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08-09-2017, 08:42 AM
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Join Date: Jan 2005
Posts: 3,646
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Quote:
Originally Posted by RV6_flyer
The O-320 carb filter air box has the filter attached to a plate on the carb.
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Old design yes, but since at least 2007 the FWF instructions and kit for 0-320 have had the filter just sit in the FAB, just like you describe for 0-360. No longer bolted to carb plate.
__________________
Steve M.
Ellensburg WA
RV-9 Flying, 0-320, Catto
Donation reminder: Jan. 2021
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08-09-2017, 08:59 AM
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Join Date: Jun 2017
Location: Palm Springs, CA
Posts: 121
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Interesting replies. Yes - the air box also shows signs of fretting where the filter sits. I was going to beef-up the fibreglass, but an aluminium plate sounds like a good idea. Anyone have photos of a similar modification?
With regards to the design of the air box, I understand to the newer boxes have a bypass / carb heat inlet at the bottom where the Cone of Silence was located in mine. There is no hole under the cone, or evidence of there ever having been one.
I flew the aircraft without the cone last night and it appeared to run just the same.
Other than the cone, the aircraft looks to be a nice build to the point where people comment on it.
I moved to the US from the UK. Back there, you can only build to plans and any modifications need to be approved by our version of the EAA. My inspector there was excellent and I'm fairly sure he would have been all over this weird cone. I feel like I have let him down for not having spotted this.
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08-09-2017, 09:03 AM
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Join Date: Jan 2005
Location: NC25
Posts: 3,507
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Quote:
Originally Posted by alpinelakespilot2000
Old design yes, but since at least 2007 the FWF instructions and kit for 0-320 have had the filter just sit in the FAB, just like you describe for 0-360. No longer bolted to carb plate.
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I cracked so many of the carb plate to filter over the past 20-years that I now have one made out of titanium. The 320 B series of engines have the carb mounted as far aft on the oil sump that there is no trimming of the fiberglass FAB. This creates additional vibration causing cracks. The 320 B series sump typically are not used on the -A model RVs.
Not about to replace something that is still working.
__________________
Gary A. Sobek
NC25 RV-6 Flying
3,400+ hours
Where is N157GS
Building RV-8 S/N: 80012
To most people, the sky is the limit.
To those who love aviation, the sky is home.
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08-09-2017, 09:12 AM
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Join Date: Feb 2007
Location: colorado
Posts: 873
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Part of the inspection mentallity is...
What on this airplane has the potential to fail and kill me..?
If the engine keeps running chances of a bad outcome
Are greatly reduced... so what makes the engine quit in most cases?
Fuel supply or metering issue
Air blockage
Ignition failure rarely
My globe swife nearly did me in when a piece of 600mph foil tape made its way from the heat muff to the carb..choked until it quit.. an A&P put the tape in a place where if it came loose it would be an issue..
My airplane rarely flys more than 10 hours without the cowl coming off for a look see..
Cm
Airframe...flight controls
__________________
RV-4 "Mr. Twister"
Pitts S1S "Mexican Red" sold and missed
Mr. Twister Airshows
Rocky Mountain Renegades
the mission... have fun.
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08-09-2017, 09:18 AM
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Join Date: Jul 2005
Location: Hubbard Oregon
Posts: 9,035
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Quote:
Originally Posted by alpinelakespilot2000
Old design yes, but since at least 2007 the FWF instructions and kit for 0-320 have had the filter just sit in the FAB, just like you describe for 0-360. No longer bolted to carb plate.
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This is correct.
__________________
Opinions, information and comments are my own unless stated otherwise. They do not necessarily represent the direction/opinions of my employer.
Scott McDaniels
Van's Aircraft Engineering Prototype Shop Manager
Hubbard, Oregon
RV-6A (aka "Junkyard Special ")
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08-09-2017, 09:49 AM
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Join Date: Sep 2005
Location: Maple Grove, MN
Posts: 2,333
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Quote:
Originally Posted by jamlip
Interesting replies. Yes - the air box also shows signs of fretting where the filter sits. I was going to beef-up the fibreglass, but an aluminium plate sounds like a good idea. Anyone have photos of a similar modification?
SNIP
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I do not think aluminum under the filter is a great idea. I beefed mine up with fiberglass and epoxy at somewhere in the few hundred hour range. While the filter has worn into the new glass, it is still quite serviceable after another 1200 or so hours. If I need to re-glass it again, no big deal. I made sure all the new glass extended well out under the filter.
Aluminum undergoing cyclic stressing will fatigue and crack, the only question is over how many hours (yes, every part in our planes...). There are significant vibrations/movements on the floor of the air box, as the filter fretting into the bottom proves. Certain crack modes of the aluminum could send a piece into the engine. Why risk it?
__________________
Alex Peterson
RV6A N66AP 1700+ hours
KADC, Wadena, MN
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08-09-2017, 10:13 AM
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Join Date: Apr 2011
Location: Cincinnati, OH
Posts: 2,791
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Quote:
Originally Posted by jamlip
Interesting replies. Yes - the air box also shows signs of fretting where the filter sits. I was going to beef-up the fibreglass, but an aluminium plate sounds like a good idea. Anyone have photos of a similar modification?
With regards to the design of the air box, I understand to the newer boxes have a bypass / carb heat inlet at the bottom where the Cone of Silence was located in mine. There is no hole under the cone, or evidence of there ever having been one.
I flew the aircraft without the cone last night and it appeared to run just the same.
Other than the cone, the aircraft looks to be a nice build to the point where people comment on it.
I moved to the US from the UK. Back there, you can only build to plans and any modifications need to be approved by our version of the EAA. My inspector there was excellent and I'm fairly sure he would have been all over this weird cone. I feel like I have let him down for not having spotted this.
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cosmetics does not make and airplane good, it only makes it look good.
__________________
Steve Melton
Cincinnati, OH
RV-9A, Tip-up, Superior O-320, roller lifters, 160HP, WW 200RV, dual impulse slick mags, oil pressure = 65 psi, EGT = 1300F, flight hours = 800+ for all
Simplicity is the art in design.
My Artwork is freely given and published and cannot be patented.
www.rvplasticparts.com
Last edited by Steve Melton : 08-09-2017 at 10:17 AM.
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08-09-2017, 10:15 AM
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Join Date: Dec 2009
Location: Montreal
Posts: 1,456
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Quote:
Originally Posted by AlexPeterson
I do not think aluminum under the filter is a great idea. I beefed mine up with fiberglass and epoxy at somewhere in the few hundred hour range. While the filter has worn into the new glass, it is still quite serviceable after another 1200 or so hours. If I need to re-glass it again, no big deal. I made sure all the new glass extended well out under the filter.
Aluminum undergoing cyclic stressing will fatigue and crack, the only question is over how many hours (yes, every part in our planes...). There are significant vibrations/movements on the floor of the air box, as the filter fretting into the bottom proves. Certain crack modes of the aluminum could send a piece into the engine. Why risk it?
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I would expect (said he with NO data to back it up  ) that a plate on the floor of the box would reduce vibration. I think the vibration is due to the fact that the bottom is flat, and that is never good for stiffness. A slight crown makes all the difference.
When I riveted the top on the airbox, with the filter in place to obtain the right spacing, I guess something flexed or slipped so that now the filter is not a perfectly tight fit. I put a bead of RTV on the top of the filter so that I would get a good seal. I wonder now if that was a bad idea? Chunks of RTV have killed people as well. Perhaps I should just build up the floor with glass.
I'm glad the OP's experience ended well. Nothing like having runway in front of you. 10 seconds later.... I will be reviewing my airbox construction including the carb heat door. Thank you for posting this.
__________________
Scott Black
Old school simple VFR RV 4, O-320, wood prop, MGL iEfis Lite
VAF dues 2020
Instagram @sblack2154
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08-09-2017, 10:32 AM
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Join Date: Jul 2005
Location: Hubbard Oregon
Posts: 9,035
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Quote:
Originally Posted by sblack
I would expect (said he with NO data to back it up  ) that a plate on the floor of the box would reduce vibration. I think the vibration is due to the fact that the bottom is flat, and that is never good for stiffness. A slight crown makes all the difference.
When I riveted the top on the airbox, with the filter in place to obtain the right spacing, I guess something flexed or slipped so that now the filter is not a perfectly tight fit. I put a bead of RTV on the top of the filter so that I would get a good seal. I wonder now if that was a bad idea? Chunks of RTV have killed people as well. Perhaps I should just build up the floor with glass.
I'm glad the OP's experience ended well. Nothing like having runway in front of you. 10 seconds later.... I will be reviewing my airbox construction including the carb heat door. Thank you for posting this.
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The filters shrink over time. It mostly is evident in overall diam, but they do shrink in height also to some degree. I think this shrinkage is what primarily precipitates the wear (once it is no longer tight, vibration takes care of the rest).
I personally see no issue with bonding a piece of aluminum into the bottom to reduce wear. I would recommend not using any fasteners that if they failed, could be sucked into the engine. I do have a problem with adding soft material to the edge of the filter. It probably wouldn't cause any damage to the engine if ingested but if this is on a carburated engine, just a small piece lodged in the center venturi of the carb. could be enough to cause engine stoppage. I know of an RV-8 forced landing incident caused by exactly that.
__________________
Opinions, information and comments are my own unless stated otherwise. They do not necessarily represent the direction/opinions of my employer.
Scott McDaniels
Van's Aircraft Engineering Prototype Shop Manager
Hubbard, Oregon
RV-6A (aka "Junkyard Special ")
Last edited by rvbuilder2002 : 08-09-2017 at 02:35 PM.
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08-09-2017, 10:41 AM
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Join Date: Jan 2006
Location: Winston-Salem, N.C.
Posts: 1,213
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One more thing..
I have the variation per plans with the filter trapped between a bottom plate and an adapter plate bolted to the carb. The airbox then screws to the adapter plate. While on the subject of all this, I have found on mine, and other RV's the airbox snorkle to air inlet can be so tight that all engine movement/shake is transferred to the carburetor attach studs, and bowl screws, eventually leading to a loose carb. assembly, which leads to intake leak/backfiring and the associated problems to follow.Certainly, this shaking/movement doesn't help any of the fiberglass or aluminum parts. I made my rubber interface a bit more flexible (larger space between snorkle and inlet) and have never had the problem again. 300 hrs. since the adjustments, and no more loose carb. issues, no chaffing, no cracked adapter plates.
__________________
Bill E.
RV-4/N76WE
8A7 / Advance NC
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