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Bill Strahan
Joined: 20 Aug 2008
Posts: 145
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 Posted: Mon Sep 10, 2012 7:06 pm Post subject: Shimmy update |
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Okay, perhaps I'm doing things in a weird order, but I'm still playing with shimmy stuff. The stiffeners I made from fiberglass didn't help. I'll remove them soon. I switched to the 6-ply tires, no dice.
I was running the 6-ply tires at just below the max pressure rating of 50PSI. I read about people getting better results with low pressure, so I dropped it to 26. Holy cow! That made it a TON worse! Weird.
So tonight I hopped out to the hanger and did a quick measurement with a laser level. Held it on the brake disks and measured six feet in front and behind the axle, marked it, and calculated toe...came out to 1/2 degree toe-out.
I've read so much about this, but so much is conflicting. So now my question is has anyone solved their shimmy by going from toe-out to toe-in? It sure seems toe-in would work much better, but then I've read people claiming the exact opposite.
Assuming I decide to go with toe-in, what's the best way to reset? Drill a new hole and put in a new bolt, or drill the existing hole to the next size bolt?
Oh, last thing. I didn't verify that each wheel has 1/2 degree toe out. I just measured the difference between laser lines front and back, and it works out to a total of 1 degree. For all I know, one is set differently from the other, but I'll verify that and adjust accordingly if I reset to toe-in.
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n45bm(at)yahoo.com
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| Posted: Mon Sep 10, 2012 7:46 pm Post subject: Shimmy update |
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Bill,
Standard practice is for toe IN, not toe out. I put 1 1/2 degrees toe in on my plane, but I've yet to test it as I'm not flying yet. The build manual says 1 degree toe in, but I added another 1/2 degree, I hope it helps. Leaf spring gears have less problems with shimmy. I believe that the problem with round landing gears is that they are more likely to twist with side loads and once that starts, oh well....
I propose that to help the gear resist twisting motion, shaped wood blocks be well bonded to the front and rear of the gear and shaped to an airfoil shape, followed by several plies of fiberglass or carbon fiber. Milling the roundness to match the tapered gear is the trick. That's the hard part.
If my landing gear exhibits shimmy, that's what I plan to do. The main objective would be to stiffen the gear to prevent twisting loads. All this is just speculation on my part, but I can't think of a better way to do it.
Bernardo
[quote]
Okay, perhaps I'm doing things in a weird order, but I'm still playing with shimmy stuff. The stiffeners I made from fiberglass didn't help. I'll remove them soon. I switched to the 6-ply tires, no dice.
I was running the 6-ply tires at just below the max pressure rating of 50PSI. I read about people getting better results with low pressure, so I dropped it to 26. Holy cow! That made it a TON worse! Weird.
So tonight I hopped out to the hanger and did a quick measurement with a laser level. Held it on the brake disks and measured six feet in front and behind the axle, marked it, and calculated toe...came out to 1/2 degree toe-out.
I've read so much about this, but so much is conflicting. So now my question is has anyone solved their shimmy by going from toe-out to toe-in? It sure seems toe-in would work much better, but then I've read people claiming the exact opposite.
Assuming I decide to go with toe-in, what's the best way to reset? Drill a new hole and put in a new bolt, or drill the existing hole to the next size bolt?
Oh, last thing. I didn't verify that each wheel has 1/2 degree toe out. I just measured the difference between laser lines front and back, and it works out to a total of 1 degree. For all I know, one is set differently from the other, but I'll verify that and adjust accordingly if I reset to toe-in.
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=382840#382========================http://www.matronics.cs.matronics.com" bsp; -Matt Dralle, List Adontribution" target="_blank">http://www.matronics.com/contribution [quote][b]
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LIGHTNING AUSTRALIA
Joined: 02 Dec 2008
Posts: 11
Location: Kingston SE AUSTRALIA
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| Posted: Tue Sep 11, 2012 2:52 am Post subject: Shimmy update |
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Bernard
All of the lightning kits we have built including both of my own Lightnings we have set with toe out with good results. Not perfect but pretty close.
In the build manual "Setting Main Gear Toe" STEP 8, instead of subtracting 2.25" from each side add 2.00" to each side. My 2 cents worth.
Regards
Dennis Borchardt
LIGHTNING AIRCRAFT AUSTRALIA
lightningaustralia(at)bigpond.com (lightningaustralia(at)bigpond.com)
www.lightningaircraft.com.au Ph 0408 813501
From: owner-lightning-list-server(at)matronics.com [mailto:owner-lightning-list-server(at)matronics.com] On Behalf Of Bernard Melendez, Jr.
Sent: Tuesday, 11 September 2012 1:16 PM
To: lightning-list(at)matronics.com
Subject: Re: Shimmy update
Bill,
Standard practice is for toe IN, not toe out. I put 1 1/2 degrees toe in on my plane, but I've yet to test it as I'm not flying yet. The build manual says 1 degree toe in, but I added another 1/2 degree, I hope it helps. Leaf spring gears have less problems with shimmy. I believe that the problem with round landing gears is that they are more likely to twist with side loads and once that starts, oh well....
I propose that to help the gear resist twisting motion, shaped wood blocks be well bonded to the front and rear of the gear and shaped to an airfoil shape, followed by several plies of fiberglass or carbon fiber. Milling the roundness to match the tapered gear is the trick. That's the hard part.
If my landing gear exhibits shimmy, that's what I plan to do. The main objective would be to stiffen the gear to prevent twisting loads. All this is just speculation on my part, but I can't think of a better way to do it.
Bernardo
Okay, perhaps I'm doing things in a weird order, but I'm still playing with shimmy stuff. The stiffeners I made from fiberglass didn't help. I'll remove them soon. I switched to the 6-ply tires, no dice.
I was running the 6-ply tires at just below the max pressure rating of 50PSI. I read about people getting better results with low pressure, so I dropped it to 26. Holy cow! That made it a TON worse! Weird.
So tonight I hopped out to the hanger and did a quick measurement with a laser level. Held it on the brake disks and measured six feet in front and behind the axle, marked it, and calculated toe...came out to 1/2 degree toe-out.
I've read so much about this, but so much is conflicting. So now my question is has anyone solved their shimmy by going from toe-out to toe-in? It sure seems toe-in would work much better, but then I've read people claiming the exact opposite.
Assuming I decide to go with toe-in, what's the best way to reset? Drill a new hole and put in a new bolt, or drill the existing hole to the next size bolt?
Oh, last thing. I didn't verify that each wheel has 1/2 degree toe out. I just measured the difference between laser lines front and back, and it works out to a total of 1 degree. For all I know, one is set differently from the other, but I'll verify that and adjust accordingly if I reset to toe-in.
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=382840#382======================== href="http://www.matronics.com/Navigator?Lightning-List">http://www.mathttp://forums.matronics.com href="http://www.matronics.com/contribution">http://www.matronics.com/contribution ===========
[quote][b]
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nowacklinden(at)gmx.de
Guest
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| Posted: Tue Sep 11, 2012 3:15 am Post subject: Shimmy update |
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Bernardo,
I agree with your opinion, that the round gear legs are causing the trouble , and I like your plan to modify them.
1st:Have you started to make your gear legs or are you still planning.?
2nd: have you (or anyone else!)considered to use model builder`s foam instead of wood? The wood might have more "springiness", but one could make up for that with just more (unidirectional) epoxy-glass, maybe even carbon rovings. Andfoam is much easier to shape!
3rd: to save weight it might be a nice idea to sand or mill aluminum from the side off the gear legs first, maybe a 1/4 ", total , or .4 "( 1cm)-of course the ends have to remain round to fit their receiving tubes.
Has anybody experience with such a combined aluminum / epoxy- spring?
Well, that is roughly what I have in mind if the shimmy starts shaking my baby. During the next days I will bolt the wheel pants on , and then I will see what happens.
Btw that will be the time when I can publish a few performance data.
And pictures as my contribution for the Lightning Of The Year-contest 
Gerd D-ELIY , kit 89
-------- Original-Nachricht --------
| Quote: | Datum: Mon, 10 Sep 2012 20:45:51 -0700 (PDT)
Von: "Bernard Melendez, Jr." <n45bm(at)yahoo.com>
An: lightning-list(at)matronics.com
Betreff: Re: Shimmy update
|
| Quote: | Bill,
Standard practice is for toe IN, not toe out. I put 1 1/2 degrees toe in
on my plane, but I've yet to test it as I'm not flying yet. The build manual
says 1 degree toe in, but I added another 1/2 degree, I hope it helps.
Leaf spring gears have less problems with shimmy. I believe that the problem
with round landing gears is that they are more likely to twist with side
loads and once that starts, oh well....
I propose that to help the gear resist twisting motion, shaped wood blocks
be well bonded to the front and rear of the gear and shaped to an airfoil
shape, followed by several plies of fiberglass or carbon fiber. Milling the
roundness to match the tapered gear is the trick. That's the hard part.
If my landing gear exhibits shimmy, that's what I plan to do. The main
objective would be to stiffen the gear to prevent twisting loads. All this is
just speculation on my part, but I can't think of a better way to do it.
Bernardo
Okay, perhaps I'm doing things in a weird order, but I'm still playing
with shimmy stuff. The stiffeners I made from fiberglass didn't help. I'll
remove them soon. I switched to the 6-ply tires, no dice.
I was running the 6-ply tires at just below the max pressure rating of
50PSI. I read about people getting better results with low pressure, so I
dropped it to 26. Holy cow! That made it a TON worse! Weird.
So tonight I hopped out to the hanger and did a quick measurement with a
laser level. Held it on the brake disks and measured six feet in front and
behind the axle, marked it, and calculated toe...came out to 1/2 degree
toe-out.
I've read so much about this, but so much is conflicting. So now my
question is has anyone solved their shimmy by going from toe-out to toe-in?Â
It sure seems toe-in would work much better, but then I've read people
claiming the exact opposite.
Assuming I decide to go with toe-in, what's the best way to reset? Drill
a new hole and put in a new bolt, or drill the existing hole to the next
size bolt?
Oh, last thing. I didn't verify that each wheel has 1/2 degree toe
out. I just measured the difference between laser lines front and back, and it
works out to a total of 1 degree. For all I know, one is set differently
from the other, but I'll verify that and adjust accordingly if I reset to
toe-in.
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=382840#382840
le, List Admin.
|
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n45bm(at)yahoo.com
Guest
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| Posted: Tue Sep 11, 2012 11:24 am Post subject: Shimmy update |
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|
Hi Gerd,
The purpose of the wood fairings solidly bonded to the aluminum gear is to stiffen it and help it from twisting. The foam method is good if all you're trying to do is to streamline it, but I don't think it would prevent it from twisting. The interface between the foam and gear would be very weak.
No, I've not added the wood fairings to mine, but will do so after I fly it and see if I need them. I'm hoping the 1 1/2 degrees toe-in will help in that respect.
The REAL solution would have been to design the landing gear as leaf spring gear, in my humble opinion. That, or new leaf landing gear legs with round ends to fit into the existing mount sockets would work. Of course, this would entail expensive machining and new wheel attach weldments would have to be designed. Probably too much to ask.
Bernardo
--- On Tue, 9/11/12, Gerd Nowack <nowacklinden(at)gmx.de> wrote:
[quote]
From: Gerd Nowack <nowacklinden(at)gmx.de>
Subject: Re: Shimmy update
To: lightning-list(at)matronics.com
Date: Tuesday, September 11, 2012, 6:15 AM
--> Lightning-List message posted by: "Gerd Nowack" <[url=/mc/compose?to=nowacklinden(at)gmx.de]nowacklinden(at)gmx.de[/url]>
Bernardo,
I agree with your opinion, that the round gear legs are causing the trouble , and I like your plan to modify them.
1st:Have you started to make your gear legs or are you still planning.?
2nd: have you (or anyone else!)considered to use model builder`s foam instead of wood? The wood might have more "springiness", but one could make up for that with just more (unidirectional) epoxy-glass, maybe even carbon rovings. And foam is much easier to shape!
3rd: to save weight it might be a nice idea to sand or mill aluminum from the side off the gear legs first, maybe a 1/4 ", total , or .4 "( 1cm)-of course the ends have to remain round to fit their receiving tubes.
Has anybody experience with such a combined aluminum / epoxy- spring?
Well, that is roughly what I have in mind if the shimmy starts shaking my baby. During the next days I will bolt the wheel pants on , and then I will see what happens.
Btw that will be the time when I can publish a few performance data.
And pictures as my contribution for the Lightning Of The Year-contest
Gerd D-ELIY , kit 89
-------- Original-Nachricht --------
| Quote: | Datum: Mon, 10 Sep 2012 20:45:51 -0700 (PDT)
Von: "Bernard Melendez, Jr." <[url=/mc/compose?to=n45bm(at)yahoo.com]n45bm(at)yahoo.com[/url]>
An: [url=/mc/compose?to=lightning-list(at)matronics.com]lightning-list(at)matronics.com[/url]
Betreff: Re: Shimmy update
|
[quote] Bill,
Standard practice is for toe IN, not toe out. I put 1 1/2 degrees toe in
on my plane, but I've yet to test it as I'm not flying yet. The build manual
says 1 degree toe in, but I added another 1/2 degree, I hope it helps.
Leaf spring gears have less problems with shimmy. I believe that the problem
with round landing gears is that they are more likely to twist with side
loads and once that starts, oh well....
I propose that to help the gear resist twisting motion, shaped wood blocks
be well bonded to the front and rear of the gear and shaped to an airfoil
shape, followed by several plies of fiberglass or carbon fiber. Milling the
roundness to match the tapered gear is the trick. That's the hard part.
If my landing gear exhibits shimmy, that's what I plan to do. The main
objective would be to stiffen the gear to prevent twisting loads. All this is
just speculation on my part, but I can't think of a better way to do it.
Bernardo
Okay, perhaps I'm doing things in a weird order, but I'm still playing
with shimmy stuff. The stiffeners I made from fiberglass didn't help. I'll
remove them soon. I switched to the 6-ply tires, no dice.
I was running the 6-ply tires at just below the max pressure rating of
50PSI. I read about people getting better results with low pressure, so I
dropped it to 26. Holy cow! That made it a TON worse! Weird.
So tonight I hopped out to the hanger and did a quick measurement with a
laser level. Held it on the brake disks and measured six feet in front and
behind the axle, marked it, and calculated toe...came out to 1/2 degree
toe-out.
I've read so much about this, but so much is conflicting. So now my
question is has anyone solved their shimmy by going from toe-out to toe-in?
It sure seems toe-in would work much better, but then I've read people
claiming the exact opposite.
Assuming I decide to go with toe-in, what's the best way to reset? Drill
a new hole and put in a new bolt, or drill the existing hole to the next
size bolt?
Oh, last thing. I didn't verify that each wheel has 1/2 degree toe
out. I just measured the difference between laser lines front and back, and it
works out to a total of 1 degree. For all I know, one is set differently
from the other, but I'll verify that and adjust accordingly if I reset to
toe-in.
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=382840#382840
&-> http://www.matronics.com/Navigator?Lightning-Listh= -->
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Clive J
Joined: 03 Nov 2007
Posts: 340
Location: UK
|
| Posted: Tue Sep 11, 2012 12:33 pm Post subject: Shimmy update |
|
|
The original gear for the Esqual was flat spring steel bar. I don’t know why Francesc changed it, as I have far too stiffer U/C on my Esqual I’d rather he hadn’t.
It also has ended up on the Lightning of course.
In the UK we are mostly on grass and lots of fields are really bumpy so a little more spring would be good.
Regarding toe in or out. I always figured that the ‘toe’ was so that loaded the wheels would point directly where the vehicle is going or almost. In the case of our gear legs when loaded the legs will tend to bend out and back.
So toeing out would be bad and getting worse, strange that it seems to help the shimmy problem in Australia.
Has anyone tried a more flexible tyre? Maybe flat block tread rather than conventional aero pattern?
Mind you I read less pressure makes the shimmy worse and less pressure would be more flexible.
I have block tread square tyres but I did have aero on, got the knobbly ones as my home runway is very rough concrete
I think RVs used to bond wood on and streamline it, this was for shimmy and streamlining I believe. Though now they just have the fairings.
Aren’t RV legs steel? Is that the way to go? A bit heavier but stronger and probably springier. Anyone know?
Just thinking out load. I don’t have it despite having exactly the same set up on my plane so it baffles me.
I do have a loud tapping from the U/C on bumpy fields but I figure that is the legs slightly moving in the sockets as they are a little small. Anybody have that too?
What about the bandy legged light sport lightning, does that have shimmy?
Regards, Clive
Esqual in UK, round ally gear legs from Arion (not sure if they are Lightning or Esqual).
From: owner-lightning-list-server(at)matronics.com [mailto:owner-lightning-list-server(at)matronics.com] On Behalf Of Bernard Melendez, Jr.
Sent: 11 September 2012 20:24
To: lightning-list(at)matronics.com
Subject: Re: Shimmy update
Hi Gerd,
The purpose of the wood fairings solidly bonded to the aluminum gear is to stiffen it and help it from twisting. The foam method is good if all you're trying to do is to streamline it, but I don't think it would prevent it from twisting. The interface between the foam and gear would be very weak.
No, I've not added the wood fairings to mine, but will do so after I fly it and see if I need them. I'm hoping the 1 1/2 degrees toe-in will help in that respect.
The REAL solution would have been to design the landing gear as leaf spring gear, in my humble opinion. That, or new leaf landing gear legs with round ends to fit into the existing mount sockets would work. Of course, this would entail expensive machining and new wheel attach weldments would have to be designed. Probably too much to ask.
Bernardo
--- On Tue, 9/11/12, Gerd Nowack <nowacklinden(at)gmx.de (nowacklinden(at)gmx.de)> wrote:
From: Gerd Nowack <nowacklinden(at)gmx.de (nowacklinden(at)gmx.de)>
Subject: Re: Shimmy update
To: lightning-list(at)matronics.com (lightning-list(at)matronics.com)
Date: Tuesday, September 11, 2012, 6:15 AM
--> Lightning-List message posted by: "Gerd Nowack" <[url=/mc/compose?to=nowacklinden(at)gmx.de]nowacklinden(at)gmx.de[/url]>
Bernardo,
I agree with your opinion, that the round gear legs are causing the trouble , and I like your plan to modify them.
1st:Have you started to make your gear legs or are you still planning.?
2nd: have you (or anyone else!)considered to use model builder`s foam instead of wood? The wood might have more "springiness", but one could make up for that with just more (unidirectional) epoxy-glass, maybe even carbon rovings. And foam is much easier to shape!
3rd: to save weight it might be a nice idea to sand or mill aluminum from the side off the gear legs first, maybe a 1/4 ", total , or .4 "( 1cm)-of course the ends have to remain round to fit their receiving tubes.
Has anybody experience with such a combined aluminum / epoxy- spring?
Well, that is roughly what I have in mind if the shimmy starts shaking my baby. During the next days I will bolt the wheel pants on , and then I will see what happens.
Btw that will be the time when I can publish a few performance data.
And pictures as my contribution for the Lightning Of The Year-contest
Gerd D-ELIY , kit 89
-------- Original-Nachricht --------
| Quote: | Datum: Mon, 10 Sep 2012 20:45:51 -0700 (PDT)
Von: "Bernard Melendez, Jr." <[url=/mc/compose?to=n45bm(at)yahoo.com]n45bm(at)yahoo.com[/url]>
An: [url=/mc/compose?to=lightning-list(at)matronics.com]lightning-list(at)matronics.com[/url]
Betreff: Re: Shimmy update
|
| Quote: | Bill,
Standard practice is for toe IN, not toe out. I put 1 1/2 degrees toe in
on my plane, but I've yet to test it as I'm not flying yet. The build manual
says 1 degree toe in, but I added another 1/2 degree, I hope it helps.
Leaf spring gears have less problems with shimmy. I believe that the problem
with round landing gears is that they are more likely to twist with side
loads and once that starts, oh well....
I propose that to help the gear resist twisting motion, shaped wood blocks
be well bonded to the front and rear of the gear and shaped to an airfoil
shape, followed by several plies of fiberglass or carbon fiber. Milling the
roundness to match the tapered gear is the trick. That's the hard part.
If my landing gear exhibits shimmy, that's what I plan to do. The main
objective would be to stiffen the gear to prevent twisting loads. All this is
just speculation on my part, but I can't think of a better way to do it.
Bernardo
Okay, perhaps I'm doing things in a weird order, but I'm still playing
with shimmy stuff. The stiffeners I made from fiberglass didn't help. I'll
remove them soon. I switched to the 6-ply tires, no dice.
I was running the 6-ply tires at just below the max pressure rating of
50PSI. I read about people getting better results with low pressure, so I
dropped it to 26. Holy cow! That made it a TON worse! Weird.
So tonight I hopped out to the hanger and did a quick measurement with a
laser level. Held it on the brake disks and measured six feet in front and
behind the axle, marked it, and calculated toe...came out to 1/2 degree
toe-out.
I've read so much about this, but so much is conflicting. So now my
question is has anyone solved their shimmy by going from toe-out to toe-in?
It sure seems toe-in would work much better, but then I've read people
claiming the exact opposite.
Assuming I decide to go with toe-in, what's the best way to reset? Drill
a new hole and put in a new bolt, or drill the existing hole to the next
size bolt?
Oh, last thing. I didn't verify that each wheel has 1/2 degree toe
out. I just measured the difference between laser lines front and back, and it
works out to a total of 1 degree. For all I know, one is set differently
from the other, but I'll verify that and adjust accordingly if I reset to
toe-in.
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=382840#382840
&-> http://www.matronics.com/Navigator?Lightning-List<brsp; --> h= -->
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01234567
[quote][b]
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