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 Landing Gear
 Repair of cracked A frame landing gear
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jtball

Australia
48 Posts

Posted - 08/21/2011 :  02:17:43  Show Profile  Send jtball a Yahoo! Message  Reply


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James Ball

jtball

Australia
48 Posts

Posted - 08/21/2011 :  02:23:03  Show Profile  Send jtball a Yahoo! Message  Reply
Don't now what happened to the text I put with the photos. Here it is again.
During a routine an annual inspect of a T18 here in AU , we found some cracking in the Main landing gear. I thought I would share so others can look at their T18 in this area. We repaired the weld and added a doubler to both front and back sides.
Cheers

James Ball

Edited by - admin on 11/07/2011 11:00:00
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fytrplt

USA
182 Posts

Posted - 08/21/2011 :  05:09:55  Show Profile  Reply
Let us know how this works out as it is a common problem.

Bob Highley
N711SH
SN 835
KLAL

Edited by - admin on 11/07/2011 11:00:00
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dickwolff

Canada
182 Posts

Posted - 09/05/2011 :  08:57:25  Show Profile  Reply
Was your gear already heat treated? Did you heat treat again?

As my luck would have it, I found the exact same cracks on MLM.

DW

_________
In theory, theory and practice are the same. In practice, they are not.

Edited by - admin on 11/07/2011 11:00:00
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dickwolff

Canada
182 Posts

Posted - 09/05/2011 :  09:02:36  Show Profile  Reply
OK... question answered. Saw your notes.

Is 550 enough? I worked in a spring shop for a couple of decades, and we tempered 4130 at 825 for an hour or so. (After a full quench of course.)

_________
In theory, theory and practice are the same. In practice, they are not.

Edited by - admin on 11/07/2011 11:00:00
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jtball

Australia
48 Posts

Posted - 09/05/2011 :  19:47:14  Show Profile  Send jtball a Yahoo! Message  Reply
The main landing gear was heat treated on manufacture . We tempered as per notes after repair . Hope that will do the trick . We have repaired other legs and they seem to be ok. I personally don't think the fillet weld was adequate. The weld looked pretty but needs more metal in the weld.

James Ball

Edited by - admin on 11/07/2011 11:00:00
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hurant

USA
34 Posts

Posted - 09/05/2011 :  20:27:44  Show Profile  Reply
I would need to find and check my old receipt but I thought the tempering temperature was 1100 plus degrees.

Edited by - admin on 11/07/2011 11:00:00
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dickwolff

Canada
182 Posts

Posted - 09/06/2011 :  12:24:04  Show Profile  Reply
Well, I searched the old thorplist and found the results to be quite interesting. There was a lot of advice suggesting to do nothing more than stop-drill the ends of each crack and just monitor. Has that advice truly withstood the test of time?

Personally I'm a little uncomfortable with cracks in major load-carrying parts. I really like jtball's repair shown above. It makes a lot of sense to me to have a tapered tongue to reduce the stress concentration of the gusset.

Edited by - dickwolff on 09/06/2011 18:40:28
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fytrplt

USA
182 Posts

Posted - 09/08/2011 :  03:37:43  Show Profile  Reply
I was one who used the stop drill method and it served me about 1000 hrs. until the crack finally went around the corner. I, too, had pretty but small, inadequate welds. I suspect taxiing on unimproved surfaces was the culprit in stressing the weld.

Bob Highley
N711SH
SN 835
KLAL

Edited by - admin on 11/07/2011 11:00:00
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dickwolff

Canada
182 Posts

Posted - 10/15/2011 :  18:05:57  Show Profile  Reply
What are peoples experience with distortion after heat treat (or re-heat treat)?

Seems to me as long as the part goes into the quench oil vertically, there shouldn't be much.

Edited by - admin on 11/07/2011 11:00:00
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hurant

USA
34 Posts

Posted - 10/15/2011 :  18:52:11  Show Profile  Reply
In my experience, heat treating distorted the gear legs quite a bit. I used the bow and arrow method for straightening the gear.(Hydraulic jack and fairly heavy chain)

Edited by - admin on 11/07/2011 11:00:00
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dan

USA
175 Posts

Posted - 10/16/2011 :  18:48:07  Show Profile  Reply
Hi James, the welds look good. As Bob has said these gear legs somtimes end up with cracks in this area, I dont believe there is anything weak about this gear leg system, but if it gets banged right then somtimes these cracks show up. This is where the legs show some stress when they are loaded or over loaded. Watch the rest of the structure to make sure the stress point hasnt moved somwhere else after beefing up the one on the front of the legs. The Fillet was a little skimpy, you sure done a fine job......Dan

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jtball

Australia
48 Posts

Posted - 10/16/2011 :  20:22:10  Show Profile  Send jtball a Yahoo! Message  Reply
That T18 will be back soon due to the aged plastic brake lines which I am replacing with braided hose,so I will have better look at the surrounding structure then.

James Ball

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dickwolff

Canada
182 Posts

Posted - 10/17/2011 :  02:52:17  Show Profile  Reply
Just curious, where can one get a copy of the drawing showing the gear repair details? - DW

Edited by - dickwolff on 10/17/2011 06:53:14
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jtball

Australia
48 Posts

Posted - 10/19/2011 :  03:27:48  Show Profile  Send jtball a Yahoo! Message  Reply
I will ask the owner of the drawings, if its OK to put on the forum. The drawings are not approved as such but I use an Approved Person in the Sport aircraft association of Australia to incorporate such a modification. Who gives out certificates of airworthiness certificates for experimental category. I will get back to you soon.

James Ball

Edited by - admin on 11/07/2011 11:00:00
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dickwolff

Canada
182 Posts

Posted - 10/24/2011 :  11:11:03  Show Profile  Reply
I recall some statement in a newsletter about whether or not this particular section of weld (on the bottom side of the gusset) was even required.

Has anyone tried leaving the bottom bead un-welded and if so, have they accumulated enough time to evaluate the idea?

I am considering the idea of carefully grinding out the cracked weld bead and leaving that section of the gusset open. (Of course, I would smooth the tube to a proper finish, and do a dye-pen check after to make sure I got rid of the crack.)

Any thoughts?



Edited by - dickwolff on 10/25/2011 03:35:25
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