I worked a solution for my situation. I generally have to do my tower work
alone, atop 130' of Rohn 45G.
I built a mast raising fixture that works great for a "one man" job. It
consists of a worm drive steel cable winch which fastens to the tower (Rohn
25G or 45G or 55G) via a small steel frame with U-bolts, and pulley on a
yoke which supports the mast at its bottom. The winch mounts to the tower
near the top. The steel cable extends from the winch down inside the tower
& under the pulley/yoke assembly & back to the tower top where it hooks
onto a tower rung, opposite the winch. There is a bolt on the yoke to
tighten in against the mast to keep the mast from rotating inside the
yoke/pulley assembly.
The operator has to simply crank the winch to either raise or lower the
mast. With as much mechanical advantage as the system has, raising a 4130
Chromoly mast loaded with antennas & feed lines is no problem. Plus, it
stays put in any vertical position due to the worm drive, no braking
mechanism needed. It also stays vertical (mostly) when being raised or
lowered since the cable is strung under the mast & is cradling the system.
I use a shaft collar on my mast to keep the mast in place vertically; the
shaft collar rides on top of my TB-3 thrust bearing. Each time I raise the
mast, I lower the shaft collar to its new position. The bolts in the thrust
bearing simply help center the mast in the tower. I never have liked using
horizontal bolt ends to keep a vertical mast from sliding downward;
personal choice here.
I made a "T-bar" that fastens to the tower legs to keep the mast from
tipping over when it gets to gets to be more than half way out the top of
the tower. There is a U-bolt through the T-bar which the mast passes
through. When the mast is raised, is slides through the U-bolt on the
T-bar, then I tighten the U-bolt, leaving enough mast below it to put the
rotator clamps on & install the rotator. A second rotor shelf would
accomplish the same thing; the T-bar is removable post mast raising,
though, where the rotor shelf isn't.
My rotor shelf is also fabricated for the situation. It has only enough
steel plate to accommodate the rotor base. It has spokes (1" square steel
tubing) welded to the plate which are bored for U-bolts which attach the
plate to the tower. In this configuration, the rotor plate can be placed
almost anywhere in the tower AND inserted into the tower between rungs.
I have pics if anyone would like me to send them via E-mail. I plan to put
them on a web page...someday.
I am willing to loan the gear out to anyone willing to pay shipping both
ways & a refundable deposit, just for insurance that the gear comes home
since I have a fair amount of time & a small amount of money invested in
the system. I have no profit interest in the mast raising gear.
The pulley and yoke assembly also doubles as part of a "zip line" for the
nephews; 250 feet of 1/4" steel cable streched on an angle between the
tower & another support in the yard; the kids love it!
At 10:30 AM 11/22/2001 -0600, S. Markowski Jr. wrote:
>Hi Larry, you can also check IIX Equipment Ltd, owner W9IIX (Doug).
>Advertises in QST and I believe CQ or:
>
>http://www.w9iix.com
>
>
>List Sponsored by AN Wireless: AN Wireless handles Rohn tower systems,
>Trylon Titan towers, coax, hardline and more. Also check out our self
>supporting towers up to 100 feet for under $1500!! http://www.anwireless.com
>
>-----
>FAQ on WWW: http://www.contesting.com/FAQ/towertalk
>Submissions: towertalk@contesting.com
>Administrative requests: towertalk-REQUEST@contesting.com
>Problems: owner-towertalk@contesting.com
Thank you,
Robin E. Midgett KB4IDC
IDC Technology
www.idctechnology.com
Metal Fabrication for the Radio Amateur
Distributor of Tower*Jack Products
615-773-4199
List Sponsored by AN Wireless: AN Wireless handles Rohn tower systems,
Trylon Titan towers, coax, hardline and more. Also check out our self
supporting towers up to 100 feet for under $1500!! http://www.anwireless.com
-----
FAQ on WWW: http://www.contesting.com/FAQ/towertalk
Submissions: towertalk@contesting.com
Administrative requests: towertalk-REQUEST@contesting.com
Problems: owner-towertalk@contesting.com
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