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G8MNY > TECH 01.02.08 14:01l 208 Lines 10083 Bytes #999 (0) @ WW
BID : 45205_GB7CIP
Read: GUEST
Subj: Gyn polling up large masts
Path: IZ3LSV<IW2OHX<I0TVL<ON0AR<GB7CIP
Sent: 080201/0120Z @:GB7CIP.#32.GBR.EU #:45205 [Caterham] $:45205_GB7CIP
From: G8MNY@GB7CIP.#32.GBR.EU
To : TECH@WW
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By G8MNY (Updated Oct 07)
A 20M MAST
Over the years I have tried several aerial systems. But settled on a well
tried & tested gyn pole system.
The biggest used to date uses 3x 21' (3x 6.5m) aluminium scaffold poles with
reinforced Jaybeam joiners & a 42'(2x 6.5m) steel gyn pole. (as we are getting
older a gyn pole used for putting up the gyn!)
A 3 tier of 4 guys @ 90ø ,ú:Ý\
ensures stability. ,ú ', ;'Ý `\
3 Guy ,ú ' , ',' Ý `\
This design is the Sets,ú ' , ' ,' ÝGyn `\
mainstay of nearly ,ú ' , ' ,' ÝPole `\ Gyn
all my contest & ßßßßßßßßßßßßßßßßßßßßßßßßß ` Pull up
/P activity. 20m Mast Ground^ Pivot Rope
Structures higher than 66' (20m) have been attempted, but computer calculations
showed this to would be unstable, & these were borne out in practice when
erections proved it, ie. they would fall over!
The mast is always put up with NO aerials first, to make sure all the mast
bits work properly before the mast is loaded up. With the aerial loaded the
mast should be raided slowly & a spotter used to sort any snags out. Generally
you can tie off the gyn up rope at angle up to the point of balance, above that
someone should slowly pay out the rear 3 mast guys to stop any sudden shock on
the mast as it comes vertical.
If there is to be unsupported mast as in a 17el over 17el on 2m, then an extra
top guy is needed during gyning up the mast to stop the mast bending away from
the gyn. And this is untied from the gyn & allowed to rap around the mast in
use.
REINFORCED JOINTS
________________ [³³]
___________³o__o__o__o__o__o³_____ / \
Mast Poles ³________________³_Webbing Ä´ ÃÄ
___________³~~~~~~~~~~~~~~~~³______ Webbing/ \ /
³o~~o~~o~~o~~o~~o³ [³³]
~~~~~~~~~~~~~~~~
To stop the joiners tearing along the perforated centre line extra steel
webbings (0.4 x 2 x 25cm) were welded over the weakness both sides.
SLIPPING JOINTS
If the joints stretch & start to [³³]
slip (let the aerial pole rotate), / \
then put a thin wire (coat hanger) ³ .³
under one of the sides & clamp up, \ /\Wire
this should bite into the smooth [³³]
ally pole & stop the spinning.
GROUND LAYOUT
All guy ropes use o (5x 5x 80cm)
a safe "clove hitch" | stakes
on the bottom of the |
angled stakes. Front Ground |
Stake Post | --Gyn-----> Back
Once the mast is o `8<-----12m----->o Stake
up & no further Mast'| /
adjustment is needed | /
the clove hitch can Hinge| 17m
be locked with a. Line| /
simple over knot. o
Side stakes
A short 1m steel ground pole is put it the middle (after making a hole with the
spare 5th stake first) to take all the hinge forces.
The gyn pole will need 2 side guys, these need not be @ full length 2/3 is OK.
The main pull up rope to the top of the gyn will need a strong pulley block &
suitable thick rope easy one the hands used (e.g. 15-20mm).
ROPES
A full mast rope set of 3 tiers of 4 guys & a gyn pole pulley system, takes
1,024' (312m) of rope. Using mainly 8mm polypropylene for strength & cheapness,
caused a storage problem, as the rope is ultra-violet light sensitive. For
speed we do not detach the measured ropes from the guy bearings for neat rope
hank storage, so a single guy tier of 4 ropes with its bearing is chain-laced
together to give quick & untangled storage. The bulky & UV free storage was
solved using 2 large dustbins (for 3 mast sets). One for the 1st mast & Gyn
pole, & the 2nd for the rest of the masts.
CENTRE GROUND POST
(plan views)
Gyn ³ ³ Ground Ground Ground
Pole³ ³ Post Post Post
³ ³ (_) __Swivel Mast (_) (_) Swivel clamp
ÄÄÄÄÄÄÄÄ´ÄÃÄÄÅÄÅÄ¿ Clamp ÄÄÄÄÄÄÂÄÂÄÄÅÄÅÄ¿ Mast_( )
ÄÄÄÄÄÄÄÄ´_ÃÄÄÁ=ÁÄÙLoose ÄÄÄÄÄÄÅÄÅÄÄÁ=ÁÄÙ ÚÅÄÅÄÄÄÄÄÄÄÄÄ
Mast 90øClamp clamp! (_) tight ÀÁÄÁÄÄÄÄÄÄÄÄÄ
Gyn pole Clamp 90øclamp Gyn Pole
All on the ground Gyn up in air Mast up
The top guy to the gyn needs to be low stretch or pre-tightened so that the
top of the mast ALWAYS bends towards the gyn pole.
GUY BEARINGS
Either plate of tube collars resting on a large 2" (50mm) washer above the
joiners. The top set of guys will rest on exhaust clamp, also a enlarged guy
spacer is needed to stop the guys rapping around the pole.
³ ³ ³ ³ ³ ³
===³ ³=== Or ,ÄÄ´³ ³ÃÄÄ, ,ÄÄ´³ ³ÃÄÄ,
/' ÚÁÄÁ¿ `\ / `\³³ ³³/' \ / `\³³ ³³/' \
/ ³| |³ \ / ÚÁÄÁ¿ \ / µ Æ \
³ ³ ³| |³ ³ ³ \
Exhaust
Clamp
TRANSPORT
With the large poles, only roof racks could be used, this caused noticeably top
heavy problems with the vehicles. After some research we solved the problem,
with a designed for a dismantleable pole trailer. The law on the length of long
trailers is simple, the trailer other than it's drawbar, must not be longer
then the divisible load.
____
Ý(_[]_)Þ
Tow _.-'~³] ÝÄÄÄÄÄÄÞ [³]
Hitch _.-'~X====X==========================X======X==================X=³Tail
0<'³ Þ Þ Centre pole ()XBrace Þ X ³Board
ø`"-._X====X==========================X======X==================X=³
Draw A ~"-._³] 2x steel poles ÝÄÄÄÄÄÄÞ [³]
Frame Ý(_[]_)Þ
Wheel unit
X = scaffold clamps. & mud guard
() poles
[ forward lights _.-XÄ-.._
] rear light _..-''~ Þ ~`Ä.._
_,.-''~4m 2m Þ [] 3m``Ä-.._
_..-''~ Pole PoleÞ /~~~~\ Pole ~``Ä-.._O
___ =X====X=========================Þ³ /~~\ ³==================X[³]
(_\____()___()] ÞO| {} |³O
~~~~~~~~~~~~~ \__/
We welded up the design, & it has lived up to all expectations, regarding
cornering & loadings etc. The only problem has been the requirement to manually
drag the rear & around tight corners like at the contest site entrance. With
experience the wheel unit can be bolted at a position to set the hitch load to
50kg, dependent on the planned trailer load. As well as the tail board there
are 6 other running lights to make the trailer conspicuous.
There are 2 shorter bracing poles that form 2 triangles & are tensioned up
before moving by tightening up the top clamps wile standing on the long steels,
this then forms a very ridged trailer.
The trailer can handle 6 Ally scaffold poles clamped on plus loads more on top.
So it can carry poles for 3 masts using the 2 steels as the shared gyn.
The pole trailer is completely dismantled for storage.
AERIALS USED
Mainly concentrating on VHF contests, I have used quite a collection...
Band
160m > 100m random wire to halyard with many other aerials
80m Insulated 66' mast as 1/4 Wave vertical
80m/40m Trap Dipole & also inverted Vs
20/15/10m 3el Mosley trapped beam
6m 3el Coax & Bamboo Quad
6m 5el yagi beam
4m 2x 5el yagi & phasing harness
2m 5el, 7el, 9el small beams & a 17el Met
2m 4x 17el yagis Box stacking frame & power splitter
70cm 9el, 19el, 23el yagis, 88el multibeam
70cm 27el loop Yagi
23cm 24el, 65el loop yagi
For 2m we used to use a box of 4x17el, stack/baying frame & 4 way power
splitter but due to its weight it could only be put up at 41' & took a good
hour to assemble on the mast. This gave a theoretical 20dB gain or 40KW ERP.
However the simpler, 2x17el staked at 10'(3m) apart with a coax splitter works
as well at 20m.
On 4m we stack 2x5el at 10'(3m) apart as well.
ROTATORS
Generally I use mast ground rotation, avoiding putting the heavy rotators at
the top of the mast. The slightly faster arm strong methods have been
superseded with bottom of pole rotators, mainly because of access to the mast
under all contest weathers.
_³_³_____________________________
To put a heavy mast on |__________________________ Gyn Pole
the rotator, either have ³ ³ ³³
several helpers to lift a /³\ ÝÞ
tiller bar with the guys ³ ³ ³ Þ__Ý Jack
fairly loose. Or use a car ÚÄÁÄÁÄÁÄ¿ ³ ³
jack under the horizontal ³ROTATOR³ ³ ÃÄ¿
gyn pole to lift the load Bracing____ÀÄÄÄÄÄÄÄÙ ÁÄÄÁÄÙ
while you assemble the Feet U U
rotators clamp on the pole. OR Bolts in
ground
WINDAGE
Generally this is not a problem as the gyning up process puts much higher loads
on everything than the wind will. But raising & lowering should be done side on
to the wind so the only effect it has is to keep one side set of guys tight, &
not help/hinder th mast raising & lowering.
Y Don't U send an interesting bul?
73 de John G8MNY @ GB7CIP
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