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dickwolff
PostPosted: Mon Oct 24, 2011 11:11 am 
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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?

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Last edited by dickwolff on Mon Oct 24, 2011 11:11 am, edited 1 time in total.

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dickwolff
PostPosted: Tue Oct 25, 2011 4:41 pm 
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I am considering the idea of carefully grinding out the cracked weld bead and leaving that bottom section of the gusset "open." Any thoughts?

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Last edited by admin on Tue Oct 25, 2011 4:41 pm, edited 1 time in total.

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leewwalton
PostPosted: Tue Oct 25, 2011 5:53 pm 
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Dick,
Although its probably 6 one half a dozen to another I'd probably just leave it alone, stop drill the crack and then keep an eye on it. You could certainly argue that there is little or nothing to be gained by leaving it there but thats just me. If you look back in the NL there is a "repair" outlined by Jim Paine a while back if the crack creeps. There are a lot of thorps flying with that weld cracked.

Maybe post a good pic for the more experienced welders/gear guys out there to take a look at.

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Last edited by admin on Tue Oct 25, 2011 5:53 pm, edited 1 time in total.

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Rich Brazell
PostPosted: Tue Oct 25, 2011 6:25 pm 
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Ditto. I don't see the benfit of "grinding out" the weld, if stop drilling will do the trick. Keep stop drilling until the weld is gone !

RB


Last edited by Rich Brazell on Tue Oct 25, 2011 6:25 pm, edited 1 time in total.

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dickwolff
PostPosted: Thu Oct 27, 2011 5:06 am 
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OK. How do you stop-drill the crack front that is going INTO the material?

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Last edited by admin on Thu Oct 27, 2011 5:06 am, edited 1 time in total.

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leewwalton
PostPosted: Thu Oct 27, 2011 5:40 am 
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Dick,
I'm assuming you're talking about this ...

Image


... from that point of view it looks pretty minor, I don't see the crack penetrating the gear leg. Obviously of it does you're looking at a major repair. If that's not the case I'd just get a 1/16" carbide bit and carefully stop drill it.

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fytrplt
PostPosted: Thu Oct 27, 2011 8:03 am 
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Remember, the part of the gear leg you are looking at is the "A" frame that holds the real gear leg. The smaller of the tubes is the actual gear leg.

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Last edited by admin on Thu Oct 27, 2011 8:03 am, edited 1 time in total.

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James Grahn
PostPosted: Thu Oct 27, 2011 6:24 pm 
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I wouldn't even stop drill it. It is not going anywhere. Just fly it!

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Last edited by admin on Thu Oct 27, 2011 6:24 pm, edited 1 time in total.

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dickwolff
PostPosted: Sat Mar 31, 2012 7:18 am 
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Continuing the saga.... I was grinding out the weld fillets at the bottom of the gusset with a dremel and a cut-off disk. After the second one ground away like butter, the light went on... I think my gear is soft! (ie, possible never heat treated.)

Can this be?! Could a soft A-frame go 1100+ hrs in service with no deterioration except for the classic gusset cracks?

(I know all of Fraser's landings were as smooth as a baby's bum, but there were three owners before him.)

D


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fytrplt
PostPosted: Sat Mar 31, 2012 8:34 pm 
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The heat treating called out on yhe Thorp drawings is for 180,000 PSI. This is more attuned to normalizing than heat treating for hardness. I have found that several heat treated gears I have delt with are easily machinable.

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Tom Worth
PostPosted: Mon Apr 02, 2012 7:26 pm 
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Hopefully someone will get a welding engineer involved with this issue. In my experience in industry one should never weld across a beam (it sets up a stress area). I think the welds along the beam are adequate to hold the leg to the cross member with the gusset. Tom Worth


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dan
PostPosted: Mon Apr 02, 2012 8:38 pm 
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Tom, that is absolutely correct!! Dan


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fytrplt
PostPosted: Mon Apr 02, 2012 9:29 pm 
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LLoyd Toll, a welding guru from the WWII era made the same statement as Tom W. about cross beam welding when he built his Thorp many years ago.

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ljkrume
PostPosted: Wed Apr 04, 2012 2:25 pm 
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Hey fellas, thought I'd chime in about landing gear repair too.

I didn't think welding across the leg would be a good idea either, so I didn't do mine. Sorry it hasn't flown to say good or bad, but you all know the leg inside is really the part that matters. If it's considered to be a beam in bending, then welds along the neutral axis would be better suited than those across material with higher stress. Some of the testimonies here verify T-18's have flown with soft gear or repaired gear without repeating the heat-treatment. I'm not the expert at metallurgy, but if I'd like to help if I can explain what I know to those who might not know.

To do it right, weld on steel that's been totally annealed (softened). Internal stresses can cause it to crack after welding if it's already 'hard'. Afterward, for heat treating to get the 180,000 psi strength and 'spring' in the material it first has to be heated above transition temperature, which may be roughly 1400F (above cherry-red) and then quenched. Then it's tempered by raising it back up to a different temperature (several hundred F) and cooling slowly. This potentially softens it, slightly, but with the great advantage of being less brittle and reduces built-up internal stresses. It has to remain below the transition temp or you ruin the initial treatment. Unfortunately, welding does just that.

By definition, welding is a process where materials are fused together by melting them (~3800F). It really ruins the original heat treatment. To get it back you need to repeat the whole treatment over again. Simply re-heating it actually only softens it more because it cools relatively slowly. The quenching process is the trick that 'freezes' steel in it's austenitic state. Don't do this at home unless you're an expert and have all the facilities. I sent mine to Hinterliner(sp?) in Utah. Yes, at the edge of machinability at 180,000 psi steel can still be machined, but you'll notice it may be a little harder to do than when it's soft. I reamed my steel spar fittings only after heat-treating because the process can distort things a little. Lot's of guys use a file on the edge of a part to feel and compare hardnesses. Welding on 'hard' steel can often lead to more cracking, due to internal stresses and uneven conditions within the material. Professional heat-treaters give it time to 'soak' in the oven and get it all even.

Nevertheless, there are T-18's flying without pristine heat-treatments on their gear, and evidently they seem to work. Maybe it's a matter of use or how good your landings are, but that's not the design. If the actual leg inside hasn't been affected by heat that would help. I surely hope not to have to repair my gear. If I did it would be a hard choice to remove it and sent it out again for treatment, and perhaps I wouldn't either. Thought you guys might need to know. Hope it helps.

Les Krumel,
Albuquerque


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pacer18a
PostPosted: Sun Feb 07, 2016 3:29 pm 
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JTBALL any update on how your fix has worked over time?

Dave


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