Another simple weld that worked.

wrote:


That same welder is what cost me a spare tire, the mount and my
pride.....

Glad you only used it on something small......

Gunner

--
"Confiscating wealth from those who have earned it, inherited it,
 or got lucky is never going to help 'the poor.' Poverty isn't
 caused by some people having more money than others, just as obesity
isn't caused by McDonald's serving super-sized orders of French fries
Poverty, like obesity, is caused by the life choices that dictate
results." - John Tucci,

I used to hate it, but since I added a cooling fan and learned to take my
time and flow in to one piece and then the other with a nice overlapping
puddle pattern I kinda like it for small stuff.  I still can't weld more
than 4-5 inches before it starts throwing crappy welds, but I couldn't weld
more than 2 before.

Is that a tie point for just attaching a tarp, or for holding heavy
things? If it is the latter, I would personally redo it without a
chain link.

i

I was wondering, along the same lines.

Let us take it the person and set-up gives a well-fused weld.
(though I gather you are questioning that in this case with the
Horrible Fright "Crapomatic 35" welding machine)

What's the rules for welding chain-links?

They are always quench-hardenable alloy (?)
So one thinks of issues like high HAZ hardness and cracking.

I too have reflected that chain-links are just the right shape and
readily available for quite a number of tasks.  But should you really
use them?

So how does this really pan-out?

Richard Smith

Gunner, if it wasn't for hitting that freeway exit sign, I bet that spare
would still be rolling.

And for chain attachment, a keyhole is nice.  Pass chain through, and put a
bolt with nylock on under side.  Removable, and may be a little bit safer
and stronger than a weld.  But Bob, I wouldn't put a lot of pressure on
there, or trust it to hold anything heavy.  Ask Gunner.  ;-)

Steve

I wonder about that.  Tons of trailers and older flatbed trucks out there
with welded on hooks.  I highly doubt they did anything other than bend a
piece of rod and weld it on.  We had hooks like that on my dad's old
flatbed, and we hauled as much as 10K of grain sacks on it for years and
years (over 20) lashed in place with 1/2" nylon rope.  Never had a hook
fail.  Never even considered the possibility.  I do have bolt through hooks
on some things, and I have had some of those fail.  Particularly those with
the spring and pivot mechanism.  Not an issue with this trailer anyway.
1500 pounds would break it.

Bob La Londe wrote:

Spend some time looking at the various supplier sites, there are tons of
weld-on rated hooks and loops made for exactly that purpose. Those parts
are made with appropriate materials and in appropriate thickness to not
loose strength/temper/ductility from the welding heat and are also not
plated.

Yes, those hooks are made from low carbon steel, are not heat treated,
and are not screwed up by welding.

i

Bob La Londe wrote:

Right.  The OP was talking about using a piece of CHAIN as a hook.  Mild
steel - yes, link of chain - no.

Bob

Bob Engelhardt wrote:

I've been thinking about this (I know - I should think BEFORE I post,
not after <G>).  Is chain really made out of anything other that mild
steel?  If so, why?  After all, it's only ultimate strength that counts,
not the yield strength, or not?

Puzzled and seeing an opportunity to learn something,
Bob

http://www.1st-chainsupply.com/aboutgrading.htm

jsw

Jim Wilkins wrote:

Shit, now I'm even more confused, as if that were possible <G>.

Jim's link has higher carbon steels used in higher grade chains.  'Cause
it has higher "ultimate breaking strength".

Now, what I'm confused about is that I thought all steels had about the
same ultimate strength and the difference between mild and "carbon
steel" was the yield strength.  Is that wrong?  If so, what parameter is
it that's about the same for all steels?

Thanks,
Bob

The (Young's) Modulus of Elasticity is about the same for all, 29E6
(or call it 30). A 29 million pound pull would stretch a 1" square
piece to twice its length, if it didn't break first.

Yield strength is the parameter that matters most. It's how hard you
can pull without permanently deforming the part. It's generally
proportional to hardness. Reasonable values for common steels are
36KSI (36 * 1000PSI) for hot-rolled, 60KSI for cold-rolled, 100-125KSI
for Grade 5 bolts, 150KSI for Grade 8. Fine wire can approach 500KSI.
My textbooks suggest not assuming over 2/3 of those values and in some
critical cases designing at 1/3 of it. .

Ultimate strength is where it snaps, so normally you don't want to be
there. One rule of thumb states that steel repeatedly loaded above
half its ultimate strength will eventually fail by fatigue.

When you compare the Modulus to the Yield you see that most steel can
stretch only a fraction of 1% of its length without damage.

Needs further work, but explains the terms:
http://en.wikipedia.org/wiki/Strength_of_materials

hth, ttfn, jsw

The (Young's) Modulus of Elasticity is about the same for all, 29E6
(or call it 30). A 29 million pound pull would stretch a 1" square
piece to twice its length, if it didn't break first.

Yield strength is the parameter that matters most. It's how hard you
can pull without permanently deforming the part. It's generally
proportional to hardness. Reasonable values for common steels are
36KSI (36 * 1000PSI) for hot-rolled, 60KSI for cold-rolled, 100-125KSI
for Grade 5 bolts, 150KSI for Grade 8. Fine wire can approach 500KSI.
My textbooks suggest not assuming over 2/3 of those values and in some
critical cases designing at 1/3 of it. .

Ultimate strength is where it snaps, so normally you don't want to be
there. One rule of thumb states that steel repeatedly loaded above
half its ultimate strength will eventually fail by fatigue.

When you compare the Modulus to the Yield you see that most steel can
stretch only a fraction of 1% of its length without damage.

Needs further work, but explains the terms:
http://en.wikipedia.org/wiki/Strength_of_materials

hth, ttfn, jsw

Odd, but since you brought it up, I don't recall any chains in the oilfield,
except holding down loads.  All lifting was done with wire rope slings.  And
plain 1" manila rope.  Yeah, I know, it's against regs and all, but at
times, there's just no other way.  As lifting planking when it's scattered
all over a boat that's bobbing in six foot seas.  Throw a timber hitch on
there and go.

Didn't know that fact about failure on repeated use exceeding 50%.

Steve

The converse is that steel should last forever if the loading is kept
below that, but metal fatigue is complex and sometimes unpredictable.

I heard that from an engineer who had just redesigned a failed part
(not for a Rolls-Royce jet engine).

jsw

Wire rope has a phenomenal tensile strength.  Way above that of
chains.  And it gets better.  One link fails in a chain and the chain
is broken.  One strand in a wire rope snaps and the rope is still just
fine.  And you get warning - if there are lots of snapped strands
sticking out of a wire rope, you have an readily observable warning
well before failure.


Yeah - don't we know it!  At the site of the emergency, tell Mr
white-collar-man to stick his new "safety rule" prohibiting rope where
the sun don't shine - seeing as the centuries-old tried-and-tested
rope method is way way safer than a falling-out-of-its-sling
inappropriate "new method" lift.


Just used timber hitches - had timber to move! - this summer.  Is good
- but this is another conversation!


The way you order the words is worrying.  Can we do a check on what
you understand?

If you repeatedly load steel above about 50% of its yield you will
always eventually get a fatigue failure.  Will take a lot of cycles if
you otherwise have designed things right...

Below about 50% of yield - certainly below 40% of yield, a steel will
never fatigue, ever, ever, ever.  Some physical rule stops it happening.

(Ally doesn't behave like this - it will eventually fatigue at any
stress - though the number of stress cycles to cause it makes it a
theoretical point)



Hope this is all helpful and I haven't blundered too much beyond my
practical experience.

That's what I've seen/heard. Steel and titanium -should- have infinite
fatigue life below some stress level, other metals don't. However poor
detail design and machining, rough surface finish, and imperfections
in the material can magnify the local stress level enough to start an
unexpected failure.
http://en.wikipedia.org/wiki/United_Airlines_Flight_232

Not fatigue, but a "minor" detail change:
http://en.wikipedia.org/wiki/Hyatt_Regency_walkway_collapse
The cross-section of the one-piece rod was adequate to support
everything but the threads were only strong enough to hold one level.

jsw

Hi - good direction pointers - thanks.
Got to work in this direction.

Especially as have "Design of Welded Structures" coming up in Welding
Engineering course

Are there any good suggestions as to how I might really put in some
milage on this topic?  It's the one I feel I really need to make
progress on if I am to make this year pay.

Richard S

I rely on an older, much cheaper edition of this for my home project
structural design:
http://www.bookmarki.com/AISC-Steel-Construction-Manual-13th-Edition-p/1564 =
24055x.htm
Some knowledge of Statics and Strength of Materials is essential. This
might help:
http://oli.web.cmu.edu/openlearning/forstudents/freecourses/engineering-sta=
tics

jsw