On a sunny day (Tue, 16 Jun 2015 10:12:26 +1000) it happened Chris Jones wrote in :
Yes, they can be made OK, It is well known that the Chinese do not know how to make rubber, same for engine mounts, BEWARE. But they undercut every price, so the market is flooded with bad Chinse rubber [bands], and the faster those detoriate the more are sold.
I read 'chips'.
Cheers
-- Syd
Even if you disassemble ferrite transformers and etc. with the use of heat, superglue still tends to end up being a key disassembly facilitator. :-)
Tim
-- Seven Transistor Labs, LLC Electrical Engineering Consultation and Contract Design Website: http://seventransistorlabs.com
Thanks. I was wondering how it worked. The project was a 1970's style linear power supply. 13.5v @ 25A at a 25% duty cycle for a SSB radio. Like just about everything I did at the time, it was a rush job, which meant some of the parts were missing. In this case, the clips to hold the custom E-I xfomer together were on backorder. So, I used stainless hose clamps and later stainless strapping. At full power, the strapping became slightly warm. Worse, the heating varied from xformer to xformer. When I added plastic corner protectors to make it easier to tighten the strapping, the heating seemed to be reduced. I had other problems to deal with an never pursued problem further.
With an E-I stack, the strapping is the width of the laminations and probably sufficient far away from the gap to not be a problem. However, if the core is rectangular, with the gap on the outside, the strap is very close, and will probably bridge the gap. For such a core, I presume that non-metallic strapping (i.e. ty-wrap) is required.
I just tried a magnet to an automotive hose clamp and it is slightly magnetic. The strap is 304 stainless, while the screw is 400 series (magnetic). Since I was in the marine radio biz, we also had a supply of 316 stainless straps (Aquaclip), which are acid resistant for use near battery packs and on antenna structures. Various data sheets claim that 304 is non-magnetic, but my refrigerator magnet says otherwise. I can't find any 316 to try.
The strap heating was noticeable, but perhaps I was overly concerned. My knowledge of magnetics was limited so I tended to worry about everything that seemed out of place.
That's what I was muttering about when I mentioned the rectangular core xformer. With a C-C arrangement, there are two gaps, both on the outside of the laminations. The strapping would be directly adjacent to both gaps. Are the ends of the laminations polished? Does the strap get hot? (Just curious).
-- 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 never make mistakes, so cyanoacrylate adhesives are just fine.
However, you're right. I've built some structures for HF RF power amps out of ferrite beads using super glue for assembly. When I tried to break them at the glue line, I often broke the ferrites instead. I tried some super glue remover, but didn't work very well. Acetone works great, but likes to destroy everything else it touches. I slopped some on my fingers, and even after washing my hands, I managed to impress my fingerprints in a rather expensive plastic panel. I recently repeated my performance by destroying a plastic computah keyboard.
Second best is hot water and a small amount of dishwasher soap to increase the surface tension of the water. For a really impressive mess, add ultrasonics. 3rd best is a torch. If you can heat the joint, the super glue will just crumble. Incidentally, if you have a metal syringe super glue dispenser, the easy way to clear the needle from hardened super glue is with a cigarette lighter flame under the needle. It belches a rather impressive flame, and is then clear. Since it burns from the open end towards the container, there's no internal contamination. Non-flammable acetic acid vapors inside the container will prevent the flame from converting the glue bottle into a hand grenade.
Glue selection is always a sticky subject. I would probably have used a other glue other than super glue, that was easier to handle, except that super glue produces a very thin glue line. I tried contact cement, which produced a rather large and difficult to control gap. Basically, anything that was thick enough to be a "gap filling" type of glue, was too thick. You could try plastic model airplane or nitro-cellulose (Duco cement??) glues but these will probably require thinning in order to get a narrow glue line. Both can be easily removed with acetone.
-- 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 just tried a magnet to an automotive hose clamp and it is slightly
300 series stainless is considered non-magnetic. However 300 series stainless that has been cold worked is somewhat magnetic.Dan
On a sunny day (Tue, 16 Jun 2015 06:40:13 GMT) it happened Jan Panteltje wrote in :
Amazing, package just arrived from the UK with polyurethane bands. That is a speed record fro ebay here!
Those are very small (only for ever small transformers) but look good, going to test one. Can be used for othwr things too. Snap easily too :-)
Yeah, superglue is good for putting together, as pressure makes the bond thin = better bond + less flux loss. Semi-bitchy on undo; best "solvent" seems to be acetone which tends to get to other things and people as well....
So the polyurethane bands lasted even shorter than the Chinese rubber bands, just about one hour before the first one snapped.
ElectronDepot website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.