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M Squared used to offer a commercial version of this coupling called the
PTA (Peak Torque Absorber). Their design was specifically for the Orion
rotor, and they have since dropped it from their product line. I asked why
it was no longer carried and was told (insert moderate grumbling here) that
there were too many *&#*& Hams that don't do any annual maintenance. It
seems that there were some that installed the device and never checked any
of the bolts. I installed a PTA about 4 - 5 years ago. I have a 20 foot
mast (.250 wall) with 14 feet out of the tower. It is supported with a
thrust bearing at the top of the tower and another about 18" above the
rotor (to allow removal of the rotor for service). As for loading I have a
4 el 20M monoband yagi (40 ft boom) at the top of the tower, a 40M dipole 7
feet up the mast, and a 6 el 10M monoband yagi (30 ft boom) at the top of
the mast. While it doesn't represent hardware as large as some on this
reflector, it is substantial. I check the coupling (as well as all the
other hardware) twice annually, and have not had any problem with the PTA.
Watching the antennas turn (and stop!), you can tell it absorbs much of the
start/stop torque. My greatest concern was the impact of UV on the rubber
coupling. To date I've seen no problem. In my estimation it is a valuable
addition.
de Gary W0AW
Scott Bullock <sales@advantagecomm.net> on 01/29/99 05:03:05 AM
To: towertalk@contesting.com
cc: (bcc: Gary R. Hosler/KHI/Imation)
Subject: [TowerTalk] torque dampener
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Has anyone here ever built and used the torque dampener shown in Dave
Leeson's book on yagi's? It's the one made out of the BMW rubber donut with
the extra brackets installed.
I'm having a problem with the mast slipping in my tailtwister with a th-7
and xm240 for a load.
Looks like this might be a great idea to try, but before I invest the time
and money in it, i'd like to hear from anyone who has built/used one of
these.
Scott
KA1CLX
Advantage Communications
Professional Wireless Communications
www.advantagecomm.net
978-568-1944
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