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Fergus Kyle
Joined: 03 Jun 2007
Posts: 291
Location: Burlington ON Canada
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 Posted: Sat Jun 11, 2011 7:44 am Post subject: Landing gear Failure, ATTN Graham Sing... |
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Graham,
Thanks for your latest in that $%^&* lever and its connections.
I remember seeing a ‘triangle’ plate which slide down abaft the lever to serve as a “parking” brake. After this sad event subject, it occurred to me that a similar plate could be slid behind the lever before landing so as to keep it from bobbing up when encountering bumpy surfaces.
Do you think it might serve to lock the lever or is the linkage mechanism such that it will simply bend the lever and permit inadvertent retraction? – I haven’t studied the subject, obviously, and am sloughing off the work out of pure laziness...........
Regards, Ferg
[quote][b]
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grahamsingleton(at)btinte
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| Posted: Sat Jun 11, 2011 9:16 am Post subject: Landing gear Failure, ATTN Graham Sing... |
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Hi Ferg
there have been collapses when the lock flicked up but the main problem is the over centre situation. If there is too much O/C, when the gear hangs down it pulls it off the O/C and momentum of the links can take it under centre. Then all the load is transferred to the lever which then bends and lets go.
Setting up is therefore critical, the lever must not be allowed to move forward when in the locked position to prevent the links moving away from the over centre position.
I think maybe I need to enhance my previous remarks a little. Just a bit too cryptic as usual!
Graham
From: Fergus Kyle <VE3LVO(at)rac.ca>
To: 5EUROPALIST <europa-list(at)matronics.com>
Sent: Saturday, 11 June, 2011 16:41:27
Subject: Landing gear Failure, ATTN Graham Sing...
Landing gear Failure, ATTN Graham Sing...
Graham,
Thanks for your latest in that $%^&* lever and its connections.
I remember seeing a ‘triangle’ plate which slide down abaft the lever to serve as a “parking” brake. After this sad event subject, it occurred to me that a similar plate could be slid behind the lever before landing so as to keep it from bobbing up when encountering bumpy surfaces.
Do you think it might serve to lock the lever or is the linkage mechanism such that it will simply bend the lever and permit inadvertent retraction? – I haven’t studied the subject, obviously, and am sloughing off the work out of pure laziness...........
Regards, Ferg
[quote]http://www.matronics.com/con================
[b]
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rparigoris
Joined: 24 Nov 2009
Posts: 792
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| Posted: Sat Jun 11, 2011 10:15 am Post subject: Re: Landing gear Failure, ATTN Graham Sing... |
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Hi Graham
"If there is too much O/C, when the gear hangs down it pulls it off the O/C and momentum of the links can take it under centre."
Sorry, I don't quite know what you are trying to say.
Would you mind too much to explain a little more?
If lets say we had 1/2" over center. If the gear lever held LG08 against the stop on the undercarriage mounting frame, unless there was some play, the LG08 should stay against the stop, no?
1/2" over center would fail the stops in a hard landing because of the tremendous leverage by being too much over center. Is this perhaps what you are talking about, too much over center will fail the undercarriage mounting frame and cause a collapse? The early Classic undercarriage mounting frames needed to be strengthened to prevent just this scenario with proper amount of over center.
I could see if there was play in the system that gravity could pull the gear down and get it on center or even under, but if there is no play and the down detente is solidly pushing LG08 against stop i am at a loss to visualize how too much would equate to under-center and cause a collapse?
I scuff sanded LG08 and my gear lever and reamed the holes and bonded with Redux in an attempt to keep play to a minimum, in addition to installing the stiffener angle (think Mod 51? could be wrong on the number)
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rparigoris
Joined: 24 Nov 2009
Posts: 792
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| Posted: Sat Jun 11, 2011 10:22 am Post subject: Re: Landing gear Failure, ATTN Graham Sing... |
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One solution that I liked and incorporated is a spring to hold the down latch down. No matter what I did (which included reaming holes and trying NAS hardware), if I fooled with the latch I could get it to jam in the up position once in a while. It was due to sideway racking/skew and friction from point loading and it was just not reliable enough for my taste considering consequences if it got stuck in the up position.
Anyway here are details for down-latch spring:
http://www.europaowners.org/forums/gallery2.php?g2_itemId=86937\
open the album on the left.
Simple, stupid, cheap, easy to make and lightweight.
Sorry I can't remember who sent me the .jpg of the spring.
I wound it out of some stainless spring wire i picked up from www.mcmaster.com
Ron Parigoris
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grahamsingleton(at)btinte
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| Posted: Sat Jun 11, 2011 1:56 pm Post subject: Landing gear Failure, ATTN Graham Sing... |
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<<1/2" over center would fail the stops in a hard landing because of the tremendous leverage by being too much over center. Is this perhaps what you are talking about, too much over center will fail the undercarriage mounting frame and cause a collapse? The early Classic undercarriage mounting frames needed to be strengthened to prevent just this scenario with proper amount of over center.
I could see if there was play in the system that gravity could pull the gear down and get it on center or even under, but if there is no play and the down detente is solidly pushing LG08 against stop i am at a loss to visualize how too much would equate to under-center and cause a collapse?>>
Hi Ron
yes, this is pretty much what I was trying to explain. But still haven't quite done it? The play that matters is the clearance between LG 12 and the part it locks into in the gear down position. I think there is an ideal amount of O/C which is quite small so that the load on LG12 is low. Your suggestion of 1/16" sounds about right but I suggest not more than 1/16". Then there must be very small clearance between LG12 and the lock so that it can't go forward when G (during a bounce) tries to pull the gear down from the O/C position.
You can see from the original picture Jeff posted that the loads can be considerable, enough to completely fail the LG12. I wouldn't have thought there was much gap on the one that failed but the combined effect of too much O/C and too much LG12 clearance probably caused Jeff's failure. imho of course. Hope this is a clearer explanation of my thinking, please excuse the creaking and groaning from the old gears in my head!
Graham
From: rparigoris <rparigor(at)suffolk.lib.ny.us>
To: europa-list(at)matronics.com
Sent: Saturday, 11 June, 2011 19:15:29
Subject: Re: Landing gear Failure, ATTN Graham Sing...
--> Europa-List message posted by: "rparigoris" <rparigor(at)suffolk.lib.ny.us (rparigor(at)suffolk.lib.ny.us)>
Hi Graham
"If there is too much O/C, when the gear hangs down it pulls it off the O/C and momentum of the links can take it under centre."
Sorry, I don't quite know what you are trying to say.
Would you mind too much to explain a little more?
If lets say we had 1/2" over center. If the gear lever held LG08 against the stop on the undercarriage mounting frame, unless there was some play, the LG08 should stay against the stop, no?
1/2" over center would fail the stops in a hard landing because of the tremendous leverage by being too much over center. Is this perhaps what you are talking about, too much over center will fail the undercarriage mounting frame and cause a collapse? The early Classic undercarriage mounting frames needed to be strengthened to prevent just this scenario with proper amount of over center.
I could see if there was play in the system that gravity could pull the gear down and get it on center or even under, but if there is no play and the down detente is solidly pushing LG08 against stop i am at a loss to visualize how too much would equate to under-center and cause a collapse?
I scuff sanded LG08 and my gear lever and reamed the holes and bonded with Redux in an attempt to keep play to a minimum, in addition to installing the stiffener angle (think Mod 51? could be wrong on the number)
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=342732#342732
p; -Matt Dralle, Libution" =======
[quote][b]
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rparigoris
Joined: 24 Nov 2009
Posts: 792
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| Posted: Sat Jun 11, 2011 2:35 pm Post subject: Re: Landing gear Failure, ATTN Graham Sing... |
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Hi Graham
Thanks for the reply. Sorry but I am still confused. I think a few more questions answered will get me on track.
First I think we need to absolute clarify what you mean by O/C. My interpretation is Over Center. In other words if you load the main tire, it will load the swingarm which will load LG08, and if Over Center, LG08 will try and move forward, in other words towards the prop. It will be jamming into the undercarriage mounting frame, the more you load it, the harder it will push into the undercarriage mounting frame.
Like I mentioned in a prior post, My undercarriage mounting frame was ill fabricated where the stops did not allow LG08s to go over center. One was on center and the other was under center. Under center means if you load the tire, it will load the swingarm which will load LG08s. The one that was under center will begin to push backwards towards the tail. Again this is under center. The only thing holding the LG08s forward in a situation where you are under center is the LG12. In Jeffs case I think he was under center and the loading caused the lever to bend. There is a good chance he has an ill fabricated undercarriage mounting frame that did not allow over center, but caused an under center situation.
So, do you mean O/C is Over center, or do you mean by O/C is what Iconsider under center?
Thus you want 1/16" in my term Over center where when you push up on swingarm LG08 is loaded and pushes forward. You want LG12 held by the down indent where LG08 is held forward against the undercarriage mounting frame stop where there is little to no slop that would allow LG08 to go under center (in others allow LG08 to swing aft towards the tail).
Ron Parigoris
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