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Default DIY magnetic bend brake - was "Magnabend"

I just made a 2-MOTE (MOT electromagnet) brake as an evaluation of the idea:

--------

I made it small to keep the time, effort, and materials small. But it
has an 8-1/2" capacity, which would be enough for a lot of the stuff I
do (e.g. electronics project boxes).

Unfortunately the results are very disappointing. I ran the MOTE's on
250v (AC into the bridge) and could not quite finish the bend on .040
(about 20 ga) steel. 18ga (.050) started, but only got to about 45
degrees before the clamping bar started sliding back. .030 bent very
nicely and although too light for a lot of stuff, boxes in that guage
would be useful.

So I have definitely ruled out MOTE's for the 24 inch brake that I'd
like to make. I'll be thinking about what it would take to wind the
coil for that. I expect that it would be painful, but the challenge
would be interesting.

Bob
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Default DIY magnetic bend brake - was "Magnabend"

Bob Engelhardt wrote:
I just made a 2-MOTE (MOT electromagnet) brake as an evaluation of the
idea:

--------


Oops ... that "-----" was a placeholder for the pic's URL that I forgot
to do.

http://home.comcast.net/~bobengelhardt/MOTEbrake.jpg
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Default DIY magnetic bend brake - was "Magnabend"


"Bob Engelhardt" wrote in message
...
I just made a 2-MOTE (MOT electromagnet) brake as an evaluation of the
idea:

--------

I made it small to keep the time, effort, and materials small. But it has
an 8-1/2" capacity, which would be enough for a lot of the stuff I do
(e.g. electronics project boxes).

Unfortunately the results are very disappointing. I ran the MOTE's on
250v (AC into the bridge) and could not quite finish the bend on .040
(about 20 ga) steel. 18ga (.050) started, but only got to about 45
degrees before the clamping bar started sliding back. .030 bent very
nicely and although too light for a lot of stuff, boxes in that guage
would be useful.

So I have definitely ruled out MOTE's for the 24 inch brake that I'd like
to make. I'll be thinking about what it would take to wind the coil for
that. I expect that it would be painful, but the challenge would be
interesting.

Bob


You have room to add another coil on each core. If you put the added
coil in parallel with the existing coil, I think that would double the
holding power.
That is "if you don't saturate the iron core".
I have no clue where you are an the saturation curve.
Mikek


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Default DIY magnetic bend brake - was "Magnabend"

Bob Engelhardt wrote:
I just made a 2-MOTE (MOT electromagnet) brake as an evaluation of the
idea:

--------

I made it small to keep the time, effort, and materials small. But it
has an 8-1/2" capacity, which would be enough for a lot of the stuff I
do (e.g. electronics project boxes).

Unfortunately the results are very disappointing. I ran the MOTE's on
250v (AC into the bridge) and could not quite finish the bend on .040
(about 20 ga) steel. 18ga (.050) started, but only got to about 45
degrees before the clamping bar started sliding back. .030 bent very
nicely and although too light for a lot of stuff, boxes in that guage
would be useful.

So I have definitely ruled out MOTE's for the 24 inch brake that I'd
like to make. I'll be thinking about what it would take to wind the coil
for that. I expect that it would be painful, but the challenge would be
interesting.


BRAVO Bob! I love this stuff! (And I don't often shout.)

http://home.comcast.net/~bobengelhardt/MOTEbrake.jpg

1) It did occur to me that the line between the center of your
hinge and the gap between the clamping leaf and bending leaf
appears off - center a bit, which would cause the workpiece
to be lifted unnecessarily.

See how Dave used a *piano* hinge? Kewl!
http://www.ch601.org/tools/bendbrake/brakeplans.pdf

2) Can you use a permanent magnet to be sure your MOTEs are
indeed out-of phase magnetically? (With your head *out*
of the path of the magnet, preferably!)

3) As practice for the next design, would you consider removing
both of your windings, welding both your cores together and
providing a rectangular winding that encloses both center
legs?

--Winston
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Default DIY magnetic bend brake - was "Magnabend"

Bob Engelhardt wrote:
I just made a 2-MOTE (MOT electromagnet) brake as an evaluation of
the idea:
--------

I made it small to keep the time, effort, and materials small. But it
has an 8-1/2" capacity, which would be enough for a lot of the stuff I
do (e.g. electronics project boxes).

Unfortunately the results are very disappointing. I ran the MOTE's on
250v (AC into the bridge) and could not quite finish the bend on .040
(about 20 ga) steel. 18ga (.050) started, but only got to about 45
degrees before the clamping bar started sliding back. .030 bent very
nicely and although too light for a lot of stuff, boxes in that guage
would be useful.

So I have definitely ruled out MOTE's for the 24 inch brake that I'd
like to make. I'll be thinking about what it would take to wind the
coil for that. I expect that it would be painful, but the challenge
would be interesting.


Interesting experiment. If you have any MOTs left over it might be
interesting to ignore the secondaries and hook up three of them with the
primaries in series.

Jon




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Default DIY magnetic bend brake - was "Magnabend"


"Bob Engelhardt" wrote in message
...
I just made a 2-MOTE (MOT electromagnet) brake as an evaluation of the idea:

--------

I made it small to keep the time, effort, and materials small. But it
has an 8-1/2" capacity, which would be enough for a lot of the stuff I
do (e.g. electronics project boxes).

Unfortunately the results are very disappointing. I ran the MOTE's on
250v (AC into the bridge) and could not quite finish the bend on .040
(about 20 ga) steel. 18ga (.050) started, but only got to about 45
degrees before the clamping bar started sliding back. .030 bent very
nicely and although too light for a lot of stuff, boxes in that guage
would be useful.

So I have definitely ruled out MOTE's for the 24 inch brake that I'd
like to make. I'll be thinking about what it would take to wind the
coil for that. I expect that it would be painful, but the challenge
would be interesting.

Bob


Very nice Bob.
An observation & comments.
The bar you have welded to the front (hinge side) legs of the MOTs
will short out a lot of the flux if the MOTs are wired out of phase.
This is happening right where the most flux is needed to effectively
clamp the work piece. The steel angle piece the MOTs are sitting on
will also short flux. Fixing that is trivial - wire them in phase.

Is your top clamping bar too thin? A thin bar will saturate and not
provide the full force the MOTs are capable of delivering.

Adding a block of steel between the center legs and another across
the back legs will distribute the external flux more evenly across the
unit. This will provide better hold down force especially with a
saturating top bar. Don't add any steel which narrows the gap between
the center and outer legs of the MOT as this will reduce the external
flux available.
Art



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Default DIY magnetic bend brake - was "Magnabend"

Rich Grise wrote:
mike wrote:
On Feb 12, 12:43?pm, Bob Engelhardt wrote:


I just made a 2-MOTE (MOT electromagnet) brake as an evaluation of the

,,,
Cool, the way you just go ahead and make things is inspiring.

Looking at the picture, I was surprised that one end was left open on
the electro-magnets,
I thought you'd need it 'capped' to concentrate the flux, but it's
been along time since I
studied that kind of stuff in school.


A "cap" would "short out" the magnetic field - the workpiece itself
completes the "magnetic circuit."

Cheers!
Rich


there's no way a piece of 20 guage sheet steel will complete the magnetic
circuit. If the work was 3/4" thick tranformer iron, like the missing I's
off the E cores, that would be perfect, and the clamping force would be as
good as it gets for transformer cores.

A keeper plate over the work would help too with getting the most clamping
force when using something like transformer cores in a lifting/holding
type application.
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Default DIY magnetic bend brake - was "Magnabend"

Bob Engelhardt wrote:
Bob Engelhardt wrote:
I just made a 2-MOTE (MOT electromagnet) brake as an evaluation of the
idea:

--------


Oops ... that "-----" was a placeholder for the pic's URL that I forgot
to do.

http://home.comcast.net/~bobengelhardt/MOTEbrake.jpg

Well it looks like you have room for about twice as many turns on the
coils so you should be in petty good shape if you fill the winding
space.
...lew...
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Default DIY magnetic bend brake - was "Magnabend"

On Sat, 12 Feb 2011 13:52:48 -0800, "Artemus"
wrote:


"Bob Engelhardt" wrote in message
...
I just made a 2-MOTE (MOT electromagnet) brake as an evaluation of the idea:

--------

I made it small to keep the time, effort, and materials small. But it
has an 8-1/2" capacity, which would be enough for a lot of the stuff I
do (e.g. electronics project boxes).

Unfortunately the results are very disappointing. I ran the MOTE's on
250v (AC into the bridge) and could not quite finish the bend on .040
(about 20 ga) steel. 18ga (.050) started, but only got to about 45
degrees before the clamping bar started sliding back. .030 bent very
nicely and although too light for a lot of stuff, boxes in that guage
would be useful.

So I have definitely ruled out MOTE's for the 24 inch brake that I'd
like to make. I'll be thinking about what it would take to wind the
coil for that. I expect that it would be painful, but the challenge
would be interesting.

Bob


Very nice Bob.
An observation & comments.
The bar you have welded to the front (hinge side) legs of the MOTs
will short out a lot of the flux if the MOTs are wired out of phase.
This is happening right where the most flux is needed to effectively
clamp the work piece. The steel angle piece the MOTs are sitting on
will also short flux. Fixing that is trivial - wire them in phase.

Is your top clamping bar too thin? A thin bar will saturate and not
provide the full force the MOTs are capable of delivering.

Adding a block of steel between the center legs and another across
the back legs will distribute the external flux more evenly across the
unit. This will provide better hold down force especially with a
saturating top bar. Don't add any steel which narrows the gap between
the center and outer legs of the MOT as this will reduce the external
flux available.
Art


A workmanlike effort - I'm surprised that it's not satisfactory.
A few possible thoughts

You've welded the Es to the fixed bar. As Art has pointed out
it's essential that these are both N (or both S) Poles. The weld
also needs to be machined dead flat - even a few thou gap reduces
the holding force.

You haven't shown the keeper bar that needs to be placed over the
workpiece. This again needs to be flat and at least as thick as
the outer arm of the E.

With the two old primaries parallel connected and fed from a
bridge rectifier The DC component of the rectified AC will be the
MEAN value of the supply voltage i.e. 0.9 x RMS value.
About 1000uf across the primaries will raise it to near the
supply voltage peak value - about 1.4 x RMS.

As a final desperate move feed the primaries from a voltage
doubler.

Leave the rectifier + and - outputs connnected to the windings.

Link the two rectifier AC inputs together.

Connect the + side of a 1000uf electrolytic to the two joined AC
inputs.

Connect one side of the supply to the minus end of the winding

Connect the other side of the supply to the minus side of the
capacitor.

This should give you close to 1.8 x RMS supply voltage

A further 1000uF connrcted across the winding would raise this to
near 2.8 x RMS supply voltage.

good luck!

Jim
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Default DIY magnetic bend brake - was "Magnabend"

On Sun, 13 Feb 2011 08:23:37 -0700, Lewis Hartswick
wrote:

Bob Engelhardt wrote:
Bob Engelhardt wrote:
I just made a 2-MOTE (MOT electromagnet) brake as an evaluation of the
idea:

--------


Oops ... that "-----" was a placeholder for the pic's URL that I forgot
to do.

http://home.comcast.net/~bobengelhardt/MOTEbrake.jpg

Well it looks like you have room for about twice as many turns on the
coils so you should be in petty good shape if you fill the winding
space.
...lew...




The primary winding of an MOT occupies less than half the window
space so the easy solution is to simply install two ex MOT
primaries on each E core.
With all primaries parallel connected this doubles the ampere
turns which will make a substantial difference


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Default DIY magnetic bend brake - was "Magnabend"

Lewis Hartswick wrote:

Well it looks like you have room for about twice as many turns on the
coils so you should be in petty good shape if you fill the winding
space.
...lew...


That's a good idea! I have a bunch of MOT's - I might have another 2
with coils that fit. Or not - in the past I've had trouble
cross-fitting them to make an isolation transformer. I'll look.

Thanks,
Bob
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Default DIY magnetic bend brake - was "Magnabend"

amdx wrote:
You have room to add another coil on each core. ...
That is "if you don't saturate the iron core".
I have no clue where you are an the saturation curve.


Right ... I don't either. Now that I have my scope working again, I
should look into it (I had forgotten what I got my scope out for & this
was it).

But consider this: assume that in normal use, the xformer runs near
saturation (otherwise there is "wasted" iron in the core). Which means
that normal current in the primary saturates. At 1.5kw & 120v the
primary current would be 12A, more or less. Or .75A in the secondary
(2000:120 turns ratio). I don't remember exactly, but I'm pretty sure
that as a MOTE, I'm running it higher than that.

Bob
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Default DIY magnetic bend brake - was "Magnabend"

Winston wrote:
....

1) It did occur to me that the line between the center of your
hinge and the gap between the clamping leaf and bending leaf
appears off - center a bit, which would cause the workpiece
to be lifted unnecessarily.


Good catch. I went to great effort to make the hinge axis on the bend
line, but didn't get it quite right.

Nevertheless, the clamp resists lifting well enough and fails when the
bending force starts pushing horizontally more (after 45 degrees).

See how Dave used a *piano* hinge? Kewl!
http://www.ch601.org/tools/bendbrake/brakeplans.pdf


That is a nice solution for his problem, but not very extensible.
First, a piano hinge is WAY too weak for any non-trivial bending. Also,
it puts the hinge axis below the bend line, which might not be too bad -
I'll have to think about it. That would leave the ends open, like the
MagnaBend does.

2) Can you use a permanent magnet to be sure your MOTEs are
indeed out-of phase magnetically? (With your head *out*
of the path of the magnet, preferably!)


Yep, but I want them to be in-phase, to avoid the magnetic shorting that
later posts point out.

3) As practice for the next design, would you consider removing
both of your windings, welding both your cores together and
providing a rectangular winding that encloses both center
legs?


Well then I'd have to wind a coil. I'd really rather avoid that.

Thanks,
Bob




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Default DIY magnetic bend brake - was "Magnabend"

Bob Engelhardt wrote:
Oh ... of course!! The removed I's! Why didn't I think of that?!
Somebody give me a dope smack.


Oh, wait ... that won't work: they won't cover the space between the
cores. The to-be-bent material needs to be clamped continuously.

Bob
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Default DIY magnetic bend brake - was "Magnabend"

Bob Engelhardt wrote:
Winston wrote:
...

1) It did occur to me that the line between the center of your
hinge and the gap between the clamping leaf and bending leaf
appears off - center a bit, which would cause the workpiece
to be lifted unnecessarily.


Good catch. I went to great effort to make the hinge axis on the bend
line, but didn't get it quite right.

Nevertheless, the clamp resists lifting well enough and fails when the
bending force starts pushing horizontally more (after 45 degrees).


I can envision that, now that you mention it,
given the axial discrepancy.

See how Dave used a *piano* hinge? Kewl!
http://www.ch601.org/tools/bendbrake/brakeplans.pdf


That is a nice solution for his problem, but not very extensible. First,
a piano hinge is WAY too weak for any non-trivial bending.


One could always stack regular door hinges side by side, too.
*That* is extensible! *And there is prior art*.

Also, it puts
the hinge axis below the bend line, which might not be too bad - I'll
have to think about it. That would leave the ends open, like the
MagnaBend does.


Interesting, wot? Boring to look at, but very effective.

2) Can you use a permanent magnet to be sure your MOTEs are
indeed out-of phase magnetically? (With your head *out*
of the path of the magnet, preferably!)


Yep, but I want them to be in-phase, to avoid the magnetic shorting that
later posts point out.


Experiment time!

Take two button magnets and place them flat on a table.
bring them together *edge on* so that they are 180 degrees
out of phase magnetically. (That is, flip one over if they do
not attract each other initially). You now have two button
magnets snapped together side - by - side and they are
magnetically 'shorted out' right? North to South and South
to North. Bring a piece of steel down on the magnets
axially. What happens? If their fields are really 'shorted
out' then nothing happens, right?

It's not as if both magnets fly up to the steel or anything.



Now repeat the experiment with the magnets *in phase*.

(When I do this, only *one* magnet flies up to the steel
and the other magnet is *repelled* by the combination!)

'Like' poles repel. Opposites attract.

3) As practice for the next design, would you consider removing
both of your windings, welding both your cores together and
providing a rectangular winding that encloses both center
legs?


Well then I'd have to wind a coil. I'd really rather avoid that.


It is a lot less time and bother than you imagine.
I envision a jig cut from scrap lumber using a scrap 1/2"
machine bolt as an axle. A plywood base aligns the
axis of your 'winding crank' with your spool of magnet
wire. A few hundred turns goes more quickly than you
might think. A lot of inspirational work is
available on Youtube.

--Winston


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Default DIY magnetic bend brake - was "Magnabend" - - - Update

Bob Engelhardt wrote:
I just made a 2-MOTE (MOT electromagnet) brake ...


I checked the phasing of the MOTE's & they were indeed out-of-phase,
meaning that there was some flux shorting through the brake's structure.

I put them in phase and tried bending some test pieces. There was a
distinct improvement: it will now bend 20 ga (.040 +-), where it would
only do .030 before.

That's good news and bad news. The good news is obvious, the bad news
is now I'm uncertain what to do. Before, I had ruled out using MOTE's -
now, I don't know. MOTE's would be easier and faster than winding my
own electromagnet in the style of the Magnabend, but just barely strong
enough.

The other thing I did was look into doubling up the windings by adding a
winding from another MOT. The problem is that other windings either
don't fit at all, or just fit. The just-fit ones are really too tight
to use without damaging them. This is 30 ga wire.

Bob
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Default DIY magnetic bend brake - was "Magnabend" - - - Update

On Sun, 20 Feb 2011 17:20:54 -0500, Bob Engelhardt
wrote:

Bob Engelhardt wrote:
I just made a 2-MOTE (MOT electromagnet) brake ...


I checked the phasing of the MOTE's & they were indeed out-of-phase,
meaning that there was some flux shorting through the brake's structure.

I put them in phase and tried bending some test pieces. There was a
distinct improvement: it will now bend 20 ga (.040 +-), where it would
only do .030 before.

That's good news and bad news. The good news is obvious, the bad news
is now I'm uncertain what to do. Before, I had ruled out using MOTE's -
now, I don't know. MOTE's would be easier and faster than winding my
own electromagnet in the style of the Magnabend, but just barely strong
enough.

The other thing I did was look into doubling up the windings by adding a
winding from another MOT. The problem is that other windings either
don't fit at all, or just fit. The just-fit ones are really too tight
to use without damaging them. This is 30 ga wire.

Bob


Have you tried adding a big capacitor to boost the rectified
volts a bit?
Jim

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Default DIY magnetic bend brake - was "Magnabend" - - - Update

On Sun, 20 Feb 2011 17:20:54 -0500, Bob Engelhardt
wrote:

Bob Engelhardt wrote:
I just made a 2-MOTE (MOT electromagnet) brake ...


I checked the phasing of the MOTE's & they were indeed out-of-phase,
meaning that there was some flux shorting through the brake's structure.

I put them in phase and tried bending some test pieces. There was a
distinct improvement: it will now bend 20 ga (.040 +-), where it would
only do .030 before.

That's good news and bad news. The good news is obvious, the bad news
is now I'm uncertain what to do. Before, I had ruled out using MOTE's -
now, I don't know. MOTE's would be easier and faster than winding my
own electromagnet in the style of the Magnabend, but just barely strong
enough.

The other thing I did was look into doubling up the windings by adding a
winding from another MOT. The problem is that other windings either
don't fit at all, or just fit. The just-fit ones are really too tight
to use without damaging them. This is 30 ga wire.


Can you round the edges of the laminations to ease the fit and prevent
shorts?

--
The more passions and desires one has,
the more ways one has of being happy.
-- Charlotte-Catherine
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Default DIY magnetic bend brake - was "Magnabend" - - - Update

In article ,
Bob Engelhardt wrote:

Bob Engelhardt wrote:
I just made a 2-MOTE (MOT electromagnet) brake ...


I checked the phasing of the MOTE's & they were indeed out-of-phase,
meaning that there was some flux shorting through the brake's structure.

I put them in phase and tried bending some test pieces. There was a
distinct improvement: it will now bend 20 ga (.040 +-), where it would
only do .030 before.

That's good news and bad news. The good news is obvious, the bad news
is now I'm uncertain what to do. Before, I had ruled out using MOTE's -
now, I don't know. MOTE's would be easier and faster than winding my
own electromagnet in the style of the Magnabend, but just barely strong
enough.

The other thing I did was look into doubling up the windings by adding a
winding from another MOT. The problem is that other windings either
don't fit at all, or just fit. The just-fit ones are really too tight
to use without damaging them. This is 30 ga wire.


The MagnaBend 650E (24" wide) draws 4 amps at 220/240 volts, call it 230
volts AC, which is 4*230= 920 watts. One can simplify the winding task
by using a stepdown transformer, if one can come by such a big
transformer cheaply enough.

I suppose that a MOT or a pair of MOTs would do, a task similar to
making a spot welder from MOTs.

The general approach would be to remove the MOT secondary winding, and
replace it with a new secondary having a reasonable number turns and
feeding a fullwave rectifier which in turn feeds a big filter capacitor
and the MagnaBend flux coil. The main limit on how few turns the
secondary can be is that the voltage has to be high enough the one does
not have excessive losses due to the forward voltage drop in the
rectifiers, at least 12 volts or so.

So there - we found a way to use MOTs.

We also need to find out the needed number of ampere turns. Probably
the easiest approach (aside from being told the answer by the inventors)
is to figure out the ampere-turn product to just saturate a mild (1018)
steel magnetic path of the dimensions given in the users guide.

Length is 630 mm. Cross section is EI, apparently (to my eye) with
standard transformer-lamination proportions. The center leg is 30mm
wide. The magnetic pathlength (computed from the cross-section drawing)
is 160mm. Needed are the magnetic properties of 1018 steel, which is
known. Anyway, this is enough to figure out the maximum possible
ampere-turns needed.

But it will probably turn out that keeping the coil from melting
prevents us from going quite that far. The MagnaBend duty cycle is 30%
maximum, and the built-in thermal cutout trips at 70 C.

The surface area (not including the clamping bar) is 2(98+45)*630=
286+630 mm^2= 279.3 square inches, call it 280 square inches, so the
power loading is 920/280=3.28 watts per square inch. The rule of thumb
for air cooling is 0.008 watts per square inch per degree centigrade
http://www.vias.org/eltransformers/l...mers_03_11.htm
l, we get (0.008)(105-25)(280)= 179 watts can be dissipated in
continuous duty, or one fifth of the actual dissipation. The flaw in
the calculation is that the transformer rule-of-thumb assumes a
spherical object, a reasonable approximation for a transformer, but the
Magnabend is instead long and thin. Some empiricism may be in order.

Potting the winding in situ may also be useful in getting the heat out
of the copper and into the steel, thus reducing the core temperature.

But we need to insulate the coil from the iron to withstand something
like 1000 Volts AC, for safety.

Is there a power tranformer and/or motor designer in the house?


Joe Gwinn
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Default DIY magnetic bend brake - was "Magnabend" - - - Update

Larry Jaques wrote:
Bob Engelhardt wrote:

....
The other thing I did was look into doubling up the windings by adding a
winding from another MOT. The problem is that other windings either
don't fit at all, or just fit. The just-fit ones are really too tight
to use without damaging them. This is 30 ga wire.



Can you round the edges of the laminations to ease the fit and prevent
shorts?


That's a good idea, I'll try it. And I was wrong - this is 26ga wire -
still thin, but not 30ga thin.

Bob


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Default DIY magnetic bend brake - was "Magnabend" - - - Update

Please help me to build electromagnetic bending machine
Please your what'sapp number to contact u easily
Mine is +919028710886
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