Greetings to all the microwave oven scroungers,
I have a job coming up that requires soldering the corners of brass
frames. These frames are made of 1 1/2 x 1 1/2 x 1/4 brass angle. In
the past I've used a torch to heat the brass. This leads to a little
distortion. This can be troublesome because the brass expands so much
that it moves the joint even though everything is clamped. The parts
must then be straightened when cool. Because of the application and
fit the frames must be straight within .010" in 36". I saw some
resistance soldering units in a catalog and the description of how
they operate says that only a small area is heated and gets to heat
fast. This would be ideal. However, the ones I saw were too small and
the price too large for me. But I've got several microwave
transformers and they seem like they might be perfect. A rough
calculation from the specs and pictures given in the catalog leads me
to believe that they output about 12 volts open circuit. Some have
variable outputs. So I have a few questions:
1) Does 12 volts sound reasonable? Would a different voltage be
better?
2) Is DC better than AC? Does it matter?
3)What would be good ways to limit the current? Would a lamp dimmer on
the input side of the xmfr work? Wouldn't that also lower the voltage?
Would that matter?
4) I have a timer that pulses a relay on and off. I can set the length
of the pulses. Sort of what a lamp dimmer does but much longer pulses
(1 second and up) and the voltage would be the same out as in. But the
brass would average the heating. Would this work almost as well as
lowering the current? Better?
Any other input is much appreciated.
Thank You,
Eric R Snow,
E T Precision Machine

On Tue, 13 Jul 2004 18:02:35 -0700, Eric R Snow
wrote:

Greetings to all the microwave oven scroungers,
I have a job coming up that requires soldering the corners of brass
frames. These frames are made of 1 1/2 x 1 1/2 x 1/4 brass angle. In
the past I've used a torch to heat the brass. This leads to a little
distortion. This can be troublesome because the brass expands so much
that it moves the joint even though everything is clamped. The parts
must then be straightened when cool. Because of the application and
fit the frames must be straight within .010" in 36". I saw some
resistance soldering units in a catalog and the description of how
they operate says that only a small area is heated and gets to heat
fast. This would be ideal. However, the ones I saw were too small and
the price too large for me. But I've got several microwave
transformers and they seem like they might be perfect. A rough
calculation from the specs and pictures given in the catalog leads me
to believe that they output about 12 volts open circuit. Some have
variable outputs. So I have a few questions:
1) Does 12 volts sound reasonable? Would a different voltage be
better?
2) Is DC better than AC? Does it matter?
3)What would be good ways to limit the current? Would a lamp dimmer on
the input side of the xmfr work? Wouldn't that also lower the voltage?
Would that matter?
4) I have a timer that pulses a relay on and off. I can set the length
of the pulses. Sort of what a lamp dimmer does but much longer pulses
(1 second and up) and the voltage would be the same out as in. But the
brass would average the heating. Would this work almost as well as
lowering the current? Better?
Any other input is much appreciated.
Thank You,
Eric R Snow,
E T Precision Machine


How are you planning to connect the transformer to get 12 volts? Put
power to the high voltage secondary?

If you put power to the normal primary you get 10s of thousands of
volts at relatively low current. Only way to use a microwave
transformer for resistance soldering is to remove the HV secondary and
install a very husky secondary of several windings - to give you a
couple volts at very high current.

AC or DC is not important and a"motor duty" dimmer can be used to
control output. A variac works better.

on Tuesday 13 July 2004 06:02 pm, Eric R Snow wrote:

Greetings to all the microwave oven scroungers,
I have a job coming up that requires soldering the corners of brass
frames. These frames are made of 1 1/2 x 1 1/2 x 1/4 brass angle. In
the past I've used a torch to heat the brass. This leads to a little
distortion. This can be troublesome because the brass expands so much
that it moves the joint even though everything is clamped. The parts
must then be straightened when cool. Because of the application and
fit the frames must be straight within .010" in 36".

All you need is to work on your torch technique. Try preheating.
There's a NG - news:sci.engr.joining.welding where they discuss this
sort of thing. And don't use OA - use propane/air. (i.e. Bernz-O-
Matic o.e.)

I've seen spot welders (well, web pages with them) that used a
microwave transformer, and they replaced the secondary with
enough turns of wire to get 4V. That sounds like a good starting
ballpark. Use #2 or #4 weld cable, and big copper electrodes.

A simple timed on-off switch should work, like a 555 one-shot,
tranny, and relay (or SSR). You control the heat by on-time.
You might even be able to use the SSR out of the microwave
itself. :-)
--
Have Fun!
Rich

On Wed, 14 Jul 2004 02:01:46 GMT, wrote:

On Tue, 13 Jul 2004 18:02:35 -0700, Eric R Snow
wrote:

Greetings to all the microwave oven scroungers,
I have a job coming up that requires soldering the corners of brass
frames. These frames are made of 1 1/2 x 1 1/2 x 1/4 brass angle. In
the past I've used a torch to heat the brass. This leads to a little
distortion. This can be troublesome because the brass expands so much
that it moves the joint even though everything is clamped. The parts
must then be straightened when cool. Because of the application and
fit the frames must be straight within .010" in 36". I saw some
resistance soldering units in a catalog and the description of how
they operate says that only a small area is heated and gets to heat
fast. This would be ideal. However, the ones I saw were too small and
the price too large for me. But I've got several microwave
transformers and they seem like they might be perfect. A rough
calculation from the specs and pictures given in the catalog leads me
to believe that they output about 12 volts open circuit. Some have
variable outputs. So I have a few questions:
1) Does 12 volts sound reasonable? Would a different voltage be
better?
2) Is DC better than AC? Does it matter?
3)What would be good ways to limit the current? Would a lamp dimmer on
the input side of the xmfr work? Wouldn't that also lower the voltage?
Would that matter?
4) I have a timer that pulses a relay on and off. I can set the length
of the pulses. Sort of what a lamp dimmer does but much longer pulses
(1 second and up) and the voltage would be the same out as in. But the
brass would average the heating. Would this work almost as well as
lowering the current? Better?
Any other input is much appreciated.
Thank You,
Eric R Snow,
E T Precision Machine


How are you planning to connect the transformer to get 12 volts? Put
power to the high voltage secondary?

If you put power to the normal primary you get 10s of thousands of
volts at relatively low current. Only way to use a microwave
transformer for resistance soldering is to remove the HV secondary and
install a very husky secondary of several windings - to give you a
couple volts at very high current.

AC or DC is not important and a"motor duty" dimmer can be used to
control output. A variac works better.
I will remove the secondary and wind my own. I have done this to make
a spot welder. It works well.
ERS

On Wed, 14 Jul 2004 03:37:17 GMT, Rich Grise wrote:

on Tuesday 13 July 2004 06:02 pm, Eric R Snow wrote:

Greetings to all the microwave oven scroungers,
I have a job coming up that requires soldering the corners of brass
frames. These frames are made of 1 1/2 x 1 1/2 x 1/4 brass angle. In
the past I've used a torch to heat the brass. This leads to a little
distortion. This can be troublesome because the brass expands so much
that it moves the joint even though everything is clamped. The parts
must then be straightened when cool. Because of the application and
fit the frames must be straight within .010" in 36".

All you need is to work on your torch technique. Try preheating.
There's a NG - news:sci.engr.joining.welding where they discuss this
sort of thing. And don't use OA - use propane/air. (i.e. Bernz-O-
Matic o.e.)

I've seen spot welders (well, web pages with them) that used a
microwave transformer, and they replaced the secondary with
enough turns of wire to get 4V. That sounds like a good starting
ballpark. Use #2 or #4 weld cable, and big copper electrodes.

A simple timed on-off switch should work, like a 555 one-shot,
tranny, and relay (or SSR). You control the heat by on-time.
You might even be able to use the SSR out of the microwave
itself. :-)
My technique is not the problem. Even preheating the whole frame does
not solve the problem. I'm good at this. Had lots of practice. It's
because of the really close straightness tolerance.
ERS

I dunno much about the specific outputs/capacity of the resistance soldering
units, but I'll throw a few observations into the thread.
The units that I've seen in use in a starter/generator repair shop were
fairly compact units with a transformer housing of about a 6" cube. The
plier/tweezer-style handpiece appeared to have carbon jaws that made the
contact to the joint to be soldered. The heat was rapid, and they used heavy
gauge solder, 1/8" maybe.

Some butt welding machines that I used to repair were used to weld ends of
heavy steel wire together (similar to a bandsaw blade welder). The sizes
ranged up to about 1/4" diameter.
The secondary of the transformer was only a couple of turns of flat braided
cable securely clamped at the ends. The cable was the type that was used as
engine ground strap in autos decades ago. This stuff would be good for using
as a secondary winding in a modified transformer, easy to thread thru the
frame aand flat for fitting into a square shape.
For insulation, a good product would be fiberglas tape.. thin, high temp
resistant and an effective barrier/insulator.

WB
..................

"Eric R Snow" wrote in message
...
Greetings to all the microwave oven scroungers,
I have a job coming up that requires soldering the corners of brass
frames. These frames are made of 1 1/2 x 1 1/2 x 1/4 brass angle. In
the past I've used a torch to heat the brass. This leads to a little
distortion. This can be troublesome because the brass expands so much
that it moves the joint even though everything is clamped. The parts
must then be straightened when cool. Because of the application and
fit the frames must be straight within .010" in 36". I saw some
resistance soldering units in a catalog and the description of how
they operate says that only a small area is heated and gets to heat
fast. This would be ideal. However, the ones I saw were too small and
the price too large for me. But I've got several microwave
transformers and they seem like they might be perfect. A rough
calculation from the specs and pictures given in the catalog leads me
to believe that they output about 12 volts open circuit. Some have
variable outputs. So I have a few questions:
1) Does 12 volts sound reasonable? Would a different voltage be
better?
2) Is DC better than AC? Does it matter?
3)What would be good ways to limit the current? Would a lamp dimmer on
the input side of the xmfr work? Wouldn't that also lower the voltage?
Would that matter?
4) I have a timer that pulses a relay on and off. I can set the length
of the pulses. Sort of what a lamp dimmer does but much longer pulses
(1 second and up) and the voltage would be the same out as in. But the
brass would average the heating. Would this work almost as well as
lowering the current? Better?
Any other input is much appreciated.
Thank You,
Eric R Snow,
E T Precision Machine

Eric, I had a simillar idea a few months back when I needed a spot
welder. The main thing with using a microwave xformer based welder
is the power output, the "big" xformers are rated for around 1500 VAs.
That's O.K. for spot welding thin sheet metal & thats what the plans
available on the web seem to be aimed at, such as

http://www.5bears.com/welder.htm


1/4" brass is probably more than a single transformer home built will
handle. As a comparison, commercial units rated for spot welding
3/16" steel are rated around 2500 VAs w/ a 250 V primary. I ended up
buying a unit off of Ebay, they seem to go for about $70. Thats
probably a lot cheaper & certainly quicker than trying to roll my own.

If you're trying to butt weld the brass as I suspect then I really
have no idea how much juice you'll need but you're certainly talking
about a lot more than you'll get from a m/w trans. or the 70 bucks on
Ebay.

Howard.

On Tue, 13 Jul 2004 18:02:35 -0700, Eric R Snow
wrote:

Greetings to all the microwave oven scroungers,
I have a job coming up that requires soldering the corners of brass
frames. These frames are made of 1 1/2 x 1 1/2 x 1/4 brass angle. In
the past I've used a torch to heat the brass. This leads to a little
distortion. This can be troublesome because the brass expands so much
that it moves the joint even though everything is clamped. The parts
must then be straightened when cool. Because of the application and
fit the frames must be straight within .010" in 36". I saw some
resistance soldering units in a catalog and the description of how
they operate says that only a small area is heated and gets to heat
fast. This would be ideal. However, the ones I saw were too small and
the price too large for me. But I've got several microwave
transformers and they seem like they might be perfect. A rough
calculation from the specs and pictures given in the catalog leads me
to believe that they output about 12 volts open circuit. Some have
variable outputs. So I have a few questions:
1) Does 12 volts sound reasonable? Would a different voltage be
better?
2) Is DC better than AC? Does it matter?
3)What would be good ways to limit the current? Would a lamp dimmer on
the input side of the xmfr work? Wouldn't that also lower the voltage?
Would that matter?
4) I have a timer that pulses a relay on and off. I can set the length
of the pulses. Sort of what a lamp dimmer does but much longer pulses
(1 second and up) and the voltage would be the same out as in. But the
brass would average the heating. Would this work almost as well as
lowering the current? Better?
Any other input is much appreciated.
Thank You,
Eric R Snow,
E T Precision Machine

1. I suspect 12 volts is a bit high. 2. AC ought to be as good as DC.
3. Use fewer turns on the secondary. 4 Set the length of the pulse
so one pulse is the right amount of heat. 5. Use very heavy wire. 6
gauge or bigger. Might be easier to wind three or more #10 wires in
parallel.

Dan


Eric R Snow wrote in message

1) Does 12 volts sound reasonable? Would a different voltage be
better?
2) Is DC better than AC? Does it matter?
3)What would be good ways to limit the current? Would a lamp dimmer on
the input side of the xmfr work? Wouldn't that also lower the voltage?
Would that matter?
4) I have a timer that pulses a relay on and off. I can set the length
of the pulses. Sort of what a lamp dimmer does but much longer pulses
(1 second and up) and the voltage would be the same out as in. But the
brass would average the heating. Would this work almost as well as
lowering the current? Better?
Any other input is much appreciated.
Thank You,
Eric R Snow,
E T Precision Machine

resistance solder units that I have output between 1 and 2.5 V

"Wild Bill" wrote in message
...
I dunno much about the specific outputs/capacity of the resistance
soldering
units, but I'll throw a few observations into the thread.
The units that I've seen in use in a starter/generator repair shop were
fairly compact units with a transformer housing of about a 6" cube. The
plier/tweezer-style handpiece appeared to have carbon jaws that made the
contact to the joint to be soldered. The heat was rapid, and they used
heavy
gauge solder, 1/8" maybe.

Some butt welding machines that I used to repair were used to weld ends of
heavy steel wire together (similar to a bandsaw blade welder). The sizes
ranged up to about 1/4" diameter.
The secondary of the transformer was only a couple of turns of flat
braided
cable securely clamped at the ends. The cable was the type that was used
as
engine ground strap in autos decades ago. This stuff would be good for
using
as a secondary winding in a modified transformer, easy to thread thru the
frame aand flat for fitting into a square shape.
For insulation, a good product would be fiberglas tape.. thin, high temp
resistant and an effective barrier/insulator.

WB
.................

"Eric R Snow" wrote in message
...
Greetings to all the microwave oven scroungers,
I have a job coming up that requires soldering the corners of brass
frames. These frames are made of 1 1/2 x 1 1/2 x 1/4 brass angle. In
the past I've used a torch to heat the brass. This leads to a little
distortion. This can be troublesome because the brass expands so much
that it moves the joint even though everything is clamped. The parts
must then be straightened when cool. Because of the application and
fit the frames must be straight within .010" in 36". I saw some
resistance soldering units in a catalog and the description of how
they operate says that only a small area is heated and gets to heat
fast. This would be ideal. However, the ones I saw were too small and
the price too large for me. But I've got several microwave
transformers and they seem like they might be perfect. A rough
calculation from the specs and pictures given in the catalog leads me
to believe that they output about 12 volts open circuit. Some have
variable outputs. So I have a few questions:
1) Does 12 volts sound reasonable? Would a different voltage be
better?
2) Is DC better than AC? Does it matter?
3)What would be good ways to limit the current? Would a lamp dimmer on
the input side of the xmfr work? Wouldn't that also lower the voltage?
Would that matter?
4) I have a timer that pulses a relay on and off. I can set the length
of the pulses. Sort of what a lamp dimmer does but much longer pulses
(1 second and up) and the voltage would be the same out as in. But the
brass would average the heating. Would this work almost as well as
lowering the current? Better?
Any other input is much appreciated.
Thank You,
Eric R Snow,
E T Precision Machine

On Wed, 14 Jul 2004 22:14:16 -0700, "william_b_noble"
wrote:

resistance solder units that I have output between 1 and 2.5 V

"Wild Bill" wrote in message
...
I dunno much about the specific outputs/capacity of the resistance
soldering
units, but I'll throw a few observations into the thread.
The units that I've seen in use in a starter/generator repair shop were
fairly compact units with a transformer housing of about a 6" cube. The
plier/tweezer-style handpiece appeared to have carbon jaws that made the
contact to the joint to be soldered. The heat was rapid, and they used
heavy
gauge solder, 1/8" maybe.

Some butt welding machines that I used to repair were used to weld ends of
heavy steel wire together (similar to a bandsaw blade welder). The sizes
ranged up to about 1/4" diameter.
The secondary of the transformer was only a couple of turns of flat
braided
cable securely clamped at the ends. The cable was the type that was used
as
engine ground strap in autos decades ago. This stuff would be good for
using
as a secondary winding in a modified transformer, easy to thread thru the
frame aand flat for fitting into a square shape.
For insulation, a good product would be fiberglas tape.. thin, high temp
resistant and an effective barrier/insulator.

WB
.................

"Eric R Snow" wrote in message
...
Greetings to all the microwave oven scroungers,
I have a job coming up that requires soldering the corners of brass
frames. These frames are made of 1 1/2 x 1 1/2 x 1/4 brass angle. In
the past I've used a torch to heat the brass. This leads to a little
distortion. This can be troublesome because the brass expands so much
that it moves the joint even though everything is clamped. The parts
must then be straightened when cool. Because of the application and
fit the frames must be straight within .010" in 36". I saw some
resistance soldering units in a catalog and the description of how
they operate says that only a small area is heated and gets to heat
fast. This would be ideal. However, the ones I saw were too small and
the price too large for me. But I've got several microwave
transformers and they seem like they might be perfect. A rough
calculation from the specs and pictures given in the catalog leads me
to believe that they output about 12 volts open circuit. Some have
variable outputs. So I have a few questions:
1) Does 12 volts sound reasonable? Would a different voltage be
better?
2) Is DC better than AC? Does it matter?
3)What would be good ways to limit the current? Would a lamp dimmer on
the input side of the xmfr work? Wouldn't that also lower the voltage?
Would that matter?
4) I have a timer that pulses a relay on and off. I can set the length
of the pulses. Sort of what a lamp dimmer does but much longer pulses
(1 second and up) and the voltage would be the same out as in. But the
brass would average the heating. Would this work almost as well as
lowering the current? Better?
Any other input is much appreciated.
Thank You,
Eric R Snow,
E T Precision Machine



Thank You. That's just what I was looking for.
ERS

Required voltage depends on whether the heat is produced by the
resistance of the workpiece (brass) or by the contact which might be
copper, SS, tungsten, or even carbon.

I have a Wassco Glo-Melt resistance soldering unit model 105-B2, 500
watts. It's output is variable in steps from 1.0 to 5.8 volts AC.

A microwave transformer's capacity will depend on the power rating of
the microwave from which it came. They vary from 600 watts to 1200
watts. I don't know if that power rating is input to or output from
the magnetron. A given sized core can only handle so many VA at
given frequency (60 Hz), but I'd think a few experiments with such a
trannie and your own lowvoltage secondary would have you knowing a
good deal more than the "experts", at least about your particular
application!

I'd wind a one-turn secondary and measure that voltage as a reference
point for volts per turn. Secondary material is up to the guy winding
it, and if you built a spot welder than you know the drill.

I'd then experiment with electrode material and configuration. That
may affect your results as much as available power.



On Tue, 13 Jul 2004 18:02:35 -0700, Eric R Snow
wrote:

Greetings to all the microwave oven scroungers,
I have a job coming up that requires soldering the corners of brass
frames. These frames are made of 1 1/2 x 1 1/2 x 1/4 brass angle. In
the past I've used a torch to heat the brass. This leads to a little
distortion. This can be troublesome because the brass expands so much
that it moves the joint even though everything is clamped. The parts
must then be straightened when cool. Because of the application and
fit the frames must be straight within .010" in 36". I saw some
resistance soldering units in a catalog and the description of how
they operate says that only a small area is heated and gets to heat
fast. This would be ideal. However, the ones I saw were too small and
the price too large for me. But I've got several microwave
transformers and they seem like they might be perfect. A rough
calculation from the specs and pictures given in the catalog leads me
to believe that they output about 12 volts open circuit. Some have
variable outputs. So I have a few questions:
1) Does 12 volts sound reasonable? Would a different voltage be
better?
2) Is DC better than AC? Does it matter?
3)What would be good ways to limit the current? Would a lamp dimmer on
the input side of the xmfr work? Wouldn't that also lower the voltage?
Would that matter?
4) I have a timer that pulses a relay on and off. I can set the length
of the pulses. Sort of what a lamp dimmer does but much longer pulses
(1 second and up) and the voltage would be the same out as in. But the
brass would average the heating. Would this work almost as well as
lowering the current? Better?
Any other input is much appreciated.
Thank You,
Eric R Snow,
E T Precision Machine

"Don Foreman" wrote in message
...
A given sized core can only handle so many VA at
given frequency (60 Hz)...

No, it can handle a certain number of turns per volt (which of course has a
factor of frequency, yadda yadda, but we're at 50/60Hz only so forget about
it). Current depends on the wire. That's why you can short a transformer
and get the windings smokin'...

I'd wind a one-turn secondary and measure that voltage as a reference
point for volts per turn. Secondary material is up to the guy winding
it, and if you built a spot welder than you know the drill.

Personally I'd probably melt some aluminum wire into bars (I've got 13
pounds as weighed, soft crap to burn.... literally? HMMMM.....) and wrap
that around the core, a turn or two. Some duct tape would make good
insulation I bet.
Most MOT welders have uh...3-5T? Maybe pile up four, run them in
series-parallel off 240V and loop some heavy welding cable through the space
where the secondaries used to be.

Tim

--
"I've got more trophies than Wayne Gretsky and the Pope combined!"
- Homer Simpson
Website @ http://webpages.charter.net/dawill/tmoranwms

On Mon, 19 Jul 2004 22:52:38 -0500, Don Foreman
wrote:

Required voltage depends on whether the heat is produced by the
resistance of the workpiece (brass) or by the contact which might be
copper, SS, tungsten, or even carbon.

I have a Wassco Glo-Melt resistance soldering unit model 105-B2, 500
watts. It's output is variable in steps from 1.0 to 5.8 volts AC.

A microwave transformer's capacity will depend on the power rating of
the microwave from which it came. They vary from 600 watts to 1200
watts. I don't know if that power rating is input to or output from
the magnetron. A given sized core can only handle so many VA at
given frequency (60 Hz), but I'd think a few experiments with such a
trannie and your own lowvoltage secondary would have you knowing a
good deal more than the "experts", at least about your particular
application!

I'd wind a one-turn secondary and measure that voltage as a reference
point for volts per turn. Secondary material is up to the guy winding
it, and if you built a spot welder than you know the drill.

I'd then experiment with electrode material and configuration. That
may affect your results as much as available power.



On Tue, 13 Jul 2004 18:02:35 -0700, Eric R Snow
wrote:

Greetings to all the microwave oven scroungers,
I have a job coming up that requires soldering the corners of brass
frames. These frames are made of 1 1/2 x 1 1/2 x 1/4 brass angle. In
the past I've used a torch to heat the brass. This leads to a little
distortion. This can be troublesome because the brass expands so much
that it moves the joint even though everything is clamped. The parts
must then be straightened when cool. Because of the application and
fit the frames must be straight within .010" in 36". I saw some
resistance soldering units in a catalog and the description of how
they operate says that only a small area is heated and gets to heat
fast. This would be ideal. However, the ones I saw were too small and
the price too large for me. But I've got several microwave
transformers and they seem like they might be perfect. A rough
calculation from the specs and pictures given in the catalog leads me
to believe that they output about 12 volts open circuit. Some have
variable outputs. So I have a few questions:
1) Does 12 volts sound reasonable? Would a different voltage be
better?
2) Is DC better than AC? Does it matter?
3)What would be good ways to limit the current? Would a lamp dimmer on
the input side of the xmfr work? Wouldn't that also lower the voltage?
Would that matter?
4) I have a timer that pulses a relay on and off. I can set the length
of the pulses. Sort of what a lamp dimmer does but much longer pulses
(1 second and up) and the voltage would be the same out as in. But the
brass would average the heating. Would this work almost as well as
lowering the current? Better?
Any other input is much appreciated.
Thank You,
Eric R Snow,
E T Precision Machine
Greetings Don,
I am using the experience of others to get to the starting point. I
will be using three xmfrs in parallel. Because I have them and because
I don't think two will be enough. I may end up buying a spotwelder on
ebay too. The heat must come from the resistance of the brass.
Hopefully, right at the joint will be hottest. The best part about
this project is expanding my knowledge. Getting the job done is
important but learning how and applying it to other situations is the
ultimate goal.
Cheers,
Eric

I mention this to include it in this thread, for anyone that's not familiar
with this type of AC circuit wiring.
I'm supposing that you've got enough knowledge and experience in setting up
this project to know that the transformer windings need to be wired to
accomplish the correct phasing to have the circuit perform properly.
This same method is required for xfmrs that have multiple windings.. dual
secondaries for example, where the two windings could be connected either in
series, parallel, or used separately (depending upon the application).

It'd be a problem if the primaries aren't phased, and worser if the
secondaries aren't.

WB
...............

"Eric R Snow" wrote in message
...
Greetings Don,
I am using the experience of others to get to the starting point. I
will be using three xmfrs in parallel. Because I have them and because
I don't think two will be enough. I may end up buying a spotwelder on
ebay too. The heat must come from the resistance of the brass.
Hopefully, right at the joint will be hottest. The best part about
this project is expanding my knowledge. Getting the job done is
important but learning how and applying it to other situations is the
ultimate goal.
Cheers,
Eric

It'd be a problem if the primaries aren't phased, and worser if the
secondaries aren't.

Just thought I would add another note here. Since resistance welders are used
very intermittantly, I wouldn't hesitate to try just one and overload it for
your welding operation. Similar to the Lincoln buzz box welder, it is rated for
a certain duty cycle depending on the output current.

A microwave transformer rated at 1000 watts can probably put out twice that
power if used at no more than a 10 to 20% duty cycle. Just a guess, but an
educated one. :)

Earle Rich
Mont Vernon, NH

On Wed, 14 Jul 2004 22:14:16 -0700, "william_b_noble"
wrote:

resistance solder units that I have output between 1 and 2.5 V

"Wild Bill" wrote in message
...
I dunno much about the specific outputs/capacity of the resistance
soldering
units, but I'll throw a few observations into the thread.
The units that I've seen in use in a starter/generator repair shop were
fairly compact units with a transformer housing of about a 6" cube. The
plier/tweezer-style handpiece appeared to have carbon jaws that made the
contact to the joint to be soldered. The heat was rapid, and they used
heavy
gauge solder, 1/8" maybe.

Some butt welding machines that I used to repair were used to weld ends of
heavy steel wire together (similar to a bandsaw blade welder). The sizes
ranged up to about 1/4" diameter.
The secondary of the transformer was only a couple of turns of flat
braided
cable securely clamped at the ends. The cable was the type that was used
as
engine ground strap in autos decades ago. This stuff would be good for
using
as a secondary winding in a modified transformer, easy to thread thru the
frame aand flat for fitting into a square shape.
For insulation, a good product would be fiberglas tape.. thin, high temp
resistant and an effective barrier/insulator.

WB
.................

"Eric R Snow" wrote in message
...
Greetings to all the microwave oven scroungers,
I have a job coming up that requires soldering the corners of brass
frames. These frames are made of 1 1/2 x 1 1/2 x 1/4 brass angle. In
the past I've used a torch to heat the brass. This leads to a little
distortion. This can be troublesome because the brass expands so much
that it moves the joint even though everything is clamped. The parts
must then be straightened when cool. Because of the application and
fit the frames must be straight within .010" in 36". I saw some
resistance soldering units in a catalog and the description of how
they operate says that only a small area is heated and gets to heat
fast. This would be ideal. However, the ones I saw were too small and
the price too large for me. But I've got several microwave
transformers and they seem like they might be perfect. A rough
calculation from the specs and pictures given in the catalog leads me
to believe that they output about 12 volts open circuit. Some have
variable outputs. So I have a few questions:
1) Does 12 volts sound reasonable? Would a different voltage be
better?
2) Is DC better than AC? Does it matter?
3)What would be good ways to limit the current? Would a lamp dimmer on
the input side of the xmfr work? Wouldn't that also lower the voltage?
Would that matter?
4) I have a timer that pulses a relay on and off. I can set the length
of the pulses. Sort of what a lamp dimmer does but much longer pulses
(1 second and up) and the voltage would be the same out as in. But the
brass would average the heating. Would this work almost as well as
lowering the current? Better?
Any other input is much appreciated.
Thank You,
Eric R Snow,
E T Precision Machine




Reading the original post it seems that it's soldering
that you need rather than flash or resistance butt welding
which would need a much higher peak power input.

It takes time for heat to travel and distribute itself
into a workpiece. The shorter the heating time the smaller
the volume of the workpiece affected and, for a defined
temperature rise, the smallest total heat input and smallest
heat affected volume. This means that the aim should be for
a high peak power input to permit a very short heating time.

Some resistance soldering units use either one or a
pair of carbon electrodes sharpened to a point. These can
apply intense local heat but it flows non uniformly into the
brass and can only melt the solder after heating a
relatively large volume of brass.

A better approach (and probably the one you're
already intending to try) is to resistance melt the solder
directly by clamping the transformer output leads to the
brass frame just either side of the joint and applying
pressure and time controlled current pulse for a second or
so.
If you can succeed in mostly filling with copper the
vacant space left by the high voltage secondary AND removing
any magnetic shunt pieces, a single microwave oven
transformer should be enough. You probably need about three
volts. These transformers are typically about 1 turn per
volt so two to four turns is the right range.

If there's a choice solder should be in the form of
flat preform lightly fluxed on both sides.

This is all partly informed guesswork so let us know
how you get on.
Jim

On Tue, 20 Jul 2004 15:33:14 -0400, "Wild Bill"
wrote:

I mention this to include it in this thread, for anyone that's not familiar
with this type of AC circuit wiring.
I'm supposing that you've got enough knowledge and experience in setting up
this project to know that the transformer windings need to be wired to
accomplish the correct phasing to have the circuit perform properly.
This same method is required for xfmrs that have multiple windings.. dual
secondaries for example, where the two windings could be connected either in
series, parallel, or used separately (depending upon the application).

It'd be a problem if the primaries aren't phased, and worser if the
secondaries aren't.

WB
Bill,
I know the windings need to be phased. I've never done this but I
gather all that needs to be done is to measure the voltage out. It
should be the same when two are connected in paralell. If less, then
one is out of phase. I don't know any other way to tell if my home
wound windings are connected correctly. I do know that there are phase
dots on some xmfrs that I have on the shelf.
Eric

"Eric R Snow" wrote in message
.. .
Greetings Don,
I am using the experience of others to get to the starting point. I
will be using three xmfrs in parallel. Because I have them and because
I don't think two will be enough. I may end up buying a spotwelder on
ebay too. The heat must come from the resistance of the brass.
Hopefully, right at the joint will be hottest. The best part about
this project is expanding my knowledge. Getting the job done is
important but learning how and applying it to other situations is the
ultimate goal.
Cheers,
Eric

On Wed, 21 Jul 2004 12:33:50 +0000 (UTC), wrote:

On Wed, 14 Jul 2004 22:14:16 -0700, "william_b_noble"
wrote:

resistance solder units that I have output between 1 and 2.5 V

"Wild Bill" wrote in message
...
I dunno much about the specific outputs/capacity of the resistance
soldering
units, but I'll throw a few observations into the thread.
The units that I've seen in use in a starter/generator repair shop were
fairly compact units with a transformer housing of about a 6" cube. The
plier/tweezer-style handpiece appeared to have carbon jaws that made the
contact to the joint to be soldered. The heat was rapid, and they used
heavy
gauge solder, 1/8" maybe.

Some butt welding machines that I used to repair were used to weld ends of
heavy steel wire together (similar to a bandsaw blade welder). The sizes
ranged up to about 1/4" diameter.
The secondary of the transformer was only a couple of turns of flat
braided
cable securely clamped at the ends. The cable was the type that was used
as
engine ground strap in autos decades ago. This stuff would be good for
using
as a secondary winding in a modified transformer, easy to thread thru the
frame aand flat for fitting into a square shape.
For insulation, a good product would be fiberglas tape.. thin, high temp
resistant and an effective barrier/insulator.

WB
.................

"Eric R Snow" wrote in message
...
Greetings to all the microwave oven scroungers,
I have a job coming up that requires soldering the corners of brass
frames. These frames are made of 1 1/2 x 1 1/2 x 1/4 brass angle. In
the past I've used a torch to heat the brass. This leads to a little
distortion. This can be troublesome because the brass expands so much
that it moves the joint even though everything is clamped. The parts
must then be straightened when cool. Because of the application and
fit the frames must be straight within .010" in 36". I saw some
resistance soldering units in a catalog and the description of how
they operate says that only a small area is heated and gets to heat
fast. This would be ideal. However, the ones I saw were too small and
the price too large for me. But I've got several microwave
transformers and they seem like they might be perfect. A rough
calculation from the specs and pictures given in the catalog leads me
to believe that they output about 12 volts open circuit. Some have
variable outputs. So I have a few questions:
1) Does 12 volts sound reasonable? Would a different voltage be
better?
2) Is DC better than AC? Does it matter?
3)What would be good ways to limit the current? Would a lamp dimmer on
the input side of the xmfr work? Wouldn't that also lower the voltage?
Would that matter?
4) I have a timer that pulses a relay on and off. I can set the length
of the pulses. Sort of what a lamp dimmer does but much longer pulses
(1 second and up) and the voltage would be the same out as in. But the
brass would average the heating. Would this work almost as well as
lowering the current? Better?
Any other input is much appreciated.
Thank You,
Eric R Snow,
E T Precision Machine




Reading the original post it seems that it's soldering
that you need rather than flash or resistance butt welding
which would need a much higher peak power input.

It takes time for heat to travel and distribute itself
into a workpiece. The shorter the heating time the smaller
the volume of the workpiece affected and, for a defined
temperature rise, the smallest total heat input and smallest
heat affected volume. This means that the aim should be for
a high peak power input to permit a very short heating time.

Some resistance soldering units use either one or a
pair of carbon electrodes sharpened to a point. These can
apply intense local heat but it flows non uniformly into the
brass and can only melt the solder after heating a
relatively large volume of brass.

A better approach (and probably the one you're
already intending to try) is to resistance melt the solder
directly by clamping the transformer output leads to the
brass frame just either side of the joint and applying
pressure and time controlled current pulse for a second or
so.
If you can succeed in mostly filling with copper the
vacant space left by the high voltage secondary AND removing
any magnetic shunt pieces, a single microwave oven
transformer should be enough. You probably need about three
volts. These transformers are typically about 1 turn per
volt so two to four turns is the right range.

If there's a choice solder should be in the form of
flat preform lightly fluxed on both sides.

This is all partly informed guesswork so let us know
how you get on.
Jim
Thanks for the input Jim. You have hit exactly on the head what I'm
trying to do. Often it is hard, for me, to get an idea across
consisely. And I end up clarifying over and over. It must be hard to
be a teacher. Since I have already stripped out the secondaries and
shunts of two xmfrs I'll be wiring them in parallel. I will then
machine two copper electrodes to match the shape of the pieces to be
soldered and clamp the wires to them. I hope that getting the
electrodes within 1/4" of the joint will get me lots of heat fast. The
method of joining will be to use small .002" thick shim pieces in the
joint to provide capillary action. I have done this when using a torch
and it works very well.
Eric

I know the windings need to be phased. I've never done this but I
gather all that needs to be done is to measure the voltage out. It
should be the same when two are connected in paralell. If less, then
one is out of phase. I don't know any other way to tell if my home
wound windings are connected correctly. I do know that there are phase
dots on some xmfrs that I have on the shelf.

Almost correct, BUT!!

Place the two windings in series, If the voltage across the two free windings
is zero, then you can connect them together and the windings will be
paralleled. Connecting them in parallel wrong will give you maximum fault
current.

If you read twice the voltage of either one seperatly, then they are phased
wrong. Reversing the primary phase is usually easier than trying to rewire the
secondary.

Unless the two transformers are identical, you will probably have some small
voltage difference in the two windings. That will cause some loss due to
circulating currents, probably not too important unless its more than 1/2 volt
or so. Connecting transformer secondaries in parallel is not common due to this
problem. But, for an intermittant service where the primaries are switched, I
wouldn't worry about that.

Earle Rich
Mont Vernon, NH

On Tue, 20 Jul 2004 02:12:47 -0500, "Tim Williams"
wrote:

"Don Foreman" wrote in message
.. .
A given sized core can only handle so many VA at
given frequency (60 Hz)...

No, it can handle a certain number of turns per volt (which of course has a
factor of frequency, yadda yadda, but we're at 50/60Hz only so forget about
it). Current depends on the wire. That's why you can short a transformer
and get the windings smokin'...

Well, golly, do you suppose I've been designing transformers wrong
for 35 years?

Given 60 Hz, and given max flux density determined by the core
material , volts per turn (or turns per volt if you prefer) are a fn
of cross sectional area enclosed by the winding. However, for more
VA (at given voltage) you need to use larger wire for those turns.
This dictates more "window" area so the overall dimensions
(envelope), volume and weight of the core must be larger to make a
larger window.

The reply from ERich sums it up well. The explanation of swapping the
primary leads of one transformer will be easier than jumpering the heavy
gauge secondary leads.

The main factor of knowing when the secondaries are phased properly for this
application, is because the secondary conductors will be heavy gauge
conductors, and this could pose a physical parts layout problem
(particularly if you've already chosen an enclosure for your project).
The phasing factor is a result of the direction that the windings are wound
around the core. Since it's undetermined (because the primaries were
existing windings and usually covered), although it's not really important
since you're working with two xfmr cores and you'll be adding your own
secondaries.

The phase can be checked by winding a few turns of any small conductor on
the cores. Two secondary leads from separate xfmrs are connected and two are
left separated. When the test confirms that you've got the leads connected
correctly, you'll want to wind your secondaries in the same direction as the
test windings, and you'll want the four primary windings to retain the same
relationship to being paired together.

If you dont have your secondary windings wound yet..
A low voltage test light will light (6 to 12V) when connected across the
open leads when the windings are not correctly connected or out-of-phase for
the application you want. This is the unwanted maximum current condition
that ERich mentioned.
This lamp test will show how the the xfmrs are phased. You would probably
want your secondary windings to be wound for your convenience, in that the
leads can be attached in parallel to the soldering unit's output cables or
terminals, without any leads needing to be much longer than the other set.

You can bond the xfmr frames to the unit's safety earth ground in the event
of a component failure.

WB
.................

"Eric R Snow" wrote in message
news
Bill,
I know the windings need to be phased. I've never done this but I
gather all that needs to be done is to measure the voltage out. It
should be the same when two are connected in paralell. If less, then
one is out of phase. I don't know any other way to tell if my home
wound windings are connected correctly. I do know that there are phase
dots on some xmfrs that I have on the shelf.
Eric

On Thu, 22 Jul 2004 00:44:17 -0400, "Wild Bill"

"Eric R Snow" wrote in message
news
Bill,
I know the windings need to be phased. I've never done this but I
gather all that needs to be done is to measure the voltage out. It
should be the same when two are connected in paralell. If less, then
one is out of phase. I don't know any other way to tell if my home
wound windings are connected correctly. I do know that there are phase
dots on some xmfrs that I have on the shelf.
Eric

Just a few comments.

If you are paralleling secondaries be very sure that
you are using identical twin transformers - even a tenth of
a volt difference in turns per volt will result in large
circulating currents.

Phasing is no big deal. Join together one end of the
two secondaries and link the two free ends with a short bit
of 10A fuse wire or thin flex. Apply power. If nothing
happens it's OK to parallel the two windings. If the fuse
wire disappears reverse the connections to one of the
primaries.

Jim

"Don Foreman" wrote in message
...
However, for more
VA (at given voltage) you need to use larger wire for those turns.
^^^^^^^^^^^
Given the duty cycle, it can be ran "safely" at a rather abhorrent current
density. By "safely" I mean, if it melts, hell with it. Make another.

Tim

--
"I've got more trophies than Wayne Gretsky and the Pope combined!"
- Homer Simpson
Website @ http://webpages.charter.net/dawill/tmoranwms

Ya got me there, Tiim. I've never designed one-shot transformers.

On Thu, 22 Jul 2004 04:22:38 -0500, "Tim Williams"
wrote:

"Don Foreman" wrote in message
.. .
However, for more
VA (at given voltage) you need to use larger wire for those turns.
^^^^^^^^^^^
Given the duty cycle, it can be ran "safely" at a rather abhorrent current
density. By "safely" I mean, if it melts, hell with it. Make another.

Tim

"Don Foreman" wrote in message
...
Ya got me there, Tiim. I've never designed one-shot transformers.

How about superconducting transformers? I've got to imagine it's been done
by now, unless iron loses its ferromagnetic properties at low temperatures
(reverse-curie temp? heh).
In that case, the wire can be microns in diameter, thousands of turns can be
applied in a very small area, while still maintaining a high current density
due to the material.

Tim

--
"I've got more trophies than Wayne Gretsky and the Pope combined!"
- Homer Simpson
Website @ http://webpages.charter.net/dawill/tmoranwms

Tim Williams wrote:
"Don Foreman" wrote in message
...

Ya got me there, Tiim. I've never designed one-shot transformers.


How about superconducting transformers? I've got to imagine it's been done
by now, unless iron loses its ferromagnetic properties at low temperatures
(reverse-curie temp? heh).
In that case, the wire can be microns in diameter, thousands of turns can be
applied in a very small area, while still maintaining a high current density
due to the material.

Umm, no. There's a surprisingly low critical
current density where the superconductivity
disappears.

"Jim Stewart" wrote in message
...
Umm, no. There's a surprisingly low critical
current density where the superconductivity
disappears.

As I recall the critical field is up around 20T in the tougher
superconductors, I don't know what field is present at and slightly inside
the conductor's surface for a given current and diameter though. Suppose I
should drag out our old friends Biot-Savart and Mr. Integral...

Tim

--
"I've got more trophies than Wayne Gretsky and the Pope combined!"
- Homer Simpson
Website @ http://webpages.charter.net/dawill/tmoranwms

That sounds pretty neat. Pls keep us posted on your work with
superconducting transformers. I am not competent in that technology.

I hope Eric Snow also keeps us posted on his progress with
resistance-soldering. I'm interested in learning from Eric's
discoveries because I may be able to understand them and apply them.



On Thu, 22 Jul 2004 20:09:11 -0500, "Tim Williams"
wrote:

"Don Foreman" wrote in message
.. .
Ya got me there, Tiim. I've never designed one-shot transformers.

How about superconducting transformers? I've got to imagine it's been done
by now, unless iron loses its ferromagnetic properties at low temperatures
(reverse-curie temp? heh).
In that case, the wire can be microns in diameter, thousands of turns can be
applied in a very small area, while still maintaining a high current density
due to the material.

Tim

On Fri, 23 Jul 2004 01:53:37 -0500, Don Foreman
wrote:

That sounds pretty neat. Pls keep us posted on your work with
superconducting transformers. I am not competent in that technology.

I hope Eric Snow also keeps us posted on his progress with
resistance-soldering. I'm interested in learning from Eric's
discoveries because I may be able to understand them and apply them.

It looks like next week I'll know about this latest project. Stay
tuned...
ERS