Just remember that the loads on a temporary support can be quite large.
If the support is half-way from the pivot then the entire weight that
section of the tower is on that support plus the translated moment from
the beam, mast, and rotator. For a support further out the weight will
reduce to half the tower weight with a support at the top and
substantially reduce the chance of bending the tower. Make sure the
support can't slip.
Grant KZ1W
On 7/6/2014 2:39 PM, Don wrote:
Up till this year I’ve had a friend down the coast who had a tow truck come up
and lay the tower over for me when needed. He retired and sold the truck. So, a friend
in the Phoenix area gave me an old layover fixture (given to him) that resembles both
the HyGain and TRX-80 fixtures.
I had a local fleet rigging and welding shopup the coast refurbish and strengthen the
fixture. It looks very similar to the current TRX-80 which seems to equipped with a Fulton
K1550 winch and 1/4 in cable. My K1550 spare however has a different mounting hole
arrangement than that of the layover winch mounting plate on my fixture (so I have two
assumptions – the original winch was not a K1550 or the fixture was an early HyGain -
maybe an early TRX?), In any case I’ve adapted of course.
Here comes the question. The original fixture had a single pulley. I had the shop
adapt it to accommodate two pulleys. Since the tower did not have a welded bracket on
it for attaching the cable I had the shop make a two pulley device that is held by a
1/4 in cable around the outer tower at about the 8 foot level which appears to be a
height consistent with pictures I can find. I calculated that I would need about 60
feet of cable with a double pulley system to do the layover but before I cast this in
stone I’d like someone to double check my number.
Because of the lower beam boom length I plan to lay the tower over onto a
wooden X frame with a cross-piece at the top, placed far enough along so that
the boom of the bottom beam will clear the ground (did this with my Triex
WT-51). Then will use a short ladder to get to the mast and rotator etc. The
layover fixture for the WT-51 was a 15 foot piece of tubular steel put in the
concrete behind the tower. Single pulley and smaller cable since the tower and
antennas were less heavy.
I do have some pics of the fixture and maybe someone knows what it was.
Anyway, before I complete this effort (a long long way from anything or anywhere so
want to be sure I’ve thought everything thru!!). Any suggestions welcome.
Don W7WLL
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