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Thread: Prop balance

  1. #1

    Join Date
    Aug 2011
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    Fort Vermilion Alberta
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    196

    Prop balance

    I tried to balance my Mcaulay club and after about 1/8 inch of paint on one tip I quit, it all blew off anyway.

    I'm looking at options and found this on Barnstormers.

    http://balancemasters.com/ultralights/experimental.html

    Has anyone experience with this gadget.

    The theory sounds solid $385 for a permanent fix seems good but,,,,,,,,,?

  2. #2
    gbrasch's Avatar
    Join Date
    Nov 2011
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    Arizona
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    530
    I just heard of them and a fellow RV guy ordered one. He is going to get his prop tested before and after install, this will all happen in the next week, I would be glad to report back his findings. They make some pretty tall claims, but the concept has been around for awhile in other applications.
    Glenn Brasch
    KRYN Tucson, Arizona
    2013 RV-9A
    Medevac helicopter pilot (Ret)
    EAA member since 1980
    Owner, "Airport Courtesy Cars" website.
    www.airportcourtesycars.com
    Volunteer Mentor www.SoAZTeenAviation.org

  3. #3

    Join Date
    Sep 2011
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    155
    Liquid balancing devices have been around for years in the automotive world. They work once the rpm gets sufficient to force the fluid to proper place and counteract imbalance.

    I have a different approach to prop balancing. I bought a motorcycle wheel balancer from Harbor Freight ($50) intended for static balancing of smaller wheels. I use it on 5.00-5 and smaller nose wheels very successfully. With some minor adadptation, I also use it for static balancing my 2-blade GSC wood prop for a Rotax 912. The system is very sensitive because the prop blades are so long. To balance, I take a spray can of spar varnish and lightly coat the backside of the light blade for about 10" from tip. It usually takes 2-3 passes to add sufficient weight to even out the blades and allow the blades to balance perfectly. In fact, as the solvent evaporates in the varnish, the blade may move gradually and a quick hit brings it back. I compared my static system to the dynamic balance operation by having it done on mine and found them to be equivalent for light blades. And it does tires too.

  4. #4

    Join Date
    Jul 2011
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    2,575
    Does anyone know if most props have some type of balancing done at the factory before they are put on the market?

    I have never used a do-it-yourself balance method, but I have used one of the many places that will do a dynamic balance job on your plane, last time the cost was around $200 0r $250.
    Balancing is one of the "hop up" type things, for car or airplane that is all positive and has no downside. It doesn't sacrifice starting or idle for top end power, etc.
    I have used it from a Cub with a simple 2 blade fixed prop to Mooney and Bonanza to a 4 blade constant speed warbird prop, and benfited from all.

    It is my guess that the simpler the prop the less likely it was balanced at installation.
    On more complex 4 blade ones, we have found that first it is vital to check and be sure all blades are tracking true, and if one is off track it can be in balance weight wise and still be rough. Then you go on to dynamic balance while running the engine, and also found that it may be smooth at one rpm say, 1800 and rough at another say 2200.
    Dynamic balancing is done with a stroboscopic light to find the heavy spot.
    Turbines and especially helicopters really use balancing.

    Note that any good auto shop spin balances tires, not just static bubble balance.

  5. #5

    Join Date
    Sep 2011
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    155
    Static balancing works on low mass/low polar moment props, like 2-blade wood on the order of 62" dia. For a metal blade with 2X/3X the mass, may not be as effective.
    There is nothing wrong with paying $250 for a dynamic balance if you want to. I prefer to balance my own whenever I feel prop needs it. Takes about 10 min to accomplish off the plane.
    Wood props are statically balanced my mfgr in much the same way as I'm doing. I have a ground adjustable GSC prop on a 912S which allows tweaking for temps and altitudes.
    When I did the comparison, my statically balanced blade was out by .01 units where the normal range is below .20 units. So I use the static method because it comes so close to good balance.

  6. #6

    Join Date
    Aug 2011
    Location
    Fort Vermilion Alberta
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    196
    I have used various balance rs over the years.

    If you have a shaft that fits tightly into the center hole a couple of leveled knife edges works well.

    A static tire balance r with a little modification works well.

    I made a tapered cone with a string in the center and hang it from the ceiling inside out of the wind is very sensitive.

    My Prop is so far out painting won't do it, I'm not sure what happened, it is not damaged, nice clean edges, no dings or radical filing been done.

    I hate to grind metal away from the heavy blade, and where do you grind, at the tip a little, closer to the root, a lot more??

    Metal props are rugged but they have real harmonics problems.

    Ray

  7. #7
    I do dynamic propeller balancing in the southwest area as a mobile repair station. DSS Micro is the manufacturer of my equipment and it works very well. Whenever you get a new spinner, new prop or have it overhauled then you will want to have a balance completed again.

    Morefield Aviation
    DVT CHD KFFZ

  8. #8

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    Aug 2011
    Location
    Alabama
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    2,236
    Bill, I know that Culver Props all get balanced before leaving their shop.
    The opinions and statements of this poster are largely based on facts and portray a possible version of the actual events.

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