Keeping it together

Self-amalgamating tape works well, especially the silicone stuff.

Cheers

--
Syd

On a sunny day (Mon, 15 Jun 2015 09:06:27 +0100) it happened Syd Rumpo wrote in :

Cool, ordered some

they don't.

use cable ties, heatshrink, or cling wrap.

--
umop apisdn

Eww-www...

I use the authentic yellow tape stuff. Or the gold tape stuff if I'm feeling frickin' /fancy/!

(3M #56 or something like that. Gold stuff is Kapton, obviously.)

Unusual constructions I've been known to superglue or epoxy,

this one is gapped with two strips of 0.8mm FR4 (bare).

Tim

-- Seven Transistor Labs, LLC Electrical Engineering Consultation and Contract Design Website:

On a sunny day (Mon, 15 Jun 2015 05:58:09 -0500) it happened "Tim Williams" wrote in :

Wow!

When looking it up on ebay I see the gold stuff seems a lot cheapr than the yelow tape, is used in 3D printing it seems?

3M #56

Kapton, Chinese:

?

I see you are really into high power, but also respect the good old Duracells... :-)

Jan Panteltje:

together:

halves fall off,

morning

silly con?

There is no glue or plastic clippy thing or rubbery bandy thing or plastic tape I would trust for long term with temperature cycling. Use proper metal springy clips or metal bands like they used to have round C core transformers.

nice pictures here:

(sorry it's audio but it's the first nice picture I found.)

Michael Kellett

The silicone self-amalgamating tape has been tested with many temperature cycles between ambient and 200'C. I like it because it maintains a pressure and works well in harsh environments.

Much to my surprise, I found that some cores don't have metal spring clips.

Cheers

--
Syd

I've used automotive hose clamps to hold E-I stacks together. Just pre-bend the stainless straps to fit the corners. They go on and off quite easily. However, I've never tried it with ferrite as I was afraid that the clamping pressure would crack the core and that the stainless band might bridge an external gap. We shipped about 15 prototypes using these bands before the real clamps arrived. There were no returns or problems.

For smaller prototypes, I used fiberglass filament reinforced packing tape: The main advantage is that it does not stretch lengthwise and holds its position under varying environmental conditions. The glue tends to be rather permanent, so I first apply a layer of vinyl electrical tape, and then add 2 layers of fiberglass tape.

--
Jeff Liebermann     jeffl@cruzio.com 
150 Felker St #D    http://www.LearnByDestroying.com 
Santa Cruz CA 95060 http://802.11junk.com 
Skype: JeffLiebermann     AE6KS    831-336-2558

On a sunny day (Mon, 15 Jun 2015 07:20:35 -0700) it happened Jeff Liebermann wrote in :

I have some of that stuff somewhere actually, never thought about using it for tranformers.

I prefer something a bit elastic, so the prssure on the core halves can be set.

+1

Dan

Den mandag den 15. juni 2015 kl. 16.20.36 UTC+2 skrev Jeff Liebermann:

you can also get metal zip ties

-Lasse

I don't have advice on how to solve your problem but I do have a rubber band anecdote.

From time to time I have bought ex-USSR NOS vacuum tubes (valves) off e-bay. Often they come in the original cardboard cartons and inside there is a vacuum tube with the test report wrapped around it and held on with a rubber band. Some of these are dated from between the late

1960s and the mid-1980s, and the rubber bands are still in good condition after sometimes >40 years. Whatever these "rubber" bands were made from, it was good stuff.

Chris

I forgot to mention that you should put something on the corners of the E-I stack. I used some right angle extruded plastic but almost anything that wraps around the corners and is rather soft will work.

Also, while the stainless steel banding is not really part of the transformer core, there's enough flux leakage to produce some heating in the stainless band due to eddy currents. In effect, you have a shorted turn. I haven't seen much in the way of problems at 60 Hz, but if the xformer is in a switcher, you might want to check if it gets hot.

I rather doubt that a constant pressure can be maintained over several years operation. The tape is going to get hot and the glue will soften. Eventually, the tape will creep, and there goes your precision tension adjustment. If you use the tape for maintaining tension, the tension will change with temperature. Try it. Make a loop with your favored tape. Hang the loop from a nail in the wall. Add a weight. Heat the tape with a heat gun and watch what happens. I've done this with the fiberglass packing tape and found it to be quite stable. However, the glue melted when hot and it fell off the nail. For really lousy results, try it with vinyl electrical tape.

For gaps, I use fiberglass (G10) as if it were shim stock, and glue the fiberglass in place. With adequate pressure, it's not going anywhere. You can get some really thin stuff:

--
Jeff Liebermann     jeffl@cruzio.com 
150 Felker St #D    http://www.LearnByDestroying.com 
Santa Cruz CA 95060 http://802.11junk.com 
Skype: JeffLiebermann     AE6KS    831-336-2558

I still have a box of green rubber bands from when I had a paper route as a kid. They are still in serviceable condition. I expect they last because they are in a closed box just as your tubes were. My understanding is that rubber holds up quite well except for ozone in the air. Eliminate ozone from circulating into the box and the rubber remains intact.

--

Rick

I understand most of what was written here, like "silly con", but what is "sjips"? Anyone know? Or do most people just read over the parts that aren't clear?

--

Rick

There's No Such Thing As OZONE DAMAGE and There's No Such Thing As Human-Caused Global WARMING.

It's figment.

RUBBER is latex when it lasts a really long time.

Today's 'rubber' isn't Latex so it suxorz.

A shorted turn, yes, but not parallel to the direction of the coil. (A copper strap, going around both core legs and the winding, is handy to reduce leakage. A common sight on switching transformers, and occasionally seen on 'low noise' line frequency types.) It will only heat up where field leaks out nonuniformly (i.e., high divergence): not directly axial to the coil (there's no field there), but a little bit along the 'spine' of the E/I. If the core is gapped, there will be considerable fringing around the gap, and anything within about two or three gap widths will get induction.

At line frequency and using stainless (it's not very conductive, and presumably nonmagnetic, or nearly so), I'd be surprised if it was even noticeable anywhere.

Speaking of steel straps, I have a peculiar C-C style core (possibly GOSS stripwound, cut halves, hence the shape) which uses steel strapping, of the ratchet-and-crimp kind used e.g. for shipping (a bit more permanent than hose clamps, but very much the same idea).

Tim

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

On a sunny day (Mon, 15 Jun 2015 18:01:13 -0700) it happened Jeff Liebermann wrote in :

Right, that is actually what I ment.

That is why I was using the rubber bands, I will try the polyurethane too.

Yes, but the problem with glue is that sometimes I modify things, breaking ferrite is very easy I have found.

On a sunny day (Mon, 15 Jun 2015 12:40:36 -0700 (PDT)) it happened Lasse Langwadt Christensen wrote in :

Interesting, had not seen those yet.

At least when you tie up the bad guys with those, they cannot get free with a ligther..