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Thread: Nate Ashton's Kitfox SS7

  1. #21

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    Default

    As you can see, its actually pretty close. The spinner location on the Aeromomentum is a bit lower than where the Lycoming spinner location would be. With enough modifying it will work. But their is just enough modifying that I would rather start from scratch and go for an original look. The firewall and boot cowl are per plans and work great.

    Its also liquid cooled. So who needs a cowling anyways!
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  2. #22

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    Default Re: Nate Ashton's Kitfox SS7

    Thanks I guess you could use the existing cowl as a mold starting point. What prop are you using just planning ahead. The only thing that concerns me is the longevity of the engine. Not many in use yet. Also the 50 lbs of added weight in front of cg that will have to be countered.
    Last edited by Hawkertech; 11-28-2019 at 08:48 PM.

  3. #23

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    Default Re: Nate Ashton's Kitfox SS7

    I guess time will tell with the longevity. Maybe a glider rating wouldn't be such a bad idea:/ Prop is the Luga 69" ground adjustable. When designing the engine mount, we were able to press the engine much closer to the firewall then the lycoming would be. This brought the CG back to normal. It also meant I didn't have to add any forward sweep to the wings.

  4. #24
    Senior Member jrevens's Avatar
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    Default Re: Nate Ashton's Kitfox SS7

    Nate,

    That's an interesting looking engine mount design... aluminum? Just curious - did you do any stress or fatigue analysis? Nice workmanship.
    John Evens
    Arvada, CO
    Kitfox SS7 N27JE
    EAA Lifetime
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  5. #25

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    Default Re: Nate Ashton's Kitfox SS7

    That's my other concern, with that heavy engine cantalivered off that mount, with vibration.

  6. #26

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    Default Re: Nate Ashton's Kitfox SS7

    Quote Originally Posted by jrevens View Post
    Nate,

    That's an interesting looking engine mount design... aluminum? Just curious - did you do any stress or fatigue analysis? Nice workmanship.
    Yes, milled aluminum construction. Aeromomentum did the engineering along with the stress/fatigue analysis. It's designed and engineered for continuous 9'gs in all cardinal directions, and 2 to 1 safety factor. I think the wings will come off before the engine does.

  7. #27
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    Default Re: Nate Ashton's Kitfox SS7

    Honest question, and not trying to troll. Just curious why you went with aluminum and not steel or chrome-moly? Seems like steel is a better choice for engine mounts to help flex and dampen vibrations? Nice work for sure though.
    Dustin Dickerson

    Building 7ss STI x 2
    Oratex
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  8. #28
    Senior Member jrevens's Avatar
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    Default Re: Nate Ashton's Kitfox SS7

    Quote Originally Posted by Shadowrider View Post
    Honest question, and not trying to troll. Just curious why you went with aluminum and not steel or chrome-moly? Seems like steel is a better choice for engine mounts to help flex and dampen vibrations? Nice work for sure though.
    Nate can answer this for himself, but I just wanted to say that aluminum, in general, can be much more vulnerable to fatigue cracking than steel, which is a serious concern with something usually experiencing constant vibration (like an engine mount). Engine mounts are normally designed to be rigid structures... you don't want it to be flexing, whether steel or aluminum. That's the job of the rubber parts of the structure. And concerning flexibility, aluminum can be very flexible - just think about the spars in our Kitfox wings.
    John Evens
    Arvada, CO
    Kitfox SS7 N27JE
    EAA Lifetime
    Chap. 43 honorary Lifetime

  9. #29
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    Default Re: Nate Ashton's Kitfox SS7

    My experience is more with dirt bikes and mountain bikes. An aluminum frame is a lot stiffer than a steel. A steel frame has much more “flex” and dampens vibrations better.
    Dustin Dickerson

    Building 7ss STI x 2
    Oratex
    29" shock monster
    EP912STI 155hp
    Garmin
    N33TF......FLYING!
    N53TF......FLYING!

  10. #30

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    Default Re: Nate Ashton's Kitfox SS7

    Quote Originally Posted by Shadowrider View Post
    Honest question, and not trying to troll. Just curious why you went with aluminum and not steel or chrome-moly? Seems like steel is a better choice for engine mounts to help flex and dampen vibrations? Nice work for sure though.
    I share the same concerns and appreciate the questions! Long story short, Mark with Aeromomentum has been doing these engine mounts for over 10 years without any failures or indications of fatigue, to my knowledge. He was the most qualified available resource I had to bolt this engine on the plane. But doesn't mean I won't be keeping a close eye! I like to think about the cast engine ears bolted onto bigger conventional engines like the IO540, then bolted to an aluminum airframe with lord mounts in-between. Both materials should work if engineered correctly, I hope. Side note, my previous plane was a piper pacer which needed a new engine mount due to corrosion and zipties chafing through. (That was an expensive annual, thank goodness for experimental!)

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