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Old Dec 21, 2012, 02:41 AM
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Christiansburg, VA
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Is the spreadsheet posted somewhere? It would sure make my life easier!
Thanks guys, good thread!
Mike
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Old Jan 11, 2013, 03:48 PM
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United States, MO, Fenton
Joined Jul 2012
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Quote:
Originally Posted by ForeverFlying View Post
Is the spreadsheet posted somewhere? It would sure make my life easier!
Thanks guys, good thread!
Mike
If you go back to Thread #9 you should see a post by vtdiy. He posted a link to the spreadsheet he made. I am reposting his link below:

http://www.rcgroups.com/forums/showthread.php?t=1625684

However, please do read his posts to understand the spreadsheet. vtdiy is very helpful; so, if you have any questions, please don't hesitate to ask him. I finally got my electronic components figured out. I am ready to build a complete cutter. I will post my results soon.
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Old Sep 27, 2013, 08:33 PM
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Joined Dec 2008
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Hi electronics gurus , I realize this is an old thread but need advice on power supply. I just bought a 5 amp 12 volt power supply to controlled with a 1000 watt dimmer . I was hoping to use mig welder wire . Not sure of the diameter but it does look thinner than say .020 . I'm not at all an electrically minded person and was hoping to get some advice on whether this will be enough power . I'm thinking of making a 3 foot bow . Will the 5 amp be enough ? I think it's Acdc current . The guy at the electronic supply said the dimmer should go on the output side on the power supply on the positive wire . Does this sound right ?
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Old Sep 27, 2013, 10:20 PM
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Christiansburg, VA
Joined Sep 2002
790 Posts
Hot Wire Cutter

Hi Pencon!

You definately need to put the dimmer on the AC side (input) of your power supply. If your power supply does not have a transformer, then you need to get one for safety purposes (to provide isolation, to prevent shock). Here is an Instructable that is pretty good:

http://www.instructables.com/id/Hot-...tter/?ALLSTEPS

If you have trouble with the mig wire, consider this:

http://www.skykingrcproducts.com/acc.../renewire.html

If you want to simplify all of this, and make life easy and safe, consider this:

http://www.circuitspecialists.com/csi3005sm.html

I didn't have much luck with a bow cutter. This one for tapered wings, however worked pretty good for me:

Hotwire demonstration (3 min 30 sec)


Best of luck!
Mike
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Last edited by ForeverFlying; Sep 27, 2013 at 10:48 PM.
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Old Sep 28, 2013, 01:51 AM
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Staffs, UK
Joined Nov 2003
10,768 Posts
Can you provide details of exactly what "5 amp 12 volt power supply" and "1000 watt dimmer" you have ?

If it's a regulated supply putting the dimmer on the input side won't do anything.

If it's a DC supply then most dimmers will not work on the output side.

And 12V is not enough for most 3ft long bows but it does depend critically on EXACTLY what wire you're using (I've got wire of 5 different sizes and materials for my MIG welder).

Steve
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Old Sep 28, 2013, 06:00 AM
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Kingston, Canada
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The Mig welding wire I use is .023 thou. I also use a variac

Gord.
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Old Sep 28, 2013, 10:36 AM
serial scratchbuilder
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Canada, BC, Mission
Joined Sep 2012
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Quote:
Originally Posted by flypaper 2 View Post
The Mig welding wire I use is .023 thou. I also use a variac

Gord.
I started out using .023" welding wire and was happy with the results until I tried Rene wire. No comparison. Faster, cleaner cuts and a much nicer finish on the cut piece.
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Old Dec 01, 2013, 05:42 AM
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Joined Jun 2012
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Battery Charger + Dimmer?

Hello all,

I am looking to build a hot wire foam cutter. I am wondering if I can use the following battery charger and add a Lutron rotary dimmer to it for variable output:

Maypole 716 12A Metal Battery Charger 12/24V
Voltage: 12/24V
Current: 9/4 Amp

My wire cutter spec is as follows (used an online calculator to get the spec):
Temperature: 300 C
Length: 1200 mm (47 inches)
SGW: 22 (0.635 mm)
Volts: 15 volts
Amps: 3.62 amp
Watts: 54 Watts
Resistance per foot (OHMS): 1.055
Total Resistance: 4.176

Your help and advice is much appreciated.
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Old Dec 01, 2013, 06:40 AM
gpw
“There’s no place like Foam”
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United States, LA, New Orleans
Joined Jul 2002
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Update : guys , our sliding plank hot wire cutter didn’t work , so we got out the old HW Bow ... Stainless fishing leader wire.. Worked fine... Used the Variac (it’s what I had ) with Safety considerations... No problem ....
Here’s the finished project ... The Rolling Hanger ... Styrofoam , covered with canvas ...

Ps. the hole in the side is for the AC ...
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Old Dec 01, 2013, 06:51 AM
gpw
“There’s no place like Foam”
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United States, LA, New Orleans
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Here’s a shot inside ... Comfortable for camping (like at a Fun-Fly) , plenty room for planes ... ...the wife is , or course, texting ...
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Old Dec 01, 2013, 07:12 AM
Canadian Bacon
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Kingston, Canada
Joined Jun 2004
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Beautiful job. What/how are the mainframe bows made from.

Gord.
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Old Dec 01, 2013, 07:33 AM
gpw
“There’s no place like Foam”
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United States, LA, New Orleans
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CNC cut 3/4” plywood ... Much like an old time fuselage former eh ...
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Old Dec 01, 2013, 03:42 PM
Canadian Bacon
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Kingston, Canada
Joined Jun 2004
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Beautiful job. Would take a while to do on my old beater bandsaw.

Gord.
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Old Dec 01, 2013, 04:50 PM
flyin' fool
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Vancouver Island, Canada
Joined Jul 2003
7,381 Posts
Hi Gord.

Here's a good cutter plan, complete with safety features................ http://www.utahflyers.org/index.php?...ask=view&id=37
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Old Dec 01, 2013, 05:01 PM
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New Zealand, Canterbury, Rolleston
Joined Oct 2011
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Just remember that though a Variac uses transformer principles it is not an isolating transformer. In other words, don't touch the wire, it could be hot, electrically as well as temperature wise. Otherwise it is a good tool for the job.
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