Ferrite core mounting, U- brackets anywhere?

[Joerg]

Gents,

Is there a company that offers plastic or metal U-brackets of numerous
sizes? Preferably domestic (US). Grainger and McMaster are rather
limited in size choices.

I have yet another RF project where large ferrite cores are needed. This
time squarish double-hole cores of roughly 1.15" by 1.15" and 0.56"
high. And as usual the ferrite mfg offers nothing in terms of mounting
HW, they all seem to assume that having such heavy cores slosh around or
being buried under a blob of hot glue is going to be ok. I want to rivet
them to a circuit board, or screw it down if needed. Cable ties are not
so great because they become brittle over the years and break. Lacing
cord would be excellent but people stare at me when I suggest that,
probably thinking am a Luddite

 

[Martin Riddle]

Gents,

Is there a company that offers plastic or metal U-brackets of numerous
sizes? Preferably domestic (US). Grainger and McMaster are rather
limited in size choices.

I have yet another RF project where large ferrite cores are needed.
This
time squarish double-hole cores of roughly 1.15" by 1.15" and 0.56"
high. And as usual the ferrite mfg offers nothing in terms of mounting
HW, they all seem to assume that having such heavy cores slosh around
or
being buried under a blob of hot glue is going to be ok. I want to
rivet
them to a circuit board, or screw it down if needed. Cable ties are
not
so great because they become brittle over the years and break. Lacing
cord would be excellent but people stare at me when I suggest that,
probably thinking am a Luddite

Tried FormCo ?
http://web1.userinstinct.com/21658253-formco.htm

cheers

 

[Joerg]

What company are you using for your cores? ...

The BN-43-7051 from Amidon top of the page):

https://www.amidoncorp.com/specs/2-34.pdf

... I last did this in the
late '80's, but I was able to get all kinds of mounting clips that
were springy (so as not to crack the core), and thru-hole solderable.

Like...

www.milesplatts.co.uk/assets/File/07_mp_product_guide_section_05.pdf

for one example.

The ones on page 5-43 don't look solderable and too big, our core would
slosh around in there. But one of those in solderable and smaller would
certainly be cool. Not sure if they'd sell to us after we celebrated
their voting off of the island yesterday

 

[Joerg]

Tried FormCo ?
http://web1.userinstinct.com/21658253-formco.htm

Thanks. Guess I'll have to ask for a catalog on dead tree since they
don't seem to have a web site ;-)

 

[Joerg]

http://www.keyelco.com/pdfs/M55-prod34.pdf

2 x "CAT. NO. 4325" one on each side of the core?

If we absolutely have to. The risk is that a major hit during transport
might cause one or both to rotate out of position.

 

[Joerg]

Check Lodestone Pacific and Robison. Both make lots of coil mounts.

Thanks! Will write to them right now. In case anyone else is in need:

http://www.lodestonepacific.com/

Couldn't find Robison.

 

[Joerg]

Vaguely remembering... Fairite ??

Maybe, but then likely one they make for Amidon. You can't get it at
Fair-Rite. The ones in their catalog aren't quite big enough for this
application:

http://www.fair-rite.com/cgibin/cat...ent&THEPART=Multi-Aperture+cores#select:freq1

 

[Joerg]

http://www.cornucopiaplastics.com/robison/index.htm

Thanks, but looks like the don't have anything suitable under coil
mounting products. But let's see what Lodestones responds.

Sometimes it makes sense to mount your inductor in a shell, with pins
maybe, and solder that to the board as a component. Bigger ones
sometimes have a hole for a mounting screw.

I did this little one, with a Lodesone shell...

ftp://jjlarkin.lmi.net/L_Assy.jpg

which is surface-mountable.

Neat. Unfortunately most of the time I get RF projects it's higher power
stuff. So I need the big old fat cores.

 

[Joerg]

Ages ago I used Ferroxcube.

I had checked them. No mounts, not for such big cores.

 

[Martin Riddle]

If we absolutely have to. The risk is that a major hit during
transport
might cause one or both to rotate out of position.

If I have a chance tomorrow, I'll scan the Catalog into a PDF and email
it.
I think it's just E-I core stuff but they might have something.

Cheers

 

[Martin Riddle]

Ages ago I used Ferroxcube.
Art

I believe the Philips Ferrite core line is part of them now.

Cheers

 

[Joerg]

If I have a chance tomorrow, I'll scan the Catalog into a PDF and email
it.
I think it's just E-I core stuff but they might have something.

Thanks, Martin, but only if that doesn't tie you up at the scanner.

I was kind of surprised that Grainer and McMaster had nothing. I mean,
you can get everything else including salt and pepper shakers there.

 

[Joerg]

---
And yet, you're right.

Years and years ago we used to use "mouse tails", elastomeric ties
thicker through the body than through the tapered ends, the ends of
which we inserted into holes drilled on either side of the object we
wanted to immobilize, then inserted and pulled on the ends until the
stretched, thick parts of the tie went through the holes.

After that, releasing the ends allowed the elastomer to expand, again,
catching the edges of the holes and exerting tension on the device,
forcing it to fall to, and be retained on, the surface of the PCB.

I've seen versions where the thick part would ratchet into the hole just
like a cable tie but at a finer pitch. However, personally I do not
trust plastics over the long haul. Some last forever, others give up
after a few years. And you never know. Some day the elasticity has sort
of evaporated and ... ping ... hiss ... *BAM*

This is for med gear so I don't want to take any chances. Machines like
that can remain in service for decades.

 

[Ecnerwal]

Lacing

....
However, personally I do not
trust plastics over the long haul. Some last forever, others give up
after a few years. And you never know. Some day the elasticity has sort
of evaporated and ... ping ... hiss ... *BAM*

This is for med gear so I don't want to take any chances. Machines like
that can remain in service for decades.

So, go with lacing cord - and if anyone looks at you funny, point out
that you are doing that for the same reason that the military does - and
you can look to mil-spec suppliers to find the stuff, last I bothered to
look. You certainly won't find anything as versatile from a "one part
number in stock will hold down any of a wide range of cores, even if the
cores change" point of view.

Allied and Newark both seem to still have it. Here's the general
description of the types of Alpha Wire cord available at Allied:

Nylon and Dacron Flat Braided Lacing Tape. All types are nylon. All types are
designation MIL-T-43435 with variations for type, size, and finish. LC-132
has a finish of synthetic rubber-like resin with non-mercuricfungicidal
properties. Melting point is above 190°F. Softens at 140°F, but doesn't flow.
LC-134 and LC-136 have a finish of micro-Crystalline wax with amelting point
above 130°F, compounded with a fungicide containing neither copper nor
mercury. Soft, pliable and easy to tie. Also meets MIL-T-713 Type P,Class 2.
LC-140 has a finish of a special continuous coating of fungistatic synthetic
rubber. Knots tied with this finish will not slip. Extremely pliable and
soft. LC-143 has a thermoplastic synthetic resin with a melting point above
350°F for use where a ³wax free² type is specified. Dry, non-flaking finish.
Available in white and black ‹ insert 1 (white) or 2 (black) where X appears
in Stock Number.

I laced the harness for my CNC router - it was the most efficient way to
make it work at a price I could stand...while it may see little use
outside the military in "present-day" throwaway crap-tronics, there's
still a place for it where reliability matters over the long run. So use
it...

 

[Joerg]

So, go with lacing cord - and if anyone looks at you funny, point out
that you are doing that for the same reason that the military does - and
you can look to mil-spec suppliers to find the stuff, last I bothered to
look. You certainly won't find anything as versatile from a "one part
number in stock will hold down any of a wide range of cores, even if the
cores change" point of view.

Allied and Newark both seem to still have it. Here's the general
description of the types of Alpha Wire cord available at Allied:

They even have the cool black stuff:

http://www.newark.com/alpha-wire/80...lar Products&MER=PPSO_N_C_EverywhereElse_None

I laced the harness for my CNC router - it was the most efficient way to
make it work at a price I could stand...while it may see little use
outside the military in "present-day" throwaway crap-tronics, there's
still a place for it where reliability matters over the long run. So use
it...

Yeah, but it has two downsides: Drill holes in FR4 much be rounded to
make this kosher. Then, I'll have to make an elaborate and
ECO-releasable hand-drawing about how to lace it, knot it, and all that.
Else they'd have to hire an aircraft electrician

 

[Joerg]

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Screw, spring, large diameter washer, toroid, board, lock nut. Possibly
a spacer in the hole of the toroid, to keep the thing from rattling
around in x and y.

The spring presses on the washer (possibly fiber or plastic, to be nice
to the coil wires), to maintain tension on the toroid without breaking
the core. The screw does what screws do, and the lock nut is because
you can't really snug things down -- you want the spring to be compressed.

What you really want is a shoulder screw, so the screw is tight up
against the PC board but has a controlled distance to the head, and
maybe controls the lateral coil position to boot -- that's a short
thread and a long shoulder, so it may not be a catalog item.

Can't use a toroid because I couldn't get the leakage inductance down
low enough.

Have to use the big square BN-43-7051 double-holer from Amidon:

https://www.amidoncorp.com/specs/2-34.pdf

Have you checked with Misumi (Mitsumi?) to see if any of their
semi-custom mechanical parts can be made to work?

They cater more to the injection-molding crowd.

http://us.misumi-ec.com/

OR...

How about a spacer, screw from underneath to hold it to the board, screw
down from the top to put pressure on the spring, with a fender washer to
hold the coil down? Bed the coil in hot glue top & bottom so it's nice
and comfy, but doesn't depend on the glue very much at all for
mechanical strength. Spacers are a lot easier than oddball shoulder
screws.

Well, I need something to hold several roughly 1" square chunks of
ferrite on the board, and they are fairly heavy.

 

[Joerg]

Cable clamp!

They are all round :-(

 

[Joerg]

That's what a friend of ours would say. He is over 80 now and when I
talked with him about his job after the military he summed it up this
way: "Well, I just couldn't work with civilians"

 

[Martin Riddle]

Thanks, Martin, but only if that doesn't tie you up at the scanner.

I was kind of surprised that Grainer and McMaster had nothing. I mean,
you can get everything else including salt and pepper shakers there.

I took a look, there is some hardware, probably nothing you can use.
I did use the txfrmr brackets, bigger than the Keyelco stuff.
Here is a link to the catalog.
http://mysite.verizon.net/martine001/FormCo_Cat2010x.pdf

We have a Konica-Minolta Biz Hub, set it and forget it, works great.


Cheers

 

[Joerg]

I see what you mean, they aren't very wide.

how about something like this: http://www.te.com/catalog/Presentations/Steel Cable Ties.pdf
with milled slots on each side of the core

Stainless steel cable ties, that's actually a darn good idea! Slotting
is no problem. They just have to be thin enough so they "snuggle in" and
we can tuck the excess away. There's several kilovolts of isolation in
this module but no problem. Thanks for the hint.

Come to think of it, even a skinny hose clamp might work. In the US
those are usually stainless steel.