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Old 04-03-2011, 06:37 PM   #1936
Toyanvil
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Thank you pablo83
I took your advice, I modified my jig so I could place one tack on each side "front & back" I also fish mouthed the cross bars. With the cross bars fish mouthed, running a single pass worked much better. I play around with my heat & speed and was able to get the look I was going for.




Quote:
Originally Posted by pablo83 View Post
I took the liberty of snooping through your SmugMug account to get some better pictures of this project. You clearly know what you're doing when it comes to metal work. If you haven't seen this thread, I think you would enjoy it. I know the guys who watch that thread would love to see your formula one red wagon, as well as all your other projects.

Anyway, back to your question. Here's a better picture of the welds:



It looks like the BMW welds are done with some specialized welding style, but I could be wrong. My guess is they are brazed. I've seen tubes joined in a similar fashion on a bicycle frame. I don't know how it was done, but I was told it was done with a TIG welder and brazing rod. Another possibly is SAW (although I've never seen fish-mouthed tubing done with SAW). The last option I can think of for this type of weld is dual-shield, although dual-shield is usually done with much larger pieces (like bridges and pressure tanks).

I think it's going to be real difficult to make identical welds in a small shop unless you really want to do a lot of research into bicycle frame brazing. But I do think you can greatly improve your welds to the point that only a handful of people will notice the difference. First. you're putting two tacks per tube. This makes a very bumpy surface to weld over later:



Try using one tack in the center of each tube. Next, remove the rack from your jig and tack the back side of the tubes (single tack on each). Then do each final weld in a single pass. Reducing your heat will make the weld stand up more, but you need to be careful that you're still getting good penetration. I think this will make your final welds much smoother.

If this doesn't get you where you want to be, look into getting a tool that will allow you to fish mouth the tubes (it looks like your tubes are straight cut)



This can be done with a small lathe (screw making type) or other jigs like this:



Also, this is going to take a lot of practice before. I've spent many years joining tubing in projects like this and it probably took many hundreds of welds before I could lay down a consistent and good looking weld on fish-mouthed tube. Doing it on small tube is going to be even more difficult.


You've built some significant jigs for this rack. Are you going to do a production run of these racks?
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Old 04-03-2011, 11:56 PM   #1937
nessy357
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Quote:
Originally Posted by Benesesso View Post
One of my favorites:

"Which polarity puts more heat into the work, straight or reverse?"

So, WHY is this question dumb?
Rev polarity ,roughly 2/3 of the heat is generated at the welding rod and the rest at weld puddle. The opposite for Straight polarity.

Spin off question ?
Why do you get better penetration with Rev pol. ?
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Old 04-04-2011, 03:10 AM   #1938
PeterW
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Quote:
Originally Posted by Toyanvil View Post
Thank you pablo83
I took your advice, I modified my jig so I could place one tack on each side "front & back" I also fish mouthed the cross bars. With the cross bars fish mouthed, running a single pass worked much better. I play around with my heat & speed and was able to get the look I was going for.

FWIW: I've seen those trick bike frame welds done - many years ago, not sure how it's done now - when I saw it , they were brazed.

Pre-heat. Stick the work in an oven first, haul it out and start welding.

Don't get greedy, you may have to stick it back in half way through.

Pete
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Old 04-04-2011, 09:19 PM   #1939
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Quote:
Originally Posted by Benesesso View Post
OK, "welding rod", meaning a stick electrode? Your first sentence is wrong, which answers sentence number two.
You need to do your homework !
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Old 04-05-2011, 03:13 AM   #1940
David R
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Laugh

I use terms like DCEN OR DC Electrode Negative. Or DCEP. It saves confusion.

The heat thing has to do with the way electricity flows. I don't care which way the electrons go, I can't see them.

With TIG if you make the tungsten electrode + it will burn up in a few seconds or less. SO the heat is in the electrode.

If you look it up, Straight polarity is DCEN and Reverse polarity is DCEP.

7018, 6010 and MIG (bare wire) are run DCEP. Flux core, TIG and usually 6013 are run DCEN. When in doubt RTFM.

David
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Old 04-05-2011, 04:45 AM   #1941
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Not a question, but I picked up this auto darkening welding helmet from HF last night for $40


Here is the coupon I used:


Get it here

They let me do a trade for the skull helmet since it was the same price as the flame one.

Now I have one less excuse for why my welding sucks.
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Old 04-05-2011, 05:37 AM   #1942
David R
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Laugh Harbor freight helmet

I have 2 of the flame model. They work great except for TIG they flicker.

I also have a miller elite I use all the time and a lincoln Vista I never use.

David
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Old 04-06-2011, 06:48 AM   #1943
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Quote:
Originally Posted by side-wayz View Post
Got a tungsten question. We have been using pure tungsten while welding with ac with aluminum at school. I've been reading that the orange (cerium) and brown (zirconium), are better for aluminum, but have not tried it. Any advice or opinions?
Try Cer or Lan with a point, 80% penetration, and clean weld area and filler like crazy. Wire brushing isn't good enough, use scotch brite or similar and get all the oxide off.
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Old 04-14-2011, 08:53 PM   #1944
KTM640Dakar OP
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Quote:
Originally Posted by nessy357 View Post
Rev polarity ,roughly 2/3 of the heat is generated at the welding rod and the rest at weld puddle. The opposite for Straight polarity.

Spin off question ?
Why do you get better penetration with Rev pol. ?
Always TIG weld using DC- to the torch. Yes 80% of the heat is generated on the DC positive side of the electrical arc. So you want that heat on your part which should be DC+ or ground. The torch goes to the DC-. If your setting a machine that has a polarity selection switch use DC- for TIG. If you do try to TIG using DC+ then your electrode will heat up and lose its sharpe point fast.

Use pure tungsten green for welding aluminum in AC polarity. All the other colors can be used for welding DC (steel,stainless,nickels,copper). The rare earth elements that they use to stabilize the tungsten are all color coded and red is most popular (thoriated). Thorium at a 2% content is added to the tungsten electrode and will help the electrode to stay sharp.

http://www.youtube.com/user/lincolne.../5/0W-AdNWFs00
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Old 04-14-2011, 09:25 PM   #1945
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Here's a question: What the hell does this mean?

Quote:
Forney 1/8 x 18-Inch Brazing Flux Rod
Flux Coated
This high-quality welding rod is made in the USA
Can be used in most arc welding applications
Country of Origin: China
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Old 04-15-2011, 05:15 AM   #1946
JimVonBaden
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Quote:
Originally Posted by Skippii View Post
Here's a question: What the hell does this mean?
Harbor Freight?

Jim
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Old 04-15-2011, 08:07 AM   #1947
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Quote:
Originally Posted by Skippii View Post
Here's a question: What the hell does this mean?
It means a non-English speaker did the translation. Most likely a brazing rod not a arc welding rod.
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Old 04-15-2011, 11:05 AM   #1948
Skippii
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Quote:
Originally Posted by Strong Bad View Post
It means a non-English speaker did the translation. Most likely a brazing rod not a arc welding rod.
But where was it made???
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Old 04-15-2011, 11:38 AM   #1949
fxstbiluigi
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In a very remote corner of the USA, east coast I think, called china.
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Old 04-16-2011, 07:37 AM   #1950
sailah
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I have a tank I need to TIG weld. It's a steel Yamaha FZ1 tank that I need to "let in" a frame support. I have been practicing my tig so I feel okay getting into this. All cautions about gas fumes I have taken, tank is clean, dry and no fumes at all.

I plan on cutting a piece of 1.25" DOM tubing and then welding "legs" on the long side of the tubing to make a "U". This U will be inset into the tank and then welded to the tank metal.

I had a friend suggest bending the metal down on the tank to match the U I am making and then weld the ridge. Less chance of burnthrough etc. I have 040 red tungstens and plan on using 035 MIG wire for filler.

If the above description is too vague you can check my build thread that describes it better.

http://www.advrider.com/forums/showthread.php?t=672108

Any other tips??
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