Original Posted By: Rick Holland
I concluded vibration testing on my A75 today, with good results.Recall that before balancing, the Dynavibe was showing 0.51 IPSimbalance at 2150 RPM, which was maximum static at the condition onDec. 18. We ran some other tests using a different carb venturiand adjusted the engine thrust line, but those had nothing to dowith the vibration work. An interim test run using longer AN6 propbolts with four stacked washers under the heads resulted in a reductionof vibration to 0.27 IPS at 2150 RPM, with just a slight radialchange in location of the heavy side of the prop. We were on theright track.Today we added a small 'flyweight' clamped between the two prop boltsacross from the side of the prop that the Dynavibe had identifiedas heavy. It was purposely made a bit heavier than we think willbe the final shape of it, allowing for rounding of the edges andthen applying paint (it's 4130 steel). Warmed up the engine andran the Dynavibe averaging again, and achieved 0.07 IPS and nowthe heavy side has shifted radially on the hub, indicating thatwe would be chasing small changes from here on, with very limitedways of offsetting the heaviness. So, we called it more thanjust good (Dynavibe says to shoot for no more than 0.1 IPS).Cowlings back on, engine warmed up, and a test flight in "Scout" wasjust deee-lightful!!! What a joy, not only in the buttery smoothnessof the engine, but leveling out at cruise, the change in enginethrustline offset was very rewarding. Hands off, feet off, halftank of fuel, and the yaw is almost gone... a half-ball of left turning,which a very light touch on the right rudder would stop instantly. Inever thought this would be a hands-off airplane, but it's getting veryclose! We'll reinstall the bent-metal trim tab on the rudder andI'll bet the next flight will show NO yawing tendency with feet offthe rudders. This airplane is getting sweeter with every tweak we giveit. Of course, it was clear and COLD here today (mid-40s) so Scoutclimbed wonderfully, but still- the improvements are noticeable anduseful.This is why we call it 'EXPERIMENTAL', and why we love doing it ;o)Oscar ZunigaAir Camper NX41CC "Scout"San Antonio, TXwebsite at http://www.flysquirrel.net ________________________________________________________________________________Date: Sun, 26 Dec 2010 19:55:12 -0700Subject: Re: Pietenpol-List: One wing ready for paint
Pietenpol-List: One wing ready for paint
Pietenpol-List: One wing ready for paint
Original Posted By: Oscar Zuniga
Howdy,I have one wing ready to paint and should have both wings done by sundayevening.Stewart Systems still A+.Dave--------Covering PietRead this topic online here:http://forums.matronics.com/viewtopic.p ... ttachments: http://forums.matronics.com//files/2010 ... __________
Howdy,I have one wing ready to paint and should have both wings done by sundayevening.Stewart Systems still A+.Dave--------Covering PietRead this topic online here:http://forums.matronics.com/viewtopic.p ... ttachments: http://forums.matronics.com//files/2010 ... __________
Re: Pietenpol-List: vibration testing
Original Posted By: "Ryan Mueller"
I concluded vibration testing on my A75 today, with good results.Recall that before balancing, the Dynavibe was showing 0.51 IPSimbalance at 2150 RPM, which was maximum static at the condition onDec. 18. We ran some other tests using a different carb venturiand adjusted the engine thrust line, but those had nothing to dowith the vibration work. An interim test run using longer AN6 propbolts with four stacked washers under the heads resulted in a reductionof vibration to 0.27 IPS at 2150 RPM, with just a slight radialchange in location of the heavy side of the prop. We were on theright track.Today we added a small 'flyweight' clamped between the two prop boltsacross from the side of the prop that the Dynavibe had identifiedas heavy. It was purposely made a bit heavier than we think willbe the final shape of it, allowing for rounding of the edges andthen applying paint (it's 4130 steel). Warmed up the engine andran the Dynavibe averaging again, and achieved 0.07 IPS and nowthe heavy side has shifted radially on the hub, indicating thatwe would be chasing small changes from here on, with very limitedways of offsetting the heaviness. So, we called it more thanjust good (Dynavibe says to shoot for no more than 0.1 IPS).Cowlings back on, engine warmed up, and a test flight in "Scout" wasjust deee-lightful!!! What a joy, not only in the buttery smoothnessof the engine, but leveling out at cruise, the change in enginethrustline offset was very rewarding. Hands off, feet off, halftank of fuel, and the yaw is almost gone... a half-ball of left turning,which a very light touch on the right rudder would stop instantly. Inever thought this would be a hands-off airplane, but it's getting veryclose! We'll reinstall the bent-metal trim tab on the rudder andI'll bet the next flight will show NO yawing tendency with feet offthe rudders. This airplane is getting sweeter with every tweak we giveit. Of course, it was clear and COLD here today (mid-40s) so Scoutclimbed wonderfully, but still- the improvements are noticeable anduseful.This is why we call it 'EXPERIMENTAL', and why we love doing it ;o)Oscar ZunigaAir Camper NX41CC "Scout"San Antonio, TXwebsite at http://www.flysquirrel.net ________________________________________________________________________________Subject: Re: Pietenpol-List: vibration testing
I concluded vibration testing on my A75 today, with good results.Recall that before balancing, the Dynavibe was showing 0.51 IPSimbalance at 2150 RPM, which was maximum static at the condition onDec. 18. We ran some other tests using a different carb venturiand adjusted the engine thrust line, but those had nothing to dowith the vibration work. An interim test run using longer AN6 propbolts with four stacked washers under the heads resulted in a reductionof vibration to 0.27 IPS at 2150 RPM, with just a slight radialchange in location of the heavy side of the prop. We were on theright track.Today we added a small 'flyweight' clamped between the two prop boltsacross from the side of the prop that the Dynavibe had identifiedas heavy. It was purposely made a bit heavier than we think willbe the final shape of it, allowing for rounding of the edges andthen applying paint (it's 4130 steel). Warmed up the engine andran the Dynavibe averaging again, and achieved 0.07 IPS and nowthe heavy side has shifted radially on the hub, indicating thatwe would be chasing small changes from here on, with very limitedways of offsetting the heaviness. So, we called it more thanjust good (Dynavibe says to shoot for no more than 0.1 IPS).Cowlings back on, engine warmed up, and a test flight in "Scout" wasjust deee-lightful!!! What a joy, not only in the buttery smoothnessof the engine, but leveling out at cruise, the change in enginethrustline offset was very rewarding. Hands off, feet off, halftank of fuel, and the yaw is almost gone... a half-ball of left turning,which a very light touch on the right rudder would stop instantly. Inever thought this would be a hands-off airplane, but it's getting veryclose! We'll reinstall the bent-metal trim tab on the rudder andI'll bet the next flight will show NO yawing tendency with feet offthe rudders. This airplane is getting sweeter with every tweak we giveit. Of course, it was clear and COLD here today (mid-40s) so Scoutclimbed wonderfully, but still- the improvements are noticeable anduseful.This is why we call it 'EXPERIMENTAL', and why we love doing it ;o)Oscar ZunigaAir Camper NX41CC "Scout"San Antonio, TXwebsite at http://www.flysquirrel.net ________________________________________________________________________________Subject: Re: Pietenpol-List: vibration testing