Eagler's Nest
General Category => Off Topics and General Interest => Topic started by: LSaupe on December 14, 2021, 05:28:56 AM
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Is there an acceptable value out there for prop balance? My current prop (62" w blade Powerfin) is showing a 101 in-g out of balance condition. Is this a typical value or should I strive to improve?
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What rig are you using to balance your prop? I couldn't give you a torque value for out of balance but I can tell you what I did when I balanced the prop I carved. I had to make my own static balancer because I couldn't find/borrow one that fit my hub. I threw a pipe in a lathe and turned it down to fit into the hub (.008" less diameter than inner hub diameter). I also turned down the outside edges of the pipe to accept a couple of ball bearings I had laying around, to be placed on the outer edges of the tube sandwiching but not touching the prop. I then placed the bearings on some parallels and let the prop rotate to the heavy side, and sanded the heavy side until I could orient the prop in any 5 degree orientation (give or take) without the prop having any preference to rotate, in other words it wouldn't rotate no matter the orientation. Just a standard static balance procedure. I couldn't tell a difference between that prop or my culver prop vibration-wise. I might add that my culver prop is quite smooth, and this is wood, you will have a different procedure for adding or removing material for balancing a composite or metal prop.
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I have a 3 blade prop. Measured each blades mass and balance point, and then did a vector sum to find the resultant. I then mounted the prop on a static balance rig much like you are using (I used roller bearing V blocks on a level surface). Works very well. The result was the same as the vector sum method. I was able to obtain a good balance check by using a known mass and two sided VHB tape (well two in this case). The numbers check out. These are the V block I was using. Very nice quality.
https://www.ebay.com/itm/192563722795