On 6.2.17 14:43, Chris Jones wrote:
> On 05/02/2017 01:47, Tim Williams wrote:
>> "Winfield Hill" <hill@rowland.harvard.edu> wrote in message
>> news:o73ai1012r6@drn.newsguy.com...
>>> I often use large-diameter litz with hundreds of tiny
>>> wires.  I follow my technician's approach, which is to
>>> use a solder pot.  I dip the litz bundle into a gross-
>>> looking paste flux and then into the pot.  Voila, an
>>> instant ready-to-go solder-encrusted termination.
>>
>> "Large"?  That's cute. ;-)
>>
>> In the induction heating business, inch-wide rope is regularly used.
>> The ends are crimped into several-aught size lugs, some rosin dripped
>> in, then dipped whole into a solder pot.  When the bubbling subsides,
>> it's ready.
>>
>> On a less bragging matter:
>>
>> I've made litz myself, using whatever stuff I have laying around.  On
>> several occasions, I've made the mistake of using this old brown stuff
>> that's classic "enamel".  It just carbonizes harder and harder, on
>> heating!
>>
>> So I get out an abused teablepoon, and melt a lump of potassium
>> chlorate(!) in it.  Heat the wire briefly in the flame, then dip the
>> wire in the salt: FOOF, no more enamel!  Water quenches and dissolves
>> the salt stuck in the wire, leaving perfectly clean, pink copper, ready
>> to be tinned!
>
> You can also do it by heating the wire to red heat and then rapidly
> plunging it into alcohol (ethanol, methylated spirits etc.) whilst still
> red hot. If the wire has insufficient heat capacity to stay red hot long
> enough to do the above, then you can wrap it with some other copper wire
> just to increase the thermal mass. The added wire may get welded to the
> Litz wire if you heat it too much. That may or may not be a problem.
>
> Obviously, messing with blowtorches around a pot of alcohol is likely to
> result in a fire, so do it in a place where a fire won't be a problem,
> and limit the quantity of alcohol to the amount that would not cause a
> problem if it catches fire.


I did it without blowtorches by putting a wad of cotton in a
metal can lid, pouring some denaturated alcohol into it and
firing it up. The Litz was put into the flame and then pressed
to the wet wad and pulled out sideways. This worked fine for
the wire in IF transformers in the tube era.

The alcohol does not need to denaturated, but due to the alcohol
policies in the Nordic countries it was the only resonable. The
connoisseurs could flamber it with Courvoiser.

-- 

-TV

"Chris Jones" <lugnut808@spam.yahoo.com> wrote in message 
news:hc_lA.196424$yv3.137931@fx30.am4...
> You can also do it by heating the wire to red heat and then rapidly 
> plunging it into alcohol (ethanol, methylated spirits etc.) whilst still
> red hot. If the wire has insufficient heat capacity to stay red hot long
> enough to do the above, then you can wrap it with some other copper wire
> just to increase the thermal mass. The added wire may get welded to the 
> Litz wire if you heat it too much. That may or may not be a problem.

Hmmm.  That might work for modern enamels -- don't think it'll work for my 
particular example, which looks like it turns to glassy carbon on heating. 
(Which means it'll take a lot more heating to get it to oxidize to bare 
crusty copper.)

As for the active ingredient -- copper-catalyzed oxidation of light spirits 
(methanol, ethanol, acetone, etc.) is really cool to watch, and it does 
indeed produce a solderable surface that was (briefly) at red heat!

I'm surprised the chlorate doesn't burn the copper too, but hey, go figure. 
I'll take what I can get. :)

Additional hazard warning: definitely don't combine the two methods, and, 
say, accidentally plunge roiling, molten chlorate into a vat of alcohol. ;-D

Tim

-- 
Seven Transistor Labs, LLC
Electrical Engineering Consultation and Contract Design
Website: http://seventransistorlabs.com

On Friday, February 3, 2017 at 8:54:44 PM UTC+2, Albert van der Horst wrote:
> In article <ns70ni$oh4$1@dont-email.me>,
> P E Schoen <paul@pstech-inc.com.invalid> wrote:
> <SNIP>
> >I have some 7x3x21 Litz wire that is equivalent to about #14 AWG and should
> >be capable of about 15 amps. But it was impossible to solder it to the
> >terminals of the coilformer. I was also unable to use my soldering iron to
> >melt the insulation and make connection to all the strands.
> 
> Use tablets with 500 mg brand aspirine, (acetylsalicyl acid) to
> solder through the insulation. More about that in a recent thread.
> 
> <SNIP>
> 
> >
> >Thanks,
> >
> >Paul
> >
> -- 
> Albert van der Horst, UTRECHT,THE NETHERLANDS
> Economic growth -- being exponential -- ultimately falters.
> albert@spe&ar&c.xs4all.nl &=n http://home.hccnet.nl/a.w.m.van.der.horst

  The Aspirin trick is also described in Rev. Sci. Instr. vol.75 no.5 p.1169 (2004), a paper by I. R. Walker. Works well.

  Regards,
            Mikko

On 05/02/2017 01:47, Tim Williams wrote:
> "Winfield Hill" <hill@rowland.harvard.edu> wrote in message
> news:o73ai1012r6@drn.newsguy.com...
>> I often use large-diameter litz with hundreds of tiny
>> wires.  I follow my technician's approach, which is to
>> use a solder pot.  I dip the litz bundle into a gross-
>> looking paste flux and then into the pot.  Voila, an
>> instant ready-to-go solder-encrusted termination.
>
> "Large"?  That's cute. ;-)
>
> In the induction heating business, inch-wide rope is regularly used.
> The ends are crimped into several-aught size lugs, some rosin dripped
> in, then dipped whole into a solder pot.  When the bubbling subsides,
> it's ready.
>
> On a less bragging matter:
>
> I've made litz myself, using whatever stuff I have laying around.  On
> several occasions, I've made the mistake of using this old brown stuff
> that's classic "enamel".  It just carbonizes harder and harder, on heating!
>
> So I get out an abused teablepoon, and melt a lump of potassium
> chlorate(!) in it.  Heat the wire briefly in the flame, then dip the
> wire in the salt: FOOF, no more enamel!  Water quenches and dissolves
> the salt stuck in the wire, leaving perfectly clean, pink copper, ready
> to be tinned!

You can also do it by heating the wire to red heat and then rapidly 
plunging it into alcohol (ethanol, methylated spirits etc.) whilst still 
red hot. If the wire has insufficient heat capacity to stay red hot long 
enough to do the above, then you can wrap it with some other copper wire 
just to increase the thermal mass. The added wire may get welded to the 
Litz wire if you heat it too much. That may or may not be a problem.

Obviously, messing with blowtorches around a pot of alcohol is likely to 
result in a fire, so do it in a place where a fire won't be a problem, 
and limit the quantity of alcohol to the amount that would not cause a 
problem if it catches fire.

"Winfield Hill" <hill@rowland.harvard.edu> wrote in message 
news:o73ai1012r6@drn.newsguy.com...
> I often use large-diameter litz with hundreds of tiny
> wires.  I follow my technician's approach, which is to
> use a solder pot.  I dip the litz bundle into a gross-
> looking paste flux and then into the pot.  Voila, an
> instant ready-to-go solder-encrusted termination.

"Large"?  That's cute. ;-)

In the induction heating business, inch-wide rope is regularly used.  The 
ends are crimped into several-aught size lugs, some rosin dripped in, then 
dipped whole into a solder pot.  When the bubbling subsides, it's ready.

On a less bragging matter:

I've made litz myself, using whatever stuff I have laying around.  On 
several occasions, I've made the mistake of using this old brown stuff 
that's classic "enamel".  It just carbonizes harder and harder, on heating!

So I get out an abused teablepoon, and melt a lump of potassium chlorate(!) 
in it.  Heat the wire briefly in the flame, then dip the wire in the salt: 
FOOF, no more enamel!  Water quenches and dissolves the salt stuck in the 
wire, leaving perfectly clean, pink copper, ready to be tinned!

(!) Potassium chlorate is the schizophrenic little brother of potassium 
perchlorate, which itself is basically used in pyrotechnics and not much 
else.  Perchlorate is remarkably stable, as long as you don't drip 
concentrated sulfuric acid on it, or heat it over 600C.  Chlorate is a much 
weaker salt, and becomes a friction-sensitive explosive if paired with 
mildly acidic fuels like sulfur or phosphorus.  It's still stable enough to 
melt, but it's bubbling with oxygen all the while...

Tim

-- 
Seven Transistor Labs, LLC
Electrical Engineering Consultation and Contract Design
Website: http://seventransistorlabs.com

jrwalliker@gmail.com wrote...
>
> On 3 February 2017, Albert van der Horst  wrote:
>
>> Use tablets with 500 mg brand aspirine, (acetylsalicyl
>> acid) to solder through the insulation. [snip]
>
> ...and don't forget concentrated phosphoric acid which
> is an excellent flux, relatively non-toxic and is easy
> to wash away.  [snip]

 I often use large-diameter litz with hundreds of tiny
 wires.  I follow my technician's approach, which is to
 use a solder pot.  I dip the litz bundle into a gross-
 looking paste flux and then into the pot.  Voila, an
 instant ready-to-go solder-encrusted termination.

-- 
 Thanks,
    - Win

On Friday, 3 February 2017 18:54:44 UTC, Albert van der Horst  wrote:

> Use tablets with 500 mg brand aspirine, (acetylsalicyl acid) to
> solder through the insulation. More about that in a recent thread.

...and don't forget concentrated phosphoric acid which is an
excellent flux, relatively non-toxic and is easy to wash away.
I works nicely for stainless steel as well as copper.

John

In article <ns70ni$oh4$1@dont-email.me>,
P E Schoen <paul@pstech-inc.com> wrote:
<SNIP>
>I have some 7x3x21 Litz wire that is equivalent to about #14 AWG and should
>be capable of about 15 amps. But it was impossible to solder it to the
>terminals of the coilformer. I was also unable to use my soldering iron to
>melt the insulation and make connection to all the strands.

Use tablets with 500 mg brand aspirine, (acetylsalicyl acid) to
solder through the insulation. More about that in a recent thread.

<SNIP>

>
>Thanks,
>
>Paul
>
-- 
Albert van der Horst, UTRECHT,THE NETHERLANDS
Economic growth -- being exponential -- ultimately falters.
albert@spe&ar&c.xs4all.nl &=n http://home.hccnet.nl/a.w.m.van.der.horst

"P E Schoen"  wrote in message news:ns70ni$oh4$1@dont-email.me...

> I am making a transformer with Epcos E55 cores of N27 ferrite. The primary 
> will have four windings each rated for 12-15 VRMS at 50-70 kHz. I am 
> hoping to get up to 1500 watts, so the primary windings will need to 
> handle up to 31 amps. The coilformer (bobbin) has 14 pins, of which 8 will 
> be used for the primaries. The secondary will be two windings capable of 
> 250-300 volts each at the nominal 12/24/48 volts input. For 1500 watts, 
> these will need to be rated at about 3 amps. I have figured on four turns 
> for each primary (about 3.5 volts/turn).

[snip discussion of Litz wire and soldering]

The testing of the transformer made with Litz wire indicates that it might 
be possible to make only about 750-1000 watts, mostly because of the bulk of 
the Litz wire and difficulty getting enough copper to get the required 6 
amps at 250 volts. It was difficult to fit the 50 turns of #20 AWG 
equivalent Litz, and a second coil of the same size would be needed to get 
the power originally desired.

My testing of the small transformers seems to show that the skin effect may 
not be as significant as originally supposed. So I am considering a design 
that uses four copper strips 1/4" wide and 1/32" thick for the primary. Here 
is a rendering of how it might be built, with the primary on the outside of 
the secondary:

http://enginuitysystems.com/pix/electronics/Transformer_E55_NE.jpg

I will probably need to use at least 100 kHz to get 3.75 volts/turn instead 
of 3 V/t as presently constructed with 5 primary turns. However, I just 
realized that this design would be only for 12-15 volts at 30 amps, or 
360-450 watts. I need four sets of four, which will be more challenging. So, 
back to the drawing board.

However, my point was that these 1/32" strips would have 400 uOhms DC 
resistance, and even if AC resistance were 3x that, 30 amps through 1200 
uOhms x 4 turns would be about 4 watts. Four such turns would be 16 watts of 
losses, which is only about 1% of the target 1500 watts. Also, the exposed 
primaries would be conducive to forced air or even convection cooling.

Now to figure how to construct it... ;)

Paul