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In a previous thread we discussed a questionable weld done on the streamlined tubing of a Tcraft landing gear. I went to our local EAA welding guru and asked the following questions. I don’t think ‘Ralph’ is an IA, but his work is admired and he’s recommended throughout the chapter:
Q1: Show him the splice and see how it relates to 43.13 (repairs to landing
gear with streamlined tubing); See how to interp 43.13 as agreeing or not agreeing. It looks like Fig 4-43 but without the rosette welds.
A1: ‘Ralph’ points out 43.13 is a guide and as long as you don’t make illogical changes, you’re in good shape. For example Fig 4-43 is the external sleeve for streamlined tubing but it doesn’t show rosette welds. Since the rosette welds have little effect on the tube in tension, they can be added. I complained that I’ve been met with “that’s not how 43.13 shows it” and he replied there are a lot of new A&Ps out there with little practical experience. His recommendation was to find an older A&P!
Q2. Assuming an external sleeve is OK, does it matter what angle the cut in
the original tubing is? As part of jigging can I add a 2 inch internal sleeve?
A2: Doesn’t matter what the angle is on the damaged original tubing; in fact, I can cut out the damaged section (about 1 foot long) and use an external sleeve over the gap; no call for any internal reinforcement. He warns however that every extra piece builds up the weight.
Q3. Show him my proposed reuse of the landing gear down strut attach fitting. Get agreement on the upper splice.
A3: No problem, just do it with a minimum of added weight
Q4. Do I even _need_ to bridge the gap with original sized streamlined
tubing?
A4: Nope, use same wall thickness get the correct overlap at either end, cut the TE of the external sleeve only as long as necessary (don’t split the entire tube).
Q5: Discuss forming both an inner and outer sleeve. The outer sleeve I got from Dillsburg sprung apart when I cut the TE . Tacking and clamping won’t be a problem; however forming an inner sleeve by reducing the major and minor axis of a piece of the original material is a problem
A5: Good luck
Q6. Is there supplemental text for 43.13?
A6: No
Q7: Post-weld heating?
A7; Summer, breezeless day, shut off the fan and let the joint cool on it’s own. If there is any concern get a can, cut slots for the tubing and place the can over the newly welded joint; that will keep the heat in and allow for slower cooling
Q8: Sparking and boiling
A8: Too much O2; try adjusting the pressures at the torch to 5 and 10 psi
Q9: Remelting old poor weld –
A9: The concern is not that the metal is getting re-heated or that you have to use a lot of heat to melt the old filler, but that every time you heat the metal you develop a layer of oxide and remember, when we were discussing how deep a rust pit could be (10% of the original) so you are loosing wall thickness every time the oxide if formed. That’s one of the reasons (beside forming heat risers) you want to make the weld as continuously as possible, not doing half, going for coffee, then returning.
Q1: Show him the splice and see how it relates to 43.13 (repairs to landing
gear with streamlined tubing); See how to interp 43.13 as agreeing or not agreeing. It looks like Fig 4-43 but without the rosette welds.
A1: ‘Ralph’ points out 43.13 is a guide and as long as you don’t make illogical changes, you’re in good shape. For example Fig 4-43 is the external sleeve for streamlined tubing but it doesn’t show rosette welds. Since the rosette welds have little effect on the tube in tension, they can be added. I complained that I’ve been met with “that’s not how 43.13 shows it” and he replied there are a lot of new A&Ps out there with little practical experience. His recommendation was to find an older A&P!
Q2. Assuming an external sleeve is OK, does it matter what angle the cut in
the original tubing is? As part of jigging can I add a 2 inch internal sleeve?
A2: Doesn’t matter what the angle is on the damaged original tubing; in fact, I can cut out the damaged section (about 1 foot long) and use an external sleeve over the gap; no call for any internal reinforcement. He warns however that every extra piece builds up the weight.
Q3. Show him my proposed reuse of the landing gear down strut attach fitting. Get agreement on the upper splice.
A3: No problem, just do it with a minimum of added weight
Q4. Do I even _need_ to bridge the gap with original sized streamlined
tubing?
A4: Nope, use same wall thickness get the correct overlap at either end, cut the TE of the external sleeve only as long as necessary (don’t split the entire tube).
Q5: Discuss forming both an inner and outer sleeve. The outer sleeve I got from Dillsburg sprung apart when I cut the TE . Tacking and clamping won’t be a problem; however forming an inner sleeve by reducing the major and minor axis of a piece of the original material is a problem
A5: Good luck
Q6. Is there supplemental text for 43.13?
A6: No
Q7: Post-weld heating?
A7; Summer, breezeless day, shut off the fan and let the joint cool on it’s own. If there is any concern get a can, cut slots for the tubing and place the can over the newly welded joint; that will keep the heat in and allow for slower cooling
Q8: Sparking and boiling
A8: Too much O2; try adjusting the pressures at the torch to 5 and 10 psi
Q9: Remelting old poor weld –
A9: The concern is not that the metal is getting re-heated or that you have to use a lot of heat to melt the old filler, but that every time you heat the metal you develop a layer of oxide and remember, when we were discussing how deep a rust pit could be (10% of the original) so you are loosing wall thickness every time the oxide if formed. That’s one of the reasons (beside forming heat risers) you want to make the weld as continuously as possible, not doing half, going for coffee, then returning.