A couple of years ago I replaced K6CF's US Tower 72' tower with a new
HDX series for this very same reason Mike's failed below... The main
shaft going into the gearbox snapped allowing the pulley to release all
tension on the cables. It was a free fall after that! Both Chris' and
Mike's failures happened while in transit! CHECK OUT THE SOLID SHAFT
NEXT TO WHERE THE PULLEY IS MOUNTED! ESPECIALLY IF THE PULLEY IS NOT
SUPPORTED ON THE FREE END! There is a lot of torque pulling up by the
cables!
I've mentioned before about an unrelated Hub City gearbox failure that
happened to me. This failure happened during transit. AA6PW's Fulton
brake winch failed during transit as well! We replaced that with a
Fulton K2500 winch... http://www.wd0m.com/aa6pw.html
While I'm a BIG FAN of crank up towers, all these failures are in the
front of my mind whenever I operate them! During transit on an unknown
tower I like to throw a 4x4 in the rungs just in case something cuts
loose. I throw the 4x4 in a coule of feet below the second tower section
and bring it down. Then I stop, pull it out and move it down a couple of
feet or rungs. Rinse and repeat until the tower is down or UP! This way
the drop is minimized and so is the damage! A W-51 I've taken down
recently is a good example of this! I had no idea of the reliability of
the brake winch so took precautions. This winch and cables will be
replaced before I sell it!
So people, check out your winch systems carefully! Take precautions
during transit! Keep arms clear! If you have a Hub City gearbox, Hub
City recommends Mobil SHC-630/SHC-634 50/50 mix. Change your oil! Make
sure it is full!
As a note, the gearbox failure I witnessed has the worm gear ON TOP of
the case. I saw an older Triex tower where the gearbox was mounted
upside down (worm gear was on the bottom). With the gear on the bottom,
it is ALWAYS in oil and therefore should not rust. The failure I saw was
caused by a rusty steel worm gear taking out the softer bronze gear. Had
this gear box been maintained properly, this failure may not of
happened!
Here is Mike's story...
K6MYC writes...
http://www.m2inc.com/index.php?ax=news
"From Mike's Shack - (2012-10-12 at 3:30pm)
SUNDAY, OCT 6, ABOUT 5 PM. AFTER A LONG DAY’S WORK DOING MAINTENANCE,
ON THE WAY BACK UP TO 70 FT, THE 1” SHAFT FROM THE MAIN WORMDRIVE
FRACTURED ALLOWING THE BIG PULLEY TO LET THE TOWER FALL FROM ABOUT 15
FEET UP. NOT PRETTY. I HAVE LOTS MORE PHOTOS BUT THIS ONE PRETTY WELL
SAYS IT ALL!"
Dino - KX6D
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