Should I even try this?

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One half of the split barrel on the clutch cable perch cracked off.  I'd like to get it looking as original as possible.   There would be a dozen other ways to skin this cat otherwise with something nice and robust.    It looks like it would be a hell of a challenge for a novice alum welder.   If I can get something close to the profile welded up I'll have to do a little machining on it to get the rebate correct. I'm not yet that skilled at cast alum.  And this is a pretty delicate task. I'm pretty comfortable with settings and technique for extruded aluminum and have done a fair amount.  I'm not very confident about cast.  I'm using an ArcMaster 185 AC/DC. I have available ceriated tungsten and pure argon.  If this whole perch is likely to collapse like a stick of butter in my unskilled hands, I'll have to find a different fix.  But if I get any encouragement from you I'll go to the junkyard and get a couple of pieces of similar casting off of some old bikes and practice, practice,  practice first.  Thanks so muchLast edited by frascati; 02-21-2010 at 07:17 PM.
Reply:Your big issue will be getting the cast aluminum clean. Unlike cast iron, cast aluminum welds very similiar to wrought products. If you are accomplished at wrought aluminum, you should not have a problem.
Reply:Good news.  I assumed that cast alum was like iron in that regard.  But a few others besides yourself suggested that it's similar to wrought alum.  The broken piece is long gone, so I'm probably talking about either building it up, or much better,  just leveling off the perch and welding a newly fabbed barrel there.   As far as cleaning.  With a newly ground surface am I good?   Or is cast alum porous enough in most cases to have absorbed contaminant, oils, solvents, etc, into its structure and never end up 100 percent clean?  Suggestions for wave balance setting on the TIG?   50/50.    20/80 (more penetration).   60/40 (more cleaning)?Last edited by frascati; 02-22-2010 at 11:32 AM.
Reply:Try one of those hand held sand blastersI always tried to work with the oldest hand on the job to gain knowlege but now I can't find any.
Reply:frascati sez:  'If I can get something close to the profile welded up I'll have to do a little machining on it to get the rebate correct.' The 'little machining' mentioned can be just as much hassle as the welding.A tool to create that flat bottom counterbore dia. will be needed.Additionally, when doing the buildup, you'll need to use carbideburrs, sanding points, etc.-- to keep knocking down, blending the buildup as it progresses.Blackbird
Reply:If you have a lathe you could fab a piece to place in that steped bore to help shape the space and then fill around it. At worst a long bolt with an unthreaded top section with the head ground down while in the drill press might work. The alum won't stick to the steel and it will support tha alum filler as you build up the outside with filler carefully. Someone here did a great post on doing something like this. I want to say castweld, but I may be wrong, it's been at least 6 months since I saw the post and only vaugely remember it right now. That's how I would attempt it if I had to try..No government ever voluntarily reduces itself in size. Government programs, once launched, never disappear. Actually, a government bureau is the nearest thing to eternal life we'll ever see on this earth! Ronald Reagan
Reply:I saw that post also:I had to build custom aluminum square tubing 24 ea. 2 1/8 ID x 4". I used a steel plate to form the inside angle, so no aluminum would flow into the tube while welding. When done I nocked out the steel. Worked perfect!
Reply:How much pressure will be on it? Could it be a safety issue?
Reply:Originally Posted by digrTry one of those hand held sand blasters
Reply:cast aluminum repair is never funny, plus it likes to distort a lot.Also why did it crack? If it cracked under normal service conditions I would be weary, basically it means the design is flawed and the stressed unit is likely to crack again.good candidate for JB weld.
Reply:Yea i got to second the sandblasting aluminum to clean it for welding as a horible idea.  When you sandblast aluminum it will embed sand into the pores and aluminum and make it very dificult weld.  I welded up some motorcycle parts much like you have.  no perches but plenty of levers.Anyhow as far as cleaning the alminum for welding i find it best to grind it with an aluminum oxide soft disk.  it is possible to clean with a chiesl also.  this technich was used on high pressure boiler vessel building back in the day as oppsed to grinding as grinding just oxidises the are where your going to weld.
Reply:Originally Posted by frascatiGood news.  I assumed that cast alum was like iron in that regard.  But a few others besides yourself suggested that it's similar to wrought alum.  The broken piece is long gone, so I'm probably talking about either building it up, or much better,  just leveling off the perch and welding a newly fabbed barrel there.   As far as cleaning.  With a newly ground surface am I good?   Or is cast alum porous enough in most cases to have absorbed contaminant, oils, solvents, etc, into its structure and never end up 100 percent clean?  Suggestions for wave balance setting on the TIG?   50/50.    20/80 (more penetration).   60/40 (more cleaning)?