Don Moman wrote:
>
> The KLM log is rated at 12 sq ft and weighs 100 lbs (7.2-10-30version).
>
> A friend here locally had a similar problem with his G1000 rotor on a
> Sommer beam( quite large, has coverage from 7 to 30 mhz) and it failed
> very soon in its' career. Well within the wind spec too, but possibly not
> within the "flywheel" spec. Why bother to specify a wind area when it's
> such a vague spec anyway? Anyway it was full of parts that rattled -
> gear parts not ball bearings. He replaced it with a Emotator (not sure
> of the number) and it has behaved fine since.
>
As I remember, and unfortunately I do not have the relevant document to hand,
Emoto
are one of the few (only?) rotor manufacturers who, in addition to specifying
wind
area for their products, also specify 'Gd^2'. I take this to be moment of
inertia and
this would be what I would wish to consider, rather than the product of mass
and
boom-length.
I should perhaps relate my experiences with a Daiwa MR750PE, which was the
'four-motor' rotor from that company. I used it to turn a 20m PV-4 which in
addition
to having a 42 foot boom was not of lightweight construction. I had made no
attempt to
balance the antenna dynamically as suggested later, in his book, by W6QHS.
Initially
the clamps (surprise) slipped so I tightened them. When they slipped again I
drilled a
pin through, albeit a small one. When the pin broke I put a couple of 8mm
stainless
steel machine screws through. When, shortly after the antenna would not turn, I
took
the rotor out and as I opened it up, large pieces of metal started falling out.
The
(cast?) frame around which the rotor was built had been destroyed. What a heap
of junk
that rotator was.
It seems to me that in a well designed amateur station the weakest link is
going to be
the rotor. What a pity it is that the supply of Prop-pitch motors is not
sufficient to
go around.
73,
Chris
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Chris Pedder G3VBL/8P9EM
E-mail g3vbl@netcomuk.co.uk
AX25-mail g3vbl@gb7bnm.#45.gbr.eu
DX-Cluster g3vbl > gb7dxd
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