[TowerTalk] Yet another worm gear box failure...

[Rich Hallman - N7TR]

Having three crank-up towers here and just about ready to install one of the original HDX-689 crank-up's (Waiting for the foundation to cure), what gear box is recommended for this type of use?  

I have an HDX-572 that has a hub city gearbox and a bit concerned now.

What alternatives are there?

Thanks..
Rich N7TR
www.n7tr.com


-----Original Message-----
From: TowerTalk [mailto:towertalk-bounces at contesting.com] On Behalf Of Dino Darling
Sent: Saturday, October 13, 2012 7:17 AM
To: towertalk at contesting.com
Subject: [TowerTalk] Yet another worm gear box failure...

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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