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Mixture arm and lower cowl contact

CharlieWaffles

CharlieWaffles

Well Known Member
Has anyone else had their mixture arm contact the contour in the lower cowl? I have adjusted my mixture arm to be as far back for full rich as possible and still have the full throw of the push/pull cable to get to ICO. But just before full rich it was impacting the cowl as it slopes down to the lower portion near the FAB air inlet. I ground the inner glass back a bit but I'm beginning to wonder if I need to create a blister and grind way some more room for when the engine shakes on start/stop.

I search and saw posts for a similar problem with the RV9, but didn't see anything with the 10.
 
Mark,
Do you have photos? I am not sure how you could have the mixture arm in contact with the lower cowl. I bet I have 4-6" of clearance under the FAB to the cowl. Which servo do you have? I will be down at the hangar this morning and will try to get a shot from the rear cowl lower inlet and take a look at the distance the arm is from the side and bottom of the cowl.
 
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Control arm choice

I had a problem like this on my 7. I didn't know at the time that several different length and offset control arms were made for it.
Perhaps you only need a different control arm to clear the cowl.
 
Bill.Peyton said:
Mark,
Do you have photos? I am not sure how you could have the mixture arm in contact with the lower cowl. I bet I have 4-6" of clearance under the FAB to the cowl. Which servo do you have? I will be down at the hangar this morning and will try to get a shot from the rear cowl lower inlet and take a look at the distance the arm is from the side and bottom of the cowl.
Click to expand...

I'll try to take one, hard to get a picture in there. I have the standard Airflow Performance FI. Also, the contact is from the mixture arm to the side of the lower cowl scoop - not from the bottom of the FAB to the cowl.
 
Trying to visualize this. So you're saying your mixture control arm extends beyond the side of the FAB so that it is now hitting the interior side of the scoop? Is the control cable rod end attached inboard or outboard on the control arm? Also just to cover the bases did you install the 131Q recess on the FAB (just want to rule out it's not hitting the FAB vs the cowl)?
 
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Correct, the mixture arm (more specifically the MS nut) holding the push/pull cable contacts the interior side of the scoop (right at the top of the scoop/radius). The 131Q is on the FAB and the fab portion is fine and the arm clears.

I've thought about getting a mixture arm that isn't bent as far out, but then it seems like it might hit the FAB.

Here are some reference pictures:

May12201311_zpsf8270fa3.jpg


Capture-14_zps52d584a6.gif
 
I can’t see the pics at work (some setting they have turned off on the browser). But based upon your description, I seem to remember others having this problem and IIRC the solution was a different control arm like JD suggests. If no one chimes in with a fix, search the RV-10 forum over on Matronics and I think you’ll find your answer.
 
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Yeah I saw that, but figured it might give you some more folks to reach out to. It might be worth it to call Don at AFP to see what options they have to reduce the width of the bolted up assembly. We've got to be missing something fundemental though as apparantly this is a rare issue-- I mean it's not like you're the only guy running AFP.
 
Yes, I had the same issue. Not the nut, but the threaded end of the bolt just touched. But I cannot recall from home what I did. Sanded the cowl a bit, extra washer under the bolt head, ground down the bolt a bit, re-clocked the arm? Next time I'm at the hangar I'll check my notes.
 
I just checked mine and while it is not hitting the fg, it is hitting the silver in the self adhesive insulation. Mine is just barely rubbing, apparently only when I shut down the engine. I will post a photo when I get back home. It appears I'd I reverse the direction of the bolt and put the nut on the inside it would take care of the situation. Have you tried to adjust the arm position on the shaft?

IMG_2901.JPG
 
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Bill, I tried reversing the bolt and the nut assembly is longer and interferes with the cutout in the FAB. So far I've cut the bolt a smidge shorter (still have 1 thread past MS nut), re-clocked the arm as far back as possible and it clears, but it will likely rub during vibration like yours has.
 
It may be easier to reverse the bolt and modify the FAB then the cowl. I know that over the past 140 hours my engine has sagged at least 1/8" which may have contributed to the interference. I'm going to pull the lower cowl next week to investigate further. Let us know what you come up with.
 
Mine was initially the same as yours and Bill's. Grind, sand, turn the bolt around, and do what you have to do to get the clearance.
 
mixture arm

I'll offer a solution, call airflow performance and ask for the shortest straight arm they have. problem solved
 
I did the same - reversed the bolt/nut for extra clearance toward the cowl. The clearance toward the FAB plate is rigid and fixed, so you can get closer there. Still a bit tight but no rubbing.
 
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