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Old 02-24-2012, 10:50 AM
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ErlendM ErlendM is offline
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Default Hotwire - powersupply

I'm finally getting foam for the canard, so I'm ready to do the hotwire-thing. I've practiced on small parts earlier, using the setup as described in the plans. It worked ok, and I'm planning to use the same setup when I go "live".

I've read several posts here from people that buys or makes various types of power-supplies. My setup is a regular 70Amp 12V car-battery. Will this be enough to cut the canard-cores? My test-cutting was on smaller parts, but I had to adjust the heat down pretty much to get the smooth cuts. My concern is that the larger parts cools the wire down so much that I need more power. I can of course connect another battery, so I have 24V if that is neccessary.

Has anyone here successfully used a car-battery for this? I was hoping to avoid buying stuff that I will need for just a couple of hours, if what I have is adequate.
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Old 02-24-2012, 12:11 PM
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Default Re: Hotwire - powersupply

You might experiment with a battery charger
http://wolfstone.halloweenhost.com/H...FoamTools.html

or here's a hotwire saw idea using 230V source
http://varieze.homestead.com/hotwire.html

others here
http://cozy.caf.org/factory/index.shtml
http://www.instructables.com/id/Hot-wire-foam-cutter/

The main thing is to build-in/use some sort of isolation transformer if you are using an AC power source.
http://www.youtube.com/watch?v=QDSmv9E5VgQ
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Old 02-24-2012, 12:41 PM
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Default Re: Hotwire - powersupply

Quote:
Originally Posted by ErlendM View Post
...
Has anyone here successfully used a car-battery for this?
....
Yes!
I used a four foot frame with 22gauge (.025") nichrome wire, 12-16' of 18gauge 'lamp' cord as the feed, and two batteries. Worked very well.

I also have a small hot wire saw that I used for the elevators (and Rough River). About 2' long, same wire, but only one battery.

My main saw: http://cozy.zggtr.org/chap10/canard.blocks.jpg

Both saws get a bit hot when they're not in the foam, so the first 1/2" of cutting goes pretty quick.

Rick
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Old 02-25-2012, 05:22 AM
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Default Re: Hotwire - powersupply

Thanks guys!

Kent: I did almost buy a regular power-supply from 12-18V, but thinking back on my tests I figured it couldn't be really necessary as long as the plans setup actually works, and I happen to have a couple of 70Ah batteries standing in the garage. And one note on this forum captured my attention, it said that I would use just a couple of hours to cut both the canard and the wings. Well - another incentive to keep it simple - if it really works!

Rick: How did you determine the heat? And did you use the "regulator" as per plans? I.e. the wire on a board thing?
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Old 02-25-2012, 11:23 AM
ZG4Me ZG4Me is offline
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Default Re: Hotwire - powersupply

No regulator, at least not the zig-zag wire on a board. If I needed less heat, I added length to the feed wire. Or use a smaller feed wire. But neither was needed.

I judged the heat by how fast the wire cut, how it sounded when cutting, and the fuzz left on the surface (and at the exit). I tested the heat on a straight cut, shave off 1cm from the end of a block...

There is a fair amount of resistance in my setup, for hotwiring saws that is. The length of the feed wire, size of the feed wire, as well as using a somewhat small nichrome wire. 12v did not work for me, I had to use 24v.

Rick
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Old 04-03-2012, 05:05 AM
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Default Re: Hotwire - powersupply

Just a note for future builders. I've now cut the canard-cores using the plans setup, but with 2 12V car-batteries in series instead of a ordinary power-supply. Worked like a dream. As Rick said, it wasn't even necessary to use the zig-zag-board to regulate the heat. I just used a longer feed-wire.
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