[TheForge] weld question

Wed Apr 23 22:29:00 2003

Dan -

Thanks. That helps a ton.
I really appreciate the effort you put into this reply.
You just reminded me that I have a copy of Machinery's Handbook around here.
However, it looks like you've already done most of the work for me.
So based upon how this half-round profile works, I'll be able to easily replace
it with a stock of another size and profile if needed.

Again, thanks.

Bob

-----Original Message-----
From: [email protected]
[mailto:[email protected]]On Behalf Of Dan Hayes
Sent: Wednesday, April 23, 2003 8:14 PM
To: [email protected]
Subject: RE: [TheForge] weld question

Bob:

What you are looking for can be found in any one of many references on the
subject of "mechanics of materials" or "strength of materials". There are
many references and textbooks devoted to this subject. The subject is also
addressed in readily available handbooks. The two most common are probably
the "Standard Handbook for Mechanical Engineers" by Baumister and Marks
(often referred to as Mark's Handbook) and Machinery's Handbook. If you want
a quantitative prediction of how the part will deflect under load, you're
going to have to learn a fair amount about mechanics of materials. If you
take the time to read the chapter in either of the two above references, and
find you grasp what you read, you'll be able to handle most common
situations.

If all you're interested in is relative stiffness/strength, all you need is
to know that the property you are interested in (resistance to deflection)
is proportional to what is known as the "moment of inertia" of the cross
section under consideration. Moments of inertia for common sections (i.e.
cross sectional shapes) are easy to find in the references. Just find your
shape in the table, and look up the moment of inertia formula for the
direction in which you want to bend, and plug your actual dimensions into
the formula.

The following are a few common moment of inertia formulas:
Round: I = 0.049 diameter^4
Half round (bent the easy way): I = 0.007 diameter^4
Square: I = 0.0833 size^4
Rectangle (bent vertically): I = 0.0833 width*(height^3)
Hexagonal (bend across flats): I = 0.06 (flat-to-flat size)^4
Oval (bent vertically): I = 0.7854*(width/2)*((height/2)^3)

Where:
I = moment of inertia
d = diameter
a = height
b = width
^ means raised to the power of
* is the multiplication sign

Two sections with equal moments of inertia are equally stiff.

Hope this helps,
Dan

> -----Original Message-----
> From: [email protected]
> [mailto:[email protected]]On Behalf Of Bob Rackers
> Sent: Wednesday, April 23, 2003 6:27 PM
> To: [email protected]
> Subject: RE: [TheForge] weld question
>
>
> I had no choice but to make a convenience bend to get done what I
> needed to.
> Nonetheless, I found it a bit inconvenient to work on a piece this long.
> I'm still thinking about it.
>
> I wonder if anyone can answer this question.
> Assuming this half-round profile gives me the strength I need, is there a
> reference which would tell me what size of material in a different profile
> would give me the same strength (bending across the bar,
> perpendicular to the
> profile)?
>
> Bob
>
> -----Original Message-----
> From: [email protected]
> [mailto:[email protected]]On Behalf Of Bruce Freeman
> Sent: Wednesday, April 23, 2003 11:31 AM
> To: [email protected]
> Subject: RE: [TheForge] weld question
>
>
> Sounds like time for a "convenience bend".  One nice thing about
> blacksmithing is that that 6' piece can be bent out of your way while
> you're working on it, then rebent as you need it later.
>
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