Van's Air Force
Don't miss anything! Register now for full access to the definitive RV support community.
prop balance
- Thread starter bobnoffs
- Start date
D-Dubya
Well Known Member
From your signature block, it's unclear if you're flying an RV-12 or if you're talking about something else. Someone else may have to chime in if you're talking about Rotax engines.
Most people with Lycomings balance with the spinner on by weighing bolts and washers and installing them through the holes in the starter flywheel. In one instance, I've seen a builder fine tune the balancing results by putting slightly longer screws in specific spinner attach points.
Most people with Lycomings balance with the spinner on by weighing bolts and washers and installing them through the holes in the starter flywheel. In one instance, I've seen a builder fine tune the balancing results by putting slightly longer screws in specific spinner attach points.
rmarshall234
Well Known Member
I’ll take a crack at it…
When doing a prop balance what we are actually doing is balancing the “rotating assembly”. Prop, spinner, spinner bulkheads and even the crankshaft to a lesser degree. So yes, include the spinner. If you have the proper equipment but haven’t done this before, try to get someone with experience to help out. Prop balancing is IMO a combination of science and art, some peeps are really good at it and some just make things worse. Cheers
When doing a prop balance what we are actually doing is balancing the “rotating assembly”. Prop, spinner, spinner bulkheads and even the crankshaft to a lesser degree. So yes, include the spinner. If you have the proper equipment but haven’t done this before, try to get someone with experience to help out. Prop balancing is IMO a combination of science and art, some peeps are really good at it and some just make things worse. Cheers
I derived my computations for balancing from this document and the tips in the DynaVibe instructions. This document shows how to plot the solution after one trial run.
https://d1wqtxts1xzle7.cloudfront.n...sMSqZim35Q__&Key-Pair-Id=APKAJLOHF5GGSLRBV4ZA
https://d1wqtxts1xzle7.cloudfront.n...sMSqZim35Q__&Key-Pair-Id=APKAJLOHF5GGSLRBV4ZA
Try this one:
https://www.bksv.com/media/doc/bo0276.pdf
It is "Static and Dynamic Balancing of Rigid Rotors" from Bruel & Kjaer back when we had an HP41C handheld calculator as the best thing going.
It discussed using the initial and trial runs to derive the solution. For our Lycomings, the solution can be vector split between the two closest bolt positions.
I wrote a perl program to do the math. It could be done in excel just as easily, or graphed on paper as the document shows.
https://www.bksv.com/media/doc/bo0276.pdf
It is "Static and Dynamic Balancing of Rigid Rotors" from Bruel & Kjaer back when we had an HP41C handheld calculator as the best thing going.
It discussed using the initial and trial runs to derive the solution. For our Lycomings, the solution can be vector split between the two closest bolt positions.
I wrote a perl program to do the math. It could be done in excel just as easily, or graphed on paper as the document shows.
