---------------------------------------------------------- Europa-List Digest Archive --- Total Messages Posted Fri 03/25/16: 2 ---------------------------------------------------------- Today's Message Index: ---------------------- 1. 08:07 AM - Arplast PV50 - Help with Vibration Data (italianjon) 2. 10:13 AM - Re: Arplast PV50 - Help with Vibration Data (GRAHAM SINGLETON) ________________________________ Message 1 _____________________________________ Time: 08:07:20 AM PST US Subject: Europa-List: Arplast PV50 - Help with Vibration Data From: "italianjon" Dear All, I need some help in understanding the information I have gathered on the diagnostics of my propeller. I used the Smart Avionics PB-3, the configuration for the setup is illustrated in the diagram. The PB-3 was mounted on the port side of the manifold and the pick up reflective strip was mounted on blade 3. The red block shows the PB-3 vibration sensor and the blue line highlights the x-axis orientation. Forgive the handwriting, I did it with a mouse :) Ignore the axis in grey. I have used an illustration from the Rotax Installation manual to give context to my diagram, and are not used for my purposes. Point 1 is my starting reference. Point 2 had 1 washer (ca. 4g.) removed from blade 3. Point 3 had the washer returned to blade 3, and 1 washer from blade 2 to blade 1. Point 4 had a washer from blade 1 moved to blade 3 Point 5 had 2 washers removed and moved 1 to blade 1 and 1 to blade 2. In total blade 2 ended up 3 washer down on the start, blade 3 ended up 2 washers up on the start and blade 1 ended up 1 washer up on the start. As far as I understand the PB-3 0 is the alignment in the X-axis, when is X-axis mode on the PB-3 app. Plus it registers the out of balance when the force pulls it in the X-direction. Therefore the propeller has to rotate between the 225 and the 284 for the out of balance to be register (Very simplistically speaking). >From my first diagram, and given 120 between blades, then blade 2 sits at 240 or basically where I understand the imbalance to be if I have interpreted my data correctly. With so much weight removed from the blade 2 I would have expected the imbalance to move inwards, but instead it remains in more or less the same spot. Leading me to conclude that a bigger effect than a mass imbalance is at play. Blade 2 is also the one that I previously mentioned, in another post as having more play than the other blades. I know the Arplast PV50 has play in the blades when it is at rest. This time I attempted to measure the at rest play. Blades 1 and 3 are fairly consistent with each other and approximately 1 of play. Blade 2 has approximately 4. I think what I am looking for, and the reason for this post, is for someone else to think about my workings to sanity check if I have missed anything; or also to check the conclusion is genuine and I am not just looking for evidence of blade 2 because that is my apparent problem. Thanks all Jon Read this topic online here: http://forums.matronics.com/viewtopic.php?p=454127#454127 Attachments: http://forums.matronics.com//files/g_bxum_2016_03_241_polar_chart_20160325130741_984.jpg http://forums.matronics.com//files/propeller_194.png http://forums.matronics.com//files/results_105.png ________________________________ Message 2 _____________________________________ Time: 10:13:13 AM PST US From: GRAHAM SINGLETON Subject: Re: Europa-List: Arplast PV50 - Help with Vibration Data JonFirst thing I used to do was check each blade statically on the bench (p rop not assembled) Jerry Davis used to offer a description of how to do thi s, basically=C2- mock up a wood support for the blade, the fulcrum at one end represents the centre of the prop. (I knocked in 2 nails on a line at right angles to the blade span) The blade is then set on the rig so that it 's root end is at the equivalent distance from the centre of the assembled =C2- prop (you need to measure this carefully).=C2- A small block on th e rig near the fulcrum gives a way to butt the prop against at it's correct spanwise position. A third nail roughly 2/3 of blade span knocked through the rig acts as the datum. Now measure the weight of each blade at this datum point when placed on the rig. This weight will be proportional to the moment of the blade and all t hree need to be equal. Use an accurate digital balance. It is not satisfactory to simply compare the actual weight of=C2- each bl ade. The moment, which is what's important, can be different even if weight is equal. Arplast used to adjust the moment with lead shot dropped into a spanwise ho le down the centre of the blades.You should find it is about 8 or 9 inches deep. Theoretically it should be possible to achieve good balance this way withou t running the engine but there are more than enough variables affecting dyn amic balance, as you have not doubt realised. Graham. On Friday, 25 March 2016, 15:09, italianjon wro te: Dear All, I need some help in understanding the information I have gathered on the di agnostics of my propeller. I used the Smart Avionics PB-3, the configuration for the setup is illustra ted in the diagram. The PB-3 was mounted on the port side of the manifold a nd the pick up reflective strip was mounted on blade 3. The red block shows the PB-3 vibration sensor and the blue line highlights the x-axis orientat ion. Forgive the handwriting, I did it with a mouse :) Ignore the axis in grey. I have used an illustration from the Rotax Install ation manual to give context to my diagram, and are not used for my purpose s. Point 1 is my starting reference. Point 2 had 1 washer (ca. 4g.) removed from blade 3. Point 3 had the washer returned to blade 3, and 1 washer from blade 2 to bl ade 1. Point 4 had a washer from blade 1 moved to blade 3 Point 5 had 2 washers removed and moved 1 to blade 1 and 1 to blade 2. In total blade 2 ended up 3 washer down on the start, blade 3 ended up 2 wa shers up on the start and blade 1 ended up 1 washer up on the start. As far as I understand the PB-3 0=C3=82=C2=BA is the alignment in the X-axi s, when is X-axis mode on the PB-3 app. Plus it registers the out of balanc e when the force pulls it in the X-direction. Therefore the propeller has t o rotate between the 225=C3=82=C2=BA and the 284=C3=82=C2=BA for the out of balance to be register (Very simplistically speaking). >From my first diagram, and given 120=C3=82=C2=BA between blades, then blad e 2 sits at 240=C3=82=C2=BA=C3=A2=82=AC=C2 or basically where I under stand the imbalance to be if I have interpreted my data correctly. With so much weight removed from the blade 2 I would have expected the imba lance to move inwards, but instead it remains in more or less the same spot . Leading me to conclude that a =C3=A2=82=AC=C5=93bigger=C3=A2=82=AC effect than a mass imbalance is at play. Blade 2 is also the one that I previously mentioned, in another post as hav ing more play than the other blades. I know the Arplast PV50 has play in the blades when it is at rest. This tim e I attempted to measure the at rest play. Blades 1 and 3 are fairly consis tent with each other and approximately 1=C3=82=C2=BA of play. Blade 2 has a pproximately 4=C3=82=C2=BA. I think what I am looking for, and the reason for this post, is for someone else to think about my workings to sanity check if I have missed anything; or also to check the conclusion is genuine and I am not just =C3=A2=82 =AC=C5=93looking for evidence of blade 2 because that is my apparent proble m=C3=A2=82=AC. Thanks all Jon Read this topic online here: http://forums.matronics.com/viewtopic.php?p=454127#454127 Attachments: http://forums.matronics.com//files/g_bxum_2016_03_241_polar_chart_201603251 30741_984.jpg http://forums.matronics.com//files/propeller_194.png http://forums.matronics.com//files/results_105.png =C2- =C2- =C2- =C2- =C2- -Matt Dralle, List Admin. S - - =C2- =C2- =C2- =C2- =C2- -Matt Dralle, List Admin. ------------------------------------------------------------------------------------- Other Matronics Email List Services ------------------------------------------------------------------------------------- Post A New Message europa-list@matronics.com UN/SUBSCRIBE http://www.matronics.com/subscription List FAQ http://www.matronics.com/FAQ/Europa-List.htm Web Forum Interface To Lists http://forums.matronics.com Matronics List Wiki http://wiki.matronics.com Full Archive Search Engine http://www.matronics.com/search 7-Day List Browse http://www.matronics.com/browse/europa-list Browse Digests http://www.matronics.com/digest/europa-list Browse Other Lists http://www.matronics.com/browse Live Online Chat! http://www.matronics.com/chat Archive Downloading http://www.matronics.com/archives Photo Share http://www.matronics.com/photoshare Other Email Lists http://www.matronics.com/emaillists Contributions http://www.matronics.com/contribution ------------------------------------------------------------------------------------- These Email List Services are sponsored solely by Matronics and through the generous Contributions of its members.