From: "Stephen Izett stephen.izett@gmail.com" <flyrotary@lancaironline.net>
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Subject: Re: [FlyRotary] dynamic balance
Date: Sat, 20 Mar 2021 05:33:44 +0800
References: <list-1326806@logan.com>
To: Rotary motors in aircraft <flyrotary@lancaironline.net>
In-Reply-To: <list-1326806@logan.com>
Message-Id: <D0017904-B5A3-432C-A780-7F0A811C732A@gmail.com>

So 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


> On 20 Mar 2021, at 4:38 am, Sboese sboese@uwyo.edu =
<flyrotary@lancaironline.net> wrote:
>=20
> About 8 grams at one corner after the phase angle indicated the light =
spot 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 =
<flyrotary@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 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 =
attached 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 Instruments, and a laptop computer to collect and process the =
data.
>>>=20
>>> The photo shows the setup for balancing the prop.  The position =
reference 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 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 behind 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 the redrive with =
epoxy putty.  Before the engine was started, a  =E2=80=9Cthump 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 under =
the screws which attach the spinner to the aft bulkhead and at the =
angular location indicated by the processed data.  The final balancing =
weight was in the form of washers, nut, and bolt installed in the aft =
spinner bulkhead.  This weight took into account the difference in the =
radius from the center 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 =
where 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 various 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 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
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