---------------------------------------------------------- Lightning-List Digest Archive --- Total Messages Posted Thu 05/10/12: 5 ---------------------------------------------------------- Today's Message Index: ---------------------- 1. 06:46 AM - Re: Re: Landing gear shimmy (Gerd + Uli Nowack) 2. 07:23 AM - Re: Re: Landing gear shimmy (Nick Otterback) 3. 07:26 AM - Re: Re: Landing gear shimmy (luigi di napoli) 4. 07:55 AM - Re: Re: Landing gear shimmy (Gerd + Uli Nowack) 5. 11:22 AM - Re: Re: Landing gear shimmy (luigi di napoli) ________________________________ Message 1 _____________________________________ Time: 06:46:44 AM PST US From: Gerd + Uli Nowack Subject: Re: Lightning-List: Re: Landing gear shimmy I think some time ago somebody mentioned that round gear legs are prone to shimmy. IMHO the trouble results from the spring properties of the round gear legs and a certain toe in. You can see on the video that the gear legs do a fast fore and aft motion . If one looks at the gear geometry one sees that a bending aft will also mean a decrease in toe in ( or increase in toe out, whatever) This will momentarily increase the gear drag and result a circular motion of the wheel and the gear leg. The solution: make machined airfoil- shaped gear legs ( made from Aluminum, no expensive and difficult to machine Titan necessary!) that don`t bend fore and aft but still can do their bending outward for the necessary suspension. They could have a groove for the brake line on the inside, so we would`t even need leg fairings! Just my 3 Euro-Cents! Gerd D-ELIY No. 89 Am 10.05.2012 03:45, schrieb Craig Sumner: > --> Lightning-List message posted by: "Craig Sumner" > > Outstanding video Bill! Thanks for taking the time to mount a camera for > all to see. I will share this with others and see what our NASA/DoD > engineers think could be the right fix. I know the folks in Shelbyville > (who are outstanding folks) would like to see this issue resolved. > Best Regards, > Craig Sumner > N155JM > Esqual 074 > > -----Original Message----- > From: owner-lightning-list-server@matronics.com > [mailto:owner-lightning-list-server@matronics.com] On Behalf Of Bill Strahan > Sent: Tuesday, May 08, 2012 4:37 PM > To: lightning-list@matronics.com > Subject: Lightning-List: Re: Landing gear shimmy > > --> Lightning-List message posted by: "Bill Strahan" > > Okay, no egg on my face I suppose. Finally got a video camera to check > things out. It's clearly the main gear. > > It should be on youtube here: http://youtu.be/rzb_eeyhLJU in a few > minutes. > > This clip makes it pretty visible starting at 0:28 on the landing roll. I > don't use the brakes much to try to discount that influence, and I let the > nose drop the moment I land so I can see if it's the nose or mains. > > On taxiing back, I decided to accelerate and test it again, and the second > shimmy can be seen at 1:28. > > It may not look like much on a video camera, but that's a serious bit of > wiggling in the cockpit. > > I'm astounded that the stiffeners don't make an impact on it. I can't flex > them by hand at all in that direction. > > This is a big deal for me because I fly into some pretty busy places and it > occurs right at the speed I'd be doing on a long runway to hurry up and make > a turnoff. That, and I don't like passengers looking a little freaked out > and asking what the heck that was. And it can't be good for the whole plane > to violently shake like that. > > For the record, I've balanced tires, changed to 6 ply tires, balanced those, > and now the fiberglass stiffeners. No relief yet. Not sure what comes > next. > > > Read this topic online here: > > http://forums.matronics.com/viewtopic.php?p=372654#372654 > > ________________________________ Message 2 _____________________________________ Time: 07:23:07 AM PST US From: "Nick Otterback" Subject: RE: Lightning-List: Re: Landing gear shimmy Gerd, Its funny you mention the airfoil shape. I discussed it yesterday with our machine shop and they are getting prices on both. Nick -----Original Message----- From: owner-lightning-list-server@matronics.com [mailto:owner-lightning-list-server@matronics.com] On Behalf Of Gerd + Uli Nowack Sent: Thursday, May 10, 2012 8:46 AM Subject: Re: Lightning-List: Re: Landing gear shimmy --> I think some time ago somebody mentioned that round gear legs are prone to shimmy. IMHO the trouble results from the spring properties of the round gear legs and a certain toe in. You can see on the video that the gear legs do a fast fore and aft motion . If one looks at the gear geometry one sees that a bending aft will also mean a decrease in toe in ( or increase in toe out, whatever) This will momentarily increase the gear drag and result a circular motion of the wheel and the gear leg. The solution: make machined airfoil- shaped gear legs ( made from Aluminum, no expensive and difficult to machine Titan necessary!) that don`t bend fore and aft but still can do their bending outward for the necessary suspension. They could have a groove for the brake line on the inside, so we would`t even need leg fairings! Just my 3 Euro-Cents! Gerd D-ELIY No. 89 Am 10.05.2012 03:45, schrieb Craig Sumner: > --> Lightning-List message posted by: "Craig > --> Sumner" > > Outstanding video Bill! Thanks for taking the time to mount a camera > for all to see. I will share this with others and see what our > NASA/DoD engineers think could be the right fix. I know the folks in > Shelbyville (who are outstanding folks) would like to see this issue resolved. > Best Regards, > Craig Sumner > N155JM > Esqual 074 > > -----Original Message----- > From: owner-lightning-list-server@matronics.com > [mailto:owner-lightning-list-server@matronics.com] On Behalf Of Bill > Strahan > Sent: Tuesday, May 08, 2012 4:37 PM > To: lightning-list@matronics.com > Subject: Lightning-List: Re: Landing gear shimmy > > --> Lightning-List message posted by: "Bill Strahan" > > Okay, no egg on my face I suppose. Finally got a video camera to > check things out. It's clearly the main gear. > > It should be on youtube here: http://youtu.be/rzb_eeyhLJU in a few > minutes. > > This clip makes it pretty visible starting at 0:28 on the landing > roll. I don't use the brakes much to try to discount that influence, > and I let the nose drop the moment I land so I can see if it's the nose or mains. > > On taxiing back, I decided to accelerate and test it again, and the > second shimmy can be seen at 1:28. > > It may not look like much on a video camera, but that's a serious bit > of wiggling in the cockpit. > > I'm astounded that the stiffeners don't make an impact on it. I can't > flex them by hand at all in that direction. > > This is a big deal for me because I fly into some pretty busy places > and it occurs right at the speed I'd be doing on a long runway to > hurry up and make a turnoff. That, and I don't like passengers > looking a little freaked out and asking what the heck that was. And > it can't be good for the whole plane to violently shake like that. > > For the record, I've balanced tires, changed to 6 ply tires, balanced > those, and now the fiberglass stiffeners. No relief yet. Not sure > what comes next. > > > Read this topic online here: > > http://forums.matronics.com/viewtopic.php?p=372654#372654 > > ________________________________ Message 3 _____________________________________ Time: 07:26:19 AM PST US From: luigi di napoli Subject: Re: Lightning-List: Re: Landing gear shimmy Tha gear legs of Pioneer 200/300 are made exactly how described from Gerd. =0AMore than one third of the leg, from the wheel axle, is "sliced" from bo th side.-=0AProbably the reason is the one anounced.=0AIf I find a pictur e of this leg, I-will provide to show one.=0ARegards=0ALuigi=0AEsqual I-9 854=0A-=0A=0A=0A________________________________=0A Da: Gerd + Uli Nowack =0AA: lightning-list@matronics.com =0AInviato: Gioved =EC 10 Maggio 2012 15:46=0AOggetto: Re: Lightning-List: Re: Landing gear sh inden@gmx.de>=0A=0AI think some time ago somebody mentioned that round gear legs are prone =0Ato shimmy.=0AIMHO the trouble results from the spring pr operties of the round gear =0Alegs and a certain toe in.=0AYou can see on t he video that the gear legs do a- fast fore and aft =0Amotion . If one lo oks at the gear geometry one sees that=0Aa bending- aft will also mean a decrease in toe in ( or increase in toe =0Aout, whatever) This will momenta rily increase the gear drag and result- =0Aa circular motion of the wheel and the gear leg.=0A- The solution: make machined airfoil- shaped gear l egs ( made from =0AAluminum, no expensive and difficult to machine Titan ne cessary!) that =0Adon`t bend fore and aft but still can do their bending ou tward for the =0Anecessary suspension.- They could- have a groove for t he brake line on =0Athe inside, so we would`t even need leg fairings!=0AJus t my 3 Euro-Cents!=0A=0AGerd- D-ELIY- - No. 89=0A=0A=0A=0A=0AAm 10.05 .2012 03:45, schrieb Craig Sumner:=0A> -->- Lightning-List message posted by: "Craig Sumner"=0A>=0A> Outstanding video Bill !- Thanks for taking the time to mount a camera for=0A> all to see.- I will share this with others and see what our NASA/DoD=0A> engineers think c ould be the right fix.- I know the folks in Shelbyville=0A> (who are outs tanding folks) would like to see this issue resolved.=0A> Best Regards,=0A> Craig Sumner=0A> N155JM=0A> Esqual 074=0A>=0A> -----Original Message----- =0A> From: owner-lightning-list-server@matronics.com=0A> [mailto:owner-ligh tning-list-server@matronics.com] On Behalf Of Bill Strahan=0A> Sent: Tuesda y, May 08, 2012 4:37 PM=0A> To: lightning-list@matronics.com=0A> Subject: L ightning-List: Re: Landing gear shimmy=0A>=0A> -->- Lightning-List messag e posted by: "Bill Strahan"=0A>=0A> Okay, no egg on my face I suppose.- Finally got a video camera to check=0A> things out.- It's c learly the main gear.=0A>=0A> It should be on youtube here:- http://youtu .be/rzb_eeyhLJU- in a few=0A> minutes.=0A>=0A> This clip makes it pretty visible starting at 0:28 on the landing roll.- I=0A> don't use the brakes much to try to discount that influence, and I let the=0A> nose drop the mo ment I land so I can see if it's the nose or mains.=0A>=0A> On taxiing back , I decided to accelerate and test it again, and the second=0A> shimmy can be seen at 1:28.=0A>=0A> It may not look like much on a video camera, but t hat's a serious bit of=0A> wiggling in the cockpit.=0A>=0A> I'm astounded t hat the stiffeners don't make an impact on it.- I can't flex=0A> them by hand at all in that direction.=0A>=0A> This is a big deal for me because I fly into some pretty busy places and it=0A> occurs right at the speed I'd b e doing on a long runway to hurry up and make=0A> a turnoff.- That, and I don't like passengers looking a little freaked out=0A> and asking what the heck that was.- And it can't be good for the whole plane=0A> to violentl y shake like that.=0A>=0A> For the record, I've balanced tires, changed to 6 ply tires, balanced those,=0A> and now the fiberglass stiffeners.- No r elief yet.- Not sure what comes=0A> next.=0A>=0A>=0A>=0A>=0A> Read this t opic online here:=0A>=0A> http://forums.matronics.com/viewtopic.php?p=372 654#372654=0A>=0A>=0A>=0A>=0A>=0A>=0A>=0A>=0A>=0A>=0A>=0A>=0A>=0A>=0A>=0A ================= ________________________________ Message 4 _____________________________________ Time: 07:55:10 AM PST US From: Gerd + Uli Nowack Subject: Re: Lightning-List: Re: Landing gear shimmy Nick, If you ve got the price please tell us! I think I might pick up a pair of short ones in October! Gerd Am 10.05.2012 16:22, schrieb Nick Otterback: > --> Lightning-List message posted by: "Nick Otterback" > > Gerd, > > Its funny you mention the airfoil shape. I discussed it yesterday with our > machine shop and they are getting prices on both. > > Nick > > -----Original Message----- > From: owner-lightning-list-server@matronics.com > [mailto:owner-lightning-list-server@matronics.com] On Behalf Of Gerd + Uli > Nowack > Sent: Thursday, May 10, 2012 8:46 AM > To: lightning-list@matronics.com > Subject: Re: Lightning-List: Re: Landing gear shimmy > > --> Lightning-List message posted by: Gerd + Uli Nowack > --> > > I think some time ago somebody mentioned that round gear legs are prone to > shimmy. > IMHO the trouble results from the spring properties of the round gear legs > and a certain toe in. > You can see on the video that the gear legs do a fast fore and aft motion . > If one looks at the gear geometry one sees that a bending aft will also > mean a decrease in toe in ( or increase in toe out, whatever) This will > momentarily increase the gear drag and result a circular motion of the wheel > and the gear leg. > The solution: make machined airfoil- shaped gear legs ( made from > Aluminum, no expensive and difficult to machine Titan necessary!) that don`t > bend fore and aft but still can do their bending outward for the necessary > suspension. They could have a groove for the brake line on the inside, so > we would`t even need leg fairings! > Just my 3 Euro-Cents! > > Gerd D-ELIY No. 89 > > > Am 10.05.2012 03:45, schrieb Craig Sumner: >> --> Lightning-List message posted by: "Craig >> --> Sumner" >> >> Outstanding video Bill! Thanks for taking the time to mount a camera >> for all to see. I will share this with others and see what our >> NASA/DoD engineers think could be the right fix. I know the folks in >> Shelbyville (who are outstanding folks) would like to see this issue > resolved. >> Best Regards, >> Craig Sumner >> N155JM >> Esqual 074 >> >> -----Original Message----- >> From: owner-lightning-list-server@matronics.com >> [mailto:owner-lightning-list-server@matronics.com] On Behalf Of Bill >> Strahan >> Sent: Tuesday, May 08, 2012 4:37 PM >> To: lightning-list@matronics.com >> Subject: Lightning-List: Re: Landing gear shimmy >> >> --> Lightning-List message posted by: "Bill Strahan" >> >> Okay, no egg on my face I suppose. Finally got a video camera to >> check things out. It's clearly the main gear. >> >> It should be on youtube here: http://youtu.be/rzb_eeyhLJU in a few >> minutes. >> >> This clip makes it pretty visible starting at 0:28 on the landing >> roll. I don't use the brakes much to try to discount that influence, >> and I let the nose drop the moment I land so I can see if it's the nose or > mains. >> On taxiing back, I decided to accelerate and test it again, and the >> second shimmy can be seen at 1:28. >> >> It may not look like much on a video camera, but that's a serious bit >> of wiggling in the cockpit. >> >> I'm astounded that the stiffeners don't make an impact on it. I can't >> flex them by hand at all in that direction. >> >> This is a big deal for me because I fly into some pretty busy places >> and it occurs right at the speed I'd be doing on a long runway to >> hurry up and make a turnoff. That, and I don't like passengers >> looking a little freaked out and asking what the heck that was. And >> it can't be good for the whole plane to violently shake like that. >> >> For the record, I've balanced tires, changed to 6 ply tires, balanced >> those, and now the fiberglass stiffeners. No relief yet. Not sure >> what comes next. >> >> >> >> >> Read this topic online here: >> >> http://forums.matronics.com/viewtopic.php?p=372654#372654 >> >> >> >> >> >> >> >> >> >> >> >> >> >> >> > > ________________________________ Message 5 _____________________________________ Time: 11:22:36 AM PST US From: luigi di napoli Subject: Re: Lightning-List: Re: Landing gear shimmy Here some pictures .=0AThe tapering starts from the arrow on the tape .=0Ar egards=0ALuigi=0A=0A=0A=0A________________________________=0A Da: Nick Otte rback =0AA: lightning-list@matronics.com =0AInviato: Gioved=EC 10 Maggio 2012 16:22=0AOggetto: RE: Lightning-List: Re: Landing ick@flylightning.net>=0A=0AGerd,=0A=0AIts funny you mention the airfoil sha pe. I discussed it yesterday with our=0Amachine shop and they are getting p rices on both. =0A=0ANick ------------------------------------------------------------------------------------- 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.