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mgNOT
12-25-2008, 03:25 PM
I can't find the post where differential bridge welding was discussed (if that was the topic at all), but the gist of it was don't weld boxed sections all around. Was/is that true? I have plans to box in the vertical and horizontal section of the differential bridge, and would like to know about the welding. This may also apply to chassis sections like the T-shirts or trailing arm mountings. Was the expert "Aweman"??
I'm listening intently.
Dennis

tomshobby
12-25-2008, 05:12 PM
Was the expert "Aweman"??
I'm listening intently.
Dennis

I believe him to be the go to guy for welding information.

WedgeWorks
12-25-2008, 09:25 PM
mgNOT-
To fully weld a connection has its pros & cons. For one the filler metal, actual weld is always stronger than the base metals being joined together so to completely weld a connection means that there are more stresses than anticipated and they are to be distributed beyond the connection. In doing this you have to watch out for excessive heat input into the base metal that can distort a connection and crystallize the base metal causing fatigue. As a quick example typical sheet steel 18 to 22 gauge mild steel has a tensile strength of 20 to 30 kips (1kip=1,000lbs) and the weld rod used for welding would be an E60 series filler that equates to a minimum of 60 kips per square inch of weld in tensile. For suspension and drive train the shock of loading would not warrant full welding of a connection unless the factory has done so they know best. I know for roll cages and chassis upgrades for competition cars such as rally cars the roll cages were fully welded and boxed sections were added at the connection points of the cage mounting areas. For the remainder of the body a staggered fillet weld would be applied at a 4 inch spacing (on center) at 1 to 2 inches long. The other reason to keep from fully welding something is that stresses pool at welds due to the strength differences of base metal and weld can eventually induce a failure/crack at the base metal.

Here is some advice that may help out. If you weld a connection just on two sides out of four you can always add a ½-inch weld know as a “return” at the corners to make the connection stronger and not develop cracking at the ends of the two welds. I know Aweman should also agree and may have more advice on top of mine since he has 30 years experience as a welder. Good luck!

AweMan
12-27-2008, 05:20 PM
Sorry about not getting back sooner on this post.
As has everyone, I have been pretty busy, it`s pretty hectic around here!
Welding stiffeners {gussets} in solid {all the way around} creates what is known as stress risers {a place where a crack can form}, normally on or next to a weld!
The stress comes from any lateral or parallel movement of the base material within the weld zone against the stiffener. Skip welding the stiffener leaves an open space in between welds. These open spaces serve as stress relief points {a place for the stress to dissipate}.
One should take great care in welding, each bead must not have what is known as a weld crater at either the beginning or end of the weld. Any crater in itself is a stress riser.
Wrap the welds all of the way around any end of the stiffener and weld any inside corner too. 1 - 1 Weld one inch skip one inch or 2 - 2 or 3 - 3 ECT. {Doesn`t have to be exact!} The idea is to leave someplace for any stress to dissipate.
My choice of filler material for the welds would be Er-70s-1 for clean new material s-6 for older material {Mig wire} or ER7018 Stick electrode {D.C. only} or A.C. stick electrode machine use ER6011.
Try to get the weld zones as clean as possible before attempting any welds. that means removing any and all mill scale, rust, paint, grease ECT.
If you have little or no welding skills, the welding procedure on this type of work may be best left to a professional. Because it is imperative that no craters be left at the ends of any weldment.
If the welding is done properly changing the molecular structure of your frame around or near the welds should not be an issue. I could go into all of the Techs. of how and why and all about carbon precipitation, H.A.Z.`s {heat affected zones}. and all of that but most here would not understand anyway so I won`t bore all of you with that information.
I hope this helps you

mgNOT
12-29-2008, 04:55 PM
Michael and Kerry,
Exactly the explanation I was looking for - thanks!
Now back to the issue at hand, a HF body saw that won't.
Note to self: don't buy cheap stuff!
Dennis

martx-5
12-29-2008, 05:39 PM
...
Now back to the issue at hand, a HF body saw that won't.
Note to self: don't buy cheap stuff!
Dennis

I got the same saw. Sometimes it's reluctant to go. A little oil in the air inlet usually gets things going. If that doesn't work. Unplug the air and move the saw back and forth. Plug back in and it should work. Once things are going they tend to stay going.