From: "Sboese sboese@uwyo.edu" <flyrotary@lancaironline.net>
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Subject: Re: [FlyRotary] Re: dynamic balance
Date: Fri, 19 Mar 2021 14:38:10 -0600
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To: Rotary motors in aircraft <flyrotary@lancaironline.net>
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About 8 grams at one corner after the phase angle indicated the light spot =
was aligned with that corner.

Steve Boese=20

Sent from my iPad

> On Mar 19, 2021, at 12:57 AM, Stephen Izett stephen.izett@gmail.com <flyr=
otary@lancaironline.net> wrote:
>=20
> =EF=BB=BF=E2=97=86 This message was sent from a non-UWYO address. Please =
exercise caution when clicking links or opening attachments from external s=
ources.
>=20
>=20
> Thanks Steve B.
> Do you recall how much weight was required to balance the engine at the f=
lex plate?
> Steve Izett
>=20
>> On 19 Mar 2021, at 9:40 am, Steven W. Boese SBoese@uwyo.edu <flyrotary@l=
ancaironline.net> wrote:
>>=20
>> I did not try the procedure described by Finn where a weight was attache=
d at the four cardinal locations.
>>=20
>> I used a Freescale MMA7260Q eval board as the 3 axis accelerometer, a US=
B 6009 as an A to D unit and Signalexpress software both from National Inst=
ruments, and a laptop computer to collect and process the data.
>>=20
>> The photo shows the setup for balancing the prop.  The position referenc=
e Hall effect sensor was installed on the red mount and clamped to redrive.=
  The sensor and mount were covered in modeling clay to dampen resonance vi=
brations possible in this mount.  The Hall effect trigger was attached to t=
he prop flange with double sided tape along with an equal weight attached i=
n the same way 180 degrees from the trigger.  The accelerometer is seen beh=
ind the red clamp and was installed in a 1/4=E2=80=9D aluminum plate.  This=
 was screwed to a second 1/4=E2=80=9D aluminum plate which was bonded to th=
e redrive with epoxy putty.  Before the engine was started, a  =E2=80=9Cthu=
mp test=E2=80=9D was performed by striking the accelerometer lightly with a=
 rubber hammer and recording the results in order to verify the stiffness o=
f the accelerometer mount.  The balance was adjusted by adding washers unde=
r the screws which attach the spinner to the aft bulkhead and at the angula=
r location indicated by the processed data.  The final balancing weight was=
 in the form of washers, nut, and bolt installed in the aft spinner bulkhea=
d.  This weight took into account the difference in the radius from the cen=
ter of the prop shaft to the test washers under the spinner screws compared=
 to the radius to the location of the balancing bolt, nut, and washers.
>>=20
>> The engine was balanced by locating the Hall effect position sensor wher=
e it would see a trigger attached to one of the damper plate to flex plate =
bolts with an equal weight attached to the opposite bolt.  Washers of vario=
us weights were installed under two of the bolts until the unbalance phase =
angle was aligned with one of the four bolts.  Then the weight under that b=
olt was adjusted until the balance was acceptable.
>>=20
>> Steve Boese
>> <prop balance setup c.jpg>--
>> Homepage:  http://www.flyrotary.com/
>> Archive and UnSub:   http://mail.lancaironline.net:81/lists/flyrotary/Li=
st.html
>=20
>=20
> --
> Homepage:  http://www.flyrotary.com/
> Archive and UnSub:   http://mail.lancaironline.net:81/lists/flyrotary/Lis=
t.html