On Thu, 26 Apr 2012 02:19:07 -0400, lid wrote:

On Wed, 25 Apr 2012 20:08:13 -0500, Ignoramus18965
wrote:


Some of it would involve "Overhead" welding, operating from below the
weld.

What is the easiest way to do it correctly. These would be welds that
need to hold up when a forklift or a metal tracked vehicle drives over
that tail.

We have solid mig wire and E71T flux cored.
Thanks
i

Although, I can't see exactly what you are trying to weld from the
pictures, I would recommend stick welding with 7018. Absolutely do not
use solid MIG wire. The flux core is a much better choice if you must
use a MIG set up. It is not necessary to tip your trailer over as
others have suggested, but backing it over a garage pit would help to
give you some working room.

Get inventive to get easier access - Something so you don't have to
kill yourself crawling under there and grinding & welding in extremely
confined conditions.

Plus you have to consider emergency egress and access - if for example
you manage to light the hydraulics on fire you want to be able to get
out in a hurry. Then grab an extinguisher and decide if you want to
go back in, or just squirt and pray from outside...

Either tip the trailer up at a 45-degree angle to the side with the
forklift, or pick up all four corners a few feet off the ground with a
set of Railroad Jacks (what they were designed for!) and crib the heck
out of it for safety...

Or bring it inside through the ground level door and run it outside
the Dock door with the tail end hanging out off the end of the loading
dock over the trailer pit...

Or dig a proper lube pit, and finish it right with concrete block
walls and a poured floor slab (with a sump-pump depression too!) and a
pair of concrete wheel tracks on the sides, and stairs out the end.

And a ledge on the sides of the pit so you can cover it up with 4X6
and 4X8 cribbing lumber to keep people from falling in when you aren't
using it. "Safety's in the Top Three..."

The last one is practical for working on the tractor and other
motorized things you have, too. If you're going to use it a lot, make
provisions for getting air and power down there (a 2" conduit from the
Shop you can snake an air hose and an extension cord through) and make
the Sump Pump semi-permanent with a plumbed outlet pipe before you
pour concrete.

Joint preparation is key. You should grind a vee joint between the
plates (asumming this is a butt weld) and absolutely clean it out of
any paint, rust, or grinding debris using a knotted wire wheel.

If you have no experience running a key-hole type root pass with say
6010, I'd recommend tacking a backing strip to the weld path. Usually
a piece of cold rolled steel about 1/4" thick will do the trick.
(Grind any mill scale off of it before you use it.) You can cut this
off with careful application of an oxy-acetaline torch after the weld
is completed. Then grind the remains flat and apply a capping bead
over that side of the weld.

Or clamp a chunk of Copper Busbar over the other side of the weld (the
trailer deck diamond-plate) as a chill plate. That will keep the weld
from making a bigger mess if you burn through, then go to fill in the
hole.

The root pass is also key. You must keep a very short arc length with
7018 otherwise oxygen will contaminate the weld puddle. The goal is to
lay passes that stack up evenly across the length of the weld. After
the root pass you can use weaving passes to make this stack
up.....once again remembering to keep a SHORT arc length.

Before attempting to do this on your trailer, do TEST set ups and
practice. Overhead takes practice above all else.
Dave

Overhead also takes lots of protective gear, because the red hot
molten steel dingleberries will go places you do NOT want them. Armor
up like you're going to work in a foundry.

If you don't trust yourself to do the final welds, find a local Mobile
Welder that can come out and do the work after you get it all set up,
cleaned up and primed with Weld-Through Primer and make up the repair
pieces you want and tack it together to fit.

These are the guys with the big honking Hobart Pipeliner welder
filling up the back of the truck, and they can whip out Nuclear Grade
overhead welds like nobody's business. Pay attention, you'll
probably learn a few things.

-- Bruce --