Jon & KenI always used to start by balancing each blade separately on the b
ench.=C2- I built a simple jig having a knife edge fulcrum positioned at
the centre of the prop assembly, which supported the blade so that the root
of the blade was the correct distance from the centre/fulcrum and the=C2
- blade was supported somewhere about 75% blade diameter. there is a seco
nd fulcrum at about 60% of the span (not critical) where the load is measur
ed accurately, to within 1/2 a gram. This is the moment of the blade about
the centre of the prop. Each blade must have the same moment. Surprisingly
the actual weight of each blade might not be exactly the same, it's the mom
ent that is critical.
Now measure the moment of each blade and adjust by adding a small amount of
lead in the hole drilled down the blade from the root. The lead shot is se
cured with epoxy resin and you will find it is about 300mm out from the roo
t.I hope that's clear enough to understand, I learned this method from Jerr
y Davis who used to be the UK agent for Arplast.Graham
On Sunday, 12 February 2017, 21:21, Ken Atkinson <kennethatkinson178@bt
internet.com> wrote:
rnet.com>
Hi Jon,
If something is loose inside your PV50 you must dismantle it again and
investigate. The initial balancing, I believe, would have been achieved
by fitting appropiate weights into the centre of the blade roots.I doubt
that any of these would be loose but check!
I did find on my first annual service of my PV50 that the centre
triangular block was loose on the activator tube and the grub screw was
loose!
This year I carried out a static balance following the fitting of new
thrust bearings and bushes.I was surprised at the out of balance that I
had to counteract with 8 mm threaded weights fitted onto the six 8mm hub
assembly bolts. This seemed a suitable method of fitting balance weights
to me? How have you fitted any balance weights? My propeller/engine is
running pretty smoothly now but probably would benefit from dynamic
balancing.
I have a spare set of early PV50 Classic (shorter) 80hp narrow blades,
but they would need serious balancing to match a different hub. Each set
of blades is matched to fit each hub and also each blade must be fitted
in the correct position.
My details are on the members list if you want to contact me otherwise I
will look out for you at a fly-in for some intersting PV50 tales!
Ken Atkinson=C2- G-CEKV mono no 19
On 11/02/2017 17:56, italianjon wrote:
>
> Hi All,
>
> If you recall I posted about a year ago, relating to PV50 and some vibrat
ion problems. Well, it has been an interesting year, and some stories which
I won't write on a public forum, but I might share over a beer at a fly-in
. A lot of the year has been a learning curve, and I used the time waiting
for the PH-Reg to come through, to experiment and learn more
>
> Today I was coming to the end of a careful adjustments on the propeller,
but still, alas, there is an imbalance. I'm getting about 0.25 IPS on the p
rop (attached is the outcome of the spectrum), this is now the main and see
mingly only contributor to the vibration.
>
> I've managed to get all three blade-pitches to within 0.16 degres across
all three blades, and the tracking is less than 3 mm. The blades are quite
firmly seated now, after I have installed new plastic blocks. All of this h
as had no real effect.
>
> Today was a very quiet day at the airfield. There was only myself and my
"plane work buddy". On one of the blades I heard a "tick", and on closer in
spection it is evident something is loose on the inside (One of the static
balance weights, I am assuming)
>
> Does anyone have any experience at all in setting the static weights on a
PV50 blade? Is it possible without manufacturer support?
>
> Failing that, is there anyone with a spare blade that I could try in the
position, to close off this investigation?
>
> I know the engine is not contributing, as the latest spectrum shows nothi
ng significant at key engine frequencies, and in addition I have spectra fr
om other measurements with my aircraft and a Warpdrive installed which show
s very good vibration down at 0.08IPS.
>
> Cheers
>
> Jon
>
>
> Read this topic online here:
>
> http://forums.matronics.com/viewtopic.php?p=466013#466013
>
>
> Attachments:
>
> http://forums.matronics.com//files/screenshot_20170211_182509_207.png
>
>
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