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Thread: Mangy Fox Update

  1. #1
    Super Moderator Av8r3400's Avatar
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    Default Mangy Fox Update

    I've been a little quiet lately with my 70 hour per week business getting in the way of my Kitfox-ing. But, I do have a bit of a story to tell.

    I had a bit of an incident while taxiing. I was turning around into a field next to a friend's grass strip and hit what I thought was just a patch of snow, that turned out to be more of a snow filled furrow. Long story short, I modified the tips of my Prince Prop.

    GHBIlAT.jpg R9inlLr.jpg

    That day (Saturday 11-16) I gave a call to Hal Stockman (a national treasure in my book) to place an order for a new Luga/NR prop from him. I was surprised to find out he had one on the shelf and would ship it out to me asap. It turns out he shipped it that day!! What a swell guy! With a tear in my eye, I had to leave the Mangy tied down at the grass strip for a couple days (with a winter storm coming) until the new prop arrived.

    6KJmQvl.jpg

    That Tuesday (!) my new Luga prop arrived from Hal. (Did I mention what a swell guy he is?). I quickly put the prop on, that Wednesday, and got the plane home. I found out that if I pitched the prop to where I thought it should be the trailing edge would contact my cowling. It was always close on my Prince prop, but it didn't hit. This did. So I flattened the pitch for clearance and got the plane home. I could over rev the engine at half throttle and all I could manage was 70 mph on the way home, but I got her home to her own hangar in time to avoid the coming blizzard. Here's the new prop on my kitchen table:

    cFfSN83.jpg

    My Prince was a 78" diameter by 48" pitch. It was a big prop. It was a takeoff and climb animal on my plane. Unfortunately the large diameter also meant it was pretty draggy and my top speed was a little better than 100 mph on a good day. This was never a big problem, because the STOL performance was so stellar. An acceptable trade off to me. The new Luga is only 72" in diameter. So I was preparing to take a substantial hit in STOL performance.

    To install the prop with the way my cowl is configured, I needed to add a 1" spacer. Hal happened to have a used one for a good price and he asked me if I wanted to try a balance ring with it. I had seen these in Aircraft Spruce and was curious. I have similar balance rings on my big truck wheels and know they work awesome in that application, so I said sure, why not. Here is what the stack up looks like. (Spinner options are still being explored)

    d9qaw5J.jpg s5biZVH.jpg

    AS of today, I have about 4 hours on the prop. I explored pitch settings starting at 15º which is the zero setting on the pitch gage. At that pitch, I would quickly over rev the engine on takeoff and level flight. So I bumped up the pitch to 17º. That only gave me 5200 on takeoff, but my cruise speed jumped up to over 120 mph in rough, unsettled air. I have it now at 16º with is appearing to be a nice compromise.

    My takeoff distance may be a few feet more than with the prince, but not more than literally a few feet. Climb performance with the Prince was stellar to say the least. The Luga does well, but not as well. With the Prince I was seeing sustained climb rates of 1700-2000 FPM. With the limited time I have on this new prop, I'm seeing 1400-1600 FPM. Nothing to complain about by any means. However, I am seeing cruise speeds in the 110-115 mph range with 16º of pitch. I am not complaining. More that an acceptable trade off.

    Now what everyone is waiting for: The Balance Ring. This thing is AMAZING!! This prop with the balance ring is so smooth, like nothing I have ever flown before. Every 912 I have ever flown has a little rough patch from 2500-4000 rpm give or take. Mine had it too. No amount of carb balancing or Dyna-Vibe-ing the old prop would get rid of it. With the balance ring this is GONE! Incredibly smooth! Our EAA Chapter has a Dyna-Vibe machine. I have used it many times and know they work well enough, but I was never totally satisfied with the results I saw on my plane or any other I helped with. This balance ring has, in my opinion, just obsoleted the need for a Dyna-Vibe or any other balancing machine.

    Fltdpu9.jpg
    Last edited by Av8r3400; 12-09-2019 at 08:14 PM.
    Av8r3400
    Kitfox Model IV
    The Mangy Fox
    912UL 105hp Zipper
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  2. #2
    Administrator DesertFox4's Avatar
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    Default Re: Mangy Fox Update

    Sorry to hear about your prop ding.
    Glad you got her home before that blizzard took the Mangy Fox for a flight.👍


    DesertFox4
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  3. #3
    Senior Member rv9ralph's Avatar
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    Default Re: Mangy Fox Update

    Good to hear all is well again.

    Screen Shot 2019-10-04 at 8.58.43 AM.jpg

    Hal is the best!

    Ralph

  4. #4
    Birdseyeview's Avatar
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    Default Re: Mangy Fox Update

    AV8r3400 - Your balancer experience is very interesting and I'm sure it will draw out a lot of additional questions. I've got a few questions for you: 1) I'm assuming you could have mounted the balancer on the forward end of the prop hub if it would clear the spinner you have in mind, right? 2) Does your engine flange have the 6 flanged nut plates sticking out like on my 912 ULS? If so, does the balancer web have holes large enough to clear them? 3) How thick is the bolting web of the balancer so I can do a stackup to see if my existing prop attach bolts are long enough to accommodate the added web thickness? Thanks for any input you can provide.

    prop flange 2.jpg
    Last edited by Birdseyeview; 12-09-2019 at 11:13 PM.
    Larry Olson
    Kitfox Series 6 - 1st Flight Oct 2021
    Tri-gear, smooth cowl
    912 ULS

  5. #5
    Senior Member jrevens's Avatar
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    Default Re: Mangy Fox Update

    Sorry to hear of your mishap Larry, but glad the Luga is working out. Hal is definitely a good man! I guess the balance ring doesn’t have enough mass to be detrimental to the engine/gearbox? Just thinking of the angular momentum and Rotax’s limit. What does it weigh? It’s probably not an issue... just curious. As an aside, I haven’t been real impressed with some other possibly similar units used with Lycomings, based on what I would see when checking the balance. There was frequently (like at every engine start) a period of more imbalance until things settled down. I figured that the total wear & tear on an engine over an extended period of time might be greater with the ring than without (with a good dynamic balance job). It’s like comparing apples to oranges though when we’re talking about Lycoming vs Rotax. Your experience sounds really good.
    John Evens
    Arvada, CO
    Kitfox SS7 N27JE
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  6. #6
    Super Moderator Av8r3400's Avatar
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    Default Re: Mangy Fox Update

    Quote Originally Posted by Birdseyeview View Post
    I've got a few questions for you:

    1) I'm assuming you could have mounted the balancer on the forward end of the prop hub if it would clear the spinner you have in mind, right?
    2) Does your engine flange have the 6 flanged nut plates sticking out like on my 912 ULS? If so, does the balancer web have holes large enough to clear them?
    3) How thick is the bolting web of the balancer so I can do a stackup to see if my existing prop attach bolts are long enough to accommodate the added web thickness?
    1. The balancer is mounted between the engine’s prop flange and (in my case) spacer. Clearing a spinner will not be an issue.
    2. My prop flange has the six (6) 8mm threaded inserts as shown in your photo. The balancer goes over them and the center locating hub perfectly.
    3. The thickness of the balancer plate is about the same as a washer. I used 1mm for the purpose of ordering bolts.
    Av8r3400
    Kitfox Model IV
    The Mangy Fox
    912UL 105hp Zipper
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  7. #7
    Super Moderator Av8r3400's Avatar
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    Default Re: Mangy Fox Update

    Quote Originally Posted by jrevens View Post
    Sorry to hear of your mishap Larry, but glad the Luga is working out. Hal is definitely a good man! I guess the balance ring doesn’t have enough mass to be detrimental to the engine/gearbox? Just thinking of the angular momentum and Rotax’s limit. What does it weigh? It’s probably not an issue... just curious. As an aside, I haven’t been real impressed with some other possibly similar units used with Lycomings, based on what I would see when checking the balance. There was frequently (like at every engine start) a period of more imbalance until things settled down. I figured that the total wear & tear on an engine over an extended period of time might be greater with the ring than without (with a good dynamic balance job). It’s like comparing apples to oranges though when we’re talking about Lycoming vs Rotax. Your experience sounds really good.

    The weight of of the balance ring is less than a pound, in my estimate. I didn’t weigh it directly. As far as the MMOI is concerned, I believe the impact to be negligible at most.

    I do not believe the few rotations of imbalance will effect wear in the long term. On my engine, at this time with the relatively few number of startups, I can not even notice this startup imbalance. By the time the engines ignition transitions from start to run mode the balancer ring has come into its effectiveness.
    Av8r3400
    Kitfox Model IV
    The Mangy Fox
    912UL 105hp Zipper
    YouTube Videos

  8. #8
    Birdseyeview's Avatar
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    Default Re: Mangy Fox Update

    AV8r3400 - Thanks for the answers to my questions so quickly. Based on your responses it appears that it will fit on my engines prop flange. However, depending on how thick the device is overall it might interfere with the forward edge of my smooth cowl. If it does interfere with the cowl I could possibly add a flange extension as you did or I may be able to mount it on the forward side of my prop hub but there is no pilot diameter there and the bolt circle would have to act as a centering device. The photos on ACS's website show a slotted bolt circle and I suppose I could drill some new round holes to compensate but unless these were very accurately drilled it might imbalance the assembly more than the balance ring can handle. In order to see if it will fit in my installation could you answer a couple more questions?

    1) What is the overall thickness of the device?
    2) What is the overall diameter of the device?

    Approximate dimensions are OK for both questions. If it looks like it is too close to call I'll get exact dimensions from the manufacturer.
    Larry Olson
    Kitfox Series 6 - 1st Flight Oct 2021
    Tri-gear, smooth cowl
    912 ULS

  9. #9
    Senior Member jrevens's Avatar
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    Default Re: Mangy Fox Update

    Thanks for the info Larry. Based on your comments, I’m thinking I might get one... I like the idea.
    John Evens
    Arvada, CO
    Kitfox SS7 N27JE
    EAA Lifetime
    Chap. 43 honorary Lifetime

  10. #10
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    Default Re: Mangy Fox Update

    Did you balance prop before the balance ring? Wonder if it would be best to get prop in balance and then install? That way you balance for optimum rpm and then the balance ring can balance when you are not in peak rpm?
    Dustin Dickerson

    Building 7ss STI x 2
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