Teardrops n Tiny Travel Trailers

GPW wrote:RT , the SS leader material came in a small package a few feet long , enough for a couple runs on my HW bow ... After breaking several other types of wire ( including Nichrome) One piece of the SS leader cut all the foam slabs for the FoamStream ... Variac as power supply ...
For cutting channels , we’ve used common Music wire set into wooden blocks , which worked fine with the Variac able to dial in the proper voltage ...

What diameter music wire should I get for cutting channels ? I can get sizes from .009"-.047" inch measurements/ ..not mm

I did not think of the wire I use in my Mig Welder. Not sure of the size. Don't think it is for stainless welding (I never have welded SS).

.030 Mig welding wire is what I use for my hot wires.

ghcoe wrote:.030 Mig welding wire is what I use for my hot wires.

Well I had a victory today, with my Hot Wire cutter. I used my .035" mig wire, and with my battery charger. I was able to cut channels fast and clean. The battery charger ran fine, and never popped the circuit breaker. I cut about 36" channel without a problem . So things are looking up. Thanks everyone.

I have a HF Router Speed Control Dial and I was wondering. Can this be used to very the heat of a foam wire cutter? One person says he uses it with his heat gun. I don't know if that would be considered the same thing as a hot wire. I don't want to burn the thing up because it works great at turning my single speed router into a variable speed router.

I would not try it. Hot wire works on DC. The speed control is still putting out AC.

That's what I was thinking. Thanks.

My HW bow is drawing < 5mps ( cause that’s what the fuse is ) .. AC from an old Radio Shack variac ( that’s how old it is ) … Well insulated , handled carefully … We used it to slice all the giant foam blocks into sheets for the FoamStream .. Anytime there’s electricity involved you gotta’ be CAREFUL … ! If you’re not completely sure then best do like George said ^ don’t do it !!!

I do know a little something about electricity and electronics. I spent 7 plus years in the US Navy as a Aviation Electrician. During that time I worked on Inertial Navigation systems, AFCS, and every system that had a wire going into it. I even worked in the Jet Engine Test Cell at PMTC/Pt. Mugu. I guess I should have worded my question a little better.
George had stated that by using a car battery charger there was no way to change the output from the charger. That is why he used the 3 ft of wire wrapped around the pencils to basically control the heat of the wire.
My question should have been. If you use the Router speed control to vary the AC power going into the charger. Could that give you the ability to control the DC power coming out of the charger? Thus eliminating the need for the extra wire.
Did that make any sense at all?

Apologies, I was an ATN in the Navy some time ago, and am also a moderator on an Amplifier building forum (Wattkins.com) .. I'm always concerned someone new here could shock themselves and so we always err on the side of Safety. We can’t assume everybody knows all this stuff, and we can’t ask everyone’s background without seeming excessively Nosey … Since you know all that already then no problems …and you’ll know whether the Router speed control can handle the current …( which is why I posted my current limit as an example … )
" If you use the Router speed control to vary the AC power going into the charger. Could that give you the ability to control the DC power coming out of the charger? Thus eliminating the need for the extra wire.” …
Although we’re no fan of wire/pencil resistors dissipating several amps of current , in the old Nicad fast charging days ( 10C + ) , we just used unusually long lengths of zip cord to control the current off 12 V batteries … ( charger should be similar , eh ? I dunno ? ) I guess if we knew the resistance of a length of wire we could calcuate what we needed for a specific hot wire device … The only thing is , sometimes we make smaller wire devices to cut out channeling in the foam , and the adjustable current is handy to dial in just the right heat .
For our hotwire , we always had that old Variac , which made it simple … I’ve been hot wiring foam wings since the early 70’s … same Variac… I still use it to run up my amp builds , re-form electrolytics and occasionally use it for the hot wire .

You know what to do !!!

badgerkeeb wrote:My question should have been. If you use the Router speed control to vary the AC power going into the charger. Could that give you the ability to control the DC power coming out of the charger? Thus eliminating the need for the extra wire.
Did that make any sense at all?

Yes that does make more sense. believe that it would work ok. Not too familiar with what the internals are on a old school battery charger (new smart chargers wont work). I do believe they are just using a transformer to change and drop 110v AC to 13-14 volts DC. Looking at this hot wire build they are using a dimmer switch to control the transformer so it might just work http://www.utahflyers.org/index.php?opt ... &Itemid=33 . You guys seem to know the electrical part of this better than I do.

I came up with using the battery charger by reading about how people can weld with a battery and some welding rods. They would carry different lengths of battery cables so they could change out the lengths to get the voltage at the rod they needed for a particular material. Since a battery charger is basically putting out the same voltage, but obviously at a lower amperage than what a battery can put out, I figured it would work. You could even use a car battery to do the same thing if you had a way to control the DC output.

Of course all these things are dangerous if you do not know what you are doing, especially with DC current which will kill you much faster than AC. Once AC is converted at the transformer to DC you have to be very carful with it!

I have a 40 year old battery charger that works great for a hot wire power supply. I plugged it into my HF router speed controller. It indeed seems to modulate the charger's output voltage and resulting wire heat.

My charger puts out about 12V. Unfortunately with my controller, the change in voltage is not very smooth as one changes the controller setting dial. It abruptly moves from around 2V to nearly full power (12V) somewhere in the high range of the controller. The low and medium settings are similar at nearly 2V.

This arrangement might be useful, but it will be difficult to provide a reproducible fine control of the hot wire temperature.

tomhawk wrote:I have a 40 year old battery charger that works great for a hot wire power supply. I plugged it into my HF router speed controller. It indeed seems to modulate the charger's output voltage and resulting wire heat.

My charger puts out about 12V. Unfortunately with my controller, the change in voltage is not very smooth as one changes the controller setting dial. It abruptly moves from around 2V to nearly full power (12V) somewhere in the high range of the controller. The low and medium settings are similar at nearly 2V.

This arrangement might be useful, but it will be difficult to provide a reproducible fine control of the hot wire temperature.

Thanks for that information.