One suggestion:
ROHN says to us a taper pin punch to open up the galvanizing and not to
drill it out. The punch will leave the galvanizing in tact where
drilling removes it and exposes the edges of the hole to corrosion.
I doubt it would cause a problem, but that's a personal opinion, where
ROHN is the official stance.
It does seem a shame after all that work and money to hot dip galvanize
and then remove some to expose the steel.
73
Roger (K8RI)
On 4/24/2015 11:29 AM, Grant Saviers wrote:
Another option is to regalvanize each section. Hot dip galvanizing
here cost me $0.55/lb for 10 x 20' sections of Rohn 65. About $1500
for 20+ years of no maintenance life, good as new, at less than 10% of
new section cost. The prep process requires all paint to be removed
(none on my former AM tower sections). The caustic degrease handles
most organic contamination, then there is an acid bath which removes
light rust and the old Zn, then fluxing and into the vat of molten
zinc. Rohn designs for HDG so both the id and od get new Zn,
something you can't do with paint. Turn around at a very busy Ace
Galvanizing in Seattle was 2 weeks. Plan to ream some holes that may
have excess Zn in them. ebay usually has some cheap bridge reamers
(ironworker "bridge", not guitar "bridge") or core drills which in the
right sizes are perfect for this task, or very carefully use a two
flute twist drill bit as the soft Zn will grab.
Grant KZ1W
On 4/23/2015 18:42 PM, Mike Reublin NF4L wrote:
Mike -
If you pull the axle for the pulley, and remove the sheave, you can
push a U-loop of the cable thru the housing and then put the sheave
back in.
74, Mike NF4L
On Apr 23, 2015, at 9:27 PM, Mike Ashby <seabassm01@hotmail.com> wrote:
Sam;
I to am in the process of doing the same thing. All of the sheaves
were sluggish and I did not know the history of the cables. Went to
Kaman bearing and bought sealed heavy duty bearings and had a
machine shop bore and press the new bearings into the old sheaves.
Much less expensive than new purchase from U.S. Towers. Went to a
rigging supplier and purchased new cables. I purchased heavy duty
cable clamps for the end terminations. The rigging company could
have done the swagging cheaper but the ends would not fit through
the sheave housings. Took the tower to a welding shop and had them
grind and weld 2 or 3 spots that had some small hairline cracks. I
then went over the entire tower and put 2 coats of cold galvanizing
on questionable spots. 3 coats on the thrust bearing shelf and
rotor shelf. Wire brushed thrust bearing and painted. Squeezed
bearing grease into bearing until old was replaced with new. Bought
2 collar stops to bolt to mast and rest on top of t
he thrust bearing. Going to purchase a funnel to slide down the mast
and cover the thrust bearing for water protection. Have also
considered a vent pipe flashing instead of funnel.
I consider this as a good investment into peace of mind.
Mike
W7PIM
snip
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73
Roger (K8RI)
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