Insulator/hook dimensions General >
Member 61 posts dannyk Member 61 posts
dannyk
Trying to make the tower hook insulator assembly and believe I have everything correct, but cannot configure it to the dimensions in the drawings. I wanted to ask if anyone successfully made the pieces with the drawings dimensions so I can figure out what I am doing wrong.
The gap for the insulator is 1/4" wider than the insulator no matter how I assemble it, which makes it hard to tighten and secure the hook in place
The field at our hub kickoff used 1x2s that were 1 3/4" which would solve the problem but that is not what the drawings show.
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jgraber Moderator 275 posts
jgraber
In theory, theoretical drawings and practical reality are the same.   In practice, they are not.

I assume you are talking about dwg 19001400.    (It would have been good to reference that.)
You are not alone in this,  you have seen (or asked?) Q&A#56, I assume.  It mentions 1/4" tolerance.   
Short version: If you move the nut item 2 closer to the coupling nut, you can close that 1/4" gap.
If the hook sticks out 2" from the insulator, vs 1-3/4",  it is within the (unlisted) field tolerance. 
   I think the importance spec for the hook lip is Height over Ground, and I would hope that robots can deal with a height tolerance here of at least +/-1 inch. 

Long version, stackup analysis walk-through.  Did I get this right?
2" bolt - 1/16" washer - 3/2" wood - 1/16" washer leaves 3/8" bolt left to screw into the 7/8" coupler nut.  (OK, the washers are a little thinner than that, but its close).
 Insulator tube is 2-2/8" long;
The hook is 4-2/8" long,  threaded is 2-7/8", unthreaded is  1-3/8" 
   The insulator tube sticks out above the hook by the ~3/8" that the bolt is screwed into the coupler nut,   so the bottom of the hook loop is 4-5/8" below the top of the insulator.
  The bottom of the hook loop is 4-5/8 minus 2-2/8" = 2-3/8" below the bottom of the insulator.
The hook lip is supposed to be 1-6/8" below the insulator;   that leave 19/8 minus 14/8 = 5/8" 
for the distance from the bottom of the hook loop to the top edge of the hook lip, which is a dimension not directly shown on the mcmaster drawing.
When I print out the 2d pdf hook drawing from the mcmaster page, 9492T13, and measure it with a ruler, this distance from the hook loop bottom to the hook lip top measures about 4/8" instead of 5/8".  So it stacks up to within 1/8" of drawing.
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jgraber Moderator 275 posts
jgraber
I will also pass along this response from the Dallas Field build lead:
   ... “don’t obsess over it” –stack a few washer on the top side, and let it go. 
I still think a (Vertical) 2x4 with 3 (horizontal) arms screwed on... can sub in for (the) pretty tower.  As long as height and spacing (x-z axes) are reasonably good, abstracting out the details benefits everyone.
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