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  #21  
Old 01-05-2010, 10:32 AM
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Mel Mel is offline
 
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Just as a reference point, my airplane is 17 years with well over 1000 hrs. and I have seen no cracking anywhere in the FAB set-up (built per plans). The last 750 hrs. have been with a compression ratio of 9.5:1 which I would assume would exasperate the problem.
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  #22  
Old 01-05-2010, 10:49 AM
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DanH DanH is offline
 
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Quote:
Originally Posted by JordanGrant View Post
Dan, does increasing the thickness of the plate effectively reduce the stress? (i.e., beefing up to a .090 plate instead of .063) If so, does that add 'cycles' nonlinearly as well?
I visualize the plate to be loaded like a diaphragm, so yes, increasing plate thickness increases distance from the neutral axis to the outermost fiber and thus lowers stress at the outermost fiber. Thickness has nothing to do with cycles. Cycles is simply the number of times the part is loaded and unloaded.
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  #23  
Old 01-05-2010, 11:12 AM
Lars Lars is offline
 
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Quote:
Originally Posted by JordanGrant View Post
Dan, does increasing the thickness of the plate effectively reduce the stress? (i.e., beefing up to a .090 plate instead of .063) If so, does that add 'cycles' nonlinearly as well?
From the looks of the photo in the original post, that appears to be a bending or diaphragm failure. Bending stress goes as 1/(thickness squared) so increasing the thickness from .063 to .090 will decrease stress by about a factor of 2 (.09^2/.063^2). That'll make an aluminum part last longer. I don't have a fatigue curve handy for aluminum, but it probably isn't quite linear, so no guess on life increase. As Dan wrote though, steel (including stainless alloys) has the handy property that, if you decrease the stress below the so-called endurance or fatigue limit, it will never fail. The question is what that stress level is, and how to determine what the stress is on the part, in practice.
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  #24  
Old 01-05-2010, 11:22 AM
Wilson Hoffman Wilson Hoffman is offline
 
Join Date: Dec 2007
Location: Oakland, California
Posts: 7
Default Charles Wilhite

I am amazed to see that people are buying stuff from Charles Wilhite again.
It was just 3 years ago that he stiffed a bunch of us with his composite
canopy ripoff. He still has $1200 of my money. Beware.
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  #25  
Old 01-05-2010, 05:27 PM
dmeloche dmeloche is offline
 
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After reading about an off-airport landing due to the carb partially falling off the bottom of the engine (nuts backing off) I've added a pre-flight check where I stick my hand in the inlet and make sure the airbox is not loose.

Doug
RV6 350hrs
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  #26  
Old 01-05-2010, 06:26 PM
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JordanGrant JordanGrant is offline
 
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Quote:
Originally Posted by dmeloche View Post
After reading about an off-airport landing due to the carb partially falling off the bottom of the engine (nuts backing off) I've added a pre-flight check where I stick my hand in the inlet and make sure the airbox is not loose.

Doug
RV6 350hrs
Yup, I actually do the same. My wife (and test pilot for first 40 hours) had the compression ring slip off during one of the test flights. The FAB got lodged in the bottom of the cowling, partially blocking airflow. This led to a partial loss of power. She declared an emergency and flew back to the airport and landed without incident. Now I tighten that thing WAY down and we also check it like you do prior to flight.
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  #27  
Old 01-05-2010, 07:41 PM
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JonJay JonJay is offline
 
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Default Safety those intake bolts.

Not sure if you where referring to the bolts to the carb/servo or the bolts to the airbox? I was not happy with the fold over tab method of safety from Vans so I used Phillister Head Bolts and safety wired.

If you where talking about the AN3's that hold the airbox on, I apologize. [IMG][/IMG]
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  #28  
Old 01-05-2010, 09:17 PM
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JordanGrant JordanGrant is offline
 
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Quote:
Originally Posted by JonJay View Post
If you where talking about the AN3's that hold the airbox on, I apologize.
The Airflow Performance setup is different. You bolt the FAB into a ring that goes around the intake of the throttle body. That ring is held on by "squeezing" force supplied by a hex-head bolt. Kind of hard to explain, but easy to understand if you saw a picture.
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  #29  
Old 01-06-2010, 06:55 AM
Don at Airflow Don at Airflow is offline
 
Join Date: Jun 2006
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Default Airbox plate

We've been making the air box plate for the FM-200 and FM-100 for Van's filtered air box out of .090 aluminum for a couple of years now. Seems the clearance of the box to the front of the cowl is important.

Don
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  #30  
Old 01-06-2010, 07:49 AM
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GLPalinkas GLPalinkas is offline
 
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Location: Venice, Fl
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Quote:
Originally Posted by JordanGrant View Post
The Airflow Performance setup is different. You bolt the FAB into a ring that goes around the intake of the throttle body. That ring is held on by "squeezing" force supplied by a hex-head bolt. Kind of hard to explain, but easy to understand if you saw a picture.
OK how about a picture. I will be assembling my FAB soon and don't want to re-invent the wheel if it works.
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