[Ref. 201122 MMDigest, Force Versus Distance ... Analysis 1

Pneumatic Behavior, Part 2 -- Second Case

Note: My first illustration, No. 1 (Ref. 1), has been replaced by
a very slightly improved one, this having to do with the long X-ray
view where the dotted folds for the half-closed one were not fully
accurate. Also, are some added explanations with pointing arrows
plus various tidying touches.

(Begin.)

In the previous Part 1, I explained how two force sources combine
to produce sums, these within square and hinged pneumatics featuring
the usually encountered rolling-sealed-cloth sides.

Each of these two can be conceived and accounted for separately by
measurements and separation but it is a most difficult task, for
with every displacement of the pneumatic one, either direct or
leveraged, affects the other and vice-versa. What is far easier of
achievement is measuring done in a simple bench setup, as their
resulting properties are thus combined, for after all that really
is what we require.

That said, though, for completeness of understanding it is good,
I think, to know that direct forces and leverage forces are forever
partnering with one another, this so as to provide us with their
delightful, animating results.

This look will be at a more unusual case -- the more usual rolling
sides as now stiffened, so as to create a condition of more controlled
leverage forces.

In the second drawing I've made for this project (Ref. 2) there
are shown three, (a), (b) and (c). This time the pneumatics may be
understood to have lengths longer than the fronts and, hinged at the
back. All three sides feature stiffening (of thin card selectively
fashioned and attached so as to allow easily inward folding), the
front one extending all the way left and right, and the side ones
shaped to their own non-binding requirement.

Just as in our No. 1 drawing of-previous, in the first view, (a)
we see the pneumatic fully open and having no vacuum applied, with
magnitude and direction vectors all equal.

In the second, No. 2 at (b), it is with some vacuum applied,
displacement of the upper and lower walls having here occurred,
with resulting vectors now dissimilar in-and-out, and angled nicely
at right angles, all in-a-line, to the stiffened cloth walls.

In our third, No. 2 at (c), more vacuum with serious closure is
here to be seen. (I have lightened the topmost vectors so as to
allow close inspection of these, for otherwise if not, confusion
here-presents to the angered eye.)

The second case is really much the same story as the first case but
the resulting effect here is that the curve of force is corrected,
being no longer 'belly-like,' and although being still non-constant
over closure, it is now much more behaving.

To illustrate what happens, I've have speculatively created a curve
which will, I think, serve to make clear what wall-stiffening of
pneumatics can do for us. A quick study of it should cinch in the
viewer's comprehension, as to just what occurs.

When comparing the two curves, it must be remembered that here
they represent only what the leverage forces produce, their not
factoring-in any of direct forces. This will answer for why they appear
differing from the combined force/displacement ones usually seen.

It is so, that some instruments actuated by wondrous vacuumized
pneumaticry, do feature stiffened sides, these mostly within the
marvels having hailed from Europe. For an instance, the Welte-Mignon
three-point wind motors have stiffening placed inside out-of-sight,
these sometimes being rebuilt without this. (To this, what might Edwin
Welte have said?)

So, to stiffen or not to stiffen, that is the question! The answer
to it being -- "Well, it all depends on what you want to achieve; but
first one has to know why."

In the next part we'll take a serious look at the third case, it and
it's strangeness of reciprocity that is simply amazing. (And, yes,
just as the great and famous Spanish magician, Signor Frakson, used to
exclaim at his multifarious cigarette sparks flying all over the stage,
"It's amazing!" It is!)

(End)

As usual I solicit comments, corrections and questions from any, here
or by private messaging.

Also, although copyrighted, any having interest, do feel free to
download and print a copy of my drawings relating to this subject,
for your own personal use.

Jim Miller
Las Vegas, Nevada
akruzam@gmx.com.geentroep [delete ".geentroep" to reply]

No. 1: Six Views of First Case Striker-Pneumatic Forces
https://www.mmdigest.com/Attachments/20/12/08/201208_124905_No1%20RollingSides6Views.png 

No. 2: Three Rigid Sides Views
https://www.mmdigest.com/Attachments/20/12/11/201211_024208_No2%20RigidSides3Views.png

No. 3: Rolling & Rigid Sides Graph
https://www.mmdigest.com/Attachments/20/12/08/201208_123456_No3%20RollingRigidSidesGraph.png