---------------------------------------------------------- RV4-List Digest Archive --- Total Messages Posted Fri 03/26/04: 2 ---------------------------------------------------------- Today's Message Index: ---------------------- 1. 06:01 AM - Re: (Pat Perry) 2. 12:15 PM - Re: (rob ray) ________________________________ Message 1 _____________________________________ Time: 06:01:15 AM PST US From: "Pat Perry" Subject: RE: RV4-List: --> RV4-List message posted by: "Pat Perry" Check all of your cowl clearances. One little contact point from the engine, airbox, or baffle will cause a loud noise in the airfram. If the engine has a slight orbital cycle like a gyroscope gets when it is wandering off its axis I could imagine it making that kind of noise. I had a slight contact point with my airbox and cowl that would make a load noise during any 1.2G or more manuver that drove me nuts until I moved the box 1/4" to the left. Pat Perry Dallas, PA RV-4 N154PK Flies great! >From: "Cye Vaughan" >Reply-To: rv4-list@matronics.com >To: >Subject: RV4-List: Date: Thu, 25 Mar 2004 15:55:49 -0800 > >--> RV4-List message posted by: "Cye Vaughan" > >I have a strange one. My RV-4 with 36 total hours (Van's 180 Lyc, Sensenich >metal prop) has a very strange harmonic that seems to run through the >airframe. This happens in level flight, mostly above 140 mph indicated at >8000' and as speed is increased toward 170 indicated it seems to beat at a >faster rate. Rpm is between 2300-2500. If you have ever flown a twin with >the engines slightly out of synch you would recognize the sound. Kind of a >"wow-wow-wow" sound. I had the prop checked for balance and it was so good >it didn't need any balancing. > >There is no apparent vibration in any of the controls, everything outside >is tight, canopy locks down tight. This is a good airplane, flies straight, >and except for this strange sound I couldn't be happier with it. > >If anyone has heard of or experienced this problem I would sure like to >hear about it. By the way, I called Van's and spoke to one of his guys who >had never heard of this. > >Cye Vaughan >Elko NV >cyenjoy@ctnis.com > > download! http://toolbar.msn.com/go/onm00200413ave/direct/01/ ________________________________ Message 2 _____________________________________ Time: 12:15:43 PM PST US From: rob ray Subject: RE: RV4-List: --> RV4-List message posted by: rob ray Pat, I hate to say it, but my RV4 had the exact same airframe vibrations with a Sensy metal prop. I tried dynamic balancing, harmonic dampener and many different power settings and finally sold the prop and put a Catto on. Problem solved. That's not to say you have the same problem, but I tried a second sensy from a friend to "break it in" for him and get some performance numbers. Again, the same problem re-appeared. When I re-mounted my Catto prop, problem solved. One thing I would re-check is the mag timing and Electronic Ignition timing if you have it. It's critical on an 0-360. Also, dynamic balancing is cheap insurance, that might help too. For me, prop removal was the fix. Good Luck. Rob Ray Pat Perry wrote: --> RV4-List message posted by: "Pat Perry" Check all of your cowl clearances. One little contact point from the engine, airbox, or baffle will cause a loud noise in the airfram. If the engine has a slight orbital cycle like a gyroscope gets when it is wandering off its axis I could imagine it making that kind of noise. I had a slight contact point with my airbox and cowl that would make a load noise during any 1.2G or more manuver that drove me nuts until I moved the box 1/4" to the left. Pat Perry Dallas, PA RV-4 N154PK Flies great! >From: "Cye Vaughan" >Reply-To: rv4-list@matronics.com >To: >Subject: RV4-List: Date: Thu, 25 Mar 2004 15:55:49 -0800 > >--> RV4-List message posted by: "Cye Vaughan" > >I have a strange one. My RV-4 with 36 total hours (Van's 180 Lyc, Sensenich >metal prop) has a very strange harmonic that seems to run through the >airframe. This happens in level flight, mostly above 140 mph indicated at >8000' and as speed is increased toward 170 indicated it seems to beat at a >faster rate. Rpm is between 2300-2500. If you have ever flown a twin with >the engines slightly out of synch you would recognize the sound. Kind of a >"wow-wow-wow" sound. I had the prop checked for balance and it was so good >it didn't need any balancing. > >There is no apparent vibration in any of the controls, everything outside >is tight, canopy locks down tight. This is a good airplane, flies straight, >and except for this strange sound I couldn't be happier with it. > >If anyone has heard of or experienced this problem I would sure like to >hear about it. By the way, I called Van's and spoke to one of his guys who >had never heard of this. > >Cye Vaughan >Elko NV >cyenjoy@ctnis.com > > download! http://toolbar.msn.com/go/onm00200413ave/direct/01/ ---------------------------------