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Thread: Balance Master

  1. #41
    Senior Member jrevens's Avatar
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    Default Re: Balance Master

    Quote Originally Posted by jiott;91231[COLOR=#333333
    ...
    Very likely John was saying it took that long to reach a very fine balance condition. I doubt he meant that there was major shaking for that long...[/COLOR]
    That's exactly right, Jim. To try to further clarify... when you're looking at the vibration level sensed by the accelerometer, it is generally far more sensitive than what you can "feel" inside the airplane. I'm talking about not only minor, but also significant vibration levels at the engine in many instances. By significant I mean that they are worth reducing or eliminating, for all of the reasons that have been discussed.
    John Evens
    Arvada, CO
    Kitfox SS7 N27JE
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  2. #42
    Senior Member jrevens's Avatar
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    Default Re: Balance Master

    Quote Originally Posted by Shadowrider View Post
    ...
    As far as the BM being out of balance on startup... I bet the mercury is spun out on the crank before the engine is idling smooth.
    I'm sure it is too, but during my testing it took much longer, as I noted, for things to get to a "respectable" level & as good as it was going to get, and then it varied throughout the run. I just tried to report accurately what my results were, and the test was only with my particular engine, propeller and spinner . I'm not saying it was "bad" with the BM, but just that it was better without it (with a good dynamic balancing job). If the BM had produced better results, or at least as good, believe me I would have kept it. I'm hoping it will make a good improvement for my buddy Stan, with his IVO prop and small "skull-cap" spinner - a set-up that is difficult to effectively add balance weights to.

    Regarding the shut-down technique, it took me a little trial & error before getting it just right... the timing when shutting off the ignition in relation to the throttle movement seems to be the key.
    John Evens
    Arvada, CO
    Kitfox SS7 N27JE
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    Chap. 43 honorary Lifetime

  3. #43
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    Default Re: Balance Master

    Understood John.

    With regards to the “correct” technique. Even with “correct” technique....it’s like the Gerbals just stop running and get stuck in the wheel. Never being around a rotax, they raise eyebrows when shutdown.
    Dustin Dickerson

    Building 7ss STI x 2
    Oratex
    29" shock monster
    EP912STI 155hp
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  4. #44
    Senior Member jrevens's Avatar
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    Default Re: Balance Master

    Yes they do!
    John Evens
    Arvada, CO
    Kitfox SS7 N27JE
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  5. #45
    Senior Member jrevens's Avatar
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    Default Re: Balance Master

    Just want to provide an update. We installed the Balance Master on Stan’s Mod. IV yesterday. He’s got an Ivo 3-blade IFA with the small “bullet” spinner, and 80 hp 912. The vibration level before the BM was considerable at 0.73 ips (inches per second of acceleration). After installing the BM, the level measured between 0.49 & 0.53 ips throughout the rpm range and at various pitches. This is an improvement, but disappointing. We normally aim for a level of 0.05 ips or less when balancing with fixed weights (anything less is really just “splitting hairs”). I think we may do some further testing, and if so I’ll report the findings.
    John Evens
    Arvada, CO
    Kitfox SS7 N27JE
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    Chap. 43 honorary Lifetime

  6. #46
    Senior Member efwd's Avatar
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    Default Re: Balance Master

    Im curious. I had my ips down at an acceptable number. Thought it was smooth, and it was, definitely better than before I used the Dynavibe. Then, one day recently, I adjusted my prop pitch for something between cruise and climb since the climb setting made it too easy to overspeed the engine while in flight and not necessarily climbing with full throttle. I recall paying very close attention to getting the pitch in each blade as near as exactly the same as I could. Much like the time I did it for the first time before I got my sign off. When I flew it I believe I noted an appreciable improvement after that prop adjustment. In your case John, you didn't seem to get such great results with the balancer which leads me to the question. How much could the prop be influencing the ips if a blade is off too much?
    Eddie Forward
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  7. #47
    Senior Member jrevens's Avatar
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    Default Re: Balance Master

    That's a good question, Eddie. If you're talking about prop pitch differences in the 3 blades then yes, it can/will cause vibration. I'm not very well educated in this area, but it would seem to me that the vibration would be created axially, or basically parallel to the prop shaft, as opposed to an imbalance in weight that produces vibration perpendicular to the shaft. Either way, it's unwanted vibration. I'm sure someone on this forum could correct or clarify my crude knowledge about this. I don't believe adding balance weight or a Balance Master will correct vibration due to pitch variance among the blades. So if this is true, the IFA Ivo prop may create vibration, depending on variance in pitch between the blades, that isn't easily corrected.

    Just to make sure it is clear, I haven't been able to add conventional weights to this assembly because of the small spinner and hub. I've merely used the balancer to measure the amount of imbalance.
    John Evens
    Arvada, CO
    Kitfox SS7 N27JE
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    Chap. 43 honorary Lifetime

  8. #48
    Senior Member Delta Whisky's Avatar
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    Default Re: Balance Master

    John - I sure can't clarify - in terms of a solution or answer - but maybe more anecdotal information may help develop a provable theory. In testing a 60kW electric motor directly driving a prop by a well known and reputable American company we experienced several tests of extremely smooth performance through the complete rpm range. Then, during some tests we'd start up thru the range and experience severe vibration - so severe that on at least two occasions the test stand would jump an inch or two off of the ground. We were working on a theory that differing incoming wind angles (that was the only thing in our set up that we knew had changed) was the culprit but ended up shutting down the company before being able to prove anything.

  9. #49

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    Default Re: Balance Master

    I was interested in trying the Balance Master, so I ordered the prop Balance Master off set. And it doesn’t fit.
    I have a Rotax 912iS, with whirl wind prop 70” ground adjustable. Anyone have a suggestion as to which balancer I need? I ordered from ACS and the other Balance Master products they offer are for the engines.
    Thanks
    John

  10. #50
    Senior Member efwd's Avatar
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    Default Re: Balance Master

    Part# 15-09450 MFR Model# UL-912-914 isn't the correct one? Thats the bolt pattern I would expect as I have the same setup. I pulled that from ACS&S website.
    Eddie Forward
    Flying
    SS7, 912iS, Garmin G3X

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