Making a hot wire

Canvas covered foamies (Thrifty Alternatives...)

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Re: Making a hot wire

Postby atahoekid » Sun Apr 14, 2013 11:36 pm

Thanks for the post on that. The pics helped me a lot. I tried wrapping my brain around it a couple other times and couldn't get thru the verbiage. Funny though, I had an english teacher once tell me that I should become a technical writer because I had the ability to describe a process in words. Apparently can't understand the written word though... LOL I don't have a battery charger other than a trickle charger.. Will that work? What other kinds of power sources will work? I'm about to rebuild the rear doors on the Road Foamie and don't look forward to hand cutting the channels for the wiring and insetting the hard points. This will help!!!
Mel

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Re: Making a hot wire

Postby GPW » Mon Apr 15, 2013 4:47 am

We’ve got an old Variac , so we can just dial in the heat we need ... no pencil resistors ... But with so much adjustability , it’s easy to dial in too much and burn up the wire ... and it also puts AC on the wire ... :o Gotta’ be careful of a shock ... so all the wiring is insulated , except the cutting wire of course. :frightened:
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Re: Making a hot wire

Postby atahoekid » Mon Apr 15, 2013 10:54 pm

Being an electronic idiot, I had to google variac, but now that I see that it is a variable transformer, I know I don't have one. Maybe I can find an old train set transformer or slot car track transformer. Would those work?
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Re: Making a hot wire

Postby KCStudly » Mon Apr 15, 2013 11:27 pm

I'm pretty sure that my battery charger would be considered a "trickle" charger, and it worked okay for me.

Try it.

I was using a bow type cutter, so had some length to my wire, but as has been shown, that can be worked around.
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Re: Making a hot wire

Postby GuitarPhotog » Tue Apr 16, 2013 12:09 am

I used a surplus 6VDC wall wart power supply and a lamp dimmer for my straight cutter. I could adjust the temp to get smooth cuts.

The profile cutter required much stiffer wire (16 or 18 ga) so it took much more current. I got two 1.2 V 2000mAH NIMH cells on line and used them to power the cutter. I could get about 10 minutes of cutting out of one charge. Being hand held made it easy to profile the edges of my foam insulation.

I cobbled the whole works out of scrap wood, nuts and bolts, and electrical tape. But was too busy to take photos of it before it all went in the scrap bin again ;-(

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Re: Making a hot wire

Postby ghcoe » Tue Apr 16, 2013 6:00 am

I am using a cheap HF charger with a 2amp, 10amp and boost setting. I think I paid $32.00 for it. I tried two model train transformer, but they did not work. Probably too thick of wire.
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Re: Making a hot wire

Postby GPW » Tue Apr 16, 2013 8:23 am

Making foam RC planes for many many years now , we’ve done a good bit of hot wiring of foam , especially bead-board ... with various templates and jigs to produce specialized parts ... Using bows or short wire cutout tools , the ultimate power supply is the Variac ... We tried Everything else , and it just didn’t give the versatility of the Variac ... So if you plan on some long term foam cutting, it is a Great investment ... sometimes you can find them on Flea Bay , cheap ... I’ve used mine almost 40 years now so the investment is almost nil ... ;)


WARNING !!!! ::: They are DANGEROUS , and put AC on the wire , so it will “Bite you” .. :o or Burn you ... :frightened: Use with Respect and Caution !!!
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Re: Making a hot wire

Postby atahoekid » Wed Apr 17, 2013 12:04 am

GPW wrote: WARNING !!!! ::: They are DANGEROUS , and put AC on the wire , so it will “Bite you” .. :o or Burn you ... :frightened: Use with Respect and Caution !!!


GREEEAAATTTT! :shock: :shock: The electrical chicken in me did not know that! I think I will find another way to sculpt foam. I think a saw will do fine. I know how to safely handle those. :? :?
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Re: Making a hot wire

Postby GuitarPhotog » Wed Apr 17, 2013 1:17 am

If you engineer your foam cutter, using a resistance calculator and an appropriate power supply, your biggest danger is being burned by the wire.

My contour cutter ran on 3 VDC. No shock hazard there. I bought 16ga Nichrome wire and calculated that I needed 3 Amps at about 2 volts and decided that some rechargable D-cell batteries would do the trick.

The difference between engineering and random experimentation is that success is more predictable.

The site I linked to earlier has sources for nichrome wire, and info on low-voltage power supplies that won't kill you.

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Re: Making a hot wire

Postby eamarquardt » Wed Apr 17, 2013 7:56 am

GuitarPhotog wrote:The difference between engineering and random experimentation is that success is more predictable.
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All engineering has its roots in experimentation (or put another way first hand experience). Engineering is, IMHO, just extrapolation of the results of previous experiments.

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Re: Making a hot wire

Postby KCStudly » Wed Apr 17, 2013 8:06 pm

TLAR

:D
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Re: Making a hot wire

Postby ghcoe » Wed Apr 17, 2013 8:36 pm

You should be careful with current and hot wires just like any other tool you use. I probably could run a hotter wire to cut with, but I find the 3 feet of wire, in my case, to be a good compromise of cutting speed and safety. A hot wire, hot enough, will cut through flesh as fast as it will cut through foam.

I once had a key chain in my hands when it arched between the car body and the positive side of the battery. It just so happened that my pinky finger was in one of the key loops. When it arched it instantly cauterized the loop through my pinky to the bone! :shock: So now I had a key chain that was embedded in my pinky. Luckily the loop was just a cheapy loop and not one of the heavy duty loops. I had to cut the loop off on both sides of my finger with side cutters and then pull the rest of the loop out of my finger. The funny thing was that it never really hurt that bad, but it sure looked bad.

But hey, I also skill sawed my hand once, I'll leave that story for another day.....
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My build viewtopic.php?t=54099
Working with flashing for foamie construction viewtopic.php?f=55&t=60303
Making a hot wire http://tnttt.com/viewtopic.php?f=55&t=55323
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Re: Making a hot wire

Postby Fred Trout » Mon Jun 08, 2015 1:05 am

George, could you explain the specifics on how you used the soldering iron cutter; differences in wire gage / thickness & length kinda stuff. Also, did it do as good a job as the 2x4 gravity fed jigs you discussed here ? Anything else about soldering-iron-cutters that you think would help too. Thanks !!



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Re: Making a hot wire

Postby ghcoe » Tue Jun 16, 2015 9:13 pm

Fred Trout wrote:George, could you explain the specifics on how you used the soldering iron cutter; differences in wire gage / thickness & length kinda stuff. Also, did it do as good a job as the 2x4 gravity fed jigs you discussed here ? Anything else about soldering-iron-cutters that you think would help too. Thanks !!



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Sorry for the late reply. Just too busy around here.....unfortunately not with my foamie :x

I made a hot wire with a gun style soldering iron, if you want to call it that. I just removed the existing tip and installed a piece of baling wire I purchased at the dollar store. It is pretty easy. Again the wire can be bent into different shapes for different types of cuts. Not sure the diameter of the wire, but it is pretty small. The working length is pretty limited to keep the wire hot enough to cut nice. It is a bit slow going, but it cuts real nice.

I was a little spooked to use a hot wire at first, but the more I used one the easier it got to be. Pretty soon I was looking at hot wire solutions for all my cuts just because the cuts, when done right, are just so crisp. Best of all no foam dust :wine: . Also, when the hot wire cuts the foam it creates a nice tempered surface to the foam.
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Gorrilla Glue, Great Stuff and Gripper. The three G's of foamie construction.

My build viewtopic.php?t=54099
Working with flashing for foamie construction viewtopic.php?f=55&t=60303
Making a hot wire http://tnttt.com/viewtopic.php?f=55&t=55323
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Re: Making a hot wire

Postby Fred Trout » Tue Jun 16, 2015 10:48 pm

Thanks - late is better than not at all !

I had trouble getting the HF soldering iron gripping the welding steel wire I ended up using, about the same thickness as baling wire, so the wire would come off the soldering gun when pulled straight out. Never could figure out how to get it to grip but I didn't try too hard. Cut my spline beds and the raceway for the porch light wiring in the door 'frame' and that's all I needed.
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