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G8MNY > TECH 10.07.09 14:07l 267 Lines 13457 Bytes #999 (0) @ WW
BID : 31384_GB7CIP
Read: GUEST
Subj: Gyn polling up large masts
Path: IZ3LSV<IK2XDE<DB0RES<DK0WUE<7M3TJZ<UA6ADV<GB7CIP
Sent: 090710/1121Z @:GB7CIP.#32.GBR.EU #:31384 [Caterham] $:31384_GB7CIP
From: G8MNY@GB7CIP.#32.GBR.EU
To : TECH@WW
(8 Bit ASCII Graphics use code page 437 or 850)
By G8MNY (Updated Mar 09)
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 is used for putting up the gyn!)
.ú:Ý,Pulley
3 tiers 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 & ßßßßßßßßßßßßßßßßßßßßßßÝ ` 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, i.e. they would tend to 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 raised slowly & a spotter person used to sort any snags out.
Generally you can tie off the gyn up rope at any 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 (when total collapse failure is possible!). And this is untied from the
gyn & allowed to rap around the mast in use.
REINFORCED JOINTS
________________
³o o o o o o³
-----------³~~~~~~~~~~~~~~~~³---------
Mast Poles ³ÍÍÍÍÍÍÍØØÍÍÍÍÍÍͳWebbing
-----------³________________³--------- [³³]
³o o o o o o³ / \
~~~~~~~~~~~~~~~~ WebbingÄ´ ÃÄ
_.-Ä~~~~~~~~Ä-._Webbing \ /
-----------³~~~~~~~~~~~~~~~~³--------- [³³]
³================³
-----------³________________³---------
~Ä-.________.-Ä~
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. To lighten
it a bit the webbing ends can be cut down.
SLIPPING JOINTS
If the joints stretch & start to slip [³³]
(aerial poles rotate), then put a / \
thin wire (coat hanger) under one of ´ .Ã
the sides & clamp up, this will bite \ /\Wire
into the smooth pole & stop slips. [³³]
GROUND LAYOUT
All guy ropes use o (5x 5x 80cm)
a safe "clove hitch" | stakes
knot 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 x 49mm 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 on the hands is 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 & pre-tightened so that the top
of the mast ALWAYS bends (curved up) towards the gyn pole. This avoids the
unstable failure mode when the top guy ends up in parallel to the mast & the
very high compression forces on the mast cause a collapse.
.ú:Ý, .ú:Ý,
,ú'.;'Ý \ ,ú'.;'Ý \
,ú' .', Ý `\ ,ú' .', Ý `\
3 Guy ,ú' ,' ,' Ý `\ 3 Guy ,ú' ,' ,' Ý `\
Sets,ú' ,' ,' ÝGyn `\ Sets,ú' ,' ,' ÝGyn `\
.._,ú' ,' ,' ÝPole `\ ,ú'__...:_ ,' ÝPole `\
~~~ÄÄÄ---...:.____Ý `\ _.:-~~ ~~Ä-..__Ý `\
Good Curved Mast ^ Pivot -~Unsatbe Failing Mast ^ Pivot
GUY BEARINGS
Made from either plate or tube collars, resting on a large 2" (50mm) greased
ally washer above the joiners. The top set of guys will rest on an exhaust U
clamp, also has an enlarged guy spacer is needed to stop the guys rapping
around the pole.
³ ³ Plate ³ ³ Tube ³ ³ Top
==³ ³== Or ,o´³ ³Ão, oÄÄ´³ ³ÃÄÄo
.' ÚÁÄÁ¿ `. .' ³³ ³³ '. .' ³³ ³³ '.
.' ³| |³ '. .' /~ÚÁÄÁ¿~ '. .' /~µ Æ~ '.
³ ³ Washer³| |³ Washer ³ ³\
Exhaust U Clamp
Never use a long unguyed pole (e.g. 10ft) above a guyed joiner, as the wind
loading on your aerial & the pole leverage will try to sheer the joiner in two!
Always use a top guy set & U clamp close to the aerial as possible.
COAX TIES Beam Boom
With a rotary mast system ù===ù=ù===ù=Ë=ù===ù===ù===ù
reusable coaxes ties the were used ~==___º__--~Support
on the coax, are attached to the mast Coax/ ~~º> coax
above the top bearing, then 1 or 2 <º loops
lose turns/loops & then attatched Tie.'º'.U clamp
to one of the top bearing guys with .' |º '.bearing
a cable tie threaded through the rope. .' |º '.
This is then repeated at each lower .' Coax|º '.
bearing tp take each section of the .' Tie.'²'.joiner'bearing
coax's weight, & keep the coax .' .' |º '. '.
away from the bearings. .' .' |º '. '.
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.
______
Welded Ý(__[]__)Þ Arm & rubber [³]
Tow .ú'Þ] Wheel frameÝÄÄÄÄÄÄÄÄÞ suspension ³
Hitch úX====X==========================X========X==================X=³
.ú' Þ Þ Ý Þ Þ ³Tail
0<'| Þ Þ Centre pole()XBrace Þ X ³Board
'ú. Þ Þ Ý Þ Þ ³
Welded`úX====X==========================X========X==================X=³
Draw A 'ú.Þ] 2x steel poles (gyn) ÝÄÄÄÄÄÄÄÄÞ ³
Frame Ý(__[]__)Þ [³]
Wheel unit
X = scaffold clamps. & mud guard
ù poles
[ forward lights _.-XÄ-.._
] rear light _..-''~ Þ ~`Ä.._
_,.-''~4m 1m Þ [] 3m``Ä-.._
_..-''~ Pole PoleÞ /~~~~\ Pole ~``Ä-.._ o [³]
_ =X====X=========================ÞX³ /~~\ ³X=================X===
(_\____ù____ù_ Þù³³ {} ³³ù
~~~~~~~~~~~~~ \__/Mini
Wheels
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 clamped 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 additional running lights to make the trailer conspicuous as well as
being painted in bright colours. The wiring loom is rapped around the poles &
plugs in the fixed lights etc.
There are 2 shorter bracing poles, that form 2 triangles & are tensioned up
before moving by standing on the long steels & doing up the top swivel camps,
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 Dipoles, inverted Vs & also plain QRO dipoles
20/15/10m 3el Mosley trapped QRO beam
6m 3el Coax & Bamboo Quad
6m 5el yagi beam
4m 2x 5el yagi & phasing harness
2m 5el, 7el, 11el small beams, 17el & even 2x 17el 11ft apart
2m 4x 17el yagis Box, 11ft apart stacking frame & power splitter
70cm 9el, 19el, 23el yagis, 88el multibeam
70cm 27el loop Yagi
23cm 24el, 65el loop yagi
13cm 40el with tranverter on 10ft extention pole
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 stacked 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. But I have seen direct drive gearboxes & shaft into
the shack used on simular masts.
_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
EARTHING ÚÄ¿____³ ³
A when the whole mast is rotated ³X³~~~~³ ³)
I put a flexable 1-2 turn strap ³ ³ ³./
from the ground post to the mast ³ ³ /³\
rotator clamp. ³ ³ ³ ³ ³
This earth will take some of the ³ ³ ÚÄÁÄÁÄÁÄ¿
nearby lightening current to ³ ³ ³ROTATOR³
earth & not via the shack. ³ ³ ÀÄÄÄÄÄÄÄÙ
Any direct strike will do lots of ³ ³ U U
damage! ³ ³
WINDAGE
Generally this is not a problem as the gyning up process puts much higher loads
on everything than the wind will. Do check guy tensions & knots at least once a
day & after/during any storms. If there are problems & you have the extra rope
it is possible to add an additional guy in situ by lassoing a mast guy set at
ground level & slipping the new guy up the others & stake out windward etc.
In strong wind raising & lowering, should ONLY 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
the mast raising & lowering.
Y Don't U send an interesting bul?
73 de John G8MNY @ GB7CIP
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