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scratch built hot wire cutter

Old 12-11-2009, 11:56 PM
  #26  
OzMo
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Default RE: scratch built hot wire cutter

I just built new bows and used a tip from another site on this topic. Replacement fiberglass tent poles work great for the "legs" very springy and nonconductive.
Guys, do a search on foam wing cutting or similar and lots of stuff comes up.
Old 12-12-2009, 06:13 AM
  #27  
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Default RE: scratch built hot wire cutter

Nobody has answered with the thickness to buy, so I measured the actual wire I used ( old electric fire element ) and it is .020 inch ( twenty thou ) which is roughly about .5 millimetre ( half a millimetre ) The actual diameter varies along the length, probably due to residue from foam cutting etc.
Old 12-12-2009, 10:26 AM
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Default RE: scratch built hot wire cutter

Hey guys, I have been using the MECOA foam cutter system to cut wings and it works great. As far as the wire, they have their own, but I have been using a different type wire. SIG sells nichrome wire (part# SIGSH135) which seems to be about 0.0135 ~ 0.014 thick. This seems to work great for the 28" bow I am using to cut wing cores. I have cut 20 sets of main wings and tails without a breakage so far.

Best wishes,
Old 12-16-2009, 06:23 PM
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Default RE: scratch built hot wire cutter

Sig's wire is nichrome and it works ok. But for the same $5.00 more or less you can get 200 feet of SS leader from Bass Pro or other fishing outlets.

Old 04-09-2010, 01:57 PM
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Default RE: scratch built hot wire cutter

Hi, Pholks... I am having trouble with my foam cutter... I need to talk to someone who really knows about this stuph. If any of you are willing, my email is [email protected]. I really would appreciate some help. John
Old 04-09-2010, 04:49 PM
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Default RE: scratch built hot wire cutter

I cut with 115 VAC as the input to the dimmer.
Very dangerous with 115V, deadly with 240 volts!

For a large cutter (40 inch is a large cutter) you will probably find 12 volts is not enough to heat the wire enough & the thinner the wire the more volts you will need as the resistance of the wire is greater.

2 car batteries in series will give you 24 volts, should be ok but no temperature control.

What I use is a light dimmer like Combatpig but on the 240 volt side of an old 32 volt lighting transformer. The output side of the transformer will only be 32 volts max, safe to use.

Beware of using a Variac type of adjustable transformer, the type with the big black knob on the top. Many of these will have low voltage BETWEEN the output terminals but the output remains 240 volts to earth & you are at earth potential. To use one of these safely you have to, once again, feed the output through another transformer.

Stay safe! - John.
Old 04-09-2010, 06:55 PM
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Default RE: scratch built hot wire cutter

A little bit of knowledge is dangerous.

There is nothing wrong with using 115 volts as the input to the dimmer, unless you are stupid enough to place yourself across the input.

The output is very safe, unless you insist on doing the hot wiring in your bare feet while standing in a bucket full of salt water with copper ankle bracelets that lead to your grounding electrode system.

Then you might feel a tingle.

BTW....nichrome wire sucks, use stainless.
Old 04-10-2010, 06:52 AM
  #33  
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Default RE: scratch built hot wire cutter

A little bit of knowledge is dangerous.
Agreed, so take some advice from someone with 35 years in the trade.

Unless the dimmers in the US use an isolating transformer they will be the same as the electronic dimmers used around the rest of the world. A dimmer is not designed to reduce the voltage, they chop the waveform of the AC current.

http://www.sprags.com/

It's not safe & you will get booted from the output. - John.
Old 04-10-2010, 10:03 AM
  #34  
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Default RE: scratch built hot wire cutter

It's no less safe than my MIG welder, table saw, router, working around a model airplane engine, etc.
I've come in contact with the wire several times over the 24 years that I've been using this set up..outside of some warmth never felt a tingle. It takes about 2.7 amps for cutting.

As a AMA C/L Combat flyer and general modeler for all these years I've gotten my share of use out of it.

I don't know of anyone who has ever been bit by this set up and I do know a few guys in the area who use 120 volts through a dimmer to heat their wire. Just be sure to verify with a meter that you are controlling the hot and not the neutral.
Old 04-10-2010, 06:03 PM
  #35  
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Default RE: scratch built hot wire cutter

I've come in contact with the wire several times over the 24 years that I've been using this set up..outside of some warmth never felt a tingle.
And good luck to you. I'm not here to argue. All I'm saying is I've seen something potentially dangerous based on my qualifications and offer some advice on how to make the process less hazardous. If people take my advice or ignore it that's their business.

Everyone's trying to do things on the cheap these days. A transformer is much cheaper than a funeral. - John.
Old 04-10-2010, 07:52 PM
  #36  
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Default RE: scratch built hot wire cutter

Well, that's very dramatic......but it's B.S.

For the benefit of Mankind, furnish us with a list of cases you know of where someone was injured or killed hot wiring foam with a 120v dimmer.
Old 04-11-2010, 12:21 AM
  #37  
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Default RE: scratch built hot wire cutter

Like I said I'm not here to argue.

If it makes you feel happy/bigger/better/whatever, you win.

Go & do whatever you like with electricity or anything else for that matter. - John.

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