| Brazing aluminum ac line issues [message #319469] |
Thu, 22 June 2017 20:03  |
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SeanKidd
Messages: 747
Registered: June 2012
Location: Northern Neck Virginia
Karma: 4
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All of the fittings I have are new beadlock crimp fittings...except the double horse shoe adapter at the compressor...which is rare at #12 suction and #8 liquid (most are #10 and #8) the high pressure line had an integral crimp, not a ferrule, so I got a braze on beadlock fitting. For the life of me I cannot get the aluminum to flow, and blew a hole in the side of the tube twice. Using map gas and blue demon triple play low temp 1/8 brazing rods...I can sweat copper all day long but can't seam to get aluminum going...it's the last thing I need to finish for my double aux evaporators. Any suggestions?
Sean and Stephanie
73 Ex-CanyonLands 26' #317 "Oliver"
Hubler 1-Ton, Quad-Bags, Rear Disc, Reaction Arms, P.Huber TBs, 3.70:1 LSD Honda 6500 inverter gen.
Colonial Travelers
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| Re: Brazing aluminum ac line issues [message #319492 is a reply to message #319469] |
Fri, 23 June 2017 07:53  |
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Matt Colie
Messages: 8547
Registered: March 2007
Location: S.E. Michigan
Karma: 7
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Sean,
In my experience, aluminum braze will never flow like a bronze on steel or other bronze. It can work it is just different.
I still (but rarely) weld aluminum with an oxy-acetylene torch (yeah, I'm that old) and with or without flux, the surface scale of aluminum is hard (like aluminum oxide!). If you don't have that removed, it can screw up everything. I still keep stainless steel "tooth brushes" around for just this purpose. With a TIG can at least give you a chance to break it up with the rod, but the force of the flame of any torch makes that a problem.
So, if you can get by a Hazard Fright, buy the set that includes stainless brushes.
Matt
Matt & Mary Colie - Chaumière -'73 Glacier 23 - Members GMCMI, GMCGL, GMCES
Electronically Controlled Quiet Engine Cooling Fan with OE Rear Drum Brakes with Applied Control Arms
SE Michigan - Near DTW - Twixt A2 and Detroit
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| Re: Brazing aluminum ac line issues [message #319497 is a reply to message #319469] |
Fri, 23 June 2017 09:58 |
kingd
Messages: 592
Registered: June 2004
Karma: 2
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Senior Member |
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Matt, I've never tried welding or "brazing" aluminum. I know a GREAT welder
so I don't "need" to know how to do it myself.
Isn't one of the problems with brazing/welding aluminum is that it doesn't change
color before it melts and sags away? Just what I've heard.
DAVE KING
lurker, wannabe
Toronto, Ontario, Canada
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| Re: [GMCnet] Brazing aluminum ac line issues [message #319498 is a reply to message #319497] |
Fri, 23 June 2017 10:44 |
GMC.LES
Messages: 505
Registered: April 2014
Karma: -2
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My experience with brazing aluminum is that larger pieces can be a difficult problem. Small/thin stuff is easier, but only once you have figured out how to manage heat.
Heat management with TIG is easy compared to flame welding.
A few considerations for flame welding/brazing aluminum:
1- Aluminum is a good thermal conductor, quickly wicking the heat away from the weld zone, so a large piece needs to be thoroughly pre-heated to minimize this effect. Don't try to just heat the weld zone, as you will quickly learn it is harder to master, and requires a hotter flame.
2- Cleanliness of the weld zone is important.
3- if you have melted or blown out an area of the material, the surface is likely too dirty(oxidized) to be able to get the brazing to take hold. You need to stop, re-clean, and re-start your process.
I first learned how to braze aluminum by using the bottom of a soda can as practice material.
Cut a slit in the bottom, clean the surface, and try to fill the slit with the filler rod. The thin metal is easily overheated, so some finess is required. When you have mastered this, move on to tougher scrap materials for practice. I try not to practice on components that matter.
Les Burt
Montreal
'75 Eleganza 26'
> On Jun 23, 2017, at 10:58 AM, Dave King wrote:
>
> Matt, I've never tried welding or "brazing" aluminum. I know a GREAT welder
> so I don't "need" to know how to do it myself.
> Isn't one of the problems with brazing/welding aluminum is that it doesn't change
> color before it melts and sags away? Just what I've heard.
> --
> DAVE KING
> lurker, wannabe
> Toronto, Ontario, Canada
>
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> GMCnet mailing list
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| Re: Brazing aluminum ac line issues [message #319708 is a reply to message #319469] |
Wed, 28 June 2017 09:38 |
JohnL455
Messages: 4447
Registered: October 2006
Location: Woodstock, IL
Karma: 12
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Senior Member |
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Would fitting Ts be a better idea? Before and after existing evaporator would make sense to me. Are such fittings available? I never understood how you would weld into existing lines without heat ruining rubber and just being prone to leaks and cracks from vibration. And risk of slag internally.
John Lebetski
Woodstock, IL
77 Eleganza II
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