I do have some photos of K6CF's failure and it is exactly as Skip
mentioned. I'll get those to you. However, I don't think there is any
real close-ups of the shaft. But you can CLEARLY see what broke!
Skip, thanks for the clarification on Mike's failure being the shaft. I
should have made that more clear in my first message. Again, this is the
failure K6CF had too...same place also! Chris' tower used to belong to
Jim Rafferty, N6RJ (SK). Jim would have purchased only the best at the
As for the shaft failure; its unfortunate that they did not support the
shaft on BOTH ends of the multigroove pully! I was going to mention
blocking the first two sections together and taking that stress off of
pulleys when not in use. US Tower does this on their military tower
trailers and I've seen them on their towers sold to the Cell Phone
companies. However, every failure has happened during transit that I'm
aware of. Block it as you go if you are worried about it!
If it was me, I'd modify the original 1" shaft models or replace it with
a newer system. I think the modification would be easy enough though.
Dino - KX6D
-------- Original Message --------
Subject: RE: [TowerTalk] Yet another worm gear box failure...
From: "Scott MacKenzie" <firstname.lastname@example.org>
Date: Sat, October 13, 2012 10:46 am
To: <KJ6Y@aol.com>, <email@example.com>, <firstname.lastname@example.org>
Any one have any quality photographs of the shaft failure? I am looking
photographs of the fracture surface. That should tell us the mechanism
From: TowerTalk [mailto:email@example.com] On Behalf Of
Sent: Saturday, October 13, 2012 1:37 PM
To: firstname.lastname@example.org; email@example.com
Subject: Re: [TowerTalk] Yet another worm gear box failure...
Mike's tower sounds like the shaft broke and not a gearbox failure. On
the older MD-750 motor drives, the shaft was 1 inch coming out of the
gearbox. (Tristao and then US Tower). US Tower then went to a larger
shaft, 1 1/4 or 1 1/2, don't remember which. Have not seen any of the
newer ones fail.
There is a lot of tension on that multi groove pulley, especially when
hams have a tendency to overload their tower. It's not just wind load
weight. Those towers have a weight limit. Add it all up, mast, rotor,
antennas, cables, etc and I'm sure you'll see more weight then you
Regular maintenance and inspections should be done.
Skip, _KJ6Y_ (http://www.kj6y.com/)
_Communications Service Co_ (http://www.communicationsserviceco.com/)
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