air plane exhaust

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welded the exhaust yesterday and past inspection todayclose up pic didnt come out but now that im gettingall the welding jobs at the airport ill get better pics later Attached Images
Reply:Not a bad gig. Take care of those airplanes now! Attached ImagesCity of L.A. Structural; Manual & Semi-Automatic;"Surely there is a mine for silver, and a place where gold is refined. Iron is taken from the earth, and copper is smelted from ore."Job 28:1,2Lincoln, Miller, Victor & ISV BibleDanny
Reply:Originally Posted by ed macwelded the exhaust yesterday and past inspection todayclose up pic didnt come out but now that im gettingall the welding jobs at the airport ill get better pics later
Reply:Or just let the A&P deal with all that and just do the welding???LOL The customer is always right?
Reply:Originally Posted by ed macwelded the exhaust yesterday and past inspection todayclose up pic didnt come out but now that im gettingall the welding jobs at the airport ill get better pics later
Reply:Lots of interesting posts here, I wouldnt say that all the A&P schools dont teach welding, some dont do much and some do quite a bit, it seems to depend more on the teacher and less on the school. As far as IA's knowing less about welding....sometimes thats true, and sometimes it isnt. Some IA's I know study construction and repair methods as they should, others seem to try to "cover it all" by not knowing much about a specific aspect of construction. To the guy who said to use 347 filler, thats an un-justified recomendation. Taylorcraft originaly used mild steel for the exhaust systems, obviously this system was changed at some point in history, so the base metal is unknown. From my observations, the people that knew the least about welding were the welding shops and people that were not an FAA repair station or otherwise approved. However I have seen some scary stuff at some repair facilites as well. By far some of the worst people I have talked to, are some people that came from the automitive racing world, and figured since the materials were the same, so was the welding process....by far the worst. That and guys that read a welding book they bought at home depot or Lowes and think they know a lick about what they are working on.-Aaron
Reply:Originally Posted by makoman1860Lots of interesting posts here,..... To the guy who said to use 347 filler, thats an un-justified recomendation. Taylorcraft originaly used mild steel for the exhaust systems, obviously this system was changed at some point in history, so the base metal is unknown. .....     -Aaron
Reply:Good looking TCraft1  I have in my past life built several and modified a lot more.  AS for the exhaust both of you are right!  Must be signed off as a "repair and yellow tagged".  AP can not do that without either a repair station lic. or an AP/IA with an endorsement (in the good ole days in AK that meant a trip to the FSDO----Flight Standards District Office.In todays world, I wouldn't touch it!  (I am just learning to Tig Weld) after 40 years of OA, stick and mig, and the stress that is on most AC exhaust is amazing and if not welded right it will crack, if not installed right it will crack, if not designed right it will crack again and again and again!  (as in a Cessna 310, Cessna 210 and lots more!!Here is another good use for Cub exhaust: heating up lunch after landing at the campsite?Probably all changed in the last 10 years though?Tim---Highly modified PA-12 Attached ImagesA rich man is not the one who has the most but instead one who needs theleast. Retired IUEC local 19AK Bush pilot,  Chaplain  CMA Chapt 26victor torchesMiller110v migDynasty 200dx (new in Dec 08)Hypertherm PM-45MM-252 (new 2/09)
Reply:Originally Posted by dave powelsonWhat I actually said in my previous post was: '4-Using 347 ss rod, is preferred since most of the exhausts use that as the parent material.'The work I do is under an IA's supervision, the repair documented before & after, with NDT as deemed necessary.
Reply:Originally Posted by dave powelsonWhat I actually said in my previous post was: '4-Using 347 ss rod, is preferred since most of the exhausts use that as the parent material.'The work I do is under an IA's supervision, the repair documented before & after, with NDT as deemed necessary.
Reply:Personally I have seen everything from Mild Steel, 308, 309, 316, 318, 321, the whole monel and inconel series and everything in between. There is no ONE popular material. Most of the difference between the guy that does the superb repair, and the questionable one, comes down to knowledge and not skill. The best weldor in the world, using the wrong filler or procedure, still makes a useless weld. -Aaron
Reply:Not (yet a tig welder) but I have got upwards of 14k hours in Cubs and other bush planes and having rebuilt many, it seems that the older (cubs with mild steel exhausts tended to 'rust out' and that is the best guess that I have for the migration to SS alloys,  My experience is that unless they had an expansion joint (such as was done on the newer exhaust systems they cracked even more then the older stuffl.I have a friend in AK that was the chief welder in the ANG and has his own exhaust repair business and I know he was awefull meticulus obout how he performed the weld repairs on exhaust and (did not garrantee any of them as it was impossible to really determine the base metal condition from all the contamination (over time) and as well the fit up after installed (even though he jigged the most common stuff.----all I know??It was his precision that got me interested enough to now take up the learning of the process!TimA rich man is not the one who has the most but instead one who needs theleast. Retired IUEC local 19AK Bush pilot,  Chaplain  CMA Chapt 26victor torchesMiller110v migDynasty 200dx (new in Dec 08)Hypertherm PM-45MM-252 (new 2/09)
Reply:Originally Posted by UltrachopNot (yet a tig welder) but I have got upwards of 14k hours in Cubs and other bush planes and having rebuilt many, it seems that the older (cubs with mild steel exhausts tended to 'rust out' and that is the best guess that I have for the migration to SS alloys,  My experience is that unless they had an expansion joint (such as was done on the newer exhaust systems they cracked even more then the older stuffl.I have a friend in AK that was the chief welder in the ANG and has his own exhaust repair business and I know he was awefull meticulus obout how he performed the weld repairs on exhaust and (did not garrantee any of them as it was impossible to really determine the base metal condition from all the contamination (over time) and as well the fit up after installed (even though he jigged the most common stuff.----all I know??It was his precision that got me interested enough to now take up the learning of the process!Tim
Reply:William,I once did a test on a 10-520 Continental 6 cyclinder engine to prove how much they grow in width and contract when cooling,  I put some locating plates rigid mounted on the engine mount and firewall and built pointers with soft tips that compressed when they ran interference and the accomulative movement (in addition to the mounts was in excess of .250in.  Most later designed piston A/C engine exhaust systems had slip joints between the collector and the exhaust runners and flex points at the mufflers and spring mounts between the tail pipe/mufflers and the frame (most).  The 1970-s series Beechcraft light twin Barons where well known for cracked exhaust systems!  (I don't know how he did it as a proceedure), but my friend the welder in AK used to have a process to minimize the stress on his weld patches.  I know the amount of weld filler was at a minimum and he would cut out all the cracked area he could find.  He used to tell me how important it was to be real uniform in the bead width and height.TimA rich man is not the one who has the most but instead one who needs theleast. Retired IUEC local 19AK Bush pilot,  Chaplain  CMA Chapt 26victor torchesMiller110v migDynasty 200dx (new in Dec 08)Hypertherm PM-45MM-252 (new 2/09)
Reply:In the world of things being built as light as possible, with all sorts of thermal and mechanical loading on them, sometimes it just has to be accepted that a part will require constant repair. Thats why we have such close inspections every year or more often. Failures rarely even happen without warning, and neglecting the warning signs or being lazy on inspection is where the start of the failure turns dangerous. You learn this especially on antique aircraft where you just cant get a new part. Cylinder heads on some kinner engines are prone to cracking in a certain area, crank cases on certain franklin engines are the same way. This is known, so you check for it on a regular basis. If one starts cracking, its removed, repaired, and put back in service without issue. Now if you dont pay attention and fly on that cracked cylinder head for another 200 hours until it finally pops off....now your in trouble.
Reply:Makoman,So right you are!  I remember the narrow deck lycoming cylinder base problems as well as the ones you mentioned!  It seems that the lack of disciplined inspection has become more common place in todays world in all forms of transportation.  I grew up in the back country and we did more inspection/ maintenance, often just to insure less down time due to the fact that getting repairs/replacement parts was most times impractical.I once flew a beaver on floats home after a the Pratt R-985 decided to spit a cyclinder into the channel (due to the maintenance crew not properly torquing the bases!!  How do I know, cause the other cyclinders weren't properly torqued either!!  (that was expensive)I am always amazed of how people complain about European autos "costing so much to fix" when when research is done you find that those autos that were strictly maintained according to the "engineered" schedule would last nearly forever.We do indeed live now in an instant gratification lifestyle!  (I am guilty when it comes to Lawn maintenance equipment) especially!!!TimA rich man is not the one who has the most but instead one who needs theleast. Retired IUEC local 19AK Bush pilot,  Chaplain  CMA Chapt 26victor torchesMiller110v migDynasty 200dx (new in Dec 08)Hypertherm PM-45MM-252 (new 2/09)
Reply:Originally Posted by UltrachopWilliam,I once did a test on a 10-520 Continental 6 cyclinder engine to prove how much they grow in width and contract when cooling,  I put some locating plates rigid mounted on the engine mount and firewall and built pointers with soft tips that compressed when they ran interference and the accomulative movement (in addition to the mounts was in excess of .250in.  Most later designed piston A/C engine exhaust systems had slip joints between the collector and the exhaust runners and flex points at the mufflers and spring mounts between the tail pipe/mufflers and the frame (most).  The 1970-s series Beechcraft light twin Barons where well known for cracked exhaust systems!  (I don't know how he did it as a proceedure), but my friend the welder in AK used to have a process to minimize the stress on his weld patches.  I know the amount of weld filler was at a minimum and he would cut out all the cracked area he could find.  He used to tell me how important it was to be real uniform in the bead width and height.Tim
Reply:William,I seem to recall that I was told that uniformity along with minimizing the size of the bead tended to minimizae the disruption that the repair made to the original uniformity of the tubing?  I know that I have seen exhaust flange repair "patches" crack along the edge of the patches on many occasions and usually they were parallel to the flange.I am trying to get all the knowledge I can on the metalugy of the allows that I intend to weld (along with practicing the techniques.  (I hope to in the future) take a class on metalugy to fill in the blanks of my own research.I for one would not trust my skill level to the task of repairing AC exhaust. (I have cussed to many poorly repaired systems in the past)TimA rich man is not the one who has the most but instead one who needs theleast. Retired IUEC local 19AK Bush pilot,  Chaplain  CMA Chapt 26victor torchesMiller110v migDynasty 200dx (new in Dec 08)Hypertherm PM-45MM-252 (new 2/09)
Reply:Originally Posted by UltrachopWilliam,I seem to recall that I was told that uniformity along with minimizing the size of the bead tended to minimizae the disruption that the repair made to the original uniformity of the tubing?  I know that I have seen exhaust flange repair "patches" crack along the edge of the patches on many occasions and usually they were parallel to the flange.I am trying to get all the knowledge I can on the metalugy of the allows that I intend to weld (along with practicing the techniques.  (I hope to in the future) take a class on metalugy to fill in the blanks of my own research.I for one would not trust my skill level to the task of repairing AC exhaust. (I have cussed to many poorly repaired systems in the past)Tim
Reply:One other thing, backup gas. You are supposed to use backup gas on stainless steel. Meaning you have to fill the pipes with a noble gas. Some use Argon some use helium. Sometimes it is whatever bottle and regulator you have available for backup gas.        Sincerely,             William McCormick
Reply:As far as welding on aircraft exhaust pipes, better safe than sorry.  Don't do it.  When I went to school for my A&P(many moons ago) we had a situation where some repairs were done on a pipe at the school with the instructors approval.  When the inspection time came questions began to be asked about the repairs and things got ugly from there.  No one wants the possibility of liability to come back on them.  Thats why sprecialized shop do the work and when they do it, only the flanges or some other part are reused and the rest is new material.  Needless to say this incident I described was kept hush hush since there was a Fisdo office two hangers down.I'ts just not worth it for even a couple of hundred dollars.  Thats why aircraft parts cost ten times what they should and are still using technology from the 40's.  Liability, Liability, Liability.....Just my two cents.
Reply:I work for a large turbine engine builder. We mostly do aircraft work. Trust me, when a weld fails on an aircraft part there is always a huge witch hunt.  In our case, the average weld failure costs around $500K for a part that fails in the field and requires a field recall or warning notice to the tech manuals.Even so, we have several FAA approved repair facilities.  We work mostly on stainless, Inconel, Hastelloy, and Kovar alloys.  Turbines are of course different than piston engines due to the obvious temp and thermal stress requirements.  That said, last year, I reviewed and approved the repair methods for FAA repair of cracks in Inconel and stainless ducting and cowling.  The same method has been used for years.  It involves something like a TIG braze with gold filler alloy to plug all the cracks in the tubing/ducting.  I have never seen it done; I just got to read the procedure manual from an editorial “comment” perspective.
Reply:The real problem is the #$%^ trial lawyers!!!  (that is why I got out of working on or owning a "production built' AC. Experimental for personal use placarded to say if in the event of engine failure I will have the controls in one hand and my pistol in the other.  (the passenger can guess why) I already know!TimA rich man is not the one who has the most but instead one who needs theleast. Retired IUEC local 19AK Bush pilot,  Chaplain  CMA Chapt 26victor torchesMiller110v migDynasty 200dx (new in Dec 08)Hypertherm PM-45MM-252 (new 2/09)