layers of tubing 
(1/4"), examine the screw and make sure the tapered area on the tip is 
through or they can work out again.  The hole in the outer diameter tubing 
should be larger so the grip in the inner tubing can compress it to the outer 
tubing for better connection and rigidity.  To be sure get a 3/8".  Hy Gain 
used to use them and they were long enough to go through and they used lock 
washers to help anchor it.

The lose fit of the tubing (what is the wall thickness of the outer tubing?) 
apparently led to the rivets being all in a row which limits the contact area 
of 2 round objects of different diameter.  Instead of 360 degrees of contact 
area there is perhaps 10-20 degrees and it mostly just at the diameter change 
where the RF makes the jump.  The TEC screw idea at 90 degrees is great to 
anchor it wiggle wise but more rivets would do the same and they aren't a 
dissimilar metal.  Grease the hole and rivet.  It also increases the contact 
area to over 90 degrees but only at the diameter change.  I like a tight 
coated clamp on coated joints that gives 360 degrees of contact.  
Psychologically it gives a lower resistance fit also.

Properly designed quads don't use rivets or Penatrox on the one wire 
connection (just plain solder) per element, don't need rebuilding, all the 
delay and crane fees. The electrical efficiency of quad element connections 
remains at 100%--permanently!!  Longevity of design is minimized to reduce 
cost and appeal to the "tight budget ham" of many products.  They will pay 
far more in the end.  I have a Collins KW-1 and a 75A!.  In 47 years both 
have only had one component replaced or more than one hour down time.  In 
Quality Assurance that's called a "Robust Design."  The Zenith Radios of the 
30's are still working 65 years later.  

I have made arrangements for a Special Oven in Hell for those "Tight Budget 
Mfgs" and another Oven for those who buy from them.  Would you believe they 
still do business with each other down there for air conditioners and other 
hot products.
K7GCO

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