Metalworking (rec.crafts.metalworking) Discuss various aspects of working with metal, such as machining, welding, metal joining, screwing, casting, hardening/tempering, blacksmithing/forging, spinning and hammer work, sheet metal work.

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Old January 25th 20, 09:05 AM posted to rec.crafts.metalworking
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Default U channel and squire tube which one is strong

Gunner Asch writes:


On Fri, 24 Jan 2020 21:26:15 +0000, Richard Smith
wrote:

Laser'ing is really the great thing - assume it's gone even more that
way in the States?


Laser cutting is still expensive, so most heavy large items that can
be toleranced with a tape measure are still punched or torch cut.
Laser cutting (except for aerospace and medical) tends to still be
part and parcel "small parts with lots of details"...much like large
EDM. EDM has lost so much ground in the past 20 yrs its actually
becoming rather rare to find in shops. If you need something
EDM'd...send it out is the trend.
CNC plasma cutting does the yoemans share of this sort of work. Its
about the cheapest bulk cutting method out there. Getting to be a
fraction of torch cutting if you have details. You simply have to
hire a minimum wage kid to run a big angle grinder to clear off the
slag and any ridges. What wetback...er..undocumented aliens are
for..least here in Californiastan.

Avoid having to debur punched holes, flatten plates again, etc.
Holes all there laser'ed.
Get a pallet-load of plates with identities "etched" with defocussed
laser beam.


Ayup..that is one of the handy things you can do with lasers. Or water
jets. Water jetting is spendy..but much less spendy than laser
cutting these days. Its not so much the cost per hour of the two..but
the inititial cost of the machine and service costs. Water jet has
become much cheaper over the past 15 yrs. But laser is catching
up..slowly.


Gunner - you are almost certainly right. We say "lasered", but it is
probably plasma-cut.
Transfer CAD files to profiler and the CNC cutting machine makes them
to-drawing.

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Old January 25th 20, 09:16 AM posted to rec.crafts.metalworking
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Default U channel and squire tube which one is strong

Hi again Gunner, and anyone else who wants to join in...

So this thread - it's more of analysing structural performance -
strength / stiffness / load-bearing.

Something I find really exasperating here, in the UK. Is the same in
the US?
You opinion?
I think that with
* CNC plasma / laser cutting
* press-braking with a lot of software guidance
* high-strength tough thin plate
* highly-controlled welding - even if manual (GMAW processes)
* CRUCIALLY - Finite Element Analysis modelling easily done
you can make much higher performing structural assemblies from
plate, not assemblages of sections - various angles, box-sections,
etc. - for much nigher-performing steel fabrications.
Much stiffer, much more load-bearing to weight, well-predicted fatigue
resistance at high cyclic loads, etc.
Fairly-much - make in welded steel (cheap) for ad-hoc machine-chassis,
etc., to overall design strategy of riveted aluminum aircraft
sub-assemblies (expensive).
Finite Element Analysis enables you to know under design loads the
stresses, deflections and likely fatigue resistance of the proposed
design which the fabricator "details" to the overall specification of
the component.
The thinking is so conservative here and there seems to be not a
single person in any engineering / leadership (none of that - is
"management") role with whom you can talk the absolutely obvious.
I spent about 30 days busting my brain around how to use a Finite
Element Analysis package, and went from zero to being show the
falacies in shoddy work with no effort put in by contracted-in
engineering consultants.
If you know FEA at all - "shell elements" enable you to model thin
plate structures very readily and economically. It is very difficult
to make a design for a single component which will take more than a
minute of a current personal computer's time to solve.

I did a web-page about this concept
http://www.weldsmith.co.uk/skills/fe...-fold-stl.html

It's so exasperating that what is obviously and readily done by
someone working "on the tools" is invisible by reason of unfamiliarity
to most in "leadership"...

It seems that there is a "lazy" assumption that progress is only being
made in "leading" endeavours like computing, bio-whatever and so on,
and no-one but those on-the-tools can see there's similar levels of
advancement possible in "traditional" (sic.) endeavours, as the
overall technological advancement lifts the "baseline" of what is
readily possible.

Thoughts?
  #23   Report Post  
Old January 25th 20, 03:20 PM posted to rec.crafts.metalworking
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Default U channel and squire tube which one is strong

"Richard Smith" wrote in message
...
Hi again Gunner, and anyone else who wants to join in...

So this thread - it's more of analysing structural performance -
strength / stiffness / load-bearing.

Something I find really exasperating here, in the UK. Is the same
in
the US?
You opinion?
I think that with
* CNC plasma / laser cutting
* press-braking with a lot of software guidance
* high-strength tough thin plate
* highly-controlled welding - even if manual (GMAW processes)
* CRUCIALLY - Finite Element Analysis modelling easily done
you can make much higher performing structural assemblies from
plate, not assemblages of sections - various angles, box-sections,
etc. - for much nigher-performing steel fabrications.
Much stiffer, much more load-bearing to weight, well-predicted
fatigue
resistance at high cyclic loads, etc.
Fairly-much - make in welded steel (cheap) for ad-hoc
machine-chassis,
etc., to overall design strategy of riveted aluminum aircraft
sub-assemblies (expensive).
Finite Element Analysis enables you to know under design loads the
stresses, deflections and likely fatigue resistance of the proposed
design which the fabricator "details" to the overall specification
of
the component.
The thinking is so conservative here and there seems to be not a
single person in any engineering / leadership (none of that - is
"management") role with whom you can talk the absolutely obvious.
I spent about 30 days busting my brain around how to use a Finite
Element Analysis package, and went from zero to being show the
falacies in shoddy work with no effort put in by contracted-in
engineering consultants.
If you know FEA at all - "shell elements" enable you to model thin
plate structures very readily and economically. It is very
difficult
to make a design for a single component which will take more than a
minute of a current personal computer's time to solve.

I did a web-page about this concept
http://www.weldsmith.co.uk/skills/fe...-fold-stl.html

It's so exasperating that what is obviously and readily done by
someone working "on the tools" is invisible by reason of
unfamiliarity
to most in "leadership"...

It seems that there is a "lazy" assumption that progress is only
being
made in "leading" endeavours like computing, bio-whatever and so on,
and no-one but those on-the-tools can see there's similar levels of
advancement possible in "traditional" (sic.) endeavours, as the
overall technological advancement lifts the "baseline" of what is
readily possible.

Thoughts?


As a lab manager tasked with turning Ph.D's paper concepts into
working hardware I noticed a divide between those who were really good
with higher math and those who could visualize the workings of a
machine or circuit. I can look at a truss and see which elements are
in tension or compression but one of my physics teachers couldn't, he
had to look for the sign of the force vectors, even for a simple
triangular street sign support. OTOH I ran into a brick wall trying to
understand Laplace Transforms and the s plane in college, where math
was taught as an art form. Fortunately a chemist doesn't need it.
Later I took electrical engineering classes in night school, taught by
working engineers who used math to solve real-world problems, and
their explanations of applying complex number theory to AC and RF
circuit problems were MUCH easier to follow. This time instead of
nearly flunking I aced Differential Equations and AC Circuit Analysis.
Finally I could read the display on a vector network analyzer and know
what to change to improve the circuit. In FEA terms that's like
finding an unexpected stress riser.

Simulation is easier in electronics because measurements are less
intrusive and the failures aren't destructive. It was pretty good at
describing something that had already been done before, not so good at
predicting into unfamiliar territory. For that we had to build, test,
and adjust the sim and hardware models iteratively.

Here's a classic example of a failure caused by a mathematical model
that was too difficult to implement:
https://en.wikipedia.org/wiki/Hyatt_...lkway_collapse

The original design of the tie rods required the threads to support
only one level, the rods' solid cores bore the weight of the walkways
below. The redesign left the top level's threads and nuts additionally
supporting the lower level.


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Old January 25th 20, 03:58 PM posted to rec.crafts.metalworking
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Default U channel and squire tube which one is strong

On Wed, 22 Jan 2020 17:42:17 -0500
"Jim Wilkins" wrote:

snip
Our digital TV reception is much better than the old analog, and TVs
aren't taxed in the USA, however almost everyone prefers to pay
$150/month and up for cable. Antenna reception is pretty much a
do-it-yourself project with no repairmen to call. This British digital
receiver with the spectrum analyzer program is a great aid in aiming
the antenna to minimize multipath.
https://www.sdrplay.com/rsp1a/


I'm just beginning to work with an RTL-SDR I picked up some time ago:

https://www.rtl-sdr.com/wp-content/u...-Datasheet.pdf

So far I've been pleased with it, works better than I thought it
would. Sure could have used this back when I was still working as a
two-way tech...

Already considering a HackRF but the one you linked to looks pretty
good too. You could have used an RTL-SDR for your antenna job for ~$30.
So I figure you are using the RSP1A for other stuff too...

Happy with it, caveats?

Using Linux nowadays, so I have to check for software compatibility.
Looks like the RSP1A is probably supported.

--
Leon Fisk
Grand Rapids MI

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Old January 25th 20, 04:42 PM posted to rec.crafts.metalworking
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Posts: 5,543
Default U channel and squire tube which one is strong

"Leon Fisk" wrote in message
...
On Wed, 22 Jan 2020 17:42:17 -0500
"Jim Wilkins" wrote:

snip
Our digital TV reception is much better than the old analog, and TVs
aren't taxed in the USA, however almost everyone prefers to pay
$150/month and up for cable. Antenna reception is pretty much a
do-it-yourself project with no repairmen to call. This British
digital
receiver with the spectrum analyzer program is a great aid in aiming
the antenna to minimize multipath.
https://www.sdrplay.com/rsp1a/


I'm just beginning to work with an RTL-SDR I picked up some time
ago:

https://www.rtl-sdr.com/wp-content/u...-Datasheet.pdf

So far I've been pleased with it, works better than I thought it
would. Sure could have used this back when I was still working as a
two-way tech...

Already considering a HackRF but the one you linked to looks pretty
good too. You could have used an RTL-SDR for your antenna job for
~$30.
So I figure you are using the RSP1A for other stuff too...

Happy with it, caveats?

Using Linux nowadays, so I have to check for software compatibility.
Looks like the RSP1A is probably supported.

--
Leon Fisk
Grand Rapids MI


I lived in the world of high-end precision measurement long enough
that I want at least 12 bits of accuracy; the RSP1A has 14. My
portable DVM resolves to 1mV in 22.000V. Back in the early 80's I went
to the trouble of designing and building a 4-1/2 digit multimeter
because I couldn't buy one.




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Old January 25th 20, 05:55 PM posted to rec.crafts.metalworking
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Default U channel and squire tube which one is strong

On Sat, 25 Jan 2020 10:42:12 -0500
"Jim Wilkins" wrote:

snip
I lived in the world of high-end precision measurement long enough
that I want at least 12 bits of accuracy; the RSP1A has 14. My
portable DVM resolves to 1mV in 22.000V. Back in the early 80's I went
to the trouble of designing and building a 4-1/2 digit multimeter
because I couldn't buy one.


I noticed that in its specs...

Early on I concerned myself with minor differences in voltages and
other bits of minutia. I soon learned this rarely had anything to do
with my need to fix something. Watch the relative values and go for the
likely failures. Like the old quote said, "round up the usual suspects".

Thanks for the explanation

--
Leon Fisk
Grand Rapids MI

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Old January 25th 20, 06:30 PM posted to rec.crafts.metalworking
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Posts: 5,543
Default U channel and squire tube which one is strong

"Leon Fisk" wrote in message
...
On Sat, 25 Jan 2020 10:42:12 -0500
"Jim Wilkins" wrote:

snip
I lived in the world of high-end precision measurement long enough
that I want at least 12 bits of accuracy; the RSP1A has 14. My
portable DVM resolves to 1mV in 22.000V. Back in the early 80's I
went
to the trouble of designing and building a 4-1/2 digit multimeter
because I couldn't buy one.


I noticed that in its specs...

Early on I concerned myself with minor differences in voltages and
other bits of minutia. I soon learned this rarely had anything to do
with my need to fix something. Watch the relative values and go for
the
likely failures. Like the old quote said, "round up the usual
suspects".

Thanks for the explanation

--
Leon Fisk
Grand Rapids MI


I agree that repairs don't need it, but R&D requires not only high
accuracy but NIST-traceable calibration. I like it for hobby use
because it shows trends rapidly.

Inaccurate measurements and other poor lab technique have led to false
claims of room-temperature fusion etc.


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Old January 26th 20, 01:22 PM posted to rec.crafts.metalworking
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Posts: 29
Default U channel and squire tube which one is strong

Hi Jim
I read with interest.
You are describing a like situation, as I understand it. You are
seeing the same "mismatch".
Thanks for taking me into your area of expertise in explaining.

Trusses and stresses - as I learned about vectors, wishing to design a
bridge in the form of a truss, I realised I could look up at Victorian
railway station roof supports and see which were in tension and which
were in compression (here in the UK). Those in pure tension could be
and often are flat plates, while those in compression are channel
sections.

Best wishes,
Rich S
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Old January 26th 20, 01:30 PM posted to rec.crafts.metalworking
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Default U channel and squire tube which one is strong

On 1/26/2020 6:22 AM, Richard Smith wrote:
Hi Jim
I read with interest.
You are describing a like situation, as I understand it. You are
seeing the same "mismatch".
Thanks for taking me into your area of expertise in explaining.

Trusses and stresses - as I learned about vectors, wishing to design a
bridge in the form of a truss, I realised I could look up at Victorian
railway station roof supports and see which were in tension and which
were in compression (here in the UK). Those in pure tension could be
and often are flat plates, while those in compression are channel
sections.

Best wishes,
Rich S


You think in 3 dimensions ... most people just can't see what you see .
I also have that ability , which is why I was so good at building
"special projects" in the cabinet shop . I'm betting you can look at a
drawing and visualize the finished product in your mind before the first
piece of material is cut ...

--
Snag
Yes , I'm old
and crochety - and armed .
Get outta my woods !

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Old January 26th 20, 04:12 PM posted to rec.crafts.metalworking
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Posts: 29
Default U channel and squire tube which one is strong

Terry Coombs writes:

On 1/26/2020 6:22 AM, Richard Smith wrote:
Hi Jim
I read with interest.
You are describing a like situation, as I understand it. You are
seeing the same "mismatch".
Thanks for taking me into your area of expertise in explaining.

Trusses and stresses - as I learned about vectors, wishing to design a
bridge in the form of a truss, I realised I could look up at Victorian
railway station roof supports and see which were in tension and which
were in compression (here in the UK). Those in pure tension could be
and often are flat plates, while those in compression are channel
sections.

Best wishes,
Rich S


You think in 3 dimensions ... most people just can't see what you see
. I also have that ability , which is why I was so good at building
"special projects" in the cabinet shop . I'm betting you can look at a
drawing and visualize the finished product in your mind before the
first piece of material is cut ...


Hi Terry

Being "confronted" with this was a major juncture in my life.

That I can see things which few others will ever see in all their
lives / careers.

That happened when I was in my mid-20's and was feeling very confused.

What this friend said was transformational - inverted the perception.
That what I was seeing the real, and they were lost in a convenient
substitute for reality.

I gained great self-confidence to go forth to the next step(s).

I got so successful pursuing science and technology that I attracted
resentment from others who were actually very bright themselves, and
wrecked-up unable to defend against so many causes attacking
simultaneously.

But life as a welder, with occasional engineering jobs, is not bad...
:-)

This about seeing things in simulataneous multidimensional dynamic
interactions, interacting and intersecting to produce "contours" and
"envelopes" of usable / interesting conditions. Rather than a
narrative sequence of zero-dimension / single-point "rules" /
assertions - rather like a "necklace" assembly of hard immutable
points.

This is what many of "us" share (?)

In shop-floor "leadership" jobs (when I can get them in this
"service-economy" country), I have to start with little things, so the
people who have been doing the jobs a long time can see "I have
something". Then build up to bigger refinements spanning across
various processes. Delivering each time and becoming valued (given in
manufacturing, most shop-floor workers know their job and reasonable
way-of-life dependss on customers keeping on wanting what the company
makes - more than what many management bother with).

Best was working in Turkey on the 3rd Bosphorus Bridge project -
representing Hyundai (lead contractor). They expressed that I made it
possible to complete the bridge, sorting out the steel (bridge-deck
and tower + cable-anchor fitments) parts of the project.
No job back in UK though - straight back to meeting this impenetrable
wall of "non-discriminatory equal-opportunities" recruitment where
administrative grades have seized control of interview / recruitment
processes...


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