"Doug Miller" wrote in message In article , rigger
wrote:
On Nov 23, 11:13=A0am, RangersSuck wrote:
OK, the Kid Down The Street came to me with a project.
He has to make
something with all SIX(!) simple machines.

So, I said to him, "There are only THREE simple
machines. The lever,
the wheel and the inclined plane."

"No," he said, "there are SIX simple machines. The
lever, the wheel
and axle, the wedge, the pulley, the screw and the
inclined plane."

"Bull****!" says I, "A pulley is just a wheel (and
maybe, when you add
in a rope, it's got a little lever mixed in), a wedge
is just an
inclined plane and a screw is just an inclined plane
wrapped around a
wheel."

"Look it up." says the Smart Ass Down The Street.

So, I googled "Simple Machines" and, lo and behold, it
appears that
they are teaching kids about these SIX things - the
original three
plus the three inbred cousins.

What the ****?

A rose by a different name?

There are only *two*. Not three. Not six. Two: The
inclined plane, and the
lever. The others are all special cases of one or the
other of those, in that
exactly the same principle is used:
- the wheel and axle is a lever in rotary motion
- so is the pulley
- the screw is an inclined plane wrapped around a cylinder
- the wedge is an inclined plane stood on its point

So where is the fulcrum point on a wheel and axle? A lever
needs to
have a fulcrum point to work......
phil

On Tue, 25 Nov 2008 13:37:43 -0500, Phil Kangas wrote:

"Doug Miller" wrote in message In article , rigger
wrote:
On Nov 23, 11:13=A0am, RangersSuck wrote:
OK, the Kid Down The Street came to me with a project.
He has to make
something with all SIX(!) simple machines.

So, I said to him, "There are only THREE simple
machines. The lever,
the wheel and the inclined plane."

"No," he said, "there are SIX simple machines. The
lever, the wheel
and axle, the wedge, the pulley, the screw and the
inclined plane."

"Bull****!" says I, "A pulley is just a wheel (and
maybe, when you add
in a rope, it's got a little lever mixed in), a wedge
is just an
inclined plane and a screw is just an inclined plane
wrapped around a
wheel."

"Look it up." says the Smart Ass Down The Street.

So, I googled "Simple Machines" and, lo and behold, it
appears that
they are teaching kids about these SIX things - the
original three
plus the three inbred cousins.

What the ****?

A rose by a different name?

There are only *two*. Not three. Not six. Two: The
inclined plane, and the
lever. The others are all special cases of one or the
other of those, in that
exactly the same principle is used:
- the wheel and axle is a lever in rotary motion
- so is the pulley
- the screw is an inclined plane wrapped around a cylinder
- the wedge is an inclined plane stood on its point

So where is the fulcrum point on a wheel and axle? A lever
needs to
have a fulcrum point to work......
phil

At the axle.

On Nov 24, 9:22*am, Spehro Pefhany
wrote:
On Mon, 24 Nov 2008 08:53:55 -0800 (PST), rigger
wrote:





On Nov 23, 11:13*am, RangersSuck wrote:
OK, the Kid Down The Street came to me with a project. He has to make
something with all SIX(!) simple machines.

So, I said to him, "There are only THREE simple machines. The lever,
the wheel and the inclined plane."

"No," he said, "there are SIX simple machines. The lever, the wheel
and axle, the wedge, the pulley, the screw and the inclined plane."

"Bull****!" says I, "A pulley is just a wheel (and maybe, when you add
in a rope, it's got a little lever mixed in), a wedge is just an
inclined plane and a screw is just an inclined plane wrapped around a
wheel."

"Look it up." says the Smart Ass Down The Street.

So, I googled "Simple Machines" and, lo and behold, it appears that
they are teaching kids about these SIX things - the original three
plus the three inbred cousins.

What the ****?

A rose by a different name?

Do any of you machinists out there remember a number of years
ago (10? 20?) someone declared, and others agreed, there was a
new "Simple Machine" discovered?

IIRC it was a pair of roller bearings which were kept in contact by
an "S" shapped spring, and this measured "zero" rolling resistance
when used between two planes.

What ever happened to this idea? *I never saw it developed.

dennis
in nca

I don't call myself a machinist, but I remember that thing... it could
be used for a thermostat among other things. I'd guess more than 20
years ago.

Ah, thanks to Google.. the "Rolamite", ca. 1968 (40 years!):

http://www.rexresearch.com/wilkes/1wilkes.htm#me- Hide quoted text -

- Show quoted text -

Thanks for the reference Spehro. My, time really does fly I guess.
This is the article I remembered:

Popular Science (March 1966)
"Frictionless Machines from Rollers & Bands"
by
Harry Walton

Surprisingly few applications are noted. I guess the features
may have been supplanted by newer ideas. Or it may only
have been overlooked?

dennis
in nca

Spehro Pefhany wrote:
...
Ah, thanks to Google.. the "Rolamite", ca. 1968 (40 years!):


What a neat mechanism! I'm most impressed with all the variations they
thought of. But I've never seen one in a product (and I've taken apart
a lot of stuff). There must be some drawback(s) that limits their use
(if any) to apps where low friction is critical.

Bob

In article , "Phil Kangas" wrote:

"Doug Miller" wrote in message In article , rigger
wrote:

There are only *two*. Not three. Not six. Two: The
inclined plane, and the
lever. The others are all special cases of one or the
other of those, in that
exactly the same principle is used:
- the wheel and axle is a lever in rotary motion
- so is the pulley
- the screw is an inclined plane wrapped around a cylinder
- the wedge is an inclined plane stood on its point

So where is the fulcrum point on a wheel and axle? A lever
needs to
have a fulcrum point to work......

The centerline of the axle, of course.

"Doug Miller" wrote in message In article , "Phil
Kangas" wrote:

"Doug Miller" wrote in message In article , rigger

wrote:

There are only *two*. Not three. Not six. Two: The
inclined plane, and the
lever. The others are all special cases of one or the
other of those, in that
exactly the same principle is used:
- the wheel and axle is a lever in rotary motion
- so is the pulley
- the screw is an inclined plane wrapped around a
cylinder
- the wedge is an inclined plane stood on its point

So where is the fulcrum point on a wheel and axle? A
lever
needs to
have a fulcrum point to work......

The centerline of the axle, of course.

In that case it is only the radius of the wheel. A lever
_must_ have
three points of interest to be labeled a lever. The point of
application,
the fulcrum point and the resultant point. A lever can be
attached to
a wheel by connecting it at 'two' points, not just one. One
point
is the fulcrum and the other is the resultant point. Lever,
wheel,
separate items. I'm surprised no one has come up with a
simple
assembly that uses all _three_ machines in a demo! Nothing
but
blabber about the alphabet.
phil

On Sun, 23 Nov 2008 22:38:56 -0500, "Ed Huntress"
wrote:


"Gerald Miller" wrote in message
.. .
On Sun, 23 Nov 2008 19:28:58 -0700, Lew Hartswick
wrote:

Gene wrote:
On Sun, 23 Nov 2008 11:13:18 -0800 (PST), RangersSuck
wrote:

Don't feel bad. I had to learn all 7 vowels.... now they claim only
5....

What happened to the "sometimes Y and W"
From the late 30s till 1949 it was:
A E I O U and sometimes Y and W. :-)
...lew...
Never heard of "sometimes W"
Gerry :-)}
London, Canada

You probably had a better grade-school education than we did.

What they should have told us is that Y and W are consonants, but, because
of some spelling artifacts in standard English, they occasionally stand in
for certain vowels. They have no unique vowel sounds of their own. They just
fill in for others in some antique spellings.

That is, unless you're Welsh, in which case almost anything can be a vowel,
and the more of them you string together, the better. d8-)

You have a better argument with "W" than "Y." Actually, "Y" is pretty
common: cry, by, sky, why, wry, spy, gym, crypt, hymn, lynx, myth,
glyph, slyly, tryst, nymph, Gypsy, pygmy, flyby, syzygy, etc.

I grew up on a street named Twyckenham....
--

Forté Agent 5.00 Build 1160

Homepage
http://pamandgene.tranquilrefuge.net...shop/index.htm

"Gene" wrote in message
...
On Sun, 23 Nov 2008 22:38:56 -0500, "Ed Huntress"
wrote:


"Gerald Miller" wrote in message
. ..
On Sun, 23 Nov 2008 19:28:58 -0700, Lew Hartswick
wrote:

Gene wrote:
On Sun, 23 Nov 2008 11:13:18 -0800 (PST), RangersSuck
wrote:

Don't feel bad. I had to learn all 7 vowels.... now they claim only
5....

What happened to the "sometimes Y and W"
From the late 30s till 1949 it was:
A E I O U and sometimes Y and W. :-)
...lew...
Never heard of "sometimes W"
Gerry :-)}
London, Canada

You probably had a better grade-school education than we did.

What they should have told us is that Y and W are consonants, but, because
of some spelling artifacts in standard English, they occasionally stand in
for certain vowels. They have no unique vowel sounds of their own. They
just
fill in for others in some antique spellings.

That is, unless you're Welsh, in which case almost anything can be a
vowel,
and the more of them you string together, the better. d8-)

You have a better argument with "W" than "Y." Actually, "Y" is pretty
common: cry, by, sky, why, wry, spy, gym, crypt, hymn, lynx, myth,
glyph, slyly, tryst, nymph, Gypsy, pygmy, flyby, syzygy, etc.

Try substituting "i" for the "y" in each of those. Those are all "i" sounds,
some long, some short.

Again, there is no unique vowel sound signified by "y." It's just a
substitute for various pronunciations of "i."


I grew up on a street named Twyckenham....

An old street, no doubt. d8-)

--
Ed Huntress

"Phil Kangas" wrote in message
"Doug Miller" wrote in message In article , "Phil
Kangas" wrote:

"Doug Miller" wrote in message In article ,
rigger

wrote:

There are only *two*. Not three. Not six. Two: The
inclined plane, and the
lever. The others are all special cases of one or the
other of those, in that
exactly the same principle is used:
- the wheel and axle is a lever in rotary motion
- so is the pulley
- the screw is an inclined plane wrapped around a
cylinder
- the wedge is an inclined plane stood on its point

So where is the fulcrum point on a wheel and axle? A
lever
needs to
have a fulcrum point to work......

The centerline of the axle, of course.

In that case it is only the radius of the wheel. A lever
_must_ have
three points of interest to be labeled a lever. The point
of
application,
the fulcrum point and the resultant point. A lever can be
attached to
a wheel by connecting it at 'two' points, not just one.
One
point
is the fulcrum and the other is the resultant point.
Lever,
wheel,
separate items. I'm surprised no one has come up with a
simple
assembly that uses all _three_ machines in a demo! Nothing
but
blabber about the alphabet.
phil



I just thought of a way to explain the lever/wheel thing.
Say you have this
big spike sticking out of the floor and you decide that it
must be pulled.
You find this nice chunk of round bar with a small v-notch
on one end
that fits the spike. Perfect fit. You grab the other end and
try to move the
spike but nothing happens, you swing the bar around all over
the place
keeping the v-notch on the spike. All you have done is
develop the
surface of a sphere. And the spike is still there glaring at
you. Then you
find a short chunk of 2x4 and put it close to the spike and
bear down
on it. Voila! The spike comes out! What changed? You added a
fulcrum
point changing the rod from a radius of a sphere (wheel) to
a lever.
Now how can you say a wheel and a lever are the same thing?
No way...
Same thing if you put an arm onto the axle. It'll just swing
on it and do
nothing to the wheel until you tack weld it in one place.
Now the tack
weld is one point, the side of the hole in the arm making
contact with
the axle makes the second point and your hand on the
outboard end
can now turn the wheel at will. Make sense? Lever: 3
points....
phil ;))

On Tue, 25 Nov 2008 19:39:56 -0500, Phil Kangas wrote:

"Doug Miller" wrote in message In article , "Phil
Kangas" wrote:

"Doug Miller" wrote in message In article , rigger

wrote:

There are only *two*. Not three. Not six. Two: The
inclined plane, and the
lever. The others are all special cases of one or the
other of those, in that
exactly the same principle is used:
- the wheel and axle is a lever in rotary motion
- so is the pulley
- the screw is an inclined plane wrapped around a
cylinder
- the wedge is an inclined plane stood on its point

So where is the fulcrum point on a wheel and axle? A
lever
needs to
have a fulcrum point to work......

The centerline of the axle, of course.

In that case it is only the radius of the wheel. A lever
_must_ have
three points of interest to be labeled a lever. The point of
application,
the fulcrum point and the resultant point.


Nothing says that two (or even all three) of the points can not be in the
same place.

"_" wrote in message
...
On Tue, 25 Nov 2008 19:39:56 -0500, Phil Kangas wrote:

"Doug Miller" wrote in message In article , "Phil
Kangas" wrote:

"Doug Miller" wrote in message In article , rigger

wrote:

There are only *two*. Not three. Not six. Two: The
inclined plane, and the
lever. The others are all special cases of one or the
other of those, in that
exactly the same principle is used:
- the wheel and axle is a lever in rotary motion
- so is the pulley
- the screw is an inclined plane wrapped around a
cylinder
- the wedge is an inclined plane stood on its point

So where is the fulcrum point on a wheel and axle? A
lever
needs to
have a fulcrum point to work......

The centerline of the axle, of course.

In that case it is only the radius of the wheel. A lever
_must_ have
three points of interest to be labeled a lever. The point of
application,
the fulcrum point and the resultant point.


Nothing says that two (or even all three) of the points can not be in the
same place.

The special case of a lever of zero moment -- physically indistinguishable
from a wheel of zero radius, or a wedge of zero length. In effect, a point.

These are good thought problems for conceptual thinking; exercises in
practical geometry. But they're not the way to start teaching kids how
machines work, which was the original problem.

This question of whether to teach three basic machines (or two -- gawd)
versus six is a good thought problem itself, if the thought it about how to
teach and how one learns. Calling a screw a "wedge wrapped around a
cylinder" is good for geometry class or for students who have gotten past
the ideas of how basic machines work. But it's a special case, too, in which
any meaningful motion is rotary, whereas we think of a wedge as something
linear. It can confuse rather than illuminate.

I learned three basic machines in physics class, too, and it was
interesting. But six sounds better as an introduction. Keep reducing it with
the special reductive cases and you wind up with pulleys that do nothing and
everything else disappearing -- an interesting thought in itself, but an
abstract one, of no use in understanding actual machines, unless you live in
another dimension. g

I like the six machines for introducing basic mechanics. Then show them how
these can be reduced to a smaller number. Then you can reduce them all to a
point, at which event everything crawls up its own asshole and becomes a
Klein Bottle in the fifth dimension. d8-)

--
Ed Huntress

Ed Huntress wrote:
...
These are good thought problems for conceptual thinking; exercises in
practical geometry. But they're not the way to start teaching kids how
machines work, which was the original problem.

This question of whether to teach three basic machines (or two -- gawd)
versus six ...
I like the six machines for introducing basic mechanics. Then show them how
these can be reduced to a smaller number. Then you can reduce them all to a
point, at which event everything crawls up its own asshole and becomes a
Klein Bottle in the fifth dimension. d8-)

Good answer!! That SHOULD be the final word in this discussion, but I'm
sure it won't be.

Bob

They forgot the Turing Machine.

--
Paul Hovnanian
-----------------------------------------------------------------------
Have gnu, will travel.

Paul Hovnanian P.E. wrote:
They forgot the Turing Machine.

And the State Machine, Democratic Machine, Mr. Machine, Espresso Machine,
Wayback Machine, _Time Machine_ ...

--Winston Machine

On Wed, 26 Nov 2008 16:52:31 -0800, the infamous Winston
scrawled the following:

Paul Hovnanian P.E. wrote:
They forgot the Turing Machine.

And the State Machine, Democratic Machine, Mr. Machine, Espresso Machine,
Wayback Machine, _Time Machine_ ...

--Winston Machine

Don't forget Mann and Machine, poo. I loved the teeny perts on that
robot. Yancy Butler is a fox!

Good here http://www.youtube.com/watch?v=eKdKo5SFmvc

Better he http://www.youtube.com/watch?v=BrER9RzcWbo&NR=1

/Hounddog Jake

---
Tomorrow is the most important thing in life. Comes into us at midnight
very clean. It's perfect when it arrives and it puts itself in our hands.
It hopes we've learned something from yesterday.
--John Wayne (1907 - 1979)

On Nov 26, 9:03*am, "Ed Huntress" wrote:
"_" wrote in message

...



On Tue, 25 Nov 2008 19:39:56 -0500, Phil Kangas wrote:

"Doug Miller" wrote in message In article , "Phil
Kangas" wrote:

"Doug Miller" wrote in message In article , rigger

wrote:

There are only *two*. Not three. Not six. Two: The
inclined plane, and the
lever. The others are all special cases of one or the
other of those, in that
exactly the same principle is used:
- the wheel and axle is a lever in rotary motion
- so is the pulley
- the screw is an inclined plane wrapped around a
cylinder
- the wedge is an inclined plane stood on its point

So where is the fulcrum point on a wheel and axle? A
lever
needs to
have a fulcrum point to work......

The centerline of the axle, of course.

In that case it is only the radius of the wheel. A lever
_must_ have
three points of interest to be labeled a lever. The point of
application,
the fulcrum point and the resultant point.

Nothing says that two (or even all three) of the points can not be in the
same place.

The special case of a lever of zero moment -- physically indistinguishable
from a wheel of zero radius, or a wedge of zero length. In effect, a point.

"RangersSuck" wrote in message
On Nov 26, 9:03 am, "Ed Huntress" wrote:
"_" wrote in message




On Tue, 25 Nov 2008 19:39:56 -0500, Phil Kangas wrote:

"Doug Miller" wrote in message In article ,
"Phil
Kangas" wrote:

"Doug Miller" wrote in message In article ,
rigger

wrote:

There are only *two*. Not three. Not six. Two: The
inclined plane, and the
lever. The others are all special cases of one or
the
other of those, in that
exactly the same principle is used:
- the wheel and axle is a lever in rotary motion
- so is the pulley
- the screw is an inclined plane wrapped around a
cylinder
- the wedge is an inclined plane stood on its point

So where is the fulcrum point on a wheel and axle? A
lever
needs to
have a fulcrum point to work......

The centerline of the axle, of course.

In that case it is only the radius of the wheel. A
lever
_must_ have
three points of interest to be labeled a lever. The
point of
application,
the fulcrum point and the resultant point.

Nothing says that two (or even all three) of the points
can not be in the
same place.

The special case of a lever of zero moment -- physically
indistinguishable
from a wheel of zero radius, or a wedge of zero length. In
effect, a point.

These are good thought problems for conceptual thinking;
exercises in
practical geometry. But they're not the way to start
teaching kids how
machines work, which was the original problem.

This question of whether to teach three basic machines (or
two -- gawd)
versus six is a good thought problem itself, if the
thought it about how to
teach and how one learns. Calling a screw a "wedge wrapped
around a
cylinder" is good for geometry class or for students who
have gotten past
the ideas of how basic machines work. But it's a special
case, too, in which
any meaningful motion is rotary, whereas we think of a
wedge as something
linear. It can confuse rather than illuminate.

I learned three basic machines in physics class, too, and
it was
interesting. But six sounds better as an introduction.
Keep reducing it with
the special reductive cases and you wind up with pulleys
that do nothing and
everything else disappearing -- an interesting thought in
itself, but an
abstract one, of no use in understanding actual machines,
unless you live in
another dimension. g

I like the six machines for introducing basic mechanics.
Then show them how
these can be reduced to a smaller number. Then you can
reduce them all to a
point, at which event everything crawls up its own asshole
and becomes a
Klein Bottle in the fifth dimension. d8-)

--
Ed Huntress

But the whole idea of teaching about "simple machines" is to
demonstrate that every other machine is made of these
elemental
devices. To follow your logic, we may as well teach that a
bicycle is
a simple machine and, sometime in the future, clue the kids
in to the
fact that a bike is really a "special case" of a combination
of
wheels, levers, etc.

Sorry, I don't see how teaching a kid that there's a
difference
between a "wedge" and an "inclined plane" helps to build
their
understanding of mechanics, reason or intellect. Same with
"wheel" vs.
"pulley".

As for the Kid Down The Street, while discussing how he
might
incorporate screws into his design, I showed him some
examples in my
shop. There was the leadscrew on my lathe, the various
fasteners, and
the flutes on an auger bit. He had a hard time with the
auger, saying
something like "I don't know if my teacher will accept that
as a
screw, since it doesn't really screw anything together."
Sheesh.

I then took that auger bit and stuck it in a plastic tube
and dropped
a ball bearing in. Turning the auger, I raised the ball to
the top of
the tube. We then talked about the Archimedes Screw pump
http://en.wikipedia.org/wiki/Archimedes%27_screw and he
actually got
the idea of an inclined plane wrapped around a wheel. It's
really not
such an abstract concept.

Of course, this kid's idea of a "simple machine" is anything
that
predates an Xbox 360...

................................

Another example of lever, wheel, inclined plane would be the
good
old wheelbarrow, eih? Hey you, get these bricks up to those
masons
there, eih? Ya, just go up that there ramp, real
easy.......;)
phil

"RangersSuck" wrote in message
...
On Nov 26, 9:03 am, "Ed Huntress" wrote:
"_" wrote in message

...



On Tue, 25 Nov 2008 19:39:56 -0500, Phil Kangas wrote:

"Doug Miller" wrote in message In article , "Phil
Kangas" wrote:

"Doug Miller" wrote in message In article , rigger

wrote:

There are only *two*. Not three. Not six. Two: The
inclined plane, and the
lever. The others are all special cases of one or the
other of those, in that
exactly the same principle is used:
- the wheel and axle is a lever in rotary motion
- so is the pulley
- the screw is an inclined plane wrapped around a
cylinder
- the wedge is an inclined plane stood on its point

So where is the fulcrum point on a wheel and axle? A
lever
needs to
have a fulcrum point to work......

The centerline of the axle, of course.

In that case it is only the radius of the wheel. A lever
_must_ have
three points of interest to be labeled a lever. The point of
application,
the fulcrum point and the resultant point.

Nothing says that two (or even all three) of the points can not be in
the
same place.

The special case of a lever of zero moment -- physically indistinguishable
from a wheel of zero radius, or a wedge of zero length. In effect, a
point.

These are good thought problems for conceptual thinking; exercises in
practical geometry. But they're not the way to start teaching kids how
machines work, which was the original problem.

This question of whether to teach three basic machines (or two -- gawd)
versus six is a good thought problem itself, if the thought it about how
to
teach and how one learns. Calling a screw a "wedge wrapped around a
cylinder" is good for geometry class or for students who have gotten past
the ideas of how basic machines work. But it's a special case, too, in
which
any meaningful motion is rotary, whereas we think of a wedge as something
linear. It can confuse rather than illuminate.

I learned three basic machines in physics class, too, and it was
interesting. But six sounds better as an introduction. Keep reducing it
with
the special reductive cases and you wind up with pulleys that do nothing
and
everything else disappearing -- an interesting thought in itself, but an
abstract one, of no use in understanding actual machines, unless you live
in
another dimension. g

I like the six machines for introducing basic mechanics. Then show them
how
these can be reduced to a smaller number. Then you can reduce them all to
a
point, at which event everything crawls up its own asshole and becomes a
Klein Bottle in the fifth dimension. d8-)

--
Ed Huntress

But the whole idea of teaching about "simple machines" is to
demonstrate that every other machine is made of these elemental
devices. To follow your logic, we may as well teach that a bicycle is
a simple machine and, sometime in the future, clue the kids in to the
fact that a bike is really a "special case" of a combination of
wheels, levers, etc.

Yeah, I get the point, and that's how I was taught. I'm just thinking aloud
about how you really can best teach mechanics from the start. I've never
tried it so I can't be sure, but some people are better at abstract thinking
than others, and abstracting mechanisms to the three basic machine elements
from the start may not be the best way to do it. I'd have to see the results
of teaching to be sure.

But take your bicycle as an example. Specifically, take the chain. There's a
system that transmits force, and power, with...what, a couple of hundred
moving parts, if you count the rollers on the pins? And not one of them is a
wheel, a wedge, or a lever. Maybe you could make a case for the rollers
rotating on the pins, but I'd rather not, because, at best, it's confusing.

It's an interesting question from a teacher's point of view, and I'm not
convinced that the old methods are best.


"Sorry, I don't see how teaching a kid that there's a difference
"between a "wedge" and an "inclined plane" helps to build their
"understanding of mechanics, reason or intellect. Same with "wheel" vs.
""pulley".

A wedge wrapped around a cylinder cannot produce a straight screw. It's
always cone-shaped. But an inclined plane can produce a straight screw. g

As for the Kid Down The Street, while discussing how he might
incorporate screws into his design, I showed him some examples in my
shop. There was the leadscrew on my lathe, the various fasteners, and
the flutes on an auger bit. He had a hard time with the auger, saying
something like "I don't know if my teacher will accept that as a
screw, since it doesn't really screw anything together." Sheesh.

I then took that auger bit and stuck it in a plastic tube and dropped
a ball bearing in. Turning the auger, I raised the ball to the top of
the tube. We then talked about the Archimedes Screw pump
http://en.wikipedia.org/wiki/Archimedes%27_screw and he actually got
the idea of an inclined plane wrapped around a wheel. It's really not
such an abstract concept.

Good for Archimedes screw pumps, leadscrews, and such. But that isn't most
screws. So, again, it's a question of where you start for the sake of
clarity. Once the basic mechanisms are recognized, I agree, I'd show how
they reduce to a few basic elements.

Of course, this kid's idea of a "simple machine" is anything that
predates an Xbox 360...

I do wonder how kids cope with the obscure and almost magical quality of the
electronic devices with which they interact every day. When I was a kid I
believed that I could understand everything around me if I just studied it
enough. Now, much of it seems to have passed some threshold of
comprehension. They must look at things in a fundamentally different way.

--
Ed Huntress

On Tue, 25 Nov 2008 14:17:44 -0500, Bob Engelhardt wrote:
Spehro Pefhany wrote:
...
Ah, thanks to Google.. the "Rolamite", ca. 1968 (40 years!):
http://www.rexresearch.com/wilkes/1wilkes.htm

What a neat mechanism! I'm most impressed with all the variations they
thought of. But I've never seen one in a product (and I've taken apart
a lot of stuff). There must be some drawback(s) that limits their use
(if any) to apps where low friction is critical.

They were commercially available, but an expensive specialty item,
when I worked with some in the early 80's. (I wrote software for
computer-controlled centrifuge equipment, to simulate Minuteman
III launch profiles and see if the rolamites activated at the
right times during launch.) I doubt that the price ever got low
enough for non-military designers to consider them.

--
jiw