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Thread: Balance Master

  1. #11
    Senior Member PapuaPilot's Avatar
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    Default Re: Balance Master

    Does anybody know if they make one that fits on the Continental IO-240? I like the idea of having your prop & engine in balance at all RPMs.
    Phil Nelson
    A&P-IA, Maintenance Instructor
    KF 5 Outback, Cont. IO-240
    Flying since 2016

  2. #12
    Super Moderator Av8r3400's Avatar
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    Default Re: Balance Master

    If you follow the link to ACS, you’ll see they do. John and others have stated they weren’t happy with the results on a direct drive engine. I would hypothesize that the harmonic pulses in a direct drive situation may negate some of the balancing properties.
    Av8r3400
    Kitfox Model IV
    The Mangy Fox
    912UL 105hp Zipper
    YouTube Videos

  3. #13
    rdooley79's Avatar
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    Default Re: Balance Master

    I’m finishing a 912 install on my 4. Hal did the build of the engine for me and he recommended using two balance masters. One on the mag end and on the prop as well so I put them on my 912. Probably a couple weeks from first run up and no pirep yet. Hal recommended it highly so there’s that...
    Kitfox IV - 1200 (1994) #1830
    Rotax 912
    Grove Gear, Wheels, Brakes
    22" Desser Tundra Tires

  4. #14

    Default Re: Balance Master

    Two??? I was looking at getting one... now, I have to look at getting two... 😜

  5. #15
    Senior Member rv9ralph's Avatar
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    Default Re: Balance Master

    Two??? I was looking at getting one... now, I have to look at getting two... 😜
    So here is something to think about. In the Rotax 912/14/15 series there are two centers of rotation. The prop hub at the top of the gearbox, and the Crankshaft (I know the camshaft is also a different center of rotation but we will leave that one for now). These are separated by 4-6 incise. The prop and it's rotational forces are turning at 2.27 or 2.43 times slower than the crank's rotational forces. When trying to balance this, you have to consider both of these sources of acceleration.

    To this, the suggestion of two balance masters does make sense.

    Ralph

    ps - I am not an engineer nor do I claim to be.

  6. #16
    Senior Member efwd's Avatar
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    Default Re: Balance Master

    Hmmm. I used a Dynavibe to balance my prop. It worked and I may even swap to the balance master regardless. I seriously hope my $22k Rotax was balanced at the factory.
    Eddie Forward
    Flying
    SS7, 912iS, Garmin G3X

  7. #17
    Senior Member rv9ralph's Avatar
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    Default Re: Balance Master

    I used a Dynavibe to balance my prop. It worked and I may even swap to the balance master regardless.
    Eddie, didn’t you report you only had a small vibration that popped up at certain times... could it be a multiple of the reduction ratio? Just a thought.

    Ralph

  8. #18
    Senior Member jrevens's Avatar
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    Default Re: Balance Master

    IMG_1368.jpgIMG_1386.jpgIMG_1370.jpgIMG_1385.jpg
    I flew for 1.5 hours on 1/16/20 with the Balance Master installed. The airplane didn't feel as smooth as before, but definitely smoothed out more after full throttle run-up. Today I installed my balancing equipment to get some real numbers. After warm-up, I advanced to 5000 rpm, took a vibration reading, then did the same thing at 4000, 3000 & 2000 rpm. I then went back up in 1000 rpm steps to 5000. I then removed the Balance Master and performed the same exercise again. I had previously dynamically balanced the assembly to 0.02 to 0.03 ips at full-throttle static of approximately 5100 rpm. Here are my results and observations -

    With Balance Master - Starting at 5000 rpm - 0.04, 4000 - 0.04, 3000 - 0.12, 2000 - 0.02 Starting at 2000 - 0.03, 3000 - 0.07, 4000 - 0.03, 5000 - 0.10

    Without BM - Starting at 5000 rpm - 0.02, 4000 - 0.02, 3000 - 0.01, 2000 - 0.02 Starting at 2000 - 0.02, 3000 - 0.02, 4000 - 0.03, 5000 - 0.03

    I allowed time for things to "settle down" before each reading, and observed that with the BM it took a minimum of 30 sec. to 1 min. (sometimes considerably longer) to reach the best balance condition. There was no delay without the BM. I'm not certain why the spike at 5000 rpm when going from 4000 to 5000 with the BM as compared with starting at 5000. Hysteresis in the throttle cable when pushing as opposed to pulling on the throttle arm (I don't have the throttle springs) creating a little carb imbalance may be a factor, but I don't see the same thing without the BM.

    So, my experience is smoother operation without the Balance Master, and much smoother during the transition "settling down" periods. I think that the Balance Master would potentially offer a good improvement/option for an out-of-balance condition if dynamic balancing was not easily accomplished, such as when a small "skull-cap" spinner is used on a Rotax. For me, there is no doubt that my situation is better with a good dynamic balance job alone. Your mileage may vary.
    Last edited by jrevens; 01-18-2020 at 10:32 PM.
    John Evens
    Arvada, CO
    Kitfox SS7 N27JE
    EAA Lifetime
    Chap. 43 honorary Lifetime

  9. #19

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    Default Re: Balance Master

    Very interesting. Thanks much for taking the time to do this and report the findings. Maybe some others will chime in with their findings.

    Clark

  10. #20
    Senior Member JoeRuscito's Avatar
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    Default Re: Balance Master

    Great report. Thanks John.

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