welding technique for clusters

Hello everyone.

I've been practicing. Tubemiter has generated a working set of
templates, The angle grinder and my dad's 1/2 round tripple-cut
******* were given a thorough workout. I even made a pilgrimage to H-F
on Saturday and picked up a tubing notcher. (Do those (insert slur of
your choice) really have to coat every damn thing they sell in
Cosmoline and machine oil?) Suffice to say that I've got a good handle
on how to cut and fit tubing into clusters. I could use more practice,
but I've got the basics down cold.

Now, here's the question: Assume I'm about to weld a commonly-
occurring cluster in the side of a Pratt-truss. Upright joins longron
at 90 degrees. Diagonals join either side of the cluster at 45
degrees. This is a flat cluster. Everything would appear as if you
laid it out on a table using a jig.

Where should I tack the joints? Does it matter?

Assuming I've now tacked the joints, Where should I start the bead and
which is the preferred direction of travel? I started on the face of
the cluster where the points of the three tubes come together and
welded into the "crotches" of the joints. Everything went well until I
tried to close up the remaining 1/8" and make the two beads meet.
There things got kinda screwy. I had trouble getting the puddle
started. The rod kept flowing onto one tube or the other but not both,
etc. I ended up adding A LOT of rod that I'm sure the joint didn't
need.

Suggestions?


BTW: The tubing is 3/4" OD conduit with the zinc etched off using
VeeDubber's muratic acid method. I'm using 3/32" RG-45 rod and a #0
tip on my H-F torch. Gas pressures are 3-4 psi each. Neutral flame
with just a trace of feather.

Harry Frey
wood, cotton, and now steel guy

On Mar 16, 3:15*pm, wright1902glider wrote:


Now, here's the question: Assume I'm about to weld a commonly-
occurring cluster in the side of a Pratt-truss.

Where should I tack the joints? Does it matter?
-------------------------------------------------------------------------------

Of course it matters, Harry. EVERYTHING matters!

It sounds as if you've got things laid-out pretty well. So which part
of the cluster is going to take the MOST heat?

Come on; put on your thinking cap and let's figure it out. LEAST heat
is always going to be some place where the two parts come together
almost flat yet over-lapping. Where do you get that kind of a fit on
your cluster?

It SHOULD be where the vertical member intersects the top & bottom
longerons. So that's where you do the tack weld. But the tack-weld
is eventually going to become part of your FINISH weld so you keep
that in the back of your mind as you light-off and create that little
golden nugget.

Does that make sense? It should. Because you haven't gotten to the
diagonals as yet.

So let's get to them. One of them is going to be tough to fit because
the vertical is already tacked... or is it? Odds are, it is, which
means you're going to have to leave one of your diagonals sorta open.
That is, one SIDE is going to be a big HOLE because you've snipped off
the corner so as to get the diagonal to LAY FLAT.

Same story: Where is it going to take the most heat?
Same Answer: Where you have to build-up the thickest weld-ment.

----------------------------------------------------------

The 'problem' becomes a no-brainer when you drop back to the basics.
Welding the tips of your cluster FIRST takes the least amount of
heat. Welding down into those angles not only takes more metal, it
also takes MORE HEAT, maybe even two passes, allowing it to cool down
between passes.

----------------------------------------------------------

I'd like to see some other BETTER welders jump in here. John; the
John doing the fuselages for the Legal Eagle & the Double Eagle would
be a good source. Leonard's design has a couple of five-legged
clusters that can make a grown many cry but John is doing them as if
they were easy. Trouble is, John doesn't read this Newsgroup and is
probably too busy to join in.

Tubing-wise, I try to avoid those real complicated clusters but some
designs seem to forget that not all weldors were created equal :-)

I think I've already mentioned that I use MIG to tack and gas to
finish. The main reason for doing so is because the MIG'er always
gives you SOME amount of filler where as O-A does not, but when doing
a cluster there are a couple of places where you want to build-up your
weld... meaning you'll need more heat... but you want to build it up
WITHOUT adding all that much metal. Gas welding doesn't expect you to
build up metal at every pass whereas MIG does. So I use MIG to tack..
but try to keep it in the deep V's that are harder to get to with O-
A.

--------------------------------------------------------------------

-Bob

PS -- Don't blame that acid-etching on me! Blame it on the guy who
insists on getting that zinc all over the place.

PPS -- Harry, what we really need here is some pictures.

On Mar 20, 6:49*pm, Bob Hoover wrote:

Of course it matters, Harry. *EVERYTHING matters!


You can say that again.

One of the things that matters is getting the finish dimensions that
you started with. I've spent hours filing and shaping a fishmouth to
get that perfect fit, only to have the end off my tube off by 1/8"
once all the warping has finished. I've learned to minimize the
warping though. You should weld the fish mouth in 4 steps. First do
each side where the mouth reaches down the side of the non-cut tube.
As the metal shrinks, it will pull the mouth tighter into the non-cut
tube. You've welded on both sides, so the warping neutralizes
itself.

Let it cool, and then weld the side with the obtuse angle. Again, as
it cools it will draw the pieces closer together. You do the obtuse
side, because it will warp less as it cools, and then once it is cool
it provides more strength to counter the warping of the last weld.

Let it cool, and then get ready for the acute angle. You're going to
need more heat for the inside angle. May even need a larger tip.
Make sure the weld area is especially clean. Get a good puddle going
that incorporates the very end of the side weld, move quickly and
don't be stingy with the filler rod. As you move though the junction
and come out the other side, start moving your flame back slightly.
The right amount of heat for the inside of the joint is to much heat
once you come out the other side. Just keep moving the puddle and
feeding filler till the puddle meets up with the first weld on the
other side, then relax.

The joint will still warp slightly, but not nearly as much as when you
try to make everything in one go. The inside angle causes the most
warping, and this technique provides as much support as possible
before doing that one.


I think I've already mentioned that I use MIG to tack and gas to
finish. *The main reason for doing so is because the MIG'er always
gives you SOME amount of filler where as O-A does not, but when doing
a cluster there are a couple of places where you want to build-up your
weld... meaning you'll need more heat... but you want to build it up
WITHOUT adding all that much metal. *Gas welding doesn't expect you to
build up metal at every pass whereas MIG does. *So I use MIG to tack..
but try to keep it in the deep V's that are harder to get to with O-
A.

I use MIG to tack, because it leaves you a free hand to steady the
loose member. Saves on clamp-up time.

Darn you guys. I have a big Miller Stick welder, a Smith Oxy-Acetylene and
Miller TIG. Now I'm going to have to get a MIG also??
I'll use your posts to convince my wife.

Stu
"Bob Hoover" wrote in message
...
On Mar 16, 3:15 pm, wright1902glider wrote:


Now, here's the question: Assume I'm about to weld a commonly-
occurring cluster in the side of a Pratt-truss.

Where should I tack the joints? Does it matter?
-------------------------------------------------------------------------------

Of course it matters, Harry. EVERYTHING matters!

It sounds as if you've got things laid-out pretty well. So which part
of the cluster is going to take the MOST heat?

Come on; put on your thinking cap and let's figure it out. LEAST heat
is always going to be some place where the two parts come together
almost flat yet over-lapping. Where do you get that kind of a fit on
your cluster?

It SHOULD be where the vertical member intersects the top & bottom
longerons. So that's where you do the tack weld. But the tack-weld
is eventually going to become part of your FINISH weld so you keep
that in the back of your mind as you light-off and create that little
golden nugget.

Does that make sense? It should. Because you haven't gotten to the
diagonals as yet.

So let's get to them. One of them is going to be tough to fit because
the vertical is already tacked... or is it? Odds are, it is, which
means you're going to have to leave one of your diagonals sorta open.
That is, one SIDE is going to be a big HOLE because you've snipped off
the corner so as to get the diagonal to LAY FLAT.

Same story: Where is it going to take the most heat?
Same Answer: Where you have to build-up the thickest weld-ment.

----------------------------------------------------------

The 'problem' becomes a no-brainer when you drop back to the basics.
Welding the tips of your cluster FIRST takes the least amount of
heat. Welding down into those angles not only takes more metal, it
also takes MORE HEAT, maybe even two passes, allowing it to cool down
between passes.

----------------------------------------------------------

I'd like to see some other BETTER welders jump in here. John; the
John doing the fuselages for the Legal Eagle & the Double Eagle would
be a good source. Leonard's design has a couple of five-legged
clusters that can make a grown many cry but John is doing them as if
they were easy. Trouble is, John doesn't read this Newsgroup and is
probably too busy to join in.

Tubing-wise, I try to avoid those real complicated clusters but some
designs seem to forget that not all weldors were created equal :-)

I think I've already mentioned that I use MIG to tack and gas to
finish. The main reason for doing so is because the MIG'er always
gives you SOME amount of filler where as O-A does not, but when doing
a cluster there are a couple of places where you want to build-up your
weld... meaning you'll need more heat... but you want to build it up
WITHOUT adding all that much metal. Gas welding doesn't expect you to
build up metal at every pass whereas MIG does. So I use MIG to tack..
but try to keep it in the deep V's that are harder to get to with O-
A.

--------------------------------------------------------------------

-Bob

PS -- Don't blame that acid-etching on me! Blame it on the guy who
insists on getting that zinc all over the place.

PPS -- Harry, what we really need here is some pictures.

On Mar 21, 12:10*pm, wrote:
On Mar 20, 6:49*pm, Bob Hoover wrote:

Of course it matters, Harry. *EVERYTHING matters!

You can say that again.
--------------------------------------------------------------------

Okay :-)

EVERYTHING matters, Harry.

But I think Ernie said it best when he SPECIFICALLY mentions COOLING,
whereas I simply hop onto my Assumptionmobile and roar off in all
directions, ASSUMING you'll somehow KNOW that cooling is an inherent
part of the welding process.

Hot metal SHRINKS. First lessons for the Wannabee Weldor is tacking a
couple of coupons together. You lay them on the bricks a given
distance apart and perfectly parallel. The gap -- the 'distance
apart' -- is determined by the thickness of the metal and the type of
welding being taught. Stick, with quarter-inch thick coupons mebbe
4x6 inches, the gap is about equal to the thickness -- about 1/4 inch
(a fat 6mm for youse udder guys). Now simply move one coupon until
its LOWER corner - the one closest to your belt buckle -- TOUCHES the
other coupon. NOW strike your arc (MIG, stick or TIG) or create your
pool (TIG or Gas) and tack-weld that puppy. Go ahead; right there on
the corner where the coupons are touching.

Now let it COOL... and look what happened to your gap. Yes, you may
look under the bench for it. Or even frisk the student beside you (if
you can get away with it). But no matter WHAT you do, your gap has
vanished; gone forever.

Harry, SOMEONE HAS STOLEN YOUR GAP!

(Relax; it wasn't your fault... you aren't going to get Yelled At.)

What's interesting is the amount of POWER contained in that molten
puddle. If you're using TIG and haven't been given any filler rod,
you'll end up STIRRING the molten puddle until both coupons are
securely joined.

Then let it cool.

The first thing that happens is the puddle cools. In fact, we see the
puddle 'go out' like a little candle; it sort of FADES AWAY. The
puddle is still there but now it is COLD. Go on... touch it.
HAHAHAHAHAHA... gotcha! So the tiny pool of metal is no longer
GLOWING but it's still hot enough to make you a contender for the
Standing Broad-jump.

(Have you got one of those IR thermometers? You know; you just point
it at something and the read-out tells you its temperature... which in
the case above is probably about 400 degrees on the Fahrenheit scale.)

....so the golden puddle fades away... and so does the GAP. Because
just as hot metals MUST expand, so too must they shrink. So there we
are, a whole classroom of dummies wearing funny gloves and goggles
waiting for... THERE! Did you hear it? There goes another one!

Welding with TIG you can stir a puddle that's close to 4000 degrees!
(No, you didn't. I said 'you CAN,' not that you DID. Try to heat
mild steel to a temperature that high will probably set it on fire...
for a few seconds :-) The point here is that an electric arc is a lot
hotter than an oxy/acetylene flame.

What we were listening to were not crickets; it was the sound of metal
CRACKING as it cools.

A cracked weld is common with TIG, rare with gas. And since Harry is
using gas, I'll stop passing it and start talking about it.

Cooling of your weld -- the UNAVOIDABLE contraction of the metal -- is
the hand-maiden of the metal's expansion. The person doing the
welding must observe the rules to which the metal is subjected: Heat
makes it bigger, cooling makes it smaller. We must always be thinking
AHEAD of those processes. We KNOW they are going to happen so we must
allow for them.

Harry has gotten into clusters. If he were a student driver that's
about the same as his first exposure to freeways, off-ramps and the
dreaded Traffic Circle, because as Ernie has pointed out, the rules
for expansion and contraction must now be applied to inside angles and
outside angles.

And right about here Harry needs someone to shout in his ear: "YOU
CAN DO IT!" Because he can, although there will be moments... and
thousands who have tried, failed an quit! -- when he will think the
task is simply too much for him. He'll often have lots of good
reasons such as age, the state of his health, the conditions under
which he must practice... all kinds of GOOD REASONS for NOT learning
how to weld.

They're all bull****, Harry. You CAN do it. Not just lumpy little
tracks similar to something laid down by a diarrheatic rat, but a neat
'row-of-dimes' that is the hall-mark of a competent weldor.

Practice makes master of the man. That expression is as old as the
hills. Mebbe even older. It isn't something that needs explaining.
But in modern-day America corporate entities work very hard to destroy
such things, in order to replace them with cradle to the grave
dependency upon their particular brand of reality. The paradox here
is that having convinced everyone that mastery is now embodied in a
piece of paper will eventually leave no one to design the bloody
machines nor fix the old ones, when they break down. All they have is
legions of Graduates, rather vague young fellows who have a piece of
PAPER that says they are Master of all they survey. They will be in
their forties before they realize they've been lied to by their
corporate puppet masters. And by then it may be too late. Because you
balls the size of buffaloes to do what Harry is doing.

So keep practicing, Harry. Indeed, I envy you to the point of tears,
knowing what you have ahead, because once learned, it's never to be
forgotten.

-R.S.Hoover

"Bob Hoover" wrote in message
...
On Mar 21, 12:10 pm, wrote:
On Mar 20, 6:49 pm, Bob Hoover wrote:

Of course it matters, Harry. EVERYTHING matters!

You can say that again.
--------------------------------------------------------------------

Okay :-)

EVERYTHING matters, Harry.

But I think Ernie said it best when he SPECIFICALLY mentions COOLING,
whereas I simply hop onto my Assumptionmobile and roar off in all
directions, ASSUMING you'll somehow KNOW that cooling is an inherent
part of the welding process.

Hot metal SHRINKS. First lessons for the Wannabee Weldor is tacking a
couple of coupons together. You lay them on the bricks a given
distance apart and perfectly parallel. The gap -- the 'distance
apart' -- is determined by the thickness of the metal and the type of
welding being taught. Stick, with quarter-inch thick coupons mebbe
4x6 inches, the gap is about equal to the thickness -- about 1/4 inch
(a fat 6mm for youse udder guys). Now simply move one coupon until
its LOWER corner - the one closest to your belt buckle -- TOUCHES the
other coupon. NOW strike your arc (MIG, stick or TIG) or create your
pool (TIG or Gas) and tack-weld that puppy. Go ahead; right there on
the corner where the coupons are touching.

Now let it COOL... and look what happened to your gap. Yes, you may
look under the bench for it. Or even frisk the student beside you (if
you can get away with it). But no matter WHAT you do, your gap has
vanished; gone forever.

Harry, SOMEONE HAS STOLEN YOUR GAP!

(Relax; it wasn't your fault... you aren't going to get Yelled At.)

What's interesting is the amount of POWER contained in that molten
puddle. If you're using TIG and haven't been given any filler rod,
you'll end up STIRRING the molten puddle until both coupons are
securely joined.

Then let it cool.

The first thing that happens is the puddle cools. In fact, we see the
puddle 'go out' like a little candle; it sort of FADES AWAY. The
puddle is still there but now it is COLD. Go on... touch it.
HAHAHAHAHAHA... gotcha! So the tiny pool of metal is no longer
GLOWING but it's still hot enough to make you a contender for the
Standing Broad-jump.

(Have you got one of those IR thermometers? You know; you just point
it at something and the read-out tells you its temperature... which in
the case above is probably about 400 degrees on the Fahrenheit scale.)

....so the golden puddle fades away... and so does the GAP. Because
just as hot metals MUST expand, so too must they shrink. So there we
are, a whole classroom of dummies wearing funny gloves and goggles
waiting for... THERE! Did you hear it? There goes another one!

Welding with TIG you can stir a puddle that's close to 4000 degrees!
(No, you didn't. I said 'you CAN,' not that you DID. Try to heat
mild steel to a temperature that high will probably set it on fire...
for a few seconds :-) The point here is that an electric arc is a lot
hotter than an oxy/acetylene flame.

What we were listening to were not crickets; it was the sound of metal
CRACKING as it cools.

A cracked weld is common with TIG, rare with gas. And since Harry is
using gas, I'll stop passing it and start talking about it.

Cooling of your weld -- the UNAVOIDABLE contraction of the metal -- is
the hand-maiden of the metal's expansion. The person doing the
welding must observe the rules to which the metal is subjected: Heat
makes it bigger, cooling makes it smaller. We must always be thinking
AHEAD of those processes. We KNOW they are going to happen so we must
allow for them.

Harry has gotten into clusters. If he were a student driver that's
about the same as his first exposure to freeways, off-ramps and the
dreaded Traffic Circle, because as Ernie has pointed out, the rules
for expansion and contraction must now be applied to inside angles and
outside angles.

And right about here Harry needs someone to shout in his ear: "YOU
CAN DO IT!" Because he can, although there will be moments... and
thousands who have tried, failed an quit! -- when he will think the
task is simply too much for him. He'll often have lots of good
reasons such as age, the state of his health, the conditions under
which he must practice... all kinds of GOOD REASONS for NOT learning
how to weld.

They're all bull****, Harry. You CAN do it. Not just lumpy little
tracks similar to something laid down by a diarrheatic rat, but a neat
'row-of-dimes' that is the hall-mark of a competent weldor.

Practice makes master of the man. That expression is as old as the
hills. Mebbe even older. It isn't something that needs explaining.
But in modern-day America corporate entities work very hard to destroy
such things, in order to replace them with cradle to the grave
dependency upon their particular brand of reality. The paradox here
is that having convinced everyone that mastery is now embodied in a
piece of paper will eventually leave no one to design the bloody
machines nor fix the old ones, when they break down. All they have is
legions of Graduates, rather vague young fellows who have a piece of
PAPER that says they are Master of all they survey. They will be in
their forties before they realize they've been lied to by their
corporate puppet masters. And by then it may be too late. Because you
balls the size of buffaloes to do what Harry is doing.

So keep practicing, Harry. Indeed, I envy you to the point of tears,
knowing what you have ahead, because once learned, it's never to be
forgotten.

-R.S.Hoover

Bob: As a point of interest, I found this letter sent a few years ago to
EAA by a Richard Finch. I've got a copy of the whole letter but I'm
reproducing just a portion of it here. It was an eye opener for me as a
rank amateur welder. While the main thrust of his letter was regarding pre
and post heating of the weld , the predominant use of MIG to the exclusion
of Oxy-Acetylene was something that I had never heard of before. Also the
post weld cracking of the TIG didn't seem to be much of a problem for him.

"While I was researching material for my new book, Performance Welding, I
talked to several current high-volume kit plane manufacturers, to see what
their production welding methods are today. I talked to Kitfox, Avid, Rans,
Wag Aero, and Piper and Mooney aircraft companies. None of them use
oxy-acetylene to build steel aircraft fittings or even complete fuselages.
They all use MIG (wire feed) welding and none of them post heat the welds
with an open flame welding torch. When I asked Dean Wilson, designer and
builder of the huge Explorer aircraft (with umpteen hundreds of individual
tubes welded in the structure) if he gas welded or pos--weld gas heated the
structure, he said, "Are you kidding? If I had gas welded and post weld
heated it, it would still not be finished, and it would not be as strong as
it is now." He said that he MIG welded it and left it alone.

I am a certified aircraft welder, and I worked for Ted Smith Aerostar as the
head of the welding department until they closed the Santa Maria, CA plant
We TIG (heli-arced) welded all 18,00 engine mounts in an eight year period,
for the Aerostar twin engine airplane and we never pre-heated any of them.
A recent check with the AOPA and the FAA shows that Aerostars have no
cracking problem in their engine mounts or any other TIG welds.

On the other hand, I later became the chief field troubleshooter for
Fairchild-Swearingen Aircraft, and all Metroliners had cracking problems
with their engine mounts. Fairchild Aircraft pre-heated and post weld
stress relieved every engine mount but they used copper coated welding rod
to TIG weld the turboprop engine mounts."



I have seen some post weld TIG cracks but not for some time either in 4130,
aluminum or stainless. I did have some cracking on a weld on a turbocharger
exhaust, but it was dirty and very hard to get clean prior to welding.

I'm enjoying the welding discussions. I've already won the standing broad
jump and the advanced dance of slag in the socks. Or how about the
reverberation where you recoil from the hot metal, hit your hand on the
adjacent tube and recoil back to the hot metal. Repeat until either the
weld cools or you just get tired of the process and quit. Of course I
should have had a glove on but it was just going to be one little tack.

Keep up the great information and do whatever it takes to handle your health
issues. Sources like what you provide are disappearing.


Stuart Fields

Thanks everyone, especially Bob, for the tips and encouraging words.

I spent a few hours working with the tubing notcher on Fri. night and
Sat. morning. Between it and a little clean-up with the *******, I'm
getting fit-ups that look as tight as the ones shown in Finch's
"Performance Welding" book. I'm very comfortable with that process.
The only tricky item left is to get tubes that are the correct length
when notched on both ends. Shouldn't be too hard, that's just a matter
of working with the tool and making a few reference marks and maybe a
wire-pointer on the clamp of the thingy.

I practiced with the torch Sat. afternoon for about 2 hours, mostly
making 90-degree joints. They still look pretty awful and lumpy, but I
did learn what a burn-through looks like just before it blows out into
a giant hole. I think most of my tubes were cut too short though. On
the order of 2" or less. The longer tubes had better beads. I know,
heat concentration and accumulation in the short tube. Got it. I've
also learned to aim the flame at the uncut tube until it's nearly
molten and then drop the flame onto the edge of the cut tube so the
two will start to puddle at nearly the same time. Not easy. Works on
the flats though, which is where I was making my tacks. I'll keep in
mind the shrink-fit factor next weekend and watch for it when I tack.

Another method that I tried was starting in the crotch of the joints
and working out toward the flats. I would heat both tubes up to
yellow, and then aim for a few seconds more on a single tube. Just as
a pool formed, I'd put a drop of filler in it, then aim at the same
spot on the opposite tube and repeat, then back to center, which
caused the two drops of filler to spring together like two water
droplets! Now that they were joined and both molten, I aimed the torch
back to center and it was drip-drip-drip-drip right up the side and
out onto the flats! Well... it worked like that for one or two beads
anyway. Just enough to be encouraging.

I'm still having trouble controlling the heat and the timing of the
filler, but I was better this weekend than last. I'll keep working at
it. I may have to work on getting the tubes cleaner too. There seemed
to be a lot of micro-boiling this weekend. Maybe that also has
something to do with my inability to manage the heat correctly? The
micro-boiling was happening well in advance of the puddle and left
sugary-looking spots on several of the joints. I'll save that problem
until I can at least run a bead though.

Harry

On Mar 22, 1:20*pm, "Stuart Fields" wrote:
(a lotta good stuff which I've snipped)

Stu, I'm with you on the production-MIG situation. The last paying
aircraft job held by my dad was as an inspector. He said he was using
the big yellow crayon on about fifty percent of the structures. So
they fired him. (No, I don't know who the Prime Contractor was; the
Sub was a no-name shop in La Brae (?) as I recall. Dad got the job
not because of his certs but because he spoke Spanish. The guys in the
Front Office only turned up when the PC's inspector would drop in,
something everyone was well aware of even for those 'unannounced'
inspections. (Ditto for La Migra :-) Those were the days when most
of the Mexicans stayed home and a lot of kids from the shop next door
-- doing mufflers or some damn thing -- would be allowed into the shop
to chat with the 'inspectors.'

That was in the early 1970's. If anything, our nation has become even
more corrupt and ill-informed.

I'm not a very good weldor. Of the three of us, my brother was the
best. Bet him enough money and he'd weld a stainless steel razor
blade together. Not Schick, the double-edged jobbies. Then they'd
bet to see if someone could tell them apart when blind-folded. Nobody
ever did better than 50-50. He ended up welding together stills to
convert corn into alcohol. They were told it was part of the 'missile
program' when none of our ICBM's were using the stuff. Later on,
Congress voted a SUBSIDY to produce alcohol... and nobody seemed
surprised that the stills were already to go on-lline with just the
flip of a Campaign Contribution :-) (They don't call them 'bribes'
any more. In fact, a lot of them don't even involve money. Our
locally crooked Congressman would settle for used furniture (ie, the
antique kind), the occasional yacht, a lo-buck zero-down mortgage...
never anything as crass as a brown paper bag full of Franklyns
stuffed under the front seat of a car.)

When you get into a fight I think it's a good thing to know exactly
what you're fighting FOR.
-----------------------------------------------------------------------

As for welding content, whatever happened to that little handbook that
everybody usta hand out? First published in 1929, it was still in
print in the mid-1970's when I was in the Navy and pretending to be a
Welding Instructor. 'Oxy-Acetylene Weldor's Handbook' And 'weldor'
meaning a human being, NOT welder, a piece of machinery. The point is
possibly worthy of mention because I've had guys get on the Internet
and rag me for claiming to know something about welding when I
couldn't even spell 'welder.'

As for the MIG business with regards to production welding, it has to
do with the feed-rate, which they usually change as soon as the
inspector(s) are out of the shop :-) Apparently, what it does --
relative to the wall thickness -- is to increase the MASS of the
weldment to the point where the fracture zone enjoys the same
temperature distribution-over-time that it gets with O/A. The other
aspect of production welding, as for tubing but this time referring to
stuff like alcohol on one hand or natural gas and crude oil on the
other -- what we usta call 'pipe-line welding', has to do with the
geometry of the scarf or chamfer, in that MIG uses a flatter angle and
finishes with a higher bead.

But all tolled, when you're only building one air-frame at a time, you
may just as well relax and enjoy it. Stretch it out as much as you
like, even on a complex structure it's only going to amount to a few
percent of your time.

-Bob

On Mar 23, 8:14*am, wrote:
There seemed
to be a lot of micro-boiling *this weekend. Maybe that also has
something to do with my inability to manage the heat correctly? The
micro-boiling was happening well in advance of the puddle and left
sugary-looking spots on several of the joints. I'll save that problem
until I can at least run a bead though.
------------------------------------------------------------------------------------

Without seeing it I would have guessed a contaminant on your filler
rod, but if it's happening ahead of the pool it may be something on
the tubing, such as some sort of residue from the zinc. Try 'shoe-
shining' the tube with some clean sand-paper backed up with duck
tape. (Yeah, I know. But then too, a lotta folks thing you're a
'welder' just waiting to have something plugged into the wall.)

-Bob

On Mar 24, 2:02*am, Bob Hoover wrote:
On Mar 23, 8:14*am, wrote:

Without seeing it I would have guessed a contaminant on your filler
rod, but if it's happening ahead of the pool it may be something on
the tubing, such as some sort of residue from the zinc.

-Bob

I'm leaning toward that myself. When the tubes came out of the acid, I
rinsed them in clean tap water and then let them air-dry. I actually
watched them rust in a period of 5 minutes. Once the tubes were dry, I
shoe-shined them with a Scotchbrite pad. They looked nice and shiny,
but I didn't do any further cleaning. I also didn't clean the filler
rod. Its copper-coated, but that doesn't seem to be doing it, or I
would have the problem all of the time.

Next time I'll try degreasing them in Simple Green (my prefered
weapon), rinsing, etching, and rinsing again. Then air dry, polish
with 220 (cause that what 'ah got), solvent wipe with acetone, and
then give them the tan-glove treatment. Finch's book also recommends
solvent-wiping the rod. I'll try that too.

In looking at some of my work from last Sat. there are sections of the
bead that would be acceptable if the feed-rate were more even.
Overall, they look a LOT better than my first atempt. I don't have the
heart to whack the hell out of any of them yet. But I'll get there.

The first trial-project will be a chasis for a kinetic sculpture
vehicle. That would be a human-powered, art/vehicle that is capable of
traversing roads, trails, mud, sand, AND lakes while looking cool. I'm
thinking something like a Warren-truss for the basic structure.
Imagine if you chopped the back end off a Breezy and stuck three bike
wheels on it. On top of that goes the sculpture of your choice. If
that structure survives what I'm going to put it through without
cracking, I should be well on my way as a weldor.

Harry