Hi Jonas a matter of interest who built your Europa? Is it a Classic or an
XS?
Turning to the blade with loose weight, you will need a long drill, maybe 5
or 6mm diameter. You should be able to see the hole at the centre of the r
oot of the blade, carefully drill down the blade allowing the existing hole
to guide the drill. At some point the loose bit of lead should drop out. I
f the hole is already open some weight may have been lost which would accou
nt for the out of balance.
The penny washers on the balance arms are there to assist turning the blade
when it is under load. (I don't fully understand how they do that) Nothing
to do with prop balance and there should be the same number of washers on
each blade.
Graham
On Monday, 13 February 2017, 10:52, italianjon <jon.catilli@gmail.com>
wrote:
Hi Ken and Graham,
Thank you for the informative replies.
Ken, I can confirm everything inside the hub is secure and a good fit. Ther
e is very little play in the system now. I learnt a lot last year when I st
ripped the propeller down with Pete Jeffers; and put into action some of hi
s excellent advice. What I am referring to, with the =C3=A2=82=AC=C5=93t
ick=C3=A2=82=AC=EF=BD sound of something loose, is when one of the bl
ades is removed from the assembly and you rotate it around, such the tip fa
ces upwards then rotate 180=C3=82=C2=B0 downwards you can hear a =C3=A2
=82=AC=C5=93tick=C3=A2=82=AC=EF=BD sound from the (I think) lead weig
hts inside the blade In other words the static balance mass seems to have c
ome loose. It only got noticed because the airfield was so quiet on Saturda
y. It=C3=A2=82=AC=84=A2s also consistent with Graham=C3=A2=82=AC
=84=A2s =C3=A2=82=AC=C5=93300mm=C3=A2=82=AC=EF=BD comment. The
sound =C3=A2=82=AC=C5=93ticks=C3=A2=82=AC=EF=BD towards the tip wh
en held downwards, and =C3=A2=82=AC=CB=9Cmid-blade=C3=A2=82=AC=EF
=BD when held tip-upwards. Therefore, with the information provided by both
of you, my current hypothesis, which fits the evidence, is that the weight
has loosened itself from the epoxy resi!
n on the side towards the tip but the resin has remained fixed in place.
I was concerned that I do not have enough skills to address the issue, but
---From what Graham has written I might.
Graham, can I explore this a bit more with you? I understand in principle a
ll that you are saying, and you wrote, regarding the blade-moment jig, a si
milar thing to me about a year ago. I have constructed a jig, which has a p
ivot point in-line with the centre of rotation and a balance support which
can be placed along the blade to measure the moment.
>From the polar plot of my vibration analysis, I can see that at cruise RPM
the imbalance is aligned perfectly with the blade with the loose weight. T
his would be consistent with a mass that moves outwards in the rotation rad
ius and =C3=A2=82=AC=C5=93pulls=C3=A2=82=AC=EF=BD more.
What is not clear to me, using your method are the following: -
1)=C2- =C2- In my single blade, where as I mentioned above, the epoxy s
eems to still be in place, how could I remove this without damaging the bla
de, in order to remove the weight and reset it?
2)=C2- =C2- What is the best method to install the weight once it=C3=A2
=82=AC=84=A2s out? I guess it=C3=A2=82=AC=84=A2s along the line
s of bathe the lead weight in epoxy and slide it along until the desired bl
ade-moment is achieved and then wait for the epoxy to set.
Then I have one last question: -
3)=C2- =C2- If I can=C3=A2=82=AC=84=A2t remove the lead weight fr
om inside the blade, I am thinking about removing one of the washers curren
tly installed on the dynamic balance arm to see if this moves the dynamic b
alance towards the polar centre? Is this a reasonable approach?
I am going to revisit the blade-moment measurements. When I tried a year ag
o, everything was OK. But, the method I used was to lower the tip on to the
mass scale; which would, of course (if the assumptions above are correct)
reset the lead weight to the correct position for the measurement. I will e
nsure that the weight is towards the tip, on the suspect blade and then re-
measure.
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=466109#466109
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WIKI -
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=C2- =C2- =C2- =C2- =C2- -Matt Dralle, List Admin.
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