[TowerTalk] US Tower seized gearbox

[Jim Thomson]

Date: Thu, 28 Jan 2016 19:59:09 -0800
From: "James Denneny" <57jndenneny at comcast.net>
To: <towertalk at 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