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Thread: Replacing the engine mount

  1. #11
    Super Moderator Av8r3400's Avatar
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    Default Re: Replacing the engine mount

    Steve, while she's down you should do something about that funny wheel under the engine...
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  2. #12
    Administrator DesertFox4's Avatar
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    Default Re: Replacing the engine mount

    Well I guess I could remove it but it's gonna be rough on my prop.


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  3. #13
    Senior Member HighWing's Avatar
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    Default Re: Replacing the engine mount

    Quote Originally Posted by Wheels View Post
    I cannot tell you how that occurred. But, never the less, the part is now at a welding shop being TIG welded to fill the miss drill, re drilled and repowder coated.
    This caught my eye. I took an Avid elevator I am modifying for a trim tab to the local Powder coat guy. When he saw it, is first words out of his mouth were, "I thought airplane parts shouldn't be powder coated because it hides cracks". I told him that with home builts we can do pretty much what we want. Yes, occasional reports of cracks in the Model IV engine mount would surface on the lists and forums. A good checklist item for the annual inspection.
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  4. #14
    Senior Member Wheels's Avatar
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    Default Re: Replacing the engine mount

    I ordered hose for my rubber replacement and almost had a heart attack at the 460.00 bill and the tiny box of assorted hoses. They added up to a little over 10 feet of hose. So I'm sending it back. There wasn't enough hose in the box to actually do the whole job. My rubber isn't actually due yet and I thought I would just add some life while the engine was off but not for that kind of money.

    So I'm researching hoses and I have a list from CPS I got from Roger Lee on the Rotax forum. the price is coming down. significantly. There are a few specialty items that you just HAVE to have like the 90 degree bend hose on the coolant tank etc. Pricey but mandatory. I am considering buying the special tools for squeezing on clamps and getting rid of the gear driven ones. Rotax said the spring type are not working well on some of the aircraft . any druthers on that tool and part choice? Well, Happy hose replacement, anyone with a list or sources for quality hose and clamps feel free to jump in.

  5. #15
    Senior Member Wheels's Avatar
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    Default Re: Replacing the engine mount

    Here is a pic of the new dyna-focal mount for a model IV and the old one side by side. The black one is the old one. No tube thickness change, but the extra gusset welded to the extra support will change the strength tremendously.
    I measured the tube thickness and they are the same, so unless the material has changed, the beefiness is confined to the gusset and the extra member.

    I have a serious p-factor to the left and need to stand on the right rudder enough at cruise that its annoying. Was playing with the idea of shims now that the engine is off. A mechanic friend of mine asked me if I thought the shims would have an adverse affect on the equal dampening of the dyna-focal engineering. Damn I hate it when someone else is smarter than me, so I hate it a lot. Any comments?
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  6. #16
    Senior Member jrevens's Avatar
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    Default Re: Replacing the engine mount

    Quote Originally Posted by Wheels View Post
    ...
    I have a serious p-factor to the left and need to stand on the right rudder enough at cruise that its annoying. Was playing with the idea of shims now that the engine is off. A mechanic friend of mine asked me if I thought the shims would have an adverse affect on the equal dampening of the dyna-focal engineering. Damn I hate it when someone else is smarter than me, so I hate it a lot. Any comments?
    Wheels,
    I doubt that a little shimming of the mount would make any descernable difference with vibration. I've seen it done frequently with Lycoming engines - mostly to correct slight misalignment with the cowl. However, it sounds like you need a rudder trim tab.
    John Evens
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  7. #17
    Senior Member jrevens's Avatar
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    Default Re: Replacing the engine mount

    Quote Originally Posted by HighWing View Post
    This caught my eye. I took an Avid elevator I am modifying for a trim tab to the local Powder coat guy. When he saw it, is first words out of his mouth were, "I thought airplane parts shouldn't be powder coated because it hides cracks". I told him that with home builts we can do pretty much what we want. Yes, occasional reports of cracks in the Model IV engine mount would surface on the lists and forums. A good checklist item for the annual inspection.
    I know painters who hate powder coating - it is generally thick & flexible enough that it can hide cracks. It also can hide corrosion if not applied correctly, to a properly cleaned & prepared surface. I saw an example of a piece of 4130 tubing that had corroded badly underneath the powder-coating. The outer surface of the powder coat looked beautiful. I had some serious doubts about whether I wanted to order my Kitfox parts with powder coating, but I did it anyway.
    On my "other" airplane, I painted my engine mount black, but that is generally considered a no-no by some, as it makes it a little harder to spot any developing cracks. White is better in that regard.
    John Evens
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  8. #18
    Senior Member Esser's Avatar
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    Default Re: Replacing the engine mount

    Drill a hole at every intersection of pipe and then add a spot to thread in a gauge and a place to add air. Every year see if the mount holds air…if it doesn't you have a crack. No worries if you powder coat it.

  9. #19
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    Default Re: Replacing the engine mount

    Cessna and Piper both paint their engine mounts black. Personally, I prefer white for aesthetic reasons. If shimming, it might be better to shim at the firewall, rather that at the dynafocal end of the mount. Shimming will cause the crankshaft to move relative to the cowl. Sometimes there is no easy way.

  10. #20
    Senior Member jrevens's Avatar
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    Default Re: Replacing the engine mount

    Quote Originally Posted by Esser View Post
    Drill a hole at every intersection of pipe and then add a spot to thread in a gauge and a place to add air. Every year see if the mount holds air…if it doesn't you have a crack. No worries if you powder coat it.
    I'm not sure if you're joking or not, Esser. I've heard that idea before, and pressurizing a sealed structure & monitoring the pressure with certain very highly stressed and critical structures has been done. It's interesting, but it wouldn't necessarily be of any use as a crack was forming, or corrosion was forming on the surfaces of the tubing of a Kitfox. As I said, most painted pieces will show a developing crack before a powder coated one will, & hidden corrosion has been known to form under powder coating, as opposed to a properly primed & painted surface. Cracks do not necessarily occur all at once, penetrating the full depth of the structure. They can & do start at the surface, frequently the outer surface of a tube, & gradually increase in length & depth until failure of a structure. I'm not trying to infer that powder coating is necessarily bad - again, I chose the powder coating option for my Kitfox. For a builder to decide which way to go, having knowledge of the pros and cons should be part of the equation.
    John Evens
    Arvada, CO
    Kitfox SS7 N27JE
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