I need a steel rod/s. precision ground, polished, turned, heat treated
whatever is most effective. 3/8" OD and a length of 4'. I need to know
what kind of steel (1144, Stressproff, 4140 TGPHT would have the least
amount of sagging, twisting, and flexing (wasn't sure on the scientific
terms for these). Can you help me out with that one? Or maybe point me
to a graph or an equation to work it out?

Thanks in advance for your time,

Jeremy

p.s in the future I will need an eight or 10 foot rod



--
posted from
http://www.polytechforum.com/metalwo...-4-613340-.htm
using PolytechForum's Web, RSS and Social Media Interface to
rec.crafts.metalworking and other engineering groups

On Sun, 19 Apr 2015 23:18:02 +0000, Jman
wrote:

I need a steel rod/s. precision ground, polished, turned, heat treated
whatever is most effective. 3/8" OD and a length of 4'. I need to know
what kind of steel (1144, Stressproff, 4140 TGPHT would have the least
amount of sagging, twisting, and flexing (wasn't sure on the scientific
terms for these). Can you help me out with that one? Or maybe point me
to a graph or an equation to work it out?

Thanks in advance for your time,

Jeremy

p.s in the future I will need an eight or 10 foot rod

All grades will be the same (except for stainless, which will sag,
etc. slightly more). All hardness conditions will be the same.

I know this is hard to believe. When the second or third poster chimes
in, you'll start to believe it.

--
Ed Huntress

On 4/19/2015 6:29 PM, Ed Huntress wrote:
On Sun, 19 Apr 2015 23:18:02 +0000, Jman
wrote:

I need a steel rod/s. precision ground, polished, turned, heat treated
whatever is most effective. 3/8" OD and a length of 4'. I need to know
what kind of steel (1144, Stressproff, 4140 TGPHT would have the least
amount of sagging, twisting, and flexing (wasn't sure on the scientific
terms for these). Can you help me out with that one? Or maybe point me
to a graph or an equation to work it out?

Thanks in advance for your time,

Jeremy

p.s in the future I will need an eight or 10 foot rod
All grades will be the same (except for stainless, which will sag,
etc. slightly more). All hardness conditions will be the same.

I know this is hard to believe. When the second or third poster chimes
in, you'll start to believe it.


correct.

Fairly understandable essay on deflection of beams.


http://en.wikipedia.org/wiki/Deflect...engineering%29

On 2015-04-19, Ed Huntress wrote:
On Sun, 19 Apr 2015 23:18:02 +0000, Jman
wrote:

I need a steel rod/s. precision ground, polished, turned, heat treated
whatever is most effective. 3/8" OD and a length of 4'. I need to know
what kind of steel (1144, Stressproff, 4140 TGPHT would have the least
amount of sagging, twisting, and flexing (wasn't sure on the scientific
terms for these). Can you help me out with that one? Or maybe point me
to a graph or an equation to work it out?

Thanks in advance for your time,

Jeremy

p.s in the future I will need an eight or 10 foot rod

All grades will be the same (except for stainless, which will sag,
etc. slightly more). All hardness conditions will be the same.

I know this is hard to believe. When the second or third poster chimes
in, you'll start to believe it.


Can you explain why it is so?

"Ignoramus25660" wrote in message
...

On 2015-04-19, Ed Huntress wrote:
On Sun, 19 Apr 2015 23:18:02 +0000, Jman
wrote:

I need a steel rod/s. precision ground, polished, turned, heat treated
whatever is most effective. 3/8" OD and a length of 4'. I need to know
what kind of steel (1144, Stressproff, 4140 TGPHT would have the least
amount of sagging, twisting, and flexing (wasn't sure on the scientific
terms for these). Can you help me out with that one? Or maybe point me
to a graph or an equation to work it out?

Thanks in advance for your time,

Jeremy

p.s in the future I will need an eight or 10 foot rod

All grades will be the same (except for stainless, which will sag,
etc. slightly more). All hardness conditions will be the same.

I know this is hard to believe. When the second or third poster chimes
in, you'll start to believe it.


Can you explain why it is so?
================================================== =================

Iggy, the physical property that defines "stiffness" is called Young's
Modulus, or the modulus of elasticity. Pretty much all steel alloys have a
modulus between 28,500,000 psi and 30,500,000 psi, a range of 7%, so for
most calculation purposes "all" steel is basically 29,000,000 psi and
equivalent as far as stiffness goes. This does not change with heat treat
or hardness or work hardening or tensile strength or yield strength.
Similarly "all" aluminum alloys are 10,600,000 psi. Cast iron is about
10,000,000 psi for plain grey iron and up to about 15,000,000 psi for
nodular iron; that is one of the few materials whose modulus changes
significantly with minor changes in composition and heat treat. In terms of
shape, the stiffness is proportional to the fourth power of the lateral
dimension so 3/4" rod is 16 times stiffer than 3/8" rod, and pound for pound
thinwall large od tube is much stiffer than solid rod (of course, diameter
for diameter solid rod is stiffer than tube). For the OP, 4' or 3/8" rod
held parallel to the ground by supporting the ends is going to sag a good
bit under its own weight. The shape parameter that determines stiffness is
the moment of inertia (not the same rotational moment as for a spinning
object). For example, for 3/8" solid rod the moment if inertia I is
0.0009707 in^4, and 4' of 3/8" mild steel will weigh about 1.5 lbs. If you
support the ends by just sitting them on supports (as opposed to clamping
them so they can't pivot), and distribute that weight uniformly along the
length, the center will sag down 0.0767" and the maximum stress (based on
other calculations that vary with shape) will be 1740 psi, compared to a
yield strength of what, 40-50,000 psi so it is in no danger of permanently
bending. If you double the diameter the moment of inertia goes up by 16
(2^4) so it is 16 times stiffer, but the weight goes up by 4 (2^2) so the
net is one fourth the deflection (deflection is proportional to load/moment
of inertia if you keep the length constant) or 0.0192". The maximum stress
will be 870 psi. You can look up the moment of inertia for structural
shapes like rod, tubes, angles, I beams, and plug those numbers in, but for
each change of shape or dimension the maximum stress will have to be
recalculated from scratch if that is a concern (I'm too sleepy to take care
of stress and beam length, sorry). Usually it turns out that the deflection
is the limiting spec and by the time you get a design that keeps that down
below some limit you have such a strong structure that the yield rating is
overkill (like here).

As always, the program I recommend for quickie calculations like this is
engineering power tools, from www.pwr-tools.com. The freeware version will
do all of this with no time limit or ads, and the full version is only about
$50 and well worth it if you do a good bit of design.

-----
Regards,
Carl Ijames carl.ijames aat deletethis verizon dott net

"Carl Ijames" fired this volley in
:


Iggy, the physical property that defines "stiffness" is called Young's
Modulus, or the modulus of elasticity.

Bravo, Carl! A good, short treatise!

Lloyd

"Carl Ijames" wrote in message ...

"Ignoramus25660" wrote in message
...

On 2015-04-19, Ed Huntress wrote:
On Sun, 19 Apr 2015 23:18:02 +0000, Jman
wrote:

I need a steel rod/s. precision ground, polished, turned, heat treated
whatever is most effective. 3/8" OD and a length of 4'. I need to know
what kind of steel (1144, Stressproff, 4140 TGPHT would have the least
amount of sagging, twisting, and flexing (wasn't sure on the scientific
terms for these). Can you help me out with that one? Or maybe point me
to a graph or an equation to work it out?

Thanks in advance for your time,

Jeremy

p.s in the future I will need an eight or 10 foot rod

All grades will be the same (except for stainless, which will sag,
etc. slightly more). All hardness conditions will be the same.

I know this is hard to believe. When the second or third poster chimes
in, you'll start to believe it.


Can you explain why it is so?
================================================== =================

Iggy, the physical property that defines "stiffness" is called Young's
Modulus, or the modulus of elasticity. Pretty much all steel alloys have a
modulus between 28,500,000 psi and 30,500,000 psi, a range of 7%, so for
most calculation purposes "all" steel is basically 29,000,000 psi and
equivalent as far as stiffness goes. This does not change with heat treat
or hardness or work hardening or tensile strength or yield strength.
Similarly "all" aluminum alloys are 10,600,000 psi. Cast iron is about
10,000,000 psi for plain grey iron and up to about 15,000,000 psi for
nodular iron; that is one of the few materials whose modulus changes
significantly with minor changes in composition and heat treat. In terms of
shape, the stiffness is proportional to the fourth power of the lateral
dimension so 3/4" rod is 16 times stiffer than 3/8" rod, and pound for pound
thinwall large od tube is much stiffer than solid rod (of course, diameter
for diameter solid rod is stiffer than tube). For the OP, 4' or 3/8" rod
held parallel to the ground by supporting the ends is going to sag a good
bit under its own weight. The shape parameter that determines stiffness is
the moment of inertia (not the same rotational moment as for a spinning
object). For example, for 3/8" solid rod the moment if inertia I is
0.0009707 in^4, and 4' of 3/8" mild steel will weigh about 1.5 lbs. If you
support the ends by just sitting them on supports (as opposed to clamping
them so they can't pivot), and distribute that weight uniformly along the
length, the center will sag down 0.0767" and the maximum stress (based on
other calculations that vary with shape) will be 1740 psi, compared to a
yield strength of what, 40-50,000 psi so it is in no danger of permanently
bending. If you double the diameter the moment of inertia goes up by 16
(2^4) so it is 16 times stiffer, but the weight goes up by 4 (2^2) so the
net is one fourth the deflection (deflection is proportional to load/moment
of inertia if you keep the length constant) or 0.0192". The maximum stress
will be 870 psi. You can look up the moment of inertia for structural
shapes like rod, tubes, angles, I beams, and plug those numbers in, but for
each change of shape or dimension the maximum stress will have to be
recalculated from scratch if that is a concern (I'm too sleepy to take care
of stress and beam length, sorry). Usually it turns out that the deflection
is the limiting spec and by the time you get a design that keeps that down
below some limit you have such a strong structure that the yield rating is
overkill (like here).

As always, the program I recommend for quickie calculations like this is
engineering power tools, from www.pwr-tools.com. The freeware version will
do all of this with no time limit or ads, and the full version is only about
$50 and well worth it if you do a good bit of design.

-----
Regards,
Carl Ijames carl.ijames aat deletethis verizon dott net
================================================== ================

One quick addendum now that I'm more awake, it seemed odd that the variation
of I with lateral dimension was the fourth power, not third, so I double
checked and yes, with solid round rod I varies as diameter^4 but for
rectangular cross sections, like turning down an edge on a piece of sheet
metal or using angles for stiffening, I varies as the cube of the height.
For tubing it varies with the wall thickness vs. diameter but it seems to be
between ^3 and ^4 of the diameter.

-----
Regards,
Carl Ijames carl.ijames aat deletethis verizon dott net

Awesome clarification. Thank you.

On Sun, 19 Apr 2015 23:04:42 -0500, Ignoramus25660
wrote:

On 2015-04-19, Ed Huntress wrote:
On Sun, 19 Apr 2015 23:18:02 +0000, Jman
wrote:

I need a steel rod/s. precision ground, polished, turned, heat treated
whatever is most effective. 3/8" OD and a length of 4'. I need to know
what kind of steel (1144, Stressproff, 4140 TGPHT would have the least
amount of sagging, twisting, and flexing (wasn't sure on the scientific
terms for these). Can you help me out with that one? Or maybe point me
to a graph or an equation to work it out?

Thanks in advance for your time,

Jeremy

p.s in the future I will need an eight or 10 foot rod

All grades will be the same (except for stainless, which will sag,
etc. slightly more). All hardness conditions will be the same.

I know this is hard to believe. When the second or third poster chimes
in, you'll start to believe it.


Can you explain why it is so?

What Carl said. If you mean what is the physics behind it, no, you'd
have to look that up.

--
Ed Huntress

On Mon, 20 Apr 2015 07:06:27 -0400, Ed Huntress wrote:

On Sun, 19 Apr 2015 23:04:42 -0500, Ignoramus25660
wrote:

On 2015-04-19, Ed Huntress wrote:
On Sun, 19 Apr 2015 23:18:02 +0000, Jman
m wrote:

I need a steel rod/s. precision ground, polished, turned, heat
treated whatever is most effective. 3/8" OD and a length of 4'. I
need to know what kind of steel (1144, Stressproff, 4140 TGPHT would
have the least amount of sagging, twisting, and flexing (wasn't sure
on the scientific terms for these). Can you help me out with that
one? Or maybe point me to a graph or an equation to work it out?

Thanks in advance for your time,

Jeremy

p.s in the future I will need an eight or 10 foot rod

All grades will be the same (except for stainless, which will sag,
etc. slightly more). All hardness conditions will be the same.

I know this is hard to believe. When the second or third poster chimes
in, you'll start to believe it.


Can you explain why it is so?

What Carl said. If you mean what is the physics behind it, no, you'd
have to look that up.

AFAIK the physics behind it is that the Young's modulus is about how the
atoms interact wherever they may be in the crystals, and the ultimate
strength is about how readily the individual crystals (or perhaps planes
within the crystals) can slip -- and carbon atoms tend to "pin" the
crystals (or crystal planes -- see how little I know?) to one another.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

On Tue, 21 Apr 2015 14:02:23 -0500, Tim Wescott
wrote:

On Mon, 20 Apr 2015 07:06:27 -0400, Ed Huntress wrote:

On Sun, 19 Apr 2015 23:04:42 -0500, Ignoramus25660
wrote:

On 2015-04-19, Ed Huntress wrote:
On Sun, 19 Apr 2015 23:18:02 +0000, Jman
wrote:

I need a steel rod/s. precision ground, polished, turned, heat
treated whatever is most effective. 3/8" OD and a length of 4'. I
need to know what kind of steel (1144, Stressproff, 4140 TGPHT would
have the least amount of sagging, twisting, and flexing (wasn't sure
on the scientific terms for these). Can you help me out with that
one? Or maybe point me to a graph or an equation to work it out?

Thanks in advance for your time,

Jeremy

p.s in the future I will need an eight or 10 foot rod

All grades will be the same (except for stainless, which will sag,
etc. slightly more). All hardness conditions will be the same.

I know this is hard to believe. When the second or third poster chimes
in, you'll start to believe it.


Can you explain why it is so?

What Carl said. If you mean what is the physics behind it, no, you'd
have to look that up.

AFAIK the physics behind it is that the Young's modulus is about how the
atoms interact wherever they may be in the crystals, and the ultimate
strength is about how readily the individual crystals (or perhaps planes
within the crystals) can slip -- and carbon atoms tend to "pin" the
crystals (or crystal planes -- see how little I know?) to one another.

Thank you, Tim. That's a *big* help. g

As for strength, yes, you're on the right track. The martensitic
crystal phase creates a pre-strain between the crystals, and that
keeps them from slipping as easily.

But I have no clue about stiffness. It's something going on deeper
than any materials discussion I've read, or that I recall, anyway. I
read a ton of this stuff when I was materials editor at American
Machinist, but that was 34 years ago.

--
Ed Huntress

On Sunday, April 19, 2015 at 7:18:05 PM UTC-4, Jman wrote:
I need a steel rod/s. precision ground, polished, turned, heat treated
whatever is most effective. 3/8" OD and a length of 4'. I need to know
what kind of steel (1144, Stressproff, 4140 TGPHT would have the least
amount of sagging, twisting, and flexing (wasn't sure on the scientific
terms for these). Can you help me out with that one? Or maybe point me
to a graph or an equation to work it out?

Thanks in advance for your time,

Jeremy



Is the sagging only from the weight oft the rod? If so you can do a little better using a tube. Increasing the diameter will reduce the amount of sagging, and again using a tube will help even more. And decreasing the length will also help.

Dan

replying to , Aristatos wrote:
dcaster wrote:

Is the sagging only from the weight oft the rod? If so you can do a little
better using a tube. Increasing the diameter will reduce the amount of
sagging, and again using a tube will help even more. And decreasing the
length will also help.
Dan




The sagging could be from a weight of 50 pounds to 100 pounds, twisting
would be from high torque stepper motors

thanks again people, just slightly confusing with the different numbers
and what not. And I should have specified the sagging from load, not
length.

thanks again, I was worried no one would answer, new here.

thanks


--
posted from
http://www.polytechforum.com/metalwo...-4-613340-.htm
using PolytechForum's Web, RSS and Social Media Interface to
rec.crafts.metalworking and other engineering groups

On Sun, 19 Apr 2015 23:18:02 +0000, Jman
wrote:

I need a steel rod/s. precision ground, polished, turned, heat treated
whatever is most effective. 3/8" OD and a length of 4'. I need to know
what kind of steel (1144, Stressproff, 4140 TGPHT would have the least
amount of sagging, twisting, and flexing (wasn't sure on the scientific
terms for these). Can you help me out with that one? Or maybe point me
to a graph or an equation to work it out?

Thanks in advance for your time,

Jeremy

p.s in the future I will need an eight or 10 foot rod

With no more than 0.0003" sag, right? g

Maybe something like this is in your futu
http://tinyurl.com/k89zupx Support that puppy!

--
"I believe there are more instances of the abridgment of the freedom
of the people by gradual and silent encroachments of those in power
than by violent and sudden usurpations."
--James Madison, Virginia Convention, June 16, 1788

On Sunday, April 19, 2015 at 4:18:05 PM UTC-7, Jman wrote:
I need a steel rod/s. precision ground, polished, turned, heat treated
whatever is most effective. 3/8" OD and a length of 4'. I need to know
what kind of steel (1144, Stressproff, 4140 TGPHT would have the least
amount of sagging, twisting, and flexing (wasn't sure on the scientific
terms for these). Can you help me out with that one? Or maybe point me
to a graph or an equation to work it out?

Thanks in advance for your time,

Jeremy

p.s in the future I will need an eight or 10 foot rod



--
posted from
http://www.polytechforum.com/metalwo...-4-613340-.htm
using PolytechForum's Web, RSS and Social Media Interface to
rec.crafts.metalworking and other engineering groups


Knowing something about what it's going to be used for might help.

replying to Jman, Aristatos wrote:
Jman wrote:

I need a steel rod/s. precision ground, polished, turned, heat treated
whatever
is most effective. 3/8" OD and a length of 4'. I need to know what kind of
steel (1144, Stressproff, 4140 TGPHT would have the least amount of
sagging,
twisting, and flexing (wasn't sure on the scientific terms for these). Can
you
help me out with that one? Or maybe point me to a graph or an equation to
work
it out?
Thanks in advance for your time,
Jeremy
p.s in the future I will need an eight or 10 foot rod



The sagging could be from a weight of 50 pounds to 100 pounds, twisting
would be
from high torque stepper motors

thanks again people, just slightly confusing with the different numbers
and what
not. And I should have specified the sagging from load, not length.

thanks again, I was worried no one would answer, new here.

thanks


--
posted from
http://www.polytechforum.com/metalwo...-4-613340-.htm
using PolytechForum's Web, RSS and Social Media Interface to
rec.crafts.metalworking and other engineering groups

"Aristatos" wrote
in message
roups.com...
replying to Jman, Aristatos wrote:
Jman wrote:

I need a steel rod/s. precision ground, polished, turned, heat
treated
whatever
is most effective. 3/8" OD and a length of 4'. I need to know what
kind of
steel (1144, Stressproff, 4140 TGPHT would have the least amount of
sagging,
twisting, and flexing (wasn't sure on the scientific terms for
these). Can
you
help me out with that one? Or maybe point me to a graph or an
equation to
work
it out?
Thanks in advance for your time,
Jeremy
p.s in the future I will need an eight or 10 foot rod



The sagging could be from a weight of 50 pounds to 100 pounds,
twisting
would be
from high torque stepper motors

thanks again people, just slightly confusing with the different
numbers
and what
not. And I should have specified the sagging from load, not length.

thanks again, I was worried no one would answer, new here.

thanks

In the first graph here the nearly vertical line is where the metal
will return to its original shape after being deflected. The slope of
the line is the deflection (strain) vs applied force (stress), or
stiffness.
http://aluminium.matter.org.uk/conte...eid=2144417131

Stronger or harder alloys simply follow the same line further up
before permanently deforming, at the point where the lines turn toward
horizontal. This is why greater strength or hardness doesn't provide
greater stiffness.

The second graph shows the difference between aluminum and steel of
identical cross-section (not weight).

You can demonstrate the bending behavior of steel by clamping two long
hardened drywall screws upright by the tip in a bench vise. Heat one
to redness with a propane torch to anneal it soft, then after it cools
push sideways on both. For a small force they both deflect
identically. As you push harder the annealed one will suddenly bend
when it reaches its "yield point" while the hard one remains springy.

-jsw

"Jim Wilkins" wrote in message
...
"Aristatos"
wrote in message
roups.com...
replying to Jman, Aristatos wrote:
Jman wrote:

I need a steel rod/s. precision ground, polished, turned, heat
treated
whatever
is most effective. 3/8" OD and a length of 4'. I need to know
what kind of
steel (1144, Stressproff, 4140 TGPHT would have the least amount
of
sagging,
twisting, and flexing (wasn't sure on the scientific terms for
these). Can
you
help me out with that one? Or maybe point me to a graph or an
equation to
work
it out?
Thanks in advance for your time,
Jeremy
p.s in the future I will need an eight or 10 foot rod



The sagging could be from a weight of 50 pounds to 100 pounds,
twisting
would be
from high torque stepper motors

thanks again people, just slightly confusing with the different
numbers
and what
not. And I should have specified the sagging from load, not
length.

thanks again, I was worried no one would answer, new here.

thanks


Stronger or harder alloys simply follow the same line further up
before permanently deforming, at the point where the lines turn
toward horizontal. This is why greater strength or hardness doesn't
provide greater stiffness.


The Wiki describes elastic behavior in more detail, with examples:
http://en.wikipedia.org/wiki/Young%27s_modulus

It doesn't mention that the values are the force per unit area
required to stretch the sample by 100%, or to twice its length, which
can't be done in practice since it would break or become thinner,
decreasing the area.
http://en.wikipedia.org/wiki/Talk%3AYoung's_modulus
"it may be better to leave it out, to avoid confusing people, or at
least putting it down the bottom in some sort of "vaguely interesting
but complicated stuff" section, well away from the main definitons."

Some common materials like Tungsten are stiffer than steel, but also
heavier so they'd sag about the same if held horizontally. Beryllium
would be a great structural material if it wasn't poisonous.

You could try gently and unobstrusively bending a 3/8" steel rod in a
hardware store to get a hands-on feel for how stiff steel is, and
isn't.

-jsw

On Mon, 20 Apr 2015 10:42:34 -0400, "Jim Wilkins"
wrote:

"Jim Wilkins" wrote in message
...
"Aristatos"
wrote in message
roups.com...
replying to Jman, Aristatos wrote:
Jman wrote:

I need a steel rod/s. precision ground, polished, turned, heat
treated
whatever
is most effective. 3/8" OD and a length of 4'. I need to know
what kind of
steel (1144, Stressproff, 4140 TGPHT would have the least amount
of
sagging,
twisting, and flexing (wasn't sure on the scientific terms for
these). Can
you
help me out with that one? Or maybe point me to a graph or an
equation to
work
it out?
Thanks in advance for your time,
Jeremy
p.s in the future I will need an eight or 10 foot rod



The sagging could be from a weight of 50 pounds to 100 pounds,
twisting
would be
from high torque stepper motors

thanks again people, just slightly confusing with the different
numbers
and what
not. And I should have specified the sagging from load, not
length.

thanks again, I was worried no one would answer, new here.

thanks


Stronger or harder alloys simply follow the same line further up
before permanently deforming, at the point where the lines turn
toward horizontal. This is why greater strength or hardness doesn't
provide greater stiffness.


The Wiki describes elastic behavior in more detail, with examples:
http://en.wikipedia.org/wiki/Young%27s_modulus

It doesn't mention that the values are the force per unit area
required to stretch the sample by 100%, or to twice its length, which
can't be done in practice since it would break or become thinner,
decreasing the area.
http://en.wikipedia.org/wiki/Talk%3AYoung's_modulus
"it may be better to leave it out, to avoid confusing people, or at
least putting it down the bottom in some sort of "vaguely interesting
but complicated stuff" section, well away from the main definitons."

Some common materials like Tungsten are stiffer than steel, but also
heavier so they'd sag about the same if held horizontally. Beryllium
would be a great structural material if it wasn't poisonous.

You could try gently and unobstrusively bending a 3/8" steel rod in a
hardware store to get a hands-on feel for how stiff steel is, and
isn't.

-jsw


Coat hangers are good for that, too. They're what I use to demonstrate
the principle to people. When you're talking about how even the
crappiest steel has the same elastic properties as, say, 200,000
psi-yield music wire of the same diameter, it makes a good demo. Steel
doesn't come much crappier than coat hangers.

--
Ed Huntress

"Ed Huntress" wrote in message
...
On Mon, 20 Apr 2015 10:42:34 -0400, "Jim Wilkins"
wrote:


You could try gently and unobstrusively bending a 3/8" steel rod in
a
hardware store to get a hands-on feel for how stiff steel is, and
isn't.

-jsw


Coat hangers are good for that, too. They're what I use to
demonstrate
the principle to people. When you're talking about how even the
crappiest steel has the same elastic properties as, say, 200,000
psi-yield music wire of the same diameter, it makes a good demo.
Steel
doesn't come much crappier than coat hangers.

--
Ed Huntress

How did you do it?

I usually had a bench vise and drywall screws available in the labs
where I worked. My demo was less convincing in someone's office with
only paper clips and a lighter, though they are enough to show how
fire severely weakens steel.

-jsw

On Monday, April 20, 2015 at 10:49:22 AM UTC-4, Ed Huntress wrote:
On Mon, 20 Apr 2015 10:42:34 -0400, "Jim Wilkins"
wrote:

"Jim Wilkins" wrote in message
...
"Aristatos"
wrote in message
roups.com...
replying to Jman, Aristatos wrote:
Jman wrote:

I need a steel rod/s. precision ground, polished, turned, heat
treated
whatever
is most effective. 3/8" OD and a length of 4'. I need to know
what kind of
steel (1144, Stressproff, 4140 TGPHT would have the least amount
of
sagging,
twisting, and flexing (wasn't sure on the scientific terms for
these). Can
you
help me out with that one? Or maybe point me to a graph or an
equation to
work
it out?
Thanks in advance for your time,
Jeremy
p.s in the future I will need an eight or 10 foot rod



The sagging could be from a weight of 50 pounds to 100 pounds,
twisting
would be
from high torque stepper motors

thanks again people, just slightly confusing with the different
numbers
and what
not. And I should have specified the sagging from load, not
length.

thanks again, I was worried no one would answer, new here.

thanks


Stronger or harder alloys simply follow the same line further up
before permanently deforming, at the point where the lines turn
toward horizontal. This is why greater strength or hardness doesn't
provide greater stiffness.


The Wiki describes elastic behavior in more detail, with examples:
http://en.wikipedia.org/wiki/Young%27s_modulus

It doesn't mention that the values are the force per unit area
required to stretch the sample by 100%, or to twice its length, which
can't be done in practice since it would break or become thinner,
decreasing the area.
http://en.wikipedia.org/wiki/Talk%3AYoung's_modulus
"it may be better to leave it out, to avoid confusing people, or at
least putting it down the bottom in some sort of "vaguely interesting
but complicated stuff" section, well away from the main definitons."

Some common materials like Tungsten are stiffer than steel, but also
heavier so they'd sag about the same if held horizontally. Beryllium
would be a great structural material if it wasn't poisonous.

You could try gently and unobstrusively bending a 3/8" steel rod in a
hardware store to get a hands-on feel for how stiff steel is, and
isn't.

-jsw


Coat hangers are good for that, too. They're what I use to demonstrate
the principle to people. When you're talking about how even the
crappiest steel has the same elastic properties as, say, 200,000
psi-yield music wire of the same diameter, it makes a good demo. Steel
doesn't come much crappier than coat hangers.

Coat hangers are also good for replacing 9 wire as drop-in light supports to Hilti straps (for drop ceilings).

replying to Ed Huntress , Aristatos/Jman wrote:
huntres23 wrote:

On Mon, 20 Apr 2015 10:42:34 -0400, "Jim Wilkins"
Coat hangers are good for that, too. They're what I use to demonstrate
the principle to people. When you're talking about how even the
crappiest steel has the same elastic properties as, say, 200,000
psi-yield music wire of the same diameter, it makes a good demo. Steel
doesn't come much crappier than coat hangers.
--
Ed Huntress




Thanks again everyone, the answers are all really appreciated, and I think
I understand, but just in case;

If I understand what has been said it does not matter if it is 1144
Stressproof or 4140, it is going to sag under its own weight if it is 3/8"
X 4'. The treatment to the steel or the carbon percentage is only going
to affect how far it can bend or twist while still being able to return
to its original shape or before it will snap. Am I correct in my thinking
on this? I haven't checked out all of the links that were provided, but I
guess I could find a formula to see how much the sag will be at the center?

Would it be the same with a chromium vanadium steel alloy, or something
like that?

Thanks again everyone


ATTN ADMIN: I posted the first message under Jman before I created this
account, so I didnt know if you wanted to change the author on that post.
Great site

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