From: "Sboese sboese@uwyo.edu" <flyrotary@lancaironline.net>
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Subject: Re: [FlyRotary] Re: dynamic balance
Date: Fri, 19 Mar 2021 16:36:33 -0600
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To: Rotary motors in aircraft <flyrotary@lancaironline.net>
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My method was to add weight to the first bolt until the resultant phase ang=
le coincided with a second bolt 90 degrees from that first bolt. Then weigh=
t was added to that second bolt to minimize the overall imbalance.  This wa=
s done to avoid the method of trying to add different weights to two bolts =
at a time.  Either way should eventually work.

The weight added to each of the bolts was 8 grams or less.

Steve Boese=20

> On Mar 19, 2021, at 3:34 PM, Stephen Izett stephen.izett@gmail.com <flyro=
tary@lancaironline.net> wrote:
>=20
> =EF=BB=BFSo it lined up with one of the rubber damper bolts and you didn'=
t need to distribute the weight across two bolt locations?
> Thanks for the information Steve.
> Steve I
>=20
>=20
>> On 20 Mar 2021, at 4:38 am, Sboese sboese@uwyo.edu <flyrotary@lancaironl=
ine.net> wrote:
>>=20
>> About 8 grams at one corner after the phase angle indicated the light sp=
ot was aligned with that corner.
>>=20
>> Steve Boese=20
>>=20
>> Sent from my iPad
>>=20
>>>> On Mar 19, 2021, at 12:57 AM, Stephen Izett stephen.izett@gmail.com <f=
lyrotary@lancaironline.net> wrote:
>>>=20
>>> =EF=BB=BF=E2=97=86 This message was sent from a non-UWYO address. Pleas=
e exercise caution when clicking links or opening attachments from external=
 sources.
>>>=20
>>>=20
>>> Thanks Steve B.
>>> Do you recall how much weight was required to balance the engine at the=
 flex plate?
>>> Steve Izett
>>>=20
>>>> On 19 Mar 2021, at 9:40 am, Steven W. Boese SBoese@uwyo.edu <flyrotary=
@lancaironline.net> wrote:
>>>>=20
>>>> I did not try the procedure described by Finn where a weight was attac=
hed at the four cardinal locations.
>>>>=20
>>>> I used a Freescale MMA7260Q eval board as the 3 axis accelerometer, a =
USB 6009 as an A to D unit and Signalexpress software both from National In=
struments, and a laptop computer to collect and process the data.
>>>>=20
>>>> The photo shows the setup for balancing the prop.  The position refere=
nce Hall effect sensor was installed on the red mount and clamped to redriv=
e.  The sensor and mount were covered in modeling clay to dampen resonance =
vibrations possible in this mount.  The Hall effect trigger was attached to=
 the prop flange with double sided tape along with an equal weight attached=
 in the same way 180 degrees from the trigger.  The accelerometer is seen b=
ehind the red clamp and was installed in a 1/4=E2=80=9D aluminum plate.  Th=
is was screwed to a second 1/4=E2=80=9D aluminum plate which was bonded to =
the redrive with epoxy putty.  Before the engine was started, a  =E2=80=9Ct=
hump 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=
 of the accelerometer mount.  The balance was adjusted by adding washers un=
der the screws which attach the spinner to the aft bulkhead and at the angu=
lar location indicated by the processed data.  The final balancing weight w=
as in the form of washers, nut, and bolt installed in the aft spinner bulkh=
ead.  This weight took into account the difference in the radius from the c=
enter of the prop shaft to the test washers under the spinner screws compar=
ed 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 wh=
ere it would see a trigger attached to one of the damper plate to flex plat=
e bolts with an equal weight attached to the opposite bolt.  Washers of var=
ious weights were installed under two of the bolts until the unbalance phas=
e angle was aligned with one of the four bolts.  Then the weight under that=
 bolt 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/=
List.html
>>>=20
>>>=20
>>> --
>>> Homepage:  http://www.flyrotary.com/
>>> Archive and UnSub:   http://mail.lancaironline.net:81/lists/flyrotary/L=
ist.html
>>=20
>> --
>> 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