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-   -   Building a hot wire cutter (http://www.Wattflyer.com/forums/showthread.php?t=73282)

mclarkson 03-04-2014 03:01 AM

Building a hot wire cutter
 
I've wanted to do this for quite a while but have been too nervous about the electric part of it but I'm finally biting the bullet.

I'm starting with this -
https://fbcdn-sphotos-e-a.akamaihd.n...27303651_n.jpg

- a vintage Louis Marx Model 1209 50 Watt model train transformer. My reading has lead me to believe that this is the easiest solution and the one which requires the least electrical engineering expertise. :D

I'm hoping that I can get some hand-holding if I need it.

sidybee 03-04-2014 03:16 AM

12 volt battery and some electric fencing wire between a couple sticks works well.
i used this set up before.... i cheated and used the battery charger. i had that in the garage hahahahaha

dgjessing 03-04-2014 03:17 AM

Cool! Here's where I've gotten nichrome wire: http://jacobs-online.biz/nichrome_wire.htm

pmullen503 03-04-2014 03:18 AM

http://i.ebayimg.com/00/s/MTA2NFgxNj...TCPEi/$_12.JPG

What a coincidence. Mine arrives tomorrow. I needed the 75 watt transformer to make a longer (4 ft.) bow. I've used a 20 watt HVAC transformer with a dimmer on a 30" bow for a couple years.

kyleservicetech 03-04-2014 03:27 AM

Quote:

Originally Posted by sidybee (Post 941443)
12 volt battery and some electric fencing wire between a couple sticks works well.
i used this set up before.... i cheated and used the battery charger. i had that in the garage hahahahaha

Interesting, electric fence wire, never thought of that.

Back in the mid 1960's, I made a cutting bow with two pieces of 3/16 music wire, a 1X3 piece of oak about three feet long, and a spring with about 10 pounds tension.

The cutting wire was a piece of music wire, about 20/1000 or so. Power was a cheap battery charger without any sort of voltage regulation.

A lot of foam cores were cut with that thing back then.

mclarkson 03-04-2014 03:32 AM

Quote:

Originally Posted by pmullen503 (Post 941446)
http://i.ebayimg.com/00/s/MTA2NFgxNj...TCPEi/$_12.JPG

What a coincidence. Mine arrives tomorrow. I needed the 75 watt transformer to make a longer (4 ft.) bow. I've used a 20 watt HVAC transformer with a dimmer on a 30" bow for a couple years.

Interesting. I'll probably be starting with a 20"-30" bow. My first project is a 30" wingspan flying wing, so I don't need anything like 4 feet. :)

mclarkson 03-04-2014 03:35 AM

I'm planning to make the 'bow' out of PVC and to use electric guitar strings for cutting wire. I've read that they work well and my son-in-law is a good source of used strings.

kyleservicetech 03-04-2014 03:37 AM

Quote:

Originally Posted by mclarkson (Post 941453)
I'm planning to make the 'bow' out of PVC and to use electric guitar strings for cutting wire. I've read that they work well and my son-in-law is a good source of used strings.

PVC?

Will that be strong enough, and will the PVC be able to hold constant tension over a period of months??

Just asking.

pmullen503 03-04-2014 04:47 AM

Quote:

Originally Posted by mclarkson (Post 941453)
I'm planning to make the 'bow' out of PVC and to use electric guitar strings for cutting wire. I've read that they work well and my son-in-law is a good source of used strings.

That will work just fine. I used 1/4 steel rods, about 8" long, in holes that were drilled at about 10 degrees so the rods would be slightly splayed out when inserted. The rods have grooves cut near the ends so the wire won't slide off.

Make loops at the ends of you wire so that the bow has to be bent to put the wire on. The rods are now more or less parallel under tension of the wire.

Connect the transformer to the rods and you are ready to go. A foot switch is really handy but not necessary.

pmullen503 03-04-2014 04:49 AM

Quote:

Originally Posted by kyleservicetech (Post 941454)
PVC?

Will that be strong enough, and will the PVC be able to hold constant tension over a period of months??

Just asking.

PVC works great. Nice thing is you can store the wire and rods inside the pipe for storage.

CHELLIE 03-04-2014 04:56 AM

Quote:

Originally Posted by mclarkson (Post 941439)
I've wanted to do this for quite a while but have been too nervous about the electric part of it but I'm finally biting the bullet.

I'm starting with this -
https://fbcdn-sphotos-e-a.akamaihd.n...27303651_n.jpg

- a vintage Louis Marx Model 1209 50 Watt model train transformer. My reading has lead me to believe that this is the easiest solution and the one which requires the least electrical engineering expertise. :D

I'm hoping that I can get some hand-holding if I need it.

Its About time that you build Yourself a Hot Wire Cutter :D :D :D LOL

http://www.wattflyer.com/forums/show...ot+wire+cutter

http://www.wattflyer.com/forums/atta...0&d=1288150260

CHELLIE 03-04-2014 05:03 AM

Quote:

Originally Posted by mclarkson (Post 941451)
Interesting. I'll probably be starting with a 20"-30" bow. My first project is a 30" wingspan flying wing, so I don't need anything like 4 feet. :)

http://www.youtube.com/watch?v=YtbYKgalYXk

CHELLIE 03-04-2014 05:21 AM

Hmmmmm This Guy just uses a Dimmer Switch and 120VAC


hayofstacks 03-04-2014 05:55 AM

We are working on one now. well, bought the parts anyways.

Where do you guys buy foam?

CHELLIE 03-04-2014 10:27 AM

Places to get foam at
 
Quote:

Originally Posted by hayofstacks (Post 941469)
We are working on one now. well, bought the parts anyways.

Where do you guys buy foam?

http://www.rcfoam.com/depron-and-epp-foam-suppliers/

Walmart sells some smoothfoam 2" i never used it but you might want to check it out.

http://www.walmart.com/ip/Smoothfoam...White/25307738

Appliance stores may have a lot of it in their dumpsters. I love to dumpster dive :D I will work for foam ;-)

Check out your local hardware store for insulating foam.

http://www.foamflyer.info/plane.html

http://www.homedepot.com/b/Building-...n/N-5yc1vZbaxx

pattern14 03-04-2014 02:11 PM

Good to see someone else using an old train transformer:). I picked up one from a very dodgy S/H store for $15.00, wired up a new plug as the original had perished, and made a bow using wire from the fishing tackle box.The transformer is a 1970 vintage Hornby 240 v, which includes a reverse switch. The rheostat used for voltage control was totally shot, so I simply resoldered the correct wires ( you really need to know what you are doing here to avoid a shock or worse) and bypassed the control dial completely. I can use it for about 20 minutes before it gets too hot, and so far it has given me about 5 years of trouble free service:D

solentlife 03-04-2014 02:22 PM

I use a 240 - 12v transformer capable of 100w.. connected to a Hornby train controller.
The cutting wire is Nichrome wire used for spiral winds in electric heaters. This is fitted to a 'Spanish windlass' style H bow. Cutting length is 1m.

Nigel

mclarkson 03-04-2014 07:48 PM

Quote:

Originally Posted by pattern14 (Post 941487)
( you really need to know what you are doing here to avoid a shock or worse)

That's exactly the kind of thing I'm trying to avoid. :D I do not know what I'm doing and something like this train transformer seemed the most foolproof way to start.

pmullen503 03-05-2014 01:30 AM

5 Attachment(s)
I got my train transformer today. I took it apart to inspect the wiring and it was very good. Even where the cord exited the box was in good shape. The voltage that it actually produced was 16.8 VAC. The "speed control" was pretty bad. It might clean up and be OK with some work but for now I'll use a router speed control and wire it up at full voltage to bypass the control.

I made up a hot new wire using some 40lb test stainless leader and ferrules. A quick test showed I could only get about 44" to an adequate temperature with the 40 lb leader. I'll have to go to a thicker wire or maybe buy some proper nichrome wire to get the full 48" I wanted. I can live with 44" for my current project for now.

I thought I'd show how I do the ends of the wires. Doing it this way keeps the loops from closing up when the wire is tensioned and hot. I start by making a simple loop through the ferrule. The free end will become the attachment loop so leave the enough as you thread it back through the ferrule. Finally, loop it again through the ferrule. Work the excess wire out the end and cut it off. Crimp the ferrule with a pliers. No need to get carried away when crimping. The loop is kept open by the wire bending around the ferrule, not the crimping pressure itself. BTW, this works well for making pull-pull cables from 10 lb wire that stays the right length.

The bow is just PCV pipe with holes drilled in the ends for steel rods. The smaller bow uses 1/4" rod and the longer bow 5/16". The holes fit the rods snuggly but the rods are not glued; friction holds them in place when the bow is strung. The loop on the wire sits in a groove cut with a dremel tool and emery disk at the end of the rod. The nice thing is that the rods and wire can be stored inside the PVC pipe when not in use.

carpetbagger 03-05-2014 11:59 AM

PVC works for bow ...
 
My PVC bow set up has two cross pieces about 3" apart and about 8" legs to the wire. PVC = 1" size. Legs are drilled and have a 1/4" eye bolt to hang the wire off, then I crank the tension in via the wingnuts on eye bolts.

Power - started out with a standard size train transformer, then upscaled to an Aircraft Spruce rig = 3 amp/24 volt transformer controlled with a standard rotary dimmer switch. I use a two pin connecter on the DC wire and bow so I can switch bow sizes easily.

Siberianhusky 03-06-2014 12:11 AM

I'm a guitar player, thought sort of the same as you with used strings, save yourself the troubles and buy a new one.
The string will no longer be smooth where it has been over the frets, they may also have some oxidization depending on what he uses for strings.
.018 and works very well, the ball end is great, on my bow it sits in a slot as is. No loop needed on that end.
Costs no more than a buck for a guitar string, they are available as singles, don't have to buy a whole pack. Just ask for a .018 plain non wound guitar string.
You also can't straighten out a used string, it will break when you tension it back up, you get the full length out of a new one.

solentlife 03-06-2014 02:57 AM

Nichrome wire is available in reels of Ebay etc. - enough to make more than one bow .. you can also make small Y cutters for shaping....

Nigel

mclarkson 03-06-2014 03:53 AM

I'd read somewhere that nichrome was significantly more fragile than electric guitar strings. Dunno if it's true or not.

I'll keep in mind about the used ones, though. It's probably not worth the hassle to save a buck.

solentlife 03-06-2014 05:05 AM

Quote:

Originally Posted by mclarkson (Post 941639)
I'd read somewhere that nichrome was significantly more fragile than electric guitar strings. Dunno if it's true or not.

I'll keep in mind about the used ones, though. It's probably not worth the hassle to save a buck.

Nichrome has been the recc'd standard wire for decades ... in fact magazines back in 70's ... 80's were full of wasy to find Nichrome wire ... the main one being old electric fire tubes.
the wire was spiralled inside the tube ... you extracted it ... stretched it by fixing to garden fence and then leaning back on other end to stretch out to straight.

Only time I've seen it break was when my Builder moved the bow and dropped it while it was taught. My present bow is over 3 years old.... with still same Nichrome wire.

Nigel

kyleservicetech 03-06-2014 05:35 AM

Quote:

Originally Posted by mclarkson (Post 941639)
I'd read somewhere that nichrome was significantly more fragile than electric guitar strings. Dunno if it's true or not.

I'll keep in mind about the used ones, though. It's probably not worth the hassle to save a buck.


Back in the early days, one thing I ran into with nichrome wire is sagging, where the middle of the nichrome wire was behind the outside edges. That resulted in funny leading edges of the foam core.

What worked well was music wire, stretched to perhaps 10 pounds tension with a spring. Guitar strings would be similar material.

Brings back memories, when my wife helped make those cores. First cut was across the top, with my wife on the other side. Flipped it over, and I ran my side across the top. And, my wife ran hers across the bottom. That was a very weird foam core. :D :D


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