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  #21  
Old 09-08-2017, 07:57 PM
crystallographic crystallographic is online now
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Originally Posted by bobadame View Post
I've used propane and oxygen to gas weld platinum. That worked great. Then I tried to gas weld aluminum with the same gasses. It didn't work. Don't remember exactly why not but maybe the chemistry was wrong.
Oxy-propane works for me ....
P1150602 propane copy.jpg
P1150604 propane root copy.jpg

The platinum I tried to weld with O/A (flame temp 6300F) was .125" thick and since platinum melts at 3200F, it was slow going.
My .125" steel at 2400F welds a lot faster.

With O/P flame temp at 4100F .050" aluminum welds well at 1250F but even faster with O/H at 5100F.

It's nice to have 2-3000 extra deg.F for a heat margin when welding stuff.
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  #22  
Old 09-08-2017, 10:10 PM
bobadame bobadame is online now
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I did a google search and came full circle to this.
http://www.allmetalshaping.com/showthread.php?t=3889
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  #23  
Old 09-09-2017, 12:22 PM
crystallographic crystallographic is online now
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Default O/P welding aluminum

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Originally Posted by bobadame View Post
I did a google search and came full circle to this.
http://www.allmetalshaping.com/showthread.php?t=3889
Welding aluminum with oxy-propane is not a big deal.

You need a fuel reg to fit the propane can and some "T" grade hoses that do not deteriorate when exposed to propane, natgas, chemtane, chemolene, propylene etc. "alt fuel" gases.

You can use an oxy-fuel torch and tips and there is no explosive danger mixing one fuel gas with another through the same hose as there is with hydrogen.

There are special "alt fuel" propane tips available for some torches, like we carry for the Meco Midget. Instead of one central flame there is a "ring of fire" around a smaller central flame, giving more BTU's into the melt.

Using the same sized acet tip or one size larger works well, if you are already welding aluminum with O/A.

Use a really good flux as the propane leaves a bit of smut that the flux is required to carry off during the weld. I use our Super Premium AGW flux. (AGW= aluminum gas welding)

Bear in mind that finding the neutral flame is difficult with O/P as there is no defined sharpness of the flame achieved by adding oxygen. The flame cone either gets longer or shorter by twiddling the knobs, so I just do a weld test on an aluminum coupon while adjusting the flame.

Flux the rod and maybe also the top surface of your joint.

Have at it and see what you get. Torch handling, angle to the metal, cone distance from the work are all the same as O/A.

You will have a larger noisier flame for the same weld on the same material as you will with O/A,
using the same torch and tip, as the O/P has less thermal output than does the O/A, because acetylene is a triple-bonded hydrocarbon and the rest of the fuel gases are only double-bonded. Each bond breaks during combustion to release a certain amount of thermal energy, so you have 2/3 energy compared to 3/3 energy output.

Maybe I should post this with some pix as a new thread ..... ?
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  #24  
Old 09-10-2017, 01:37 PM
dwmh dwmh is offline
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Great info Kent
There is no substitute for years of experience.
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  #25  
Old 09-13-2017, 03:11 PM
crystallographic crystallographic is online now
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Thanks for your support, guys.
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  #26  
Old 09-13-2017, 03:23 PM
crystallographic crystallographic is online now
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Default O/A gas welding - brief checklist

Last night I was welding these landing gear leg fairings together (1937 cabin Waco) - 3003 .020 to .040
P1040279 copy.jpg
and here is my checklist:

clean aluminum with a good wipe with 91% isopropyl
brush with clean ss toothbrush
Get a good fit
P1040248 copy.jpg
mix flux with clean bottled water (Super Primo flux, in this case)
neutral flame, #2 tip, + slight feather, inner cone is 2-3X metal thickness

I try to parent metal/fusion weld the first tacks.
Then I go over that with a good long "tack."
P1040250 copy.jpg

I add to the tack, and then using the step-back method, whereby I start back from the weld and then weld to it - either forehand or backhand ...
P1040259 copy.jpg

and thus continue to the fully-welded part.
(ps, the "step-back" weld is very old and is used to limit distortion on gas-welded parts.)

thus:
top side:
P1040267 copy.jpg

and the root:
P1040268 copy.jpg

end
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Last edited by crystallographic; 09-13-2017 at 04:47 PM.
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  #27  
Old 09-14-2017, 03:48 PM
Andy Andy is offline
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I just want to give you a quick update. I managed to change the acetylene-supplier (not that easy in Germany). My old bottle was made in 1993 and the manager of my old supplier confirmed that they do not clean out the bottles, just fill up the acetone.
The new bottle I got from a different company was made in 2016...

What else can I say...no more pits in the weld:

20170914_223158.jpg

The small spots you can see were caused by me beeing impatient. Did not clean it well enough. They are really small and are right above the seam (where it was dirty).

If anybody from Germany wants to know, the new bottle is from Globalgas.

Thank you all for the support.

Cheers,
Andy
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  #28  
Old 09-14-2017, 08:27 PM
Jerry Jackson Jerry Jackson is offline
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Kent

Your LG leg fairing uses a lap weld. How do you clean the flux out of the overlap area?

Jerry
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  #29  
Old 09-14-2017, 08:48 PM
crystallographic crystallographic is online now
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Quote:
Originally Posted by Jerry Jackson View Post
Kent

Your LG leg fairing uses a lap weld. How do you clean the flux out of the overlap area?

Jerry
No.
No lap weld there.
P1040267B copy.jpg
Butt welding only.
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  #30  
Old 09-15-2017, 02:44 AM
Dave K. Dave K. is offline
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Kent nice work on those fairings! Those have a really interesting shape!
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