---------------------------------------------------------- Lightning-List Digest Archive --- Total Messages Posted Sat 06/02/12: 4 ---------------------------------------------------------- Today's Message Index: ---------------------- 1. 06:36 AM - Re: Re: Landing gear shimmy (Bernard Melendez, Jr.) 2. 08:14 AM - Re: Landing gear shimmy (Jaythree) 3. 08:24 AM - Re: Re: Landing gear shimmy (James, Clive R) 4. 10:03 PM - Re: Landing gear shimmy (Jaythree) ________________________________ Message 1 _____________________________________ Time: 06:36:22 AM PST US From: "Bernard Melendez, Jr." Subject: Re: Lightning-List: Re: Landing gear shimmy The old Cessna 150 I used to fly as a student also had nose wheel shimmy. I t even had a gas strut to help solve that issue, with little help. So, what 's new? Bernardo --- On Sat, 6/2/12, Jaythree wrote: From: Jaythree Subject: Lightning-List: Re: Landing gear shimmy This forum is a gold mine! I'll start by confessing that with only six hour s and twelve landings on my new Esqual (with Lightning upgrades) I managed to bend the nosegear leg on a soft turf runway. I bought the Esqual from th e builder, who did a magnificent job and I feel worse about dinging his cra ftsmanship than anything else right now. But to the point...shimmy. I did experience it on all landings at 35-45 mph rollout. Although the consensus on this forum is that mains gearlegs and/o r alignment seem to be the gremlin, I'm wondering if a significant factor m ay b the angled nosegear trailing fork. Angling the fork aft-down creates a geometry in which the weight on the swivel wants to rotate the forks forwa rd. It's like a ball on a ramp. I have never seen castoring trailing fork n osegear where the fork was not parallel to the ground, eg., Grumman. I don' t understand the purpose of the unstable geometry on the Esqual/Lightning. At 35-45 mph, the balancing forces of weight, fairing weathervaning and fly wheel momentum of the nosewheel would tend to create a perfect scenario for shimmy. Shimmy up front of course would translate to the mains. Any commen ts, positive or negative, appreciated. Bill Strahan wrote: > Hey, I've talked about this before, haven't I?- I've had 3 big changes I wanted to make for a long time:- 1)- Fix fuel distribution issue.- 2)- Make some short wingtips.- 3)- Eliminate the landing gear shimmy. > > I installed the flow straightener tube and vanes that Nick sent me about a year ago.- That did an amazing job.- Perfect?- No.- Good enough t hat I'm not considering installing fuel injection?- Yep.- So #1 is adre ssed. > > I still need to make short wingtips, but my passenger yesterday asked "Wh y does it shake like that after you land?"---GRRRRR. > > So I bought an axe handle and started chatting with neighbors here on the airport about cutting and shaping it.- I figured I'd buy a 1.125" ball c utter and put a radius in it.- Kept putting that off because it didn't so und like fun. > > Then it hit me:- I really just need it stiffer in fore/aft flexing.- And whatever stiffener I make needs to glue to the gear leg so it needs to be a very good fit.- Nothing fits better than fiberglass built in-place! > > I decided I would tape off the gear and lay up 3 laminations of 7oz cloth directly onto the back of the gear leg.- I did that tonight, and it's cu ring.- Tomorrow I'll sand the back of that and use some flock and 5 minut e epoxy to attach a 1/8" thick piece of balsa wood that extends about 1.5" behind the gear.- Once that's cured I'll lay up about 6 layers of cloth o n both sides of the balsa, overlapping onto the section that's on the gear. - So the gear shouldn't end up much stiffer since it only has 1/8" thickn ess between the 6 layer lamination, but it should be SUPER stiff across the 1.5" section. > > So I should get that done tomorrow, and let it cure overnight.- Then I' ll pop it off the gear, trim it, and glue it onto the landing gear leg. > > Any thoughts?- Nick, any suggestions on the best adhesive to attach to the gear?- Should I remove the paint or glue to the paint? > > When I glue it I'll put a couple of zip ties around it to hold it while i t cures, and leave them on just in case it ever comes loose. > > Fingers crossed, I can report in a few days that I have eliminated the da ng shimmy once and for all. Read this topic online here: http://forums.matronics.com/viewtopic.php?p=374512#374512 le, List Admin. ________________________________ Message 2 _____________________________________ Time: 08:14:17 AM PST US Subject: Lightning-List: Re: Landing gear shimmy From: "Jaythree" Well, the geometry and physics can be different for every shimmy, which is a mass oscillation. . I was just talking about theEsqual/Lightning. [quote="n45bm(at)yahoo.com"]The old Cessna 150 I used to fly as a student also had nose wheel shimmy. It even had a gas strut to help solve that issue, with little help. So, what's new? Bernardo --- On Sat, 6/2/12, Jaythree wrote: > > From: Jaythree > Subject: Re: Landing gear shimmy > To: lightning-list@matronics.com > Date: Saturday, June 2, 2012, 12:13 AM > > > This forum is a gold mine! I'll start by confessing that with only six hours and twelve landings on my new Esqual (with Lightning upgrades) I managed to bend the nosegear leg on a soft turf runway. I bought the Esqual from the builder, who did a magnificent job and I feel worse about dinging his craftsmanship than anything else right now. > > But to the point...shimmy. I did experience it on all landings at 35-45 mph rollout. Although the consensus on this forum is that mains gearlegs and/or alignment seem to be the gremlin, I'm wondering if a significant factor may b the angled nosegear trailing fork. Angling the fork aft-down creates a geometry in which the weight on the swivel wants to rotate the forks forward. It's like a ball on a ramp. I have never seen castoring trailing fork nosegear where the fork was not parallel to the ground, eg., Grumman. I don't understand the purpose of the unstable geometry on the Esqual/Lightning. At 35-45 mph, the balancing forces of weight, fairing weathervaning and flywheel momentum of the nosewheel would tend to create a perfect scenario for shimmy. Shimmy up front of course would translate to the mains. Any comments, positive or negative, appreciated. > > > Bill Strahan wrote: > > > Hey, I've talked about this before, haven't I? I've had 3 big changes I wanted to make for a long time: 1) Fix fuel distribution issue. 2) Make some short wingtips. 3) Eliminate the landing gear shimmy. > > > > I installed the flow straightener tube and vanes that Nick sent me about a year ago. That did an amazing job. Perfect? No. Good enough that I'm not considering installing fuel injection? Yep. So #1 is adressed. > > > > I still need to make short wingtips, but my passenger yesterday asked "Why does it shake like that after you land?" GRRRRR. > > > > So I bought an axe handle and started chatting with neighbors here on the airport about cutting and shaping it. I figured I'd buy a 1.125" ball cutter and put a radius in it. Kept putting that off because it didn't sound like fun. > > > > Then it hit me: I really just need it stiffer in fore/aft flexing. And whatever stiffener I make needs to glue to the gear leg so it needs to be a very good fit. Nothing fits better than fiberglass built in-place! > > > > I decided I would tape off the gear and lay up 3 laminations of 7oz cloth directly onto the back of the gear leg. I did that tonight, and it's curing. Tomorrow I'll sand the back of that and use some flock and 5 minute epoxy to attach a 1/8" thick piece of balsa wood that extends about 1.5" behind the gear. Once that's cured I'll lay up about 6 layers of cloth on both sides of the balsa, overlapping onto the section that's on the gear. So the gear shouldn't end up much stiffer since it only has 1/8" thickness between the 6 layer lamination, but it should be SUPER stiff across the 1.5" section. > > > > So I should get that done tomorrow, and let it cure overnight. Then I'll pop it off the gear, trim it, and glue it onto the landing gear leg. > > > > Any thoughts? Nick, any suggestions on the best adhesive to attach to the gear? Should I remove the paint or glue to the paint? > > > > When I glue it I'll put a couple of zip ties around it to hold it while it cures, and leave them on just in case it ever comes loose. > > > > Fingers crossed, I can report in a few days that I have eliminated the dang shimmy once and for all. > > > > > > > > > > Read this topic online here: > > http://forums.matronics.com/viewtosp; --> http://www.matronics.com/Navigator?Lightning-Lis --> http://www.matronics.c================== > > > > > > [b] Read this topic online here: http://forums.matronics.com/viewtopic.php?p=374535#374535 ________________________________ Message 3 _____________________________________ Time: 08:24:19 AM PST US Subject: RE: Lightning-List: Re: Landing gear shimmy From: "James, Clive R" I had the angled leg on the Esqual for the first 30 hours, no shimmy but did make the steering a little twitchy. I have the lightning one on now thankfully. Pulling the plane around the hangar it was off like a supermarket trolley. Regarding the shimmy, does it promote tyre wear? From: owner-lightning-list-server@matronics.com [mailto:owner-lightning-list-server@matronics.com] On Behalf Of Bernard Melendez, Jr. Sent: 02 June 2012 14:36 Subject: Re: Lightning-List: Re: Landing gear shimmy The old Cessna 150 I used to fly as a student also had nose wheel shimmy. It even had a gas strut to help solve that issue, with little help. So, what's new? Bernardo --- On Sat, 6/2/12, Jaythree wrote: From: Jaythree Subject: Lightning-List: Re: Landing gear shimmy This forum is a gold mine! I'll start by confessing that with only six hours and twelve landings on my new Esqual (with Lightning upgrades) I managed to bend the nosegear leg on a soft turf runway. I bought the Esqual from the builder, who did a magnificent job and I feel worse about dinging his craftsmanship than anything else right now. But to the point...shimmy. I did experience it on all landings at 35-45 mph rollout. Although the consensus on this forum is that mains gearlegs and/or alignment seem to be the gremlin, I'm wondering if a significant factor may b the angled nosegear trailing fork. Angling the fork aft-down creates a geometry in which the weight on the swivel wants to rotate the forks forward. It's like a ball on a ramp. I have never seen castoring trailing fork nosegear where the fork was not parallel to the ground, eg., Grumman. I don't understand the purpose of the unstable geometry on the Esqual/Lightning. At 35-45 mph, the balancing forces of weight, fairing weathervaning and flywheel momentum of the nosewheel would tend to create a perfect scenario for shimmy. Shimmy up front of course would translate to the mains. Any comments, positive or negative, appreciated. Bill Strahan wrote: > Hey, I've talked about this before, haven't I? I've had 3 big changes I wanted to make for a long time: 1) Fix fuel distribution issue. 2) Make some short wingtips. 3) Eliminate the landing gear shimmy. > > I installed the flow straightener tube and vanes that Nick sent me about a year ago. That did an amazing job. Perfect? No. Good enough that I'm not considering installing fuel injection? Yep. So #1 is adressed. > > I still need to make short wingtips, but my passenger yesterday asked "Why does it shake like that after you land?" GRRRRR. > > So I bought an axe handle and started chatting with neighbors here on the airport about cutting and shaping it. I figured I'd buy a 1.125" ball cutter and put a radius in it. Kept putting that off because it didn't sound like fun. > > Then it hit me: I really just need it stiffer in fore/aft flexing. And whatever stiffener I make needs to glue to the gear leg so it needs to be a very good fit. Nothing fits better than fiberglass built in-place! > > I decided I would tape off the gear and lay up 3 laminations of 7oz cloth directly onto the back of the gear leg. I did that tonight, and it's curing. Tomorrow I'll sand the back of that and use some flock and 5 minute epoxy to attach a 1/8" thick piece of balsa wood that extends about 1.5" behind the gear. Once that's cured I'll lay up about 6 layers of cloth on both sides of the balsa, overlapping onto the section that's on the gear. So the gear shouldn't end up much stiffer since it only has 1/8" thickness between the 6 layer lamination, but it should be SUPER stiff across the 1.5" section. > > So I should get that done tomorrow, and let it cure overnight. Then I'll pop it off the gear, trim it, and glue it onto the landing gear leg. > > Any thoughts? Nick, any suggestions on the best adhesive to attach to the gear? Should I remove the paint or glue to the paint? > > When I glue it I'll put a couple of zip ties around it to hold it while it cures, and leave them on just in case it ever comes loose. > > Fingers crossed, I can report in a few days that I have eliminated the dang shimmy once and for all. Read this topic online here: http://forums.matronics.com/viewtosp; --> http://www.matronics.com/Navigator?Lightning-Lis --> http://www.matronics.c================= = ________________________________ Message 4 _____________________________________ Time: 10:03:59 PM PST US Subject: Lightning-List: Re: Landing gear shimmy From: "Jaythree" Well, the geometry and physics can be different for every shimmy, which is a mass oscillation. . I was just talking about theEsqual/Lightning. [quote="n45bm(at)yahoo.com"]The old Cessna 150 I used to fly as a student also had nose wheel shimmy. It even had a gas strut to help solve that issue, with little help. So, what's new? Bernardo --- On Sat, 6/2/12, Jaythree wrote: > > From: Jaythree > Subject: Re: Landing gear shimmy > To: lightning-list@matronics.com > Date: Saturday, June 2, 2012, 12:13 AM > > > This forum is a gold mine! I'll start by confessing that with only six hours and twelve landings on my new Esqual (with Lightning upgrades) I managed to bend the nosegear leg on a soft turf runway. I bought the Esqual from the builder, who did a magnificent job and I feel worse about dinging his craftsmanship than anything else right now. > > But to the point...shimmy. I did experience it on all landings at 35-45 mph rollout. Although the consensus on this forum is that mains gearlegs and/or alignment seem to be the gremlin, I'm wondering if a significant factor may b the angled nosegear trailing fork. Angling the fork aft-down creates a geometry in which the weight on the swivel wants to rotate the forks forward. It's like a ball on a ramp. I have never seen castoring trailing fork nosegear where the fork was not parallel to the ground, eg., Grumman. I don't understand the purpose of the unstable geometry on the Esqual/Lightning. At 35-45 mph, the balancing forces of weight, fairing weathervaning and flywheel momentum of the nosewheel would tend to create a perfect scenario for shimmy. Shimmy up front of course would translate to the mains. Any comments, positive or negative, appreciated. > > > Bill Strahan wrote: > > > Hey, I've talked about this before, haven't I? I've had 3 big changes I wanted to make for a long time: 1) Fix fuel distribution issue. 2) Make some short wingtips. 3) Eliminate the landing gear shimmy. > > > > I installed the flow straightener tube and vanes that Nick sent me about a year ago. That did an amazing job. Perfect? No. Good enough that I'm not considering installing fuel injection? Yep. So #1 is adressed. > > > > I still need to make short wingtips, but my passenger yesterday asked "Why does it shake like that after you land?" GRRRRR. > > > > So I bought an axe handle and started chatting with neighbors here on the airport about cutting and shaping it. I figured I'd buy a 1.125" ball cutter and put a radius in it. Kept putting that off because it didn't sound like fun. > > > > Then it hit me: I really just need it stiffer in fore/aft flexing. And whatever stiffener I make needs to glue to the gear leg so it needs to be a very good fit. Nothing fits better than fiberglass built in-place! > > > > I decided I would tape off the gear and lay up 3 laminations of 7oz cloth directly onto the back of the gear leg. I did that tonight, and it's curing. Tomorrow I'll sand the back of that and use some flock and 5 minute epoxy to attach a 1/8" thick piece of balsa wood that extends about 1.5" behind the gear. Once that's cured I'll lay up about 6 layers of cloth on both sides of the balsa, overlapping onto the section that's on the gear. So the gear shouldn't end up much stiffer since it only has 1/8" thickness between the 6 layer lamination, but it should be SUPER stiff across the 1.5" section. > > > > So I should get that done tomorrow, and let it cure overnight. Then I'll pop it off the gear, trim it, and glue it onto the landing gear leg. > > > > Any thoughts? Nick, any suggestions on the best adhesive to attach to the gear? Should I remove the paint or glue to the paint? > > > > When I glue it I'll put a couple of zip ties around it to hold it while it cures, and leave them on just in case it ever comes loose. > > > > Fingers crossed, I can report in a few days that I have eliminated the dang shimmy once and for all. > > > > > > > > > > Read this topic online here: > > http://forums.matronics.com/viewtosp; --> http://www.matronics.com/Navigator?Lightning-Lis --> http://www.matronics.c================== > > > > > > [b] Read this topic online here: http://forums.matronics.com/viewtopic.php?p=374567#374567 ------------------------------------------------------------------------------------- Other Matronics Email List Services ------------------------------------------------------------------------------------- Post A New Message lightning-list@matronics.com UN/SUBSCRIBE http://www.matronics.com/subscription List FAQ http://www.matronics.com/FAQ/Lightning-List.htm Web Forum Interface To Lists http://forums.matronics.com Matronics List Wiki http://wiki.matronics.com Full Archive Search Engine http://www.matronics.com/search 7-Day List Browse http://www.matronics.com/browse/lightning-list Browse Digests http://www.matronics.com/digest/lightning-list Browse Other Lists http://www.matronics.com/browse Live Online Chat! http://www.matronics.com/chat Archive Downloading http://www.matronics.com/archives Photo Share http://www.matronics.com/photoshare Other Email Lists http://www.matronics.com/emaillists Contributions http://www.matronics.com/contribution ------------------------------------------------------------------------------------- These Email List Services are sponsored solely by Matronics and through the generous Contributions of its members.