AirTalk.org Aviation discussions newsgroups   Archives   FAQ   Search   Memberlist   Usergroups   Register   Profile   Log in to check your private messages   Log in  Engine Balancing and Resonance Vibration Problem          AirTalk.org Forum Index -> Owning Airplanes View previous topic :: View next topic   Author Message AllanFuller Guest Posted: Wed Sep 07, 2005 2:16 am    Post subject: Engine Balancing and Resonance Vibration Problem Fly Wrote: Quote: I concur with ToeCutter. Especially in your case, you need two vibration sensors, fore and aft to gather info on the engine and prop. You can surmise what th crankshaft balnce quality is. You cannot do it with one sensor alone unless yo move the sensor to different locations during subsequent runs.. Your post stroungly suggests you need to get find someone o experience to give you good advice. I wonder where are you located? Wish I could help with a good answer but internet makes it difficult. Answer is only a good as the information provided. couple of other things: Sounds as if the operator has a Micorvibe DSS prop balancing rig. Their manual suggest checking the balnce at 2000 rpm. Usually I find higher amplitudes of imbalnce and sometimes differen phase at higher rpms. The previous balance of 13 washers was beyond the FAA approved maximum correction. After 600 hours, the isolation mounts can take a set, maybe even have metal-to metal contact between the bolt and engine mount. I recall Toecutter suggesting at least a rotation every 500 hours. Doublecheck the ring gear installation. It will only go on in on position. And verify the crankshaft index bushing is in the correct location fo your engine. How are you percieving the resonance at 1500? How did you measure th freq? have you consider that it might be an idle mixture problem? good luck Kent Felkins Tulsa Ok. Reply below in quotes: Fly Wrote: Quote: I concur with ToeCutter. Especially in your case, you need two vibration sensors, fore and aft to gather info on the engine and prop. You can surmise what th crankshaft balnce quality is. You cannot do it with one sensor alone unless yo move the sensor to different locations during subsequent runs.. "Thank you for the suggestion. It is something to learn mor about and try." Your post stroungly suggests you need to get find someone o experience to give you good advice. "That is why I have posted this request for information. We ar learning a lot through this process. The feedback is good and opens u a number of things to think about and try. There is a problem tha probably was in the engine when it was new. The prop overhaul ha either added to the problem or heightened the concern. One would thin the engine/prop should be smooth as silk since the engine is relativel new and the prop has been just overhauled. I spend a lot of mone keeping the plane in good repair. I have owned it since 1985. When i is not right, I know it quickly." I wonder where are you located? "Nashua, NH" Wish I could help with a good answer but internet makes it difficult. Answer is only a good as the information provided. couple of other things: Sounds as if the operator has a Micorvibe DSS prop balancing rig. Their manual suggest checking the balnce at 2000 rpm. Usually I find higher amplitudes of imbalnce and sometimes differen phase at higher rpms. "It is a chadwick-helmuth spectrum analyzer." The previous balance of 13 washers was beyond the FAA approved maximum correction. After 600 hours, the isolation mounts can take a set, maybe even have metal-to metal contact between the bolt and engine mount. I recall Toecutter suggesting at least a rotation every 500 hours. Doublecheck the ring gear installation. It will only go on in on position. And verify the crankshaft index bushing is in the correct location fo your engine. "We Will double check the ring gear." How are you percieving the resonance at 1500? How did you measure th freq? "The vibration is by feel as the engine RPM is reduced from 200 to idle slowly. The vibration increases as one slows to 1500, peaks a 1500 and decrease to normal engine vibration." have you consider that it might be an idle mixture problem? "No, net yet, but something to consider." good luck "Thank you. Next step is to double check the prop at the prop shop." Kent Felkins Tulsa Ok. -- AllanFuller Back to top Fly Guest Posted: Wed Sep 07, 2005 2:05 pm    Post subject: Re: Engine Balancing and Resonance Vibration Problem You message suggests that the washers are bolted at the holes on the circumference of the ring gear. IIRC, your prop model has the extended hub. Extended hubs do not respond very well to balance correction at the ring gear because the plane of correction is not close to the plane of imbalnce. Sure, a balance can be achieved but the amount of correction weight will be 30-50% more that if placed closer to the plane of imbalance. After the prop is installed again, the final dynamic balance should be checked above 2300 rpm. 2000 rpm readings are not valid. Kent Felkins Back to top Display posts from previous: All Posts1 Day7 Days2 Weeks1 Month3 Months6 Months1 Year Oldest FirstNewest First         AirTalk.org Forum Index -> Owning Airplanes All times are GMT Page 1 of 1   Jump to: Select a forum Aviation----------------alt.aviationAviation safety EnhancementPlanes, gliders and flying in AustraliaAviation et pilotage (Français)rec.aviationAviation (Aerobatics)Hot air, gas balloons and airshipsHang-gliding, paragliding, foot-launched flightAircraft Design & BuildingInstrument Flight RulesAviation (Classifieds)Military AircraftNaval AviationAviation (Miscellaneous Topics)Owning AirplanesAviators (General Discussions)Aviation related productsAircraft RestorationHelicopters and rotary wing aircraftsFlight SimulationSailplanesAviation (Students)Light aircraftFlying related activities in the UK Airports----------------alt.airportsEdinburgh Airport Glasgow Airport Humberside Airport Luton Airport Aberdeen Airport Glasgow Prestwick Airport  You cannot post new topics in this forum You cannot reply to topics in this forum You cannot edit your posts in this forum You cannot delete your posts in this forum You cannot vote in polls in this forum Powered by phpBB © 2001, 2006 phpBB Group SEO toolkit © 2004-2006 webmedic.