Date: Thu, 28 Jan 2016 19:59:09 -0800
From: "James Denneny" <57jndenneny@comcast.net>
To: <towertalk@contesting.com>
Subject: [TowerTalk] US Tower seized gearbox
The Hub City W300 gearbox on my US Tower 85 ft rotating mast appears to have
seized after 12 years. Un fortunately the tower is at the 55 ft level and
will neither raise nor lower. Fortunately, it is at a safe height with
respect to wind. Unfortunately, I am uncertain how to get it down to
repair/replace the gearbox. The lifting cable drum mounts on the gearbox
output shaft. I cannot pull the gearbox as the cable drum system is what
keeps the tower from freefall. I do Have the tiltover fixture. There is a
SteppIR DB-18E yagi at the top. I am resisting bringing in a crane to
support the tower. Any suggestions?
Thanks
Jim K7EG
## This is my worst nightmare, esp with my old style 5000 lb HDX-689.
Which ends up being 5600 lbs with the mast, rotor, yagis on it.
## On a working hub city gear box, the oil can be drained, and flushing liquid
then used to flush out all the oil dino oil. Then replaced with the better
synthetic.
## UST sez to check the gear box oil monthly..and replace every 2 years. Dunno
anybody
who follows that advice. The stories where I have heard of the gear boxes
being seized up, they
could not be freed up. Gears, etc, inside, got mashed in there good...and they
were stuck solid.
The only fix was to buy a new gear box, pre-filled with synthetic lube, and
replace the gear box.
easier said than done. Where sections 1+ 2 overlap, horz steel could be
placed, to take the load off
the raising cable. 20 ton jacks used to lift the section #2 up a tiny bit,
enough to take the weight off the
raising cable. Chain removed, gear box removed and swapped to a working brand
new one.
## A crane could also be used, but that is dicey as well. take too much slack
of the cables, and some of them
could jump the myriad of pulleys. I think I counted 23 on mine in total. But
the crane could be used to safely
lower the entire tower down..fully nested. Then you could use various methods
to swap out the gear box. It may
not be worth sending in the old trashed box to hub city for a rebuild.
## contact UST, since they must have heard this horror story before. I
think it was Dino who told me that when
he talked to Hub city, the eng went nuts when he found out their gear redux
boxes were being used on motorized
towers..with a constant load on the gear box. They were really designed for
stuff like conveyor belts in factories etc.
## id almost be inclined to swap the gear redux box out on spec every 5-6
years, with a new one. Then send in the
old one to hub city for a total refurb job.
Jim VE7RF
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