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Thread: SC with Dynafocal mount - engine clearance problems

  1. #1

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    SC with Dynafocal mount - engine clearance problems

    A friend bought a very nice looking SC recently. the rebuilder put a lot of experimental parts on it, that have been removed and replaced with certified. (waste of time IMHO) But the main issue is the engine and mount. A wide deck 160 hp 320 was installed using the STC from CC for this application. But there is no clearance between the plug for the screen and the engine mount. So far we've determined the lord mounts installed are not correct, they are a smaller diameter than what the STC calls for, which leads me to believe the engine mount is not correct as the spec'd lord mount don't fit the engine mount. There is no p/n on the mount that we can find.

    I know that someone out here knows what the issue is...any help appreciated.
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  2. #2
    wireweinie's Avatar
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    Pics of the lord mounts/hardware?

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    Life's tough . . . wear a cup.

  3. #3

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    The owner has spent the morning on the phone with CC, Lord, Airframes Ak, and Svenn's Aviation in Wi. Svenn had the most info so far. CC never built a mount for the STC, so this is a Rubik's cube of parts. The are 3 versions of the mount installed J-7402-1, -16, -24. Headed to see if he can do a side by side comparison of those mounts. The lord mount called out in the STC is J-9613-40 which doesn't match up with the diameter of the cups in the mount.

    Thanks for the help.

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  4. #4
    supercrow's Avatar
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    I have run into this on 2 occasions, but both were wag-aero mounts on exp. aircraft of my own build. The first one was many yrs. ago but as I recall it was interference with a standard super cub exhaust tail pipe. The second a couple yrs. ago was on an 0360 base and was hitting in the same place as your picture. In both cases I welded in a new tubing ( one was a straight and the last was a type of dog-leg) and cut out the tubing where it was rubbing. In neither case was the interference in the dynafocal ring itself, but in the straight tubing to the right and below the ring. I have kept an eye on both and there have been no issues with either of them. In a certified aircraft you won't be able to do this type of mod, but I suspect the mount may be an exp. type?

  5. #5

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    I went through this debacle years ago when I was researching an engine install in my PA18A. I wanted a dynafocal mount which led me to the CC STC. I was somewhat taken back in a conversation with CC's that they did not have an engine mount to attach the STC listed dynafocal engines to the airframe. CC's told me I didn't want a dynafocal mount anyways. I just moved on. That experience led me to two questions. How incompetent was the FAA in issuing an STC for an engine install with no physical way to attach the engine to the airplane, and how incompetent would an A&P/IA have to be to try and jury rig such a thing? Inquiring minds want to know although I think I know the answer to both questions.

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    gntw's Avatar
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    Mount

    Quote Originally Posted by bubb2 View Post
    I went through this debacle years ago when I was researching an engine install in my PA18A. I wanted a dynafocal mount which led me to the CC STC. I was somewhat taken back in a conversation with CC's that they did not have an engine mount to attach the STC listed dynafocal engines to the airframe. CC's told me I didn't want a dynafocal mount anyways. I just moved on. That experience led me to two questions. How incompetent was the FAA in issuing an STC for an engine install with no physical way to attach the engine to the airplane, and how incompetent would an A&P/IA have to be to try and jury rig such a thing? Inquiring minds want to know although I think I know the answer to both questions.
    I put pen Yan 180 hp engine in my cub 18 yrs ago .uses dynafocal mount with the big lord mounts . Kit came with airbox lower cowl nose bowl and hard ware with stc. Check with them
    Thanks bubb2 thanked for this post

  7. #7

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    Quote Originally Posted by gntw View Post
    I put pen Yan 180 hp engine in my cub 18 yrs ago .uses dynafocal mount with the big lord mounts . Kit came with airbox lower cowl nose bowl and hard ware with stc. Check with them
    That's exactly what I did.

  8. #8
    SteveE's Avatar
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    That’s what I have but I think Aero owns that stc now. Randy Rupert still builds the cowl for it, we’ll actually his son Logan. I think he originally designed that stc and sold it to pen yan. I’d call them and I bet u get the correct answer


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  9. #9

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    When I bought the STC it was from Aero. I heard they sold it again, Not sure to who.

  10. #10
    Crash, Jr.'s Avatar
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    This isn't an O-360 conversion. It's an O-320 dynafocal mount installed under a CubCrafters STC that they no longer support apparently.

    My question is what is the goal? Just to be able to get clearance between the plug and the mount? Or do you want to be able to remove the plug with the engine installed? This may end up being a lot of hassle for something that you may want to just move past as long as it isn't causing a safety issue.

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    Quote Originally Posted by Crash, Jr. View Post
    This isn't an O-360 conversion. It's an O-320 dynafocal mount installed under a CubCrafters STC that they no longer support apparently.

    My question is what is the goal? Just to be able to get clearance between the plug and the mount? Or do you want to be able to remove the plug with the engine installed? This may end up being a lot of hassle for something that you may want to just move past as long as it isn't causing a safety issue.
    You're missing the point. Cub Crafters NEVER supported the STC. I don't think there is any way to legally install that STC. Jury rig it maybe. Legal, no.

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    What an interesting topic. I am aware of one 160 HP on an 18 (a PA-18-95 converted). I have never seen the logs, but it goes through annual easily, and has for two decades. One relatively expensive annual about seven years ago had the shop (FAA repair station) questioning the mount, but apparently they got paperwork from somewhere. Not wanting to open a can of worms, I don't think I will look.

    My Decathlon has the straight mounts that look a lot like stock Super Cub mounts. They seem to work fine.

  13. #13

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    Quote Originally Posted by bob turner View Post
    Not wanting to open a can of worms, I don't think I will look.
    Excellent idea.

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    Steve Pierce's Avatar
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    What model O-320? I have never seen that style suction screen on an O-320 model that is approved under Cub Crafters STC. Wag Aero makes the dyna-focal O-320 engine mount for the Super Cub. Curious why you say Cub Crafters doesn't support that STC. Vera called me about it recently to answer a question for a customer.

    Do you dimensions of the cups? I have pictures and notes on the Lord mounts if we are talking about the same mount.
    Steve Pierce

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    It's an O-320 D3G which is covered under the CC STC, along with most other O-320 models. The problem is that the STC specifically calls for J-9613-40 x4 mounts. Those mounts are 3 inches in diameter. I believe to be legal one would have to use what is called for in the STC. CC never built or Sub'd a Dynafocal mount. They have a drawing of a mount and they have a cross section drawing depicting how the 9613-40 mounts are to be installed but a mount that accommodates the 9613-40 was never built and certified.

    The current shock mount depicted in the photos above is a J-7402-1. According to Lords, the difference between the -1,-16, and -24 mounts is the insert and the elastomer used. These mounts are used in PA-28's 140-180. According to the Piper repair manual, if you are replacing 1-3 use the specific mount. If you are replacing all of them then use the -24 mounts.

    I guess the big issue here is finding an STC that is valid for the engine, mount, and shock mount. I think that if you don't follow the STC guidance its not valid. I believe a hard mount would need to be built according to the CC STC drawings or another STC purchased from someone else depicting the use of the 7402 mounts, or equivalent, that will also provide adequate clearance for the suction screen cap. I could be very wrong though. I am not above reproach.
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    Last edited by NoodleF15E; 01-12-2022 at 11:32 AM.

  16. #16
    Steve Pierce's Avatar
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    Anyone know how the Wag Aero dynafocal engine mount compares to the CC drawing? If you had the 72362 sump with separate suction screen would everything fit ok vs the LW-10828 sump and integrated suction tube? As far as I can see if the mount was built to the CC STC you don't need an STC for the mount.

    From my notes on the subject:
    Just got off the phone with Lords.
    J7401 is the component piece #
    J7402-16 is the kit# with steel inserts.
    J7402-24 is the kit # with the jell inserts.
    Looks like the steel inserts come on the 150hp and the jell comes on the 160hp pa-28. She also said the jell is for low hormonic damping at start up and idle.
    Steve Pierce

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    Thats correct about the Lord mounts. I believe you are also correct about the hard mount. The sump question is an unknown, but I will investigate that. The problem is all the mounts available use a 2 ¾" cup and the CC STC calls for a 3" cup to accommodate the 9613-40 isolators. Wag Aero sells a Type 1 Dynafocal mount that use the smaller cups. Airframes Alaska also sells one, but I believe its for a different application. Wag Aero sells an EXP version only. The big ? is: If the STC calls for specifics, isn't it a requirement to follow those. Maybe I am being too Type A/OCD, but it seems to reason.

    Svenn's Aviation (good Guy), in WI also sells the O320 STC. He built his own mount with smaller cups that went with the STC but doesn't currently have any available. It provides ample clearance.

    The primary concern, obviously, is safety. That cap hitting the frame is no bueno. It will eventually damage the mount or worse crack the oil case. Secondly is legality. Its a Certified Cub and regardless of opinion, it should be done correctly. "Correctly" seems to be like beauty, its in the eye of the beholder.

    Thank you all for your help.
    Last edited by NoodleF15E; 01-12-2022 at 03:21 PM.

  18. #18

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    This is what the O-320 D3G parts manual calls for. I don't know if the 72362 can be substituted and the 72362 is $4,000.00 Yikes



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  19. #19
    skywagon8a's Avatar
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    Quote Originally Posted by NoodleF15E View Post
    It's an O-320 D3G which is covered under the CC STC, along with most other O-320 models. The problem is that the STC specifically calls for J-9613-40 x4 mounts. Those mounts are 3 inches in diameter. I believe to be legal one would have to use what is called for in the STC. CC never built or Sub'd a Dynafocal mount. They have a drawing of a mount and they have a cross section drawing depicting how the 9613-40 mounts are to be installed but a mount that accommodates the 9613-40 was never built and certified.

    The current shock mount depicted in the photos above is a J-7402-1. According to Lords, the difference between the -1,-16, and -24 mounts is the insert and the elastomer used. These mounts are used in PA-28's 140-180. According to the Piper repair manual, if you are replacing 1-3 use the specific mount. If you are replacing all of them then use the -24 mounts.

    I guess the big issue here is finding an STC that is valid for the engine, mount, and shock mount. I think that if you don't follow the STC guidance its not valid. I believe a hard mount would need to be built according to the CC STC drawings or another STC purchased from someone else depicting the use of the 7402 mounts, or equivalent, that will also provide adequate clearance for the suction screen cap. I could be very wrong though. I am not above reproach.
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    Quote Originally Posted by NoodleF15E View Post
    Thats correct about the Lord mounts. I believe you are also correct about the hard mount. The sump question is an unknown, but I will investigate that. The problem is all the mounts available use a 2 ¾" cup and the CC STC calls for a 3" cup to accommodate the 9613-40 isolators. Both Univair and Wag Aero sell Type 1 Dynafocal mounts and both mounts use the smaller cups. Airframes Alaska also sells one, but I believe its for a different application. Univair and Wag Aero both sell STC and EXP versions. I believe the currently installed mount is a Univair or WAG Aero from the looks of it, but not certain. Whether it is STC'd, I don't know, and whether using either is legal under the CC STC is also unknown. The big ? is: If the STC calls for specifics, isn't it a requirement to follow those. Maybe I am being too Type A/OCD, but it seems to reason.

    Thank you all for your help.
    Since you haven't shown the 1st page of the STC, I'll assume the rest of what you've shown is part of it. With that assumption the drawing shown is the proper approved drawing. Using this drawing you are authorized to build your own engine mount under the authority of "owner produced parts". IF CC had made the mount for sale, they would have been required to get PMA authorization to manufacture the mount for you. However with the approved information you can legally make your own.

    I do not see the material specs for the tubing.
    N1PA

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    If I understand this, the 101950-1 mount is nonexistent? That is a bigger issue that the mount rubbers. Sounds like the STC is pretty much worthless for a dynafocal installation if that part number engine mount isn't available.

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    Do you know what mount you have now? It might be possible to do a deviation to your existing CC STC to allow a different engine mount, but you indicated the existing mount doesn't provide clearance. I guess the correct methodology is to define the configuration that will work, then come up with the paperwork that defines the configuration you have. First confirm that the engine you have actually conforms to the D3G configuration. If not, what configuration does it conform to, and does that configuration conform to one of the STCs? Next, either buy the STC and related parts that will make it work, reconfigure the engine so it conforms to one of the STCs, then use an engine mount called for on the STC you are using or get a deviation to the STC (Either field approval or DER approval) that allows a different engine mount.

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    I was not correct when I said Univair and Wag Aero sell STC mounts. Only Wag Aero carries the Dynafocal mount for the O-320 and it is Experimental. "Code 8" The only place that I have found that has a STC approval for the O-320 series with a Type 1 Dynafocal mount is Svenn's Aviation.
    Last edited by NoodleF15E; 01-12-2022 at 03:38 PM.
    Thanks vj88 thanked for this post

  23. #23

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    Quote Originally Posted by dgapilot View Post
    Do you know what mount you have now? It might be possible to do a deviation to your existing CC STC to allow a different engine mount, but you indicated the existing mount doesn't provide clearance. I guess the correct methodology is to define the configuration that will work, then come up with the paperwork that defines the configuration you have. First confirm that the engine you have actually conforms to the D3G configuration. If not, what configuration does it conform to, and does that configuration conform to one of the STCs? Next, either buy the STC and related parts that will make it work, reconfigure the engine so it conforms to one of the STCs, then use an engine mount called for on the STC you are using or get a deviation to the STC (Either field approval or DER approval) that allows a different engine mount.
    Agreed. That is what I will work towards. Uncertain what is currently installed. I will have to dig to see.

  24. #24
    RaisedByWolves's Avatar
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    I put airforms baffles on an exp cub this year and they hit the mount. Airforms said yeah we had someone who had that problem, one manufacture mount is a different length or something. I had to modify the baffles to fit. Last (certified) cub I put airforms on, they fit no problem


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  25. #25

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    FWIW….another very valuable source of info I haven’t seen mentioned here….Charley Center. He has worked with many certified and experimental mounts, dynafocals, and other STCs and has great insight into what works with what. He’s been at this stuff long enough he’s seen pretty much all of it. Doesn’t cost anything but time to see what light he might shed on this. Just a thought. He’s a good guy and has been very helpful to me in the past.

    Regards, Oz
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  26. #26

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    Quote Originally Posted by OzAK View Post
    FWIW….another very valuable source of info I haven’t seen mentioned here….Charley Center. He has worked with many certified and experimental mounts, dynafocals, and other STCs and has great insight into what works with what. He’s been at this stuff long enough he’s seen pretty much all of it. Doesn’t cost anything but time to see what light he might shed on this. Just a thought. He’s a good guy and has been very helpful to me in the past.

    Regards, Oz
    Fairbanks
    Thanks for the post. Are you referring to Crosswinds STOL in Wasilla, AK?

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    Quote Originally Posted by NoodleF15E View Post
    Thanks for the post. Are you referring to Crosswinds STOL in Wasilla, AK?
    Yes, Charley Center is Crosswinds STOL. The Cub guru for many years.....

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    Quote Originally Posted by NoodleF15E View Post
    Thanks for the post. Are you referring to Crosswinds STOL in Wasilla, AK?
    Yep, thanks Narrow Deck, beat me to it. Charley is a walking talking encyclopedia of all things Cub.

  29. #29
    Cub Builder's Avatar
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    Quote Originally Posted by Steve Pierce View Post
    Anyone know how the Wag Aero dynafocal engine mount compares to the CC drawing?

    From my notes on the subject:
    I put a wide deck O-320-E2G on my Cubby using the Wag Aero dynafocal mount. I think the guy at Aero Fabricators is dyslexic among other problems. It was built as a reverse image and had >10° of nose down down thrust in the mount. It sat on the shelf for several months before I mounted it and found the issues. The reverse image wasn't a problem as I wasn't using a stock Cub exhaust (I had bought one from them, but it was also FUBAR and had been returned). I ended up cutting the mount apart and rebuilding it to take out most of the down thrust. I don't recommend the Wag Aero mount unless you are looking for something to use as a starting point to build your own. I mated the engine to the mount using the J-7402-16 Lord mounts. It all worked out pretty well but wasn't exactly a usable bolt on mount out of the box.

    -Cub Builder
    Last edited by Cub Builder; 01-15-2022 at 02:41 PM.

  30. #30
    supercrow's Avatar
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    Agreed. Please see post # 4 on this thread. Same issues and corrected them and have had very good service from the mounts. But certainly not plug and play.

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