I use a MicroVib II and do a spectrum analysis with each balance. I forget exactly but the alt rate is about 3.8 if I remember correctly.
Dug up some old plots I had hosted, here's an example of a 2 blade prop, pretty normal to have a 'spike' at the 2 blade rate, a 3 blade will typically have a 3 order rate spike. You can see the alt rate in the plot
Here's a 3 blade on an RV12 and you can see the 3 order spike, the Rotax also has some other accessory drive speeds you can see.
Here's a typical polar plot of the balance:
Walt Aronow, DFW, TX (52F)
EXP Aircraft Services LLC
Specializing in RV Condition Inspections, Maintenance, Avionics Upgrades
Dynamic Prop Balancing, Pitot-Static Altmeter/Transponder Certification
FAA Certified Repair Station, AP/IA/FCC GROL, EAA Technical Counselor
Authorized Garmin G3X Dealer/Installer
RV7A built 2004, 1700+ hrs, New Titan IO-370, Bendix Mags
, Email: firstname.lastname@example.org
, Cell: 972-746-5154
Last edited by Walt : 02-14-2020 at 03:33 PM.