Can someone cast a small cylinder that I need?

I need a cast iron cylinder with a 7.5 cm diameter, 6.1 cm length, and
a 2.2 cm “bore hole” lengthwise through the center.

I just need to know the cost.

Thanks a lot!

Mark Main
North Branch, MN
USA

Mark Main wrote:
Can someone cast a small cylinder that I need?

I need a cast iron cylinder with a 7.5 cm diameter, 6.1 cm length, and
a 2.2 cm “bore hole” lengthwise through the center.

I just need to know the cost.

McM-C: 3" diam, 12" long bar - $39.32 + shipping.
http://www.mcmaster.com/#8909k32/=dax7f
Cheaper, /much/ faster than custom casting.

Bob

On Jan 29, 2:18*am, Mark Main wrote:
Can someone cast a small cylinder that I need?

I need a cast iron cylinder with a 7.5 cm diameter, 6.1 cm length, and
a 2.2 cm “bore hole” lengthwise through the center.

I just need to know the cost.

Thanks a lot!

Mark Main
North Branch, MN
USA

On Jan 29, 2:18*am, Mark Main wrote:

I need a cast iron cylinder with a 7.5 cm diameter, 6.1 cm length, and
a 2.2 cm “bore hole” lengthwise through the center.
Mark Main

One end of a dumbbell might work. You might have to anneal it first.

jw

On Jan 29, 7:11*am, Bob Engelhardt wrote:
Mark Main wrote:
Can someone cast a small cylinder that I need?

I need a cast iron cylinder with a 7.5 cm diameter, 6.1 cm length, and
a 2.2 cm “bore hole” lengthwise through the center.

I just need to know the cost.

McM-C: 3" diam, 12" long bar - $39.32 + shipping.http://www.mcmaster.com/#8909k32/=dax7f
Cheaper, /much/ faster than custom casting.

Bob

Thank you, this is certainly very close to the size I'm looking for--I
assume that I'll have to have it annealed to cut it down to size and
bore the hole through it. I want to use it in for prototyping in an
air coil--will the annealing process reduce its ectromagnetic
effectiveness in an air coil? Hopefully this doesn't sound like a
stupid question, I'm new at working with metals and air coils.

On Jan 30, 12:53*am, Mark Main wrote:
On Jan 29, 7:11*am, Bob Engelhardt wrote:

Mark Main wrote:
Can someone cast a small cylinder that I need?

I need a cast iron cylinder with a 7.5 cm diameter, 6.1 cm length, and
a 2.2 cm “bore hole” lengthwise through the center.

I just need to know the cost.

McM-C: 3" diam, 12" long bar - $39.32 + shipping.http://www.mcmaster.com/#8909k32/=dax7f
Cheaper, /much/ faster than custom casting.

Bob

Thank you, this is certainly very close to the size I'm looking for--I
assume that I'll have to have it annealed to cut it down to size and
bore the hole through it. I want to use it in for prototyping in an
air coil--will the annealing process reduce its ectromagnetic
effectiveness in an air coil? Hopefully this doesn't sound like a
stupid question, I'm new at working with metals and air coils.

I've been doing some more research on this and cast iron may not not
be the best material for me to use in the air coil anyway. I just
found some references to relative permeability values (B/H):

Cast Iron 100 -150
Mild Steel 200 - 800
Silicon Iron 1000 - 5000
Cast Steel 300 - 900

And so mild steel looks better anyway, and that's easy enough to work
with. I've never heard of silicon iron, I'll need to look at it
further.

"Mark Main" wrote in message
...
On Jan 30, 12:53 am, Mark Main wrote:
On Jan 29, 7:11 am, Bob Engelhardt wrote:

Mark Main wrote:
Can someone cast a small cylinder that I need?

I need a cast iron cylinder with a 7.5 cm diameter, 6.1 cm length, and
a 2.2 cm “bore hole” lengthwise through the center.

I just need to know the cost.

McM-C: 3" diam, 12" long bar - $39.32 +
shipping.http://www.mcmaster.com/#8909k32/=dax7f
Cheaper, /much/ faster than custom casting.

Bob

Thank you, this is certainly very close to the size I'm looking for--I
assume that I'll have to have it annealed to cut it down to size and
bore the hole through it. I want to use it in for prototyping in an
air coil--will the annealing process reduce its ectromagnetic
effectiveness in an air coil? Hopefully this doesn't sound like a
stupid question, I'm new at working with metals and air coils.

I've been doing some more research on this and cast iron may not not
be the best material for me to use in the air coil anyway. I just
found some references to relative permeability values (B/H):

Cast Iron 100 -150
Mild Steel 200 - 800
Silicon Iron 1000 - 5000
Cast Steel 300 - 900

And so mild steel looks better anyway, and that's easy enough to work
with. I've never heard of silicon iron, I'll need to look at it
further.

============================================

Silicon iron is a high-silicon version of very dead-soft iron, with low
carbon content. It's used in electromagnetic applications, such as the cores
of transformers. In earlier times a plain, soft, low-carbon iron was used
for that job. Its relative permeability is much higher than cast iron, also.

The limitation with steel for motor laminations and transformer cores is
magnetic hysteresis. Even mild steel has much higher hysteresis than
dead-soft iron. However, if you're making something that doesn't reverse
fields, such as a DC solenoid, steel should work fine -- the lower-carbon
and the softer the better. It will retain some magnetism after you stop
applying power, which may or may not be a problem, depending on what you're
doing.

--
Ed Huntress

On Jan 30, 2:18*am, Mark Main wrote:
...I just
found some references to relative permeability values (B/H):

Cast Iron 100 -150
Mild Steel 200 - 800
Silicon Iron 1000 - 5000
Cast Steel 300 - 900

And so mild steel looks better anyway, and that's easy enough to work
with. *I've never heard of silicon iron, I'll need to look at it
further.

Will ferrite would do what you need?
http://digikey.com/scripts/DkSearch/...ywords=ferrite

Consider making the core out of motor or transformer laminations. They
need to be oriented to break up circulating currents.

Jim Wilkins

On Thu, 29 Jan 2009 23:18:45 -0800 (PST), Mark Main
wrote:



I've been doing some more research on this and cast iron may not not
be the best material for me to use in the air coil anyway. I just
found some references to relative permeability values (B/H):

Cast Iron 100 -150
Mild Steel 200 - 800
Silicon Iron 1000 - 5000
Cast Steel 300 - 900

And so mild steel looks better anyway, and that's easy enough to work
with. I've never heard of silicon iron, I'll need to look at it
further.

I'm imagining that your intent is to wind an axial coil either
inside the hole or outside the cylinder. If so, the permeability of
the ferromagnetic material will make very little difference. This is
because a significant part of the closed flux path is thru air, so
this will strongly dominate the total path reluctance. If half of the
geometrical path length is air and half in ferromagnetic material,
then for material mu of 100 about 99% of the mmf drop is in air. For
material mu of 1000, then 99.9% of the mmf drop is in air -- a
difference of less than 1%. Further, the flux density in the hole
will be very low: using your dimensions with an external coil of 1000
ampere turns, B in the iron varies from 36 to 54 millitesla while B
on-axis in the hole is about 0.12 millitesla.

Ed Huntress wrote:
(...)

Silicon iron is a high-silicon version of very dead-soft iron, with low
carbon content. It's used in electromagnetic applications, such as the cores
of transformers. In earlier times a plain, soft, low-carbon iron was used
for that job. Its relative permeability is much higher than cast iron, also.

The limitation with steel for motor laminations and transformer cores is
magnetic hysteresis. Even mild steel has much higher hysteresis than
dead-soft iron. However, if you're making something that doesn't reverse
fields, such as a DC solenoid, steel should work fine -- the lower-carbon
and the softer the better. It will retain some magnetism after you stop
applying power, which may or may not be a problem, depending on what you're
doing.

Mighty McM, Enco and MSC don't know about "Silicon Iron" per se.
If I wanted a hunk to play with, where could I obtain same?
Other than harvesting it from transformers, that is.

--Winston

"Winston" wrote in message
...
Ed Huntress wrote:
(...)

Silicon iron is a high-silicon version of very dead-soft iron, with low
carbon content. It's used in electromagnetic applications, such as the
cores of transformers. In earlier times a plain, soft, low-carbon iron
was used for that job. Its relative permeability is much higher than cast
iron, also.

The limitation with steel for motor laminations and transformer cores is
magnetic hysteresis. Even mild steel has much higher hysteresis than
dead-soft iron. However, if you're making something that doesn't reverse
fields, such as a DC solenoid, steel should work fine -- the lower-carbon
and the softer the better. It will retain some magnetism after you stop
applying power, which may or may not be a problem, depending on what
you're doing.

Mighty McM, Enco and MSC don't know about "Silicon Iron" per se.
If I wanted a hunk to play with, where could I obtain same?
Other than harvesting it from transformers, that is.

--Winston

I don't know,Winston, and I've been asked the same question before. It's
available in small commercial quantities from somewhere, because we bought
some when I was at Sodick to wire-EDM some custom transformer laminations.

And I don't know about "hunks." We bought sheets, which is the only form
I've ever heard of.

--
Ed Huntress

Ed Huntress wrote:
(...)

And I don't know about "hunks." We bought sheets, which is the only form
I've ever heard of.

Very good.
Thanks, Ed.

--Winston

http://www.globalsources.com/manufac...icon-Iron.html
Here is one spot.

Winston wrote:
Ed Huntress wrote:
(...)

Silicon iron is a high-silicon version of very dead-soft iron, with
low carbon content. It's used in electromagnetic applications, such as
the cores of transformers. In earlier times a plain, soft, low-carbon
iron was used for that job. Its relative permeability is much higher
than cast iron, also.

The limitation with steel for motor laminations and transformer cores
is magnetic hysteresis. Even mild steel has much higher hysteresis
than dead-soft iron. However, if you're making something that doesn't
reverse fields, such as a DC solenoid, steel should work fine -- the
lower-carbon and the softer the better. It will retain some magnetism
after you stop applying power, which may or may not be a problem,
depending on what you're doing.

Mighty McM, Enco and MSC don't know about "Silicon Iron" per se.
If I wanted a hunk to play with, where could I obtain same?
Other than harvesting it from transformers, that is.

--Winston

On Fri, 30 Jan 2009 12:34:04 -0800, Winston
wrote:

Ed Huntress wrote:
(...)

Silicon iron is a high-silicon version of very dead-soft iron, with low
carbon content. It's used in electromagnetic applications, such as the cores
of transformers. In earlier times a plain, soft, low-carbon iron was used
for that job. Its relative permeability is much higher than cast iron, also.

The limitation with steel for motor laminations and transformer cores is
magnetic hysteresis. Even mild steel has much higher hysteresis than
dead-soft iron. However, if you're making something that doesn't reverse
fields, such as a DC solenoid, steel should work fine -- the lower-carbon
and the softer the better. It will retain some magnetism after you stop
applying power, which may or may not be a problem, depending on what you're
doing.

Mighty McM, Enco and MSC don't know about "Silicon Iron" per se.
If I wanted a hunk to play with, where could I obtain same?
Other than harvesting it from transformers, that is.

--Winston

Mhttp://www.mapessprowl.com/MAPESWEB.NSF/PublishedGroup/Electrical%20Steel?OpenDocument

It's hard to scrounge "a little" of it because motor and xfmr
production is highly automated: multi-ton rolls of steel go in one
end, lams or finished products come out the other.

On Fri, 30 Jan 2009 16:45:40 -0500, "Ed Huntress"
wrote:


"Winston" wrote in message
...
Ed Huntress wrote:
(...)

Silicon iron is a high-silicon version of very dead-soft iron, with low
carbon content. It's used in electromagnetic applications, such as the
cores of transformers. In earlier times a plain, soft, low-carbon iron
was used for that job. Its relative permeability is much higher than cast
iron, also.

The limitation with steel for motor laminations and transformer cores is
magnetic hysteresis. Even mild steel has much higher hysteresis than
dead-soft iron. However, if you're making something that doesn't reverse
fields, such as a DC solenoid, steel should work fine -- the lower-carbon
and the softer the better. It will retain some magnetism after you stop
applying power, which may or may not be a problem, depending on what
you're doing.

Mighty McM, Enco and MSC don't know about "Silicon Iron" per se.
If I wanted a hunk to play with, where could I obtain same?
Other than harvesting it from transformers, that is.

--Winston

I don't know,Winston, and I've been asked the same question before. It's
available in small commercial quantities from somewhere, because we bought
some when I was at Sodick to wire-EDM some custom transformer laminations.

And I don't know about "hunks." We bought sheets, which is the only form
I've ever heard of.

Send Ig over to Fermilab. I think those guys have some of everything
that exists.

"Don Foreman" wrote in message
...
On Fri, 30 Jan 2009 16:45:40 -0500, "Ed Huntress"
wrote:


"Winston" wrote in message
...
Ed Huntress wrote:
(...)

Silicon iron is a high-silicon version of very dead-soft iron, with low
carbon content. It's used in electromagnetic applications, such as the
cores of transformers. In earlier times a plain, soft, low-carbon iron
was used for that job. Its relative permeability is much higher than
cast
iron, also.

The limitation with steel for motor laminations and transformer cores
is
magnetic hysteresis. Even mild steel has much higher hysteresis than
dead-soft iron. However, if you're making something that doesn't
reverse
fields, such as a DC solenoid, steel should work fine -- the
lower-carbon
and the softer the better. It will retain some magnetism after you stop
applying power, which may or may not be a problem, depending on what
you're doing.

Mighty McM, Enco and MSC don't know about "Silicon Iron" per se.
If I wanted a hunk to play with, where could I obtain same?
Other than harvesting it from transformers, that is.

--Winston

I don't know,Winston, and I've been asked the same question before. It's
available in small commercial quantities from somewhere, because we bought
some when I was at Sodick to wire-EDM some custom transformer laminations.

And I don't know about "hunks." We bought sheets, which is the only form
I've ever heard of.

Send Ig over to Fermilab. I think those guys have some of everything
that exists.

Interesting. Can you buy stuff there?

--
Ed Huntress

Martin H. Eastburn wrote:
http://www.globalsources.com/manufac...icon-Iron.html
Here is one spot.

Thanks, Martin.

--Winston

Ed Huntress wrote:
"Don Foreman" wrote in message
...
On Fri, 30 Jan 2009 16:45:40 -0500, "Ed Huntress"
wrote:

"Winston" wrote in message
...

(...)

Mighty McM, Enco and MSC don't know about "Silicon Iron" per se.
If I wanted a hunk to play with, where could I obtain same?
Other than harvesting it from transformers, that is.

--Winston
I don't know,Winston, and I've been asked the same question before. It's
available in small commercial quantities from somewhere, because we bought
some when I was at Sodick to wire-EDM some custom transformer laminations.

And I don't know about "hunks." We bought sheets, which is the only form
I've ever heard of.
Send Ig over to Fermilab. I think those guys have some of everything
that exists.

Interesting. Can you buy stuff there?

I'm all ears!

--Winston

Don Foreman wrote:
(...)


Mhttp://www.mapessprowl.com/MAPESWEB.NSF/PublishedGroup/Electrical%20Steel?OpenDocument

It's hard to scrounge "a little" of it because motor and xfmr
production is highly automated: multi-ton rolls of steel go in one
end, lams or finished products come out the other.

O I C

Thanks, Don.

--Winston

In article ,
Winston wrote:

Ed Huntress wrote:
(...)

Silicon iron is a high-silicon version of very dead-soft iron, with low
carbon content. It's used in electromagnetic applications, such as the
cores
of transformers. In earlier times a plain, soft, low-carbon iron was used
for that job. Its relative permeability is much higher than cast iron,
also.

The limitation with steel for motor laminations and transformer cores is
magnetic hysteresis. Even mild steel has much higher hysteresis than
dead-soft iron. However, if you're making something that doesn't reverse
fields, such as a DC solenoid, steel should work fine -- the lower-carbon
and the softer the better. It will retain some magnetism after you stop
applying power, which may or may not be a problem, depending on what you're
doing.

Mighty McM, Enco and MSC don't know about "Silicon Iron" per se.
If I wanted a hunk to play with, where could I obtain same?
Other than harvesting it from transformers, that is.

It's more often called silicon steel. Places that wind custom
transformers can perhaps be persuaded to sell the steel in small
quantities. I have also seen catalogs of standard transformer
laminations.

Joe Gwinn

"Joseph Gwinn" wrote in message news:joegwinn-
It's more often called silicon steel. Places that wind custom
transformers can perhaps be persuaded to sell the steel in small
quantities. I have also seen catalogs of standard transformer
laminations.

Joe Gwinn

this whole discussion has gone off the rails - the OP didn't even hint at a
transformer at first, then when the OP revealed that a coil of some kind was
involved, he was astounded to learn that permeability varies.

If you want to offer the right material, we would need to know the operating
frequency, the desired L and Q, current, any speical constraints regarding
apace, and so on. For a transformer, a torroid is usually best, and these
are available from a wide variety of ferrite materials in a huge variety of
sizes.

Joseph Gwinn wrote:

It's more often called silicon steel. Places that wind custom
transformers can perhaps be persuaded to sell the steel in small
quantities. I have also seen catalogs of standard transformer
laminations.

Thanks, Joe!

--Winston

On Jan 31, 8:01*pm, "Bill Noble" wrote:
"Joseph Gwinn" wrote in message news:joegwinn-
It's more often called silicon steel. *Places that wind custom
transformers can perhaps be persuaded to sell the steel in small
quantities. *I have also seen catalogs of standard transformer
laminations.

Joe Gwinn

this whole discussion has gone off the rails - the OP didn't even hint at a
transformer at first, then when the OP revealed that a coil of some kind was
involved, he was astounded to learn that permeability varies.

If you want to offer the right material, we would need to know the operating
frequency, the desired L and Q, current, any speical constraints regarding
apace, and so on. *For a transformer, a torroid is usually best, and these
are available from a wide variety of ferrite materials in a huge variety of
sizes.

First, I want to extend my thanks to all who provided some very
interesting information... I was gone for a few days and so I'm
catching up on emails and this thread.

I want to build an air coil that has an I.D. or 3" or 4" and move a 3
or 4 lb plunger inside back and forth inside the coil to learn how to
do it and learn about how much amperage is needed to move it at
various speeds (horizontally). Because I plan to reverse directions,
I'm going to try this with DC power at first (although I'd like to
learn if this is possible to reverse using AC current).

I'd like to use some materials that are efficient because I'd
eventually like to put what I've learned to good use and try to make
some things with it.

Thank you again for the helpful information offered by folks. I just
bought some books to help out, and I recommend "Basic
Electricity" (www.rea.com) it's got lots of great information on
building solenoids and motors, and "Handbook of small electric motors"
from McGraw-Hill seems packed with good info.

One thing in all of my research that I can't get a good answer on is,
what is the optimal design/shape for my plunger so that it will move
the fastest possible speed for given amperage?

E.g. Length vs. Diameter? Because of the weight and the horizontal
direction I believe that I'll need a stainless steel bar running
through the coil to support the weight... and I'm thinking of a 1/2"
diameter bar... but would a 5/8" or 3/4" diameter make the plunger/
weight move faster or slower? Remember, than that weight is a fixed
weight (I'll choose 3 or 4 lbs), and so a larger diameter means longer
length or larger diameter for the plunger.

Mark Main wrote:

I want to build an air coil that has an I.D. or 3" or 4" and move a 3
or 4 lb plunger inside back and forth inside the coil to learn how to
do it and learn about how much amperage is needed to move it at
various speeds (horizontally). Because I plan to reverse directions,
I'm going to try this with DC power at first (although I'd like to
learn if this is possible to reverse using AC current).

That sounds *just* like an old hard drive
voice coil. And by old, I mean 70's and
80's pre-winchester tech. I've seen many
of them surplus, but not for about 10 years.

Hi Mark, now that the cat's outta the sack, you might find the topic of
voice coil motors of interest..

http://www.google.com/search?hl=en&q...earch&aq=f&oq=

Or try other search terms related to "voice coil"

--
WB
..........
metalworking projects
www.kwagmire.com/metal_proj.html


"Mark Main" wrote in message
...

First, I want to extend my thanks to all who provided some very
interesting information... I was gone for a few days and so I'm
catching up on emails and this thread.

I want to build an air coil that has an I.D. or 3" or 4" and move a 3
or 4 lb plunger inside back and forth inside the coil to learn how to
do it and learn about how much amperage is needed to move it at
various speeds (horizontally). Because I plan to reverse directions,
I'm going to try this with DC power at first (although I'd like to
learn if this is possible to reverse using AC current).

I'd like to use some materials that are efficient because I'd
eventually like to put what I've learned to good use and try to make
some things with it.

Thank you again for the helpful information offered by folks. I just
bought some books to help out, and I recommend "Basic
Electricity" (www.rea.com) it's got lots of great information on
building solenoids and motors, and "Handbook of small electric motors"
from McGraw-Hill seems packed with good info.

One thing in all of my research that I can't get a good answer on is,
what is the optimal design/shape for my plunger so that it will move
the fastest possible speed for given amperage?

E.g. Length vs. Diameter? Because of the weight and the horizontal
direction I believe that I'll need a stainless steel bar running
through the coil to support the weight... and I'm thinking of a 1/2"
diameter bar... but would a 5/8" or 3/4" diameter make the plunger/
weight move faster or slower? Remember, than that weight is a fixed
weight (I'll choose 3 or 4 lbs), and so a larger diameter means longer
length or larger diameter for the plunger.

On 2009-02-03, Mark Main wrote:

[ ... ]

First, I want to extend my thanks to all who provided some very
interesting information... I was gone for a few days and so I'm
catching up on emails and this thread.

I want to build an air coil that has an I.D. or 3" or 4" and move a 3
or 4 lb plunger inside back and forth inside the coil to learn how to
do it and learn about how much amperage is needed to move it at
various speeds (horizontally). Because I plan to reverse directions,
I'm going to try this with DC power at first (although I'd like to
learn if this is possible to reverse using AC current).

If you want to move it back and forth -- you will either need
two coils, or a permanent magnet.

As for AC -- you can make one which works (pull only) from AC
with a notch dividing the end of the piston into two parts, and a copper
ring or band around one of the two to shift the phase.

You will get a lot less speed out of that for a given current
than you will with a DC one.

I'd like to use some materials that are efficient because I'd
eventually like to put what I've learned to good use and try to make
some things with it.

Probably the most efficient materials would be to make a frame
and plunger out of transformer laminations. I've seen quite a few heavy
duty ones of this sort -- and lighter duty ones using a round piston of
mild steel in a frame.

Thank you again for the helpful information offered by folks. I just
bought some books to help out, and I recommend "Basic
Electricity" (www.rea.com) it's got lots of great information on
building solenoids and motors, and "Handbook of small electric motors"
from McGraw-Hill seems packed with good info.

One thing in all of my research that I can't get a good answer on is,
what is the optimal design/shape for my plunger so that it will move
the fastest possible speed for given amperage?

E.g. Length vs. Diameter?

Diameter is determined by the amount of pull you need, and
length by the required travel. (And strength will vary with the motion,
since the magnetic circuit will change with piston travel.

Because of the weight and the horizontal
direction I believe that I'll need a stainless steel bar running
through the coil to support the weight...

You mean a hollow tube? Either a 300 series (non-magnetic)
stainless or copper. The tube should have a slit running down the
length to prevent it acting as a shorted turn and absorbing energy,
especially during the turn-on or turn-off moments.

and I'm thinking of a 1/2"
diameter bar... but would a 5/8" or 3/4" diameter make the plunger/
weight move faster or slower?

At a guess, you'll need more Ampere-turns for a larger diameter
piston, because you will have more mass to move.

Remember, than that weight is a fixed
weight (I'll choose 3 or 4 lbs),

You mean the load will be a fixed mass, or the whole solenoid
will be so?

and so a larger diameter means longer
length or larger diameter for the plunger.

Experiment.

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 ---

On 2009-02-03, Jim Stewart wrote:
Mark Main wrote:

I want to build an air coil that has an I.D. or 3" or 4" and move a 3
or 4 lb plunger inside back and forth inside the coil to learn how to
do it and learn about how much amperage is needed to move it at
various speeds (horizontally). Because I plan to reverse directions,
I'm going to try this with DC power at first (although I'd like to
learn if this is possible to reverse using AC current).

That sounds *just* like an old hard drive
voice coil. And by old, I mean 70's and
80's pre-winchester tech. I've seen many
of them surplus, but not for about 10 years.

And the moving part is the coil only -- not the metal mass,
which is mostly permanent magnet. That gives you the minimum mass to
the moving part, and the ability to reverse at will -- with DC fields
applied, not AC.

The typical one is associated with a 14" diameter platter or
platter stack, so anything which you can lift with one hand does not
qualify. (Hmm ... there was a series of 8" floppy drives by Persi
(IIRC) which had voice coil head positioners. If you can find the
remains of any of these they might work well for you, depending on the
mass of your load.

The coil also moved a glass scale with a bar code printed on it,
and a matching pair of shorter glass bar codes mounted in quadrature
told the computer the current position of the drive by counting
transitions. This might be important if you want to be able to control
the motion at intermediate points instead of simply slamming to one end
or the other.

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 ---

"Mark Main" wrote in message
...
On Jan 31, 8:01 pm, "Bill Noble" wrote:
First, I want to extend my thanks to all who provided some very
interesting information... I was gone for a few days and so I'm
catching up on emails and this thread.

I want to build an air coil that has an I.D. or 3" or 4" and move a 3
or 4 lb plunger inside back and forth inside the coil to learn how to
do it and learn about how much amperage is needed to move it at
various speeds (horizontally). Because I plan to reverse directions,
I'm going to try this with DC power at first (although I'd like to
learn if this is possible to reverse using AC current).

I'd like to use some materials that are efficient because I'd
eventually like to put what I've learned to good use and try to make
some things with it.

Thank you again for the helpful information offered by folks. I just
bought some books to help out, and I recommend "Basic
Electricity" (www.rea.com) it's got lots of great information on
building solenoids and motors, and "Handbook of small electric motors"
from McGraw-Hill seems packed with good info.

One thing in all of my research that I can't get a good answer on is,
what is the optimal design/shape for my plunger so that it will move
the fastest possible speed for given amperage?

E.g. Length vs. Diameter? Because of the weight and the horizontal
direction I believe that I'll need a stainless steel bar running
through the coil to support the weight... and I'm thinking of a 1/2"
diameter bar... but would a 5/8" or 3/4" diameter make the plunger/
weight move faster or slower? Remember, than that weight is a fixed
weight (I'll choose 3 or 4 lbs), and so a larger diameter means longer
length or larger diameter for the plunger.

__________________

ok, this is good information. some hints, without directly answering your
questions:

1. how fast do you want to move it (you could think of this as frequency
response) - you can move 4 or four pounds very fast, but it takes a lot of
energy. you need to think in numbers and start calculating forces -
remember F=MA. You can move your weight at about 4000 FPS pretty "easily"
using rail gun technology

2. look up "coin crusher", look up "rail gun", look up "voice coil
actuator", look up "solenoid magnetic field" --- these phrases will help you
fourmulate the questions you want to ask

3. look at

Thank you for your notes. I though that it would be best if I clairfy
what I'm trying to do. I want to build an air coil with a 3 - 4"
diameter coil size that is about 12" long and I want to be able to
move the plunger/weight that is inside the coil from one end to the
other in about half a second or less; and then I want to do the same
thing in the reverse direction after a certain delayed period of time
(preferably by simply reversing the DC polarity).

The coil remains stationary in a horizontal position, it's the plunger/
weight inside that is moving.

Because the plunger/weight is 3 or 4 lbs and travels in a horizontal
plane, I assume that the coil will not levitate and will "rub" on the
lower part of the coil due to gravity; if this assumption is true,
then I'll need a way to support the weight efficently (with little
friction) so that it can merely glide alone the support beam (or
tube). If I have to use a support tube, then I thought the best way
would be to have it run through the center of the coil and NOT have it
be grounded to anything--possibly securing each end with rubber and
plastic braces. This way the weight would have a hole bored out in the
center and just glide on the tube. I envisioned that I'd have place a
small thin nylon tube in between the plunger and the support tube to
reduce friction.

My wife's been in the hospital since I last wrote and so I've not been
able to do anything on this... but I want to figure out what square
wire size to use--I'm hoping to read something in my books that helps
me guess what mill size to use, or possibly get a recommendation
here. My first guess is to find something that is square with the
length/width being at least equal to the a 12 guage (I would like to
learn how to design for continuous use).

I also need to play with plunger shapes; e.g. convex, concave, and
flat shaped ends, and Larger diameter vs larger length.

Any suggestions or tips are always appreciated. Thanks.

I would like to move 3 or 4 lbs a distance of 12 to 20 inches in about
half a second.

I originally considered rail gun at first and switched to air coil
because I want this to be continous duty, and I want it to be able to
handle a lot of cylces (maybe a million or more if I can), and that
threw out rail gun, but air coil is possible.

Thanks for your search tips, I've used the solenoid and magnetic
terms, but not voice coil. I also bought several nice books that
should help me out. I've been doing lots of reading and the math is
certainly more complex than I originally thought, so it's actually
been quite fun and challenging to learn. I've probably been
researching on this quite heavily for a month now.

My first tests will be using a transformer that I can find with high
amperage and low voltage, but I want to learn how to use the formulas
correctly so that I can arrive at a good guess for square wire size
(mills) to use that won't get too hot in a continous duty.

I really don't know a good source for heavy duty transformers like
this.

On Feb 2, 7:22*pm, Jim Stewart wrote:
Mark Main wrote:
I want to build an air coil that has an I.D. or 3" or 4" and move a 3
or 4 lb plunger inside back and forth inside the coil to learn how to
do it and learn about how much amperage is needed to move it at
various speeds (horizontally). *Because I plan to reverse directions,
I'm going to try this with DC power at first (although I'd like to
learn if this is possible to reverse using AC current).

That sounds *just* like an old hard drive
voice coil. *And by old, I mean 70's and
80's pre-winchester tech. *I've seen many
of them surplus, but not for about 10 years.

Thanks for the voice coil suggestion. When I hear the term "voice
coil" I immediately pictured some tiny coil used for a phone or
headphones... I had no idea they could be really big--I just didn't
know about them. Wow! These are pretty cool.

This may solve my stuggles with handling the weight because the weight
is on the outside and can be supported by a rail system. Thanks for
the idea.

I wrote my reply here before I looked at the "voice coil" suggestion,
which also seem very interesting because it looks like the "weight"
would be on the outside of the coil, and that's pretty cool, because I
could easily have it glide alone a rail to support the weight. So I'm
going to look at both methods, but this voice coil may be the ticket
if it can move the larger weight as quickly as it could within the
coil.

My first guess is that the magnetic force on the inside would be equal
to the total accumulated force on the outside and so for my purposes
the voice could would work.

Mark Main wrote:
... then I want to do the same
thing in the reverse direction after a certain delayed period of time
(preferably by simply reversing the DC polarity).

snip

Just reversing the polarity won't do it. The attraction to the iron bar
will be the same. Reversing the current /would / reverse the force on a
permanent magnet. If your "armature" could be a PM, you'd be all set.
Otherwise you will need /2/ coils, some distance apart, to attract the
armature to one or the other, alternately.

Recent comments about voice coils do it that way. I.e., a PM is used.

Bob

Mark Main wrote:
... a transformer that I can find with high
amperage and low voltage, ...

How high & how low? Rewinding a microwave oven transformer (MOT) might
be a good alternative. Specialty transformers can be pretty expensive.

Bob

On Feb 4, 6:29*pm, Bob Engelhardt wrote:
Mark Main wrote:
... *a transformer that I can find with high
amperage and low voltage, ...

How high & how low? *Rewinding a microwave oven transformer (MOT) might
be a good alternative. *Specialty transformers can be pretty expensive.

Bob

I'm working to learn the math to calculate how much amperage for a
given number of turns will be required to move a 4lb weight 20" in
half a second. I'll look into the MOT idea... I may end up winding my
own transfomer if I can't find something cheap (more math...I'll be on
my way toward an electrical engineering degree when I get done, good
thing I like math).

Mark Main wrote:
On Feb 4, 6:29 pm, Bob Engelhardt wrote:
Mark Main wrote:
... a transformer that I can find with high
amperage and low voltage, ...
How high & how low? Rewinding a microwave oven transformer (MOT) might
be a good alternative. Specialty transformers can be pretty expensive.

Bob

I'm working to learn the math to calculate how much amperage for a
given number of turns will be required to move a 4lb weight 20" in
half a second. I'll look into the MOT idea... I may end up winding my
own transfomer if I can't find something cheap (more math...I'll be on
my way toward an electrical engineering degree when I get done, good
thing I like math).


That seem like a pretty long distance for a single step.

Would it make more sense to sequence several smaller windings -
rail gun style?

On Wed, 4 Feb 2009 17:24:35 -0800 (PST), Mark Main
wrote:

On Feb 4, 6:29*pm, Bob Engelhardt wrote:
Mark Main wrote:
... *a transformer that I can find with high
amperage and low voltage, ...

How high & how low? *Rewinding a microwave oven transformer (MOT) might
be a good alternative. *Specialty transformers can be pretty expensive.

Bob

I'm working to learn the math to calculate how much amperage for a
given number of turns will be required to move a 4lb weight 20" in
half a second. I'll look into the MOT idea... I may end up winding my
own transfomer if I can't find something cheap (more math...I'll be on
my way toward an electrical engineering degree when I get done, good
thing I like math).

Don't ignore the KISS Factor - Rather than reinvent the voice coil
positioner and solve the problems from scaling it up... Might be
cheaper simpler faster to use a leadscrew and a nut to move your
load, and either a PMDC electric motor or a stepper motor to spin the
screw.

If you have a location feedback device like a linear pot or an
optical DRO scale, you can ramp the motor up to full speed for a fast
traverse, then slow down the motor as you start closing in on the
desired new location.

-- Bruce --

Mark Main fired this volley in news:d727636b-
:

That sounds *just* like an old hard drive
voice coil. ÿAnd by old, I mean 70's and
80's pre-winchester tech. ÿI've seen many
of them surplus, but not for about 10 years.



Those could do 5" of travel in about 40ms, with a 19oz head mechanism
(and that didn't count the weight of the voice coil, itself). It took
up to 30A to the voice coil at 48VDC.

I maintained those drives for many years, including doing mechanical
alignments, which encompassed things like adjusting the stop points
within 40 microns (to get the r/w head exactly centered between the
sync tracks on a standard calibration disk). They had elegantly-made
quadrature linear encoders as part of the positioning mechanism.

However, duplicating them from scratch is difficult. The originals -
say, Diablo (Xerox) Model 40 drives - had exquisite ball-bearing guide
rails for the assembly, with both vertical and horizontal bearing
elements.

That was partly because one didn't want any off-axis variations when
driving heads a few microns above a disk surface, and partly because
the gaps in the magnet assembly between poles and coil had to be in
the few (less than 10) thousanths to get the tight magnetic coupling
necessary to drive them that far, that fast.

I still have a couple of the ferrite magnets from such a head motor;
used with three strands of cord as a "parts finder" in the dirt floor
areas of my barn. G

LLoyd

"Lloyd E. Sponenburgh" lloydspinsidemindspring.com fired this volley
in .70:


Oh... just remembered... those were Diablo Model 44's, not 40's.

44A model in 1974, with external (80lb power supply), Model 44B in 1977,
with much-reduced electronics due to MSI chips, and Model 44C about
1980, which had (whew!) an integral power supply.

The basic drive weighed about 90lb, and stored 10Mb on two 19" disks.
Kilo-G

LLoyd

I thought you were talking about the Xerox Diablo Daisy Wheel printer
or the Queme printer that was close.

I worked on Pertec Hard Disks - they would retract the heads by
discharging a massive capacitor into a coil. If you had a screw
driver in the way when the scram call went it would be seared in two.

Martin

Lloyd E. Sponenburgh wrote:
Mark Main fired this volley in news:d727636b-
:

That sounds *just* like an old hard drive
voice coil. ÿAnd by old, I mean 70's and
80's pre-winchester tech. ÿI've seen many
of them surplus, but not for about 10 years.


Those could do 5" of travel in about 40ms, with a 19oz head mechanism
(and that didn't count the weight of the voice coil, itself). It took
up to 30A to the voice coil at 48VDC.

I maintained those drives for many years, including doing mechanical
alignments, which encompassed things like adjusting the stop points
within 40 microns (to get the r/w head exactly centered between the
sync tracks on a standard calibration disk). They had elegantly-made
quadrature linear encoders as part of the positioning mechanism.

However, duplicating them from scratch is difficult. The originals -
say, Diablo (Xerox) Model 40 drives - had exquisite ball-bearing guide
rails for the assembly, with both vertical and horizontal bearing
elements.

That was partly because one didn't want any off-axis variations when
driving heads a few microns above a disk surface, and partly because
the gaps in the magnet assembly between poles and coil had to be in
the few (less than 10) thousanths to get the tight magnetic coupling
necessary to drive them that far, that fast.

I still have a couple of the ferrite magnets from such a head motor;
used with three strands of cord as a "parts finder" in the dirt floor
areas of my barn. G

LLoyd