I would be cautious about using heat treated O1, W2, A2, etc as it could
break under stress. Chromium-molybdenum may be a good choice for the pin.
It can also be purchased prehardened to around 30 Rockwell which is soft
enough to machine, but hard enough to resist wear. Obviously the safest
approach is to purchase one from the manufacture if possible.
John KK9A
To: Daniel Schultz <n8fgv@usa.net>, towertalk@contesting.com
Subject: Re: [TowerTalk] Rohn foldover tower hinge pin specifications
From: Grant Saviers <grants2@pacbell.net>
Date: Mon, 25 Jul 2011 10:27:14 -0700
List-post: <towertalk@contesting.com">mailto:towertalk@contesting.com>
On Line Metals stocks normalized (annealed) 4130 chrome-moly in the
sizes you mention. Yield strength per ASTM should be 66,000 psi, which
while not Grade 8 yield strength it is far superior (almost 2x) to any
plain stock from your local hardware store. Once cut or turned to size
you could have it professionally hardened and tempered to 130+ kpsi or
so, if you think the expense is worth it. My *guess* is the tower
manufacturers would just use a larger diameter pin rather than go to the
trouble and cost of hardening the pin.
O-1 or W-1 drill rod is another choice, somewhat cheaper than 4130 and
available in 1/64" sizes and metric. Somewhere around 40 kpsi yield,
annealed. A little better than low carbon hot rolled, but should be a
known quality vs random unspec'd import. Stocked by almost all
metalworking tool suppliers (MSC, ENCO, McMaster, Travers, etc).
Either can be hardened/tempered to well above 100 kpsi yield.
as always YMMV,
Grant KZ1W
On 7/24/2011 8:33 PM, Daniel Schultz wrote:
> I have a Rohn 25 foldover kit which is missing its hinge pin. The tower
> components seem to accommodate a pin slightly larger than 1/2 inch
> diameter
> and 12 inches long.
>
> My radio club has a Rohn 45 foldover tower which is also missing its hinge
> pin. This pin appears to be about 3/8 inch diameter by 18 inches long.
>
> I have no specifications on either of these hinge pins. I assume I will
> need
> to buy some alloy steel and make them. I would greatly appreciate it if
> anyone
> who owns either of these towers could snap a picture and/or measure the
> diameter of their hinge pin, or make a sketch of what one looks like. Any
> suggestions of what steel alloy to look for would also be appreciated.
> Someone
> local to me has suggested that I use a Grade 8 bolt but I cannot find any
> bolts of the necessary length.
>
> Thanks
>
> Dan Schultz N8FGV
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