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Author: Subject: A heating source with many uses.
Tacho
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[*] posted on 25-2-2004 at 11:50
A heating source with many uses.


After trying many different solutions for the problem of heating reactions, I found that this is the most versatile solution, also the cheapest.

The idea is to insert the Nickel-Chrome coil inside a flexible fiberglass (glass fiber fabric) tube, kind of a sleeve. You end up with a flexible linear heating element that can be coiled in a spiral to make a heating mantle, or wrapped around a tube to make a tube furnace. It can be dipped in water or oil to make a heating bath and so on.

This flexible fiberglass tube is not trivial. It is used to insulate wires in high temperature industrial environments. But you can probably find it where you find the NiCr coil.

Well, the idea is here. Hope you can adapt to what you have available.

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[*] posted on 26-2-2004 at 08:09


I don't know of any retail source for the fiberglass tubes. Or curly nichrome, though I know it's found in some hair dryers. If you're going to be buying specialized kit anyway, look into getting ready-made heating tape from, say, Omega Engineering (omega.com).
Except for the short length of exposed leads, you've got a pretty slick looking device though. I tryed rigging an electric heater two nights ago. It was a dismal failure. I used nichrome from an old toaster. The wire was thin and broke easily. It wouldn't hold a cylindrical shape, so I ended up weaving it through the fiberglass cloth I was using for electrical insulation. The wire developed a break from the weaving process so it did nothing when I plugged it in. Also unfortunately, I hade failed to note that the wires were meant to be connected in series, so I ended up running my last remaining intact wire at twice the power it wanted. It too broke. Result: a broken up toaster and a floor covered with unraveled fiberglass and scorch marks.
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[*] posted on 26-2-2004 at 13:10


Yes, I admit that finding a good supplier for these things is not trivial, but, if there is one universal need in modern life, that is electrical heating. It’s in your car, home appliances, hairdryer, water heating. Every industry has lots of it.

What I am trying to point out is that if you look in yellow pages (or however you call your local commercial phone book) you will certainly find some supplier for bits and pieces.

Of course, we are always trying to save money, and that’s where creativity comes in.

Since you committed the sad mistake of replying my post, I will submit you to some more of my ideas.

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Geomancer
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[*] posted on 26-2-2004 at 13:47


The device in that second picture is a work of art. I'm actually envious I didn't think of it. Of course, I don't have any irons available at the moment, and I was lucky enough to find a (cooking-style) hotplate at the local thrift store for $4US.

Edit: Oh, and what's with the enclosure underneath? Does the thing have a stirrer too?

[Edited on 26-2-2004 by Geomancer]
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biggrin.gif posted on 26-2-2004 at 16:44
Thank god for ASS!


I have found a 27 inch fiberglass heating rope.
Heating Rope
They say they are rated at 90 watts and cost about 2$ each.

Great idea Tacho! I will buy one of these ropes soon and make a stirrer/heater.




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[*] posted on 27-2-2004 at 03:13


I use an independent magnetic stirrer made with the stepper motor driver I described in another post. It fits under the hotplate of the first picture as well as under other devices.

If I knew what that second picture is about, which I don´t, I would say the lower part is the case of an old apple-II floppy disk drive. The stepper motor of the drive could be used to power a magnetic stirring. This idea doesn´t seem to be implemented in this case though (yet).

If I had a ridiculous device like that, which I don´t, I would be careful with the dimmer control, since most dimmers cannot handle the power of most Irons. One should make the right combination.

About heating tapes, cords, ropes etc.:
Make sure they get hot enough for your needs before you buy it. "Too hot to handle" could be 80ºC. The ones I have found were either too expensive or would not get very hot. To distill water rather quickly, I have to see the thing glowing red under the flask.
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[*] posted on 27-2-2004 at 03:59


"Curly nichrome".

Me be thinking, and come to conclusion that it could be made simply by winding thin nichrome wire around a thin glass rod (or similar). If longer lengths are required, just retract the rod a bit from ze coil and continue winding. Should work, no?




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[*] posted on 27-2-2004 at 05:06


I think I'll contribute with one small idea I used once when converting a deep frier to a rocket fuel melting pot.

I found that the risk for hot spots was too great when connected to the 220V AC mains.

So I did something <b>very</b> simple: I inserted 1 rectifier diode before the melting pot. Result: Slower heating, greatly reduced risk of hot spots.

This should work with any heater unless it incorporates a motor (which would make it dependant on AC).

Edit: Oh dear. I'm close to my 200th post.


[Edited on 2004-2-27 by axehandle]




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[*] posted on 27-2-2004 at 06:10


Quote:
Originally posted by axehandle
"Curly nichrome".

Me be thinking, and come to conclusion that it could be made simply by winding thin nichrome wire around a thin glass rod (or similar). If longer lengths are required, just retract the rod a bit from ze coil and continue winding. Should work, no?


Oh yes! It works.

I buy my NiCr wire coil in a shop where they make it on demand. It´s a simple machine, just a rod (they change thickness as needed) conected to a variable speed motor. The coils comes out easily from the rod after they spun (sp? spinned?) it.

About diodes: if your fry pan is about 2200W, which is not much, at 220V, we are talking 10 amperes. A 10A diode is not usual or cheap. But if you have a proper diode, is an excellent solution to cut power in half.

The optimal solution is a dimmer, but you have to make sure it can handle your load, usual home dimmers are about 300W. You can buy or built dimmers that deal with more power.

A very good idea is to connect a commom 5w light bulb to your dimmer so you can SEE how much power you are putting in your load. After you do this, you will never work with dimmers without bulbs again!

Edit1- BTW, It´s very common to find flat NiCr tape, instead of round wire. These tapes are more efficient but are not very easy to work with. Besides, they are far more fragile.

[Edited on 27-2-2004 by Tacho]

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[*] posted on 27-2-2004 at 06:20


The deep frier is only some 600 wattish, but I used a meaty rectifier, capable of 10A at 400V, if I remember correctly.

The dimmer idea with the 5W lamp is very good, thanks. I'll use it if the need arises (the melting pot/former deep frier has a thermostat, so I didn't really need a dimmer).

NiCr tape... hmm, never seen it. I've only worked with round wire. It should be fairly simple to make tape out of wire using two rollers (can't remember the English name for the contraption)...

Edit: And I think you need to change your electronics parts supplier. These rectifiers cost me about $0.1 a piece....


[Edited on 2004-2-27 by axehandle]




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[*] posted on 27-2-2004 at 09:06


Maybe I expressed myself badly: I DO NOT like the NiCr tape!
I mentioned it to warn people NOT to buy it. Round wire is much more versatile and resistent.

You mean U$0,10 for a 10A diode? That is cheap! Here I pay the equivalent of 0,40 euros for a 6A (plastic) and 3,50 euros for a 15A (metal).

Actually, now that I think about it, it is really not much to pay for a 50% power control.

If you can get them so cheap, what about putting many of them in series? If I am not wrong, each would lower the voltage about 0,7V. Well, may not be such a good idea if you work with 220V.
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[*] posted on 27-2-2004 at 09:31


Ok, ok! Sorry....

Here is a link to a page with the rectifiers I got:
http://www.elfa.se/elfa-bin/setpage.pl?http://www.elfa.se/el...

I think I got 25 of the LT10A4/Lit type.

The prices are in Swedish crowns. Ten swedish crown is roughly the same as one US $.

Seems I got them for 1.37 SEK a piece, which is about 15 US cents a piece.

Elfa is THE electronics supplier in Scandinavia. If I'm not mistaken, they ship overseas as well.

Edit: It seems not, only to "Sweden, Norway, Denmark, Poland, Finland and Estonia, Latvia, Lithuainia, Russia, Turkey (through retailers)."

Edit2: A metal one capable of 40A at
1200V would cost approx. 0.8 Euro.
Perhaps they really are cheap, haven't thought much about it.

Edit3: As for putting them in series... well let's just say that I've had bad experiences with that kind of solution. Weakest link, etc...



[Edited on 2004-2-27 by axehandle]

[Edited on 2004-2-27 by axehandle]

[Edited on 2004-2-27 by axehandle]

[Edited on 2004-2-27 by axehandle]

[Edited on 2004-2-27 by axehandle]




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