Hello all:
I'd like find more information about acquiring or making knife edge
bearings. They are for use and experimentation in my kinetic sculpture
work. I am doing a series of experiments with balance, center of
gravity, and movable pendulums. Knife edge bearings are typically found
in balance beam type of scales. If constructed properly, I think they
will allow partial rotation on 2 planes. Left-right, forward-back. Can
anyone suggest references on this subject? I have been unable to find
anything specific to designing, making them or using them.
Thanks for the help.
-Mike

mlcorson wrote:

If constructed properly, I think they
will allow partial rotation on 2 planes.

No. One plane per blade.


Left-right, forward-back. Can anyone suggest references on this
subject?

References? Beam type balances. :-)


I have been unable to find
anything specific to designing, making them or using them.

Making them isn't difficult. Get a knive, make a V-groove and place the
edge in the groove.

There is also a similar "bearing". Thin sheets of hardened steel (like
the feeler gauges for setting valve swing). Stamp holes through a strip,
screw the two parts together and use the strip like you would use a
string. This construction is often used in pendulas of clocks.


Nick
--
Motor Modelle // Engine Models
http://www.motor-manufaktur.de
DIY-DRO - YADRO - Eigenbau-Digitalanzeige

""Nick Müller" wrote: (clip) There is also a similar "bearing". Thin sheets
of hardened steel (like the feeler gauges for setting valve swing). Stamp
holes through a strip, screw the two parts together and use the strip like
you would use a string. This construction is often used in pendulas of
clocks.
^^^^^^^^^^^^^^^^
Nick, I don't think this is what you are describing, so I will mention it as
another possibility. It is called a "taut band" suspension, sometimes used
in meters and (possibly) gauges. The suspension consists of a band of
metal, under tension, supported at its ends. The needle is attached at the
middle of the band, at right angles. The needle can swing with virtually
zero friction by twisting the band.

Now a tiny "nit": The plural of pendulum is "pendula."

In article ,
"Leo Lichtman" wrote:


Now a tiny "nit": The plural of pendulum is "pendula."



And big pendula are pendulous, right? Or is that big pudenda?

--
Don Bruder - - If your "From:" address isn't on my whitelist,
or the subject of the message doesn't contain the exact text "PopperAndShadow"
somewhere, any message sent to this address will go in the garbage without my
ever knowing it arrived. Sorry... http://www.sonic.net/~dakidd for more info

Leo Lichtman wrote:

Now a tiny "nit": The plural of pendulum is "pendula."

I didn't want to answer in Latin. :-))

Nick
--
Motor Modelle // Engine Models
http://www.motor-manufaktur.de
DIY-DRO - YADRO - Eigenbau-Digitalanzeige

On Fri, 20 Jan 2006 10:38:00 -0800, Don Bruder wrote:
In article ,
"Leo Lichtman" wrote:


Now a tiny "nit": The plural of pendulum is "pendula."

And big pendula are pendulous, right? Or is that big pudenda?

Now you're just being pendantic, Don.

"Don Bruder" wrote in message
...
In article ,
"Leo Lichtman" wrote:


Now a tiny "nit": The plural of pendulum is "pendula."



And big pendula are pendulous, right? Or is that big pudenda?
^^^^^^^^^^^^^^^
I had to look it up. Pudendum refers to the external sexual organs,
especially of a female. So, while a male may have pendulous genitalia, a
female, with pendulous mammalia is the one with a pudendum. For the
pudendum to be pendulous would be stretching it.

On 20 Jan 2006 08:55:50 -0800, "mlcorson"
wrote:

I'd like find more information about acquiring or making knife edge
bearings.

I hear there's a set of books called "Ingenious Mechanisms" around which
might describe such things 8-)


Knife edge bearings only operate in a single plane. They can be paired,
but they still have a flat bearing surface opposing each knife.

The design principle behind th eknife edge bearing is that they have a
tiny radius, so they act as a "small" bearing for friction and accuracy
(mainly backlash) but they have a long length so they act as a "large"
bearing in terms of loadbearing. Obviously any attempt to cross knife
edges wiuld give a tiny contact area, minimal load capacity, and would
probably just indent the edges.

There are two forms of them - flat bearing surface and V groove. Flat
bearings are easier (you can make them with a few carbide lathe tool
inserts and glue-gun glue). However they don't have any location
ability, so they're only suitable for intermittent lash-ups, not leaving
in situ permanently, lest they "walk" across the surface.

A V groove bearing also locates its other component, so can be used
long-term in something like a balance arm. If you can't make the
complicated grinding machine (?) that's used to make these commercially,
you can again make a workable approximation by finding a carbide lathe
tool insert with a narrow groove in it. This is OK for crude location,
but it's not perfectly accurate and so isn't reliable if you're making
up a parallelogram linkage or similar.

On Fri, 20 Jan 2006 21:13:13 GMT, "Leo Lichtman"
wrote:

Pudendum refers to the external sexual organs,
especially of a female.

"Pudenda" literally means "parts of shame".

So where and what they are, and who has them, is solely a matter of
local cultural variation. In parts of California they're vestigial and
only found where people have measurable body fat - there's nothing else
they're ashamed of showing.

In article ,
Dave Hinz wrote:

On Fri, 20 Jan 2006 10:38:00 -0800, Don Bruder wrote:
In article ,
"Leo Lichtman" wrote:


Now a tiny "nit": The plural of pendulum is "pendula."

And big pendula are pendulous, right? Or is that big pudenda?

Now you're just being pendantic, Don.


Aw, C'mon, Dave... Don't leave me hangin' like that!

--
Don Bruder - - If your "From:" address isn't on my whitelist,
or the subject of the message doesn't contain the exact text "PopperAndShadow"
somewhere, any message sent to this address will go in the garbage without my
ever knowing it arrived. Sorry... http://www.sonic.net/~dakidd for more info

Hello all:
I'd like find more information about acquiring or making knife edge
bearings. They are for use and experimentation in my kinetic sculpture
work. I am doing a series of experiments with balance, center of
gravity, and movable pendulums. Knife edge bearings are typically found
in balance beam type of scales. If constructed properly, I think they
will allow partial rotation on 2 planes. Left-right, forward-back. Can
anyone suggest references on this subject? I have been unable to find
anything specific to designing, making them or using them.
Thanks for the help.
-Mike

Check "Dual axis pivot" subject around Jul 7 2004 involving Ned
Simmons, Glenn Ashmore, and James Crombie. There was a real nice
drawing of knife-edge pivots done by James, but it seems it's no
longer on his site, but Glenn or Ned may still have it on their
harddrives. HTH
Ken.

Dave, putting a new spin on an old word, sez: " Now you're just being
pendantic, Don."

At risk of being one myself, I should point out the correct spelling is
"pedantic".

But who cares really? Besides, I was recently plonked by Dave and he won't
see this.

Bob Swinney




"Dave Hinz" wrote in message
...
On Fri, 20 Jan 2006 10:38:00 -0800, Don Bruder wrote:
In article ,
"Leo Lichtman" wrote:


Now a tiny "nit": The plural of pendulum is "pendula."

And big pendula are pendulous, right? Or is that big pudenda?

"Robert Swinney" wrote: (clip) the correct spelling is "pedantic".
^^^^^^^^^^^^^^^^^
We may both be missing something here, Bob. I think it's some kind of a
joke, based on the similarity of the word "pedant" to the word "pendant."
This would be called a "pun." ;-)

Ken:
Thanks for that. It is a good discussion. I just finished a project
using a sharp end in a conical depression. IT gives a full range of
movement but I'm still interested to use a knife edge, on at least on
one plane of movement. Can anyone come up with the drawings?
-Mike

According to mlcorson :
Ken:
Thanks for that. It is a good discussion. I just finished a project
using a sharp end in a conical depression. IT gives a full range of
movement but I'm still interested to use a knife edge, on at least on
one plane of movement. Can anyone come up with the drawings?

Who needs drawings? Depending on how much precision you need
(and I suspect not as much as a good lab balance in your case), just
make a pair of V-grooves in line on either side of the thing to be
supported, then make a knife edge (really -- just like a straight-edged
knife blade), feed it though what is being swung, and rest the edges in
the V-grooves.

For a reloader's powder scales, the knife edge should be just
above a line through the center of mass of the balance beam. This
causes it to balance naturally. If the knife edge is *below* the line
through the center of mass, it will tend to topple over to one side or
the other.

If you *really* need to look at something to see how to make
one, go to a nearby firearms store and ask to see one of the less
expensive reloading scales. (The more expensive ones will either have
hard stone knife edges instead of steel, or will be purely digital in
operation.

The one which I have was made by Redding, back around 1970 or
so.

Enjoy,
DoN.
--
Email: | Voice (all times): (703) 938-4564
(too) near Washington D.C. | http://www.d-and-d.com/dnichols/DoN.html
--- Black Holes are where God is dividing by zero ---

The last one I had anything to do with was made from razor blades mounted to the outer race of a ball bearing laying flat. We
made an outer ring from aluminum that was pressed on the bearing with a notch for the blade to fit in. He was using the
single edge razor blades like the one in a razor or scraper.
R. Wink

On 20 Jan 2006 08:55:50 -0800, "mlcorson" wrote:

Hello all:
I'd like find more information about acquiring or making knife edge
bearings. They are for use and experimentation in my kinetic sculpture
work. I am doing a series of experiments with balance, center of
gravity, and movable pendulums. Knife edge bearings are typically found
in balance beam type of scales. If constructed properly, I think they
will allow partial rotation on 2 planes. Left-right, forward-back. Can
anyone suggest references on this subject? I have been unable to find
anything specific to designing, making them or using them.
Thanks for the help.
-Mike

mlcorson wrote:

I'd like find more information about acquiring or making knife edge
bearings. They are for use and experimentation in my kinetic sculpture
work. I am doing a series of experiments with balance, center of
gravity, and movable pendulums. Knife edge bearings are typically found
in balance beam type of scales. If constructed properly, I think they
will allow partial rotation on 2 planes. Left-right, forward-back.

I'm not sure if this would be what is usually meant by a "knife edge
bearing"
but it seems to my that a small wheel with a V-groove profile sitting
on a single razor blade would give you an ability to roll along the
blade and to wobble to some degree to either side. Don't know if
that's usefull to you - it would take carefull design to keep it in
place, and not have it roll off the end of the blade.

Model airplane propellor balancers are usually a little spindle that
goes through the prop hub and then sits on a pair of razor blades (you
sand the prop blade tips and check until it balances)