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TOROIDAL COILS (Liquid Filled)
TOROID - The dictionary definition is SO convoluted and com-
plicated that I cannot even understand it. For our purpose I
am treating "toroid" to equal "donut" and it is understood
that we are talking about the donut being hollow and filled
with an adequate proton liquid.
At this point in time (Mar 1, 2000) Jim Koehler's gradiometer
manual shows the best he has found, so far, for the toroidal
coil form is the large(st) ring in the Fisher-Price
"Rock-a-Stack" toy. This ring is made of a rigid (not hard)
blue plastic. The outside diameter of the donut is ap-
proximately 4.85 inches. Inside diameter of the donut is ap-
proximately 2.3 inches. The diameter of the tube runs ap-
proximately 1.15 to 1.25 inches. Apparently due to
fabrication considerations, it is NOT a true circle. Wall
thickness is estimated to be approximately .06 inches. (This
estimate was arrived at by cutting the small(est) red ring
measuring it, then cutting and measuring the next (orange)
ring and finally cutting and measuring the next (yellow) ring.
It was found each size had an increase of about .005 inches
from the smaller one.) There is a very definite "joint" where
the upper and the lower halves are joined together so it is
obvious that these are made in two pieces and then joined ei-
ther by heat or some unknown adhesive. Jim states the capac-
ity to be approximately .18 liter and says slightly more
capacity would be better. I talked to Fisher-Price and they
said this is no longer made but I just found two (only) sets
at a Target. Assuming Fisher-Price customer service is cor-
rect about the discontinuance, there apparently are still some
in stock at SOME Target stores.
According to one posting on the Forum by Jim Koehler, the fol-
lowing would be "nearly ideal" as a form for his gradiometer's
sensors:
Outside diameter 8 1/2", inside diameter 4 1/2" and the diam-
eter of the tube is 2 inches. Made of hard plastic. Used as
net floats by commercial fishermen in Ireland. Information
from Jerry Smith in Baltimore, Ireland.
Http://www.aquaventures.ie. [email protected]; Phone 353
(0) 28-20511. The really unfortunate part about this toroid
form is that it looks tough or impossible to get. I emailed
[email protected] twice and FAXed seven (7) suppliers or
commercial fishing equipment in Ireland. Net-to-date is one
reply from TRUETACKLE stating that they do NOT stock a donut
shaped float.
OTHER SUGGESTIONS
Carl Morton - 9/22/99 -Glue up to 4 PVC elbows into a
rectangular "toroid". you can make it any size you want. Keep
windings on the "flats", not the corners - maybe even wind
each flat completely before going on to the next. As long as
the number of windings are equal and dimensionally about the
same you should still get a very good rejection.
Also since there are no windings around the corners you can
drill and tap a hole on one of the outside corners and add a
fill cap. Now you could experiment with different proton flu-
ids.
Jim Koehler - 9/23/99 - more or less says above not as good as true
toroid but near as good. He thought it might be a bit large
and cumbersome for a portable instrument. AND, would have to
more careful with shielding because the corners are not cov-
ered by the coil(s).
Carl Morton - 9/23/99 - ... more or less same as Jim but he
adds; [However] "I like the idea of bending PVC into a toroid."
...special flexible PVC pipe available that is probably easier
to work with (as far as heating/bending) than even thin-wall
PVC. And, there is a soft-wall PVC tubing as well.
Cris Martin - 11/22/99 - says; "Just though I'd show my idea
for a toroid former. All that's needed is to make an add
eight "washers" at each elbow joint to hold the coils in
place. The pipe is standard 22 mm overflow pipe which we get
in the UK. The piece of wood is 22 mm dowel. To fill the
tube, remove the dowel and pour. Obviously the end of the
dowel has to be sealed, or your liquid will soak into it!"
Jim Koehler - 11/8/99 - I have wound solenoidal sensors as
well as the toroidal ones, in fact my earliest attempts at
building a PPM used solenoidal sensors. The 60 Hz pickup is
at least an order of magnitude less (i.e., better) for the
toroids compared to the solenoids. And, with the toroids, you
don't have to worry about orientation with respect to the am-
bient field. I think it is worth the trouble of winding the
toroids - but there is no doubt that winding the toroids is a
very fiddly, exasperating, time-consuming task. [This shows a
heading from Phil but I believe that in the middle it turns
into a comment from Jim.]
Duke - 11.26/99 - Here is what I ended up doing:
8 1" 45 degree elbows glued into an octagon. They were a
little too long so I trimmed them down about 3/8" from each
side. The resulting coil was surprisingly 'toroidal'. I left
a notch in the form to make winding easier although it may
lead to a slight 'orientation' problem. There are three nice
illustrations of this on the Forum. 1. One of untrimmed sec-
tions which is the 8 elbows and 8 flats and the "diameter" of
the "circle" looks to be about 9 inches. 2. One made up of
the trimmed sections with the "diameter" about 6 inches or so.
3. One of the finished coil which clearly shows the notch
that Duke left to facilitate the winding process.
Patrick Duffy - ___________ - wrote; For those of you not on
Erich Foster's MD Forum, someone recently placed an e-mail on "How
to Make Your Own Circular Coil" using PVC.
In the past Dan Fountain and others were talking about using
PVC for toroid forms. I thought the following info might be
of interest (at least the part on forming the PVC). Obvi-
ously, some of the parts and process will not apply to our ap-
plication. Patrick
A 1/2 inch-OD PVC white plumbing tubing, will serve nicely as
a housing for the coil; and a PVC T-coupling with a 1/2-inch
PVC plumbing coupling + cement. You also need some fine sand and a
Hot Gun.
METHOD:
1. Cut a circular form in 3/4" plywood to the diameter you
want your coil.
2. Cut the PVC tube at the length desired; Tap[e] the end
with masking tape and fill it with sand completely, tap[e] the
end with another masking.
3. Heat the tube with the hot gun, slowly until you feel it
soft.
4. Mold it around the plywood form until you have a perfect
circular form.
5. Refresh the PVC coil with cold water and pull out the
sand.
6. Glue the T-coupling and make it a hole for passing the co-
axial cable (RG5
.
7. Now you can assemble the turns loop wire into the tube,
making one loop at a time until all calculated turns are com-
pleted (put some grease) [what does that mean - das]; (a te-
dious work, because you must fill all the thin wire without
breakit-about 1 hour of work).
8. Glue the second part of the T-coupling for closing the
coil.
9. Pass the coaxial cable in the hole and solder the wires
coil.
10. TEST the continuity of the coil with a Multimeter before..
11. Filling the T-coupling with a silicon sealant. want the
coupling with the arm tube you can pull one cylinder of teflon
lathe work and fix it with 1/8 POP. Total working time = 3
hours and "voila" you have make your own coil, very strong,
light, WATERPROOF and you can paint it the color you like. I
have been making coils like this in 10 to 24 inch diameter
without problem.
Dan Fountain - 9/22/99 - I've been thinking about how to make
toroidal coil forms and came up with an idea using - you
guessed it! PVC pipe! Get thin wall pipe (Schedule 20 or
SDR-21) and cap both ends (to keep pressure inside and keep it
from flattening out). Heat it up to the very flexible point
(electricians use a special 10 foot long oven to heat up plas-
tic conduit for bending) and wrap it in a spiral around a
suitable diameter form. After cooling, cut it into individual
rings. Reheat these rings and take the spiral out of them,
fine tune the ends, and glue into toroids.
Dan later (10/11/99) said the above didn't work so great so he
went off to hardware store again. He then mentions 1 1/2 inch
drain traps of PVC and came up with a plan that is worth read-
ing although some elements are used later with elbows as
mentioned someplace above. Dan's will be different because
"rounder" than the elbows and of course his diameter is 1 1/2
" as opposed to the 1" elbows used above.
Couple of comments from Dale after reading and typing in all
of the above. I hope we can find the fishing net floats that
Jerry had originally mentioned. They sound ideal and Jim
Koehler said he likes them. I have a few reservations about
everything and they are as follows:
With the Fisher-Price Rock-a-Stack it seems a little bit too
soft for a klutz like me to be winding this precision coil -
but if it turns out to be the best available then I will give
it a shot. Also the Rock-a-Stack has RAISED letters that say
"FISHER-PRICE-TOYS" with the part number below and LARGE "F" and
LARGE "P" each on a cartouch above. They are only raised about a
half a millimeter or so but I am wondering if this
will introduce some distortion into the winding? I think I
can "shave" or sand them off if anyone knowledgeable thinks it
is enough to throw off a Klutz. Also the joints of the two
halves on the ID and OD are a mite rough. Maybe sand them
also.
I continue to have some degree of trepidation about the permeability
of whatever plastic is used. Let us say .01 permeability per 24
hour period. I assume this is percent. I think this means that
every 100 days we would lose one percent (1 %) of our proton liquid.
So in a thousand days I guess we would lose 10%. Would we lose
more in very hot weather - Would we lose less in very cold weather.
What happens to the plastic ring if it freezes?? Or am I just
worrying about problems that simply don't exist. One of the
problems is that permeability is different for different plastics
and I don't have any idea what type of plastic the Rock-a-Stack is.
Some of the plastic I looked at have permeability of MUCH more than
.01 per 24 hours. A couple had
TOROID - The dictionary definition is SO convoluted and com-
plicated that I cannot even understand it. For our purpose I
am treating "toroid" to equal "donut" and it is understood
that we are talking about the donut being hollow and filled
with an adequate proton liquid.
At this point in time (Mar 1, 2000) Jim Koehler's gradiometer
manual shows the best he has found, so far, for the toroidal
coil form is the large(st) ring in the Fisher-Price
"Rock-a-Stack" toy. This ring is made of a rigid (not hard)
blue plastic. The outside diameter of the donut is ap-
proximately 4.85 inches. Inside diameter of the donut is ap-
proximately 2.3 inches. The diameter of the tube runs ap-
proximately 1.15 to 1.25 inches. Apparently due to
fabrication considerations, it is NOT a true circle. Wall
thickness is estimated to be approximately .06 inches. (This
estimate was arrived at by cutting the small(est) red ring
measuring it, then cutting and measuring the next (orange)
ring and finally cutting and measuring the next (yellow) ring.
It was found each size had an increase of about .005 inches
from the smaller one.) There is a very definite "joint" where
the upper and the lower halves are joined together so it is
obvious that these are made in two pieces and then joined ei-
ther by heat or some unknown adhesive. Jim states the capac-
ity to be approximately .18 liter and says slightly more
capacity would be better. I talked to Fisher-Price and they
said this is no longer made but I just found two (only) sets
at a Target. Assuming Fisher-Price customer service is cor-
rect about the discontinuance, there apparently are still some
in stock at SOME Target stores.
According to one posting on the Forum by Jim Koehler, the fol-
lowing would be "nearly ideal" as a form for his gradiometer's
sensors:
Outside diameter 8 1/2", inside diameter 4 1/2" and the diam-
eter of the tube is 2 inches. Made of hard plastic. Used as
net floats by commercial fishermen in Ireland. Information
from Jerry Smith in Baltimore, Ireland.
Http://www.aquaventures.ie. [email protected]; Phone 353
(0) 28-20511. The really unfortunate part about this toroid
form is that it looks tough or impossible to get. I emailed
[email protected] twice and FAXed seven (7) suppliers or
commercial fishing equipment in Ireland. Net-to-date is one
reply from TRUETACKLE stating that they do NOT stock a donut
shaped float.
OTHER SUGGESTIONS
Carl Morton - 9/22/99 -Glue up to 4 PVC elbows into a
rectangular "toroid". you can make it any size you want. Keep
windings on the "flats", not the corners - maybe even wind
each flat completely before going on to the next. As long as
the number of windings are equal and dimensionally about the
same you should still get a very good rejection.
Also since there are no windings around the corners you can
drill and tap a hole on one of the outside corners and add a
fill cap. Now you could experiment with different proton flu-
ids.
Jim Koehler - 9/23/99 - more or less says above not as good as true
toroid but near as good. He thought it might be a bit large
and cumbersome for a portable instrument. AND, would have to
more careful with shielding because the corners are not cov-
ered by the coil(s).
Carl Morton - 9/23/99 - ... more or less same as Jim but he
adds; [However] "I like the idea of bending PVC into a toroid."
...special flexible PVC pipe available that is probably easier
to work with (as far as heating/bending) than even thin-wall
PVC. And, there is a soft-wall PVC tubing as well.
Cris Martin - 11/22/99 - says; "Just though I'd show my idea
for a toroid former. All that's needed is to make an add
eight "washers" at each elbow joint to hold the coils in
place. The pipe is standard 22 mm overflow pipe which we get
in the UK. The piece of wood is 22 mm dowel. To fill the
tube, remove the dowel and pour. Obviously the end of the
dowel has to be sealed, or your liquid will soak into it!"
Jim Koehler - 11/8/99 - I have wound solenoidal sensors as
well as the toroidal ones, in fact my earliest attempts at
building a PPM used solenoidal sensors. The 60 Hz pickup is
at least an order of magnitude less (i.e., better) for the
toroids compared to the solenoids. And, with the toroids, you
don't have to worry about orientation with respect to the am-
bient field. I think it is worth the trouble of winding the
toroids - but there is no doubt that winding the toroids is a
very fiddly, exasperating, time-consuming task. [This shows a
heading from Phil but I believe that in the middle it turns
into a comment from Jim.]
Duke - 11.26/99 - Here is what I ended up doing:
8 1" 45 degree elbows glued into an octagon. They were a
little too long so I trimmed them down about 3/8" from each
side. The resulting coil was surprisingly 'toroidal'. I left
a notch in the form to make winding easier although it may
lead to a slight 'orientation' problem. There are three nice
illustrations of this on the Forum. 1. One of untrimmed sec-
tions which is the 8 elbows and 8 flats and the "diameter" of
the "circle" looks to be about 9 inches. 2. One made up of
the trimmed sections with the "diameter" about 6 inches or so.
3. One of the finished coil which clearly shows the notch
that Duke left to facilitate the winding process.
Patrick Duffy - ___________ - wrote; For those of you not on
Erich Foster's MD Forum, someone recently placed an e-mail on "How
to Make Your Own Circular Coil" using PVC.
In the past Dan Fountain and others were talking about using
PVC for toroid forms. I thought the following info might be
of interest (at least the part on forming the PVC). Obvi-
ously, some of the parts and process will not apply to our ap-
plication. Patrick
A 1/2 inch-OD PVC white plumbing tubing, will serve nicely as
a housing for the coil; and a PVC T-coupling with a 1/2-inch
PVC plumbing coupling + cement. You also need some fine sand and a
Hot Gun.
METHOD:
1. Cut a circular form in 3/4" plywood to the diameter you
want your coil.
2. Cut the PVC tube at the length desired; Tap[e] the end
with masking tape and fill it with sand completely, tap[e] the
end with another masking.
3. Heat the tube with the hot gun, slowly until you feel it
soft.
4. Mold it around the plywood form until you have a perfect
circular form.
5. Refresh the PVC coil with cold water and pull out the
sand.
6. Glue the T-coupling and make it a hole for passing the co-
axial cable (RG5
.7. Now you can assemble the turns loop wire into the tube,
making one loop at a time until all calculated turns are com-
pleted (put some grease) [what does that mean - das]; (a te-
dious work, because you must fill all the thin wire without
breakit-about 1 hour of work).
8. Glue the second part of the T-coupling for closing the
coil.
9. Pass the coaxial cable in the hole and solder the wires
coil.
10. TEST the continuity of the coil with a Multimeter before..
11. Filling the T-coupling with a silicon sealant. want the
coupling with the arm tube you can pull one cylinder of teflon
lathe work and fix it with 1/8 POP. Total working time = 3
hours and "voila" you have make your own coil, very strong,
light, WATERPROOF and you can paint it the color you like. I
have been making coils like this in 10 to 24 inch diameter
without problem.
Dan Fountain - 9/22/99 - I've been thinking about how to make
toroidal coil forms and came up with an idea using - you
guessed it! PVC pipe! Get thin wall pipe (Schedule 20 or
SDR-21) and cap both ends (to keep pressure inside and keep it
from flattening out). Heat it up to the very flexible point
(electricians use a special 10 foot long oven to heat up plas-
tic conduit for bending) and wrap it in a spiral around a
suitable diameter form. After cooling, cut it into individual
rings. Reheat these rings and take the spiral out of them,
fine tune the ends, and glue into toroids.
Dan later (10/11/99) said the above didn't work so great so he
went off to hardware store again. He then mentions 1 1/2 inch
drain traps of PVC and came up with a plan that is worth read-
ing although some elements are used later with elbows as
mentioned someplace above. Dan's will be different because
"rounder" than the elbows and of course his diameter is 1 1/2
" as opposed to the 1" elbows used above.
Couple of comments from Dale after reading and typing in all
of the above. I hope we can find the fishing net floats that
Jerry had originally mentioned. They sound ideal and Jim
Koehler said he likes them. I have a few reservations about
everything and they are as follows:
With the Fisher-Price Rock-a-Stack it seems a little bit too
soft for a klutz like me to be winding this precision coil -
but if it turns out to be the best available then I will give
it a shot. Also the Rock-a-Stack has RAISED letters that say
"FISHER-PRICE-TOYS" with the part number below and LARGE "F" and
LARGE "P" each on a cartouch above. They are only raised about a
half a millimeter or so but I am wondering if this
will introduce some distortion into the winding? I think I
can "shave" or sand them off if anyone knowledgeable thinks it
is enough to throw off a Klutz. Also the joints of the two
halves on the ID and OD are a mite rough. Maybe sand them
also.
I continue to have some degree of trepidation about the permeability
of whatever plastic is used. Let us say .01 permeability per 24
hour period. I assume this is percent. I think this means that
every 100 days we would lose one percent (1 %) of our proton liquid.
So in a thousand days I guess we would lose 10%. Would we lose
more in very hot weather - Would we lose less in very cold weather.
What happens to the plastic ring if it freezes?? Or am I just
worrying about problems that simply don't exist. One of the
problems is that permeability is different for different plastics
and I don't have any idea what type of plastic the Rock-a-Stack is.
Some of the plastic I looked at have permeability of MUCH more than
.01 per 24 hours. A couple had