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        Question Hot Wire Foam Cutter Power Supply?

#1 Slope Lift Nov 29, 2005 01:34 AM

Hot Wire Foam Cutter Power Supply?
Has anyone built or tried this? It's a schematic for a hot wire foam cutter.
Click on URL to see:

Would like your opinions?



#2 lockheed martin Nov 29, 2005 02:06 PM

the um link isnt working anymore? it was and now it isnt...
Aside from that small problem.

Looks like it will work just fine. You might want to put a trasistor in conjunction with a thermistor in the circut or a variable resistor in so you can control the heat that the wire is. As the link isnt working anymore I forgot the exact layout of where you could put it but I would say if you where to put them in, do so on the right side of the bread board. Sorry for the vagueness...

#3 MtnGoat Nov 29, 2005 03:04 PM

if you do choose to put in a resistor, you'll need to make sure it can dissipate the amount of energy you are putting through it, or you'll just smoke it.

#4 lockheed martin Nov 29, 2005 06:12 PM

lol yer make sure very much! I have a 12V hot wire cutter but hotwire cutters of the mains is a different story so as MtnGoat said be careful!

#5 prplgoat Nov 29, 2005 11:39 PM

i've got a buddy that just hooked up a 110v dimmer switch,a 100watt bulb for a load and his cutting wire in a circuit,and it cut great!
set his temp with the dimmer.
cheapest way i guess!


#6 Slope Lift Nov 29, 2005 11:55 PM

A person with bare hands will get a good zap on that setup. You would probably need some type of insulating gloves to handle the cutter.

#7 prplgoat Nov 30, 2005 12:23 AM

i like a good zap on occasion!
ya, you'd have to insulate and be careful.


#8 ThermalSeeker Nov 30, 2005 08:35 PM

If it's the do-it-yourselfer trying to get out..then go for it. I'm the same way and it looks like a fun project.

If just cutting a couple wings as cheaply is possible is the goal there's a much simpler way. Many moon ago when Burt Rutan and his company Scaled were still selling homebuilt airplane plans they had a little "How to" booklet to give confidence to the would be builder that he could actually do composites. The hot wire power supply in that manual consisted of two 12 v batteries in series to give a maximum of 24v available. (I used a 12v battery and a 12v battery charger..also Nick is right that you'll need to have a means to vary the heat that the bow creates for the length of foam you're going to cut.) To vary the heat on this set up you just need to add about five feet of safety wire (variable resistor) to one of the the battery connections that's going to connect to the bow. Run the safety wire in a zig zag fashion across a bunch of nails in a board left to right. Use an alligator clip to connect your bow to the battery on one end and one of the safety wire nails on the other. The further away from the battery you connect on the safety wire the cooler your bow will be.

I used this when I first started hot wiring long ago. Currently I use 13 to 15 volts on a 30 inch long core. I've used Nichrome wire but didn't like it, .030 stainless steel safety wire for many years with great success, but now like .020 Inconel even better. You might try something close to that for a starter.

I hope that helps,

#9 Slope Lift Dec 01, 2005 02:41 AM


Which Inconel wire do you use or is best? The Black-Oxide or Silver?


#10 ThermalSeeker Dec 01, 2005 11:45 AM

It's the silver..no black oxide coating. The reason I like it is because you can get the bow tension outrageously tight and it stays there even after the heat is on. This is the same stuff they use to make little fingers that go into jet exhausts to pull out the thrust reversers...thus can maintain it's mechanical properties when hot


#11 DoonRaker Dec 29, 2005 11:20 PM

What power supply setup do you use with that .020 Inconel wire? And where do you purchase the Inconel wire?

#12 the_canuck Dec 29, 2005 11:37 PM

You can pick up a bench supply from Ebay for around 100 bucks that is variable voltage and has a current limit. Mine goes up to 35Vdc at 5amps and cost me a $130 shipping included. It's digital display as well. Very easy to use and good for lots of other things like charging lead acids etc.


#13 DoonRaker Dec 30, 2005 12:40 AM

Will this work?

#14 SkyKing RC Dec 30, 2005 10:01 AM

Wire and power supplies
Hey guys no need to spend so much for a power supply. All you really need is a Variac which you can find on e-bay for between $20 and $60 and a transformer that is capable of 30 volts/5 amps or 42 volts/2.5 amps. These should cost no more than $20.

As for wire I sell Rene in .014 for $25 for a 50' spool which should last the average modeler a few years unless they are producing hundreds of wings. Rene is the best wire we've found and we've been using it for production for several years.

You can find it on our web site: http://skykingrcproducts.com/accesso.../renewire.html


#15 DoonRaker Dec 30, 2005 11:53 AM

Moved to own thread... sorry to hijack. :)

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