J.P.,
I measured the bolt pattern on a TB-3 that our club has this afternoon. The
mounting configuration consists of 4 holes arranged in a square pattern with
centers on the circumference of a 5.375" diameter circle. This works out to a
square 3.80" on a side [5.375/sqrt(2)]. The clearance holes in the TB-3
flange are slightly larger than 9/16" in diameter. I believe the holes were
intended to accomodate 1/2" diameter hardware with margin for tolerance
buildup of the mating hole pattern.
Seems like Rohn needs to add this drawing to their catalog. Hope this
is helpful.
73 de Mike, W4EF.................
-----Original Message-----
From: J.P. Kleinhaus [SMTP:w2xx@cloud9.net]
Sent: Saturday, May 08, 1999 9:32 PM
To: towertalk@contesting.com
Subject: [TowerTalk] Help with bolt sizes
Greetings:
I am having some rotor and thrust bearing shelves made for a tower.
The intended rotor is the Orion 2800 and the thrust-bearings are
to be Rohn TB-3's. I found a .PDF file with the drawings of the
Orion bolt pattern and it states a standard 3"x3" bolt pattern.
However, it does not give the sizes for the hardware, so I have
no idea what to tell the machinist as far as the diameter of the
holes. Also, does anyone know the size of the center cut-out
that is required to pass the cable up to the rotor through
the plate? It's also not defined on the document.
Having searched the Rohn website and my Rohn catalog, I have
not been able to find a single reference to the pattern of
bolt holes needed for the TB-3 bearing, nor, obviously, the size
of the hardware needed. I am willing to assume the TB-3 also
fits a "standard" 3x3 bolt hole pattern, but still need additional
information.
If anyone has this information, I would be most grateful.
73, J.P. W2XX
w2xx@arrl.org
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