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

Gunner Asch writes:

On Mon, 20 Jan 2020 21:50:09 +0000, Richard Smith
wrote:

"Jim Wilkins" writes:

"Richard Smith" wrote in message
...
Jahan writes:

8 cm wide by 3 cm U Channel and 3 x 3 inch x 2 mm tube

....
You'll be wanting to study Second Moment of Area and the beam and
column calculations / equations.
The Euler column and the Euler-Bernoulli beam (both derived around
the
1750's - about 250 years ago) which serve well for most applications
of beams and columns.

Regards,
Rich Smith

When I built a log splitter, sawmill and a hydraulic bucket loader for
my tractor I welded every joint that wouldn't have to be taken apart
to store or modify them. However structural steel design manuals say
to avoid field welding whenever possible, due to high cost. They are
more neutral about shop welding versus bolting. Why would field
welding be prohibitably expensive? Heavy construction equipment is
almost entirely welded.

Big difference between commercial and hobby, in all practical / real
senses.

That contention, "field welding expensive", would be true for typical
commercial cases.
Commercially, you use MIG (GMAW) in a workshop, and SMAW on-site

* in a well-set-up fab-shop MIG (GMAW) is vastly faster than stick
(SMAW) applied in the same situation

* they'd be talking about bolted steel connections for buildings -
"rattle-gun" (impact wrench) a few bolts, rather than weld (SMAW)
(noting that at the ends of beams, where the bolts are, you only
have a small shear force, with all the serious big beam bending
stresses far away in the mid-length of the beam)

Hence, commercially, due to processes used and the majority
application, the statement is true.

In a hobby workshop, at best you still have a single-phase electric
power and you cannot pull those 15kW from the mains which makes
fabshop MIG so productive. Most MIG's are transformer and something
like 50% efficient, whereas many SMAW sets now are inverters and
high-90's percent efficient - so those 3.12kW (British 240V 13A max)
give almost twice the bang-per-buck and even up the productivity. No
loss of productivity outdoors with stick, which is one of the few
processes which is in reality rather tolerant of wind and rain.
Then you are going to have much more trouble making bolted joints that
in a well-set-up commercial shop, with all your marking tools,
benches, ironworker for punching holes, etc, etc, etc.

In summary - it's no wonder you see a different picture where for your
home fabs. welding is vastly easier and quicker.

It all makes complete sense - be assured of that.

Regards,
Rich Smith

Well stated!

As noted.. commercial shops tend to punch holes rather than machine
them. Its faster by far..IF you have the machinery..than drilling.

One of the biggest issues..is the difficulty transporting a gizmo that
has been welded together ..or the ease of putting a bunch of pieces in
a flat carton and shipping it off the client, to be bolted together on
site.

A perfect example is this 11 foot (on the diagonal) part I had to fab
for a project. I had to transport it on a flat bed truck, tilted on
an angle. If I had to make them for resale..Id have built it as a bolt
together out of parts to fit bundled together.

https://photos.app.goo.gl/H2t1cd5TMVzr9SDR9

Gunner

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.


I've made big-ish platforms with bolted connections not needed for any
structural reason, solely so the broken-apart structure will fit on a
3~1/2 tonne flatbed truck.

Regards,
Rich Smith

Ayup. There is a lot of stuff done like an erector set. Comes in a
box..and you put it together onsite. Some of it is actually well
engineered too!

Gunner
__

"Journalists are extremely rare and shouldn’t be harmed, but propagandists are everywhere and should be hunted for sport"

Yeah..with no bag limit.