An AC-powered car battery charger contains a transformer, does it not? Steps it down from 120V to 12V, so yeah right? I keep seeing transformers in various hot wire cutters online, but no car battery charger powered ones.
Also, anyone know about charging galvanized steel wire? It’s super cheap at the hardware store, but I figure it won’t take any heat before it breaks? It’s like only 10 lb test…Oh but I was wondering about charging it and lethal (zinc?) fumes coming from the wire, which is why the question is in this thread…
I’ve been using a 12v car charger on the 10A setting. For wire I’ve used guitar strings, broke alot of those then switched to braided 150lb test stainless steel downrigger (fishing) cable, about 25 dollars canadian for a 300 ft roll. Slow cut (10 minutes to make 8ft through 2lb eps, 24" wide) but the wire is able to handle much more current than what I’m running through it.Can’t tell you how well galvanized wire will work.
FWIW a lot of this has been addressed in the EPS Hotwire Setup Pix thread. Complete with photos and diagrams!
Braided fishing leader works fine for me now that I have the transformer sorted out (transformer cost <AU$15, stacks of leader <AU$5).
If your battery charger has variable amps, going up to at about 4+ amps you should be OK. Hope the thing is fused
The car battery charger I tried just didn’t have the juice. The model train transformer did, but the safety cutout was a bastard.
Not sure the zinc would be a problem, since the wires dont really get that hot. Fishing leader is cheap, strongly and readily available. Just make sure it isn’t nylon coated (damned fishermen)!
I’ve been using a baterry charger and a guitar chord and didn’t have any electrial problem neither the chord has broke.
I’m cutting 30kg/m3 EPS and the problem is the chord expansion when heated, it gets so much longer and looses the tension, so then the cutting has to be slower than what could be possible. I can’t not tell exactly the time… hope this afternoon I can tell.
Nichrome wire 22-25 gauge Recomended by Airframe (Segway Composites) at Cerritos College Dec of 2005 just after ClarkFoam shut down. If you use cheap wire slow down and lower your voltage. We used cheap wire at aprox 8-9 volts with out any problems. Snapped a few wires trying to go faster with more volts. I scored a used Variac for free so we could adjust our voltage. Not sure about what amps we were using. Next time I will buy quality wire.
I’m trying to figure all this stuff out also, I’ve used a battery Charger with Nichrome wire and had lncessant breakages due to over heating.
I could be wrong but as the wire heats the resistance increases so that it heats up even more……
Correct:
“as the wire heats the resistance increases”
Not correct:
“so that it heats up even more.” (assuming-- as is almost always the case–that you have a constant voltage source, and not a constant amperage source).
Calcs:
Voltage = Current x Resistance
hence: Current = Voltage/Resistance
Power dissipated = Voltage x Current = Voltage x (Voltage/Resistance) = ((Voltage)^2)/Resistance
Voltage remains constant, hence increase in resistance decreases the power dissipated in the wire.
I use a heavy duty rv/marine battery charger and 18 ga. stainless steel leaders. Have done four boards, with glue lines and haven’t have a problem yet. Built a dimmer switch/outlet box and plug the charger into that. put the charger on the highest setting and adjust with the dimmer switch. Works wonderfully! Just don’t use it barefoot, on cement in a puddle of water.
Thanks everybody, on a related topic, when glueing 2" sheets of eps together to make a block using gorilla glue, do you need to completely cover one surface, or will lines of glue 1" apart be sufficient, given that it expands ?
You’ll want to cover the sheet as much as possible to get a good strong bond. I believe it was Oneula that gave me the advice to stop within approx 2" of the rail to make it easier to shape the rails. I use those mid size, yellow spreaders that you can get at the home improvement shops and surfboard supply companies. It takes about a 3rd of a bottle of Elmers Ultimate PolyU glue to cover a 24" x 7’ sheet of foam. (The Elmers Ultimate costs much less than Gorilla Glue and works just as well.) Pour the glue in sections so that it doesn’t soak into the foam before you can spread it. Press firmly and tilt at an angle to spread it evenly.
The first time I glued sheets together was a disaster because I squeezed out some criss/cross lines over the entire sheet of foam. By the time I tried to spread it, the glue had soaked into the foam and wouldn’t go anywhere. It looked purdy but didn’t provide a very good bond.
BTW- Keep the sheets binded together with painters tape or plastic wrap. Here’s another Oneula handout; buy the industrial plastic wrap on a roller. The kind that they use to hold boxes together on shipping pallets works really well. Here’s what I do: glue the sheets together leaving 2" off the rails for shaping, tape the sheets together and then use plastic wrap and bind the the whole thing to the underside of a finless board that you want to copy the rocker from. Leave it overnight and voila!
Has there been any consensus on an inexpensive and attainable hot wire set up? Seems everyone has a version of something that works (or not in my case). A bill of materials would be sweet. These materials are so foreign to me that I’m having a tough time keeping up.
My cheapo Harbor Freight battery charger won’t get the wire hot at all. Is there a fail safe? Don’t hear a click or have to reset anything. My 11 year old son suggested connecting straight to an extra lawn mower battery. Worked like a charm while connected to the thickest non-braided guitar string. Test cut fast and clean. On the blank the wire broke within 1’, luckily it didn’t drop through the blank. Switched to stainless steel fishing leader, and cut so slowly. I think it was the thickest non-braided I could find. Did not want to break another wire. I was given a old model train power supply. It’s variable and plugs right into the wall socket. Cut the out line with that and it smoked a bit, still too slow. See my trend? Everything almost works. dougirwin13 do you have a link to your set up? I am moving forward with this mess. Got the fridge compressor working, got the bag issue worked out, got the bottom balsa on. Rail bands next. Hello slow hot wire cutting. Any pointers? Someday I’m going to post a Balsa Compsand. Ha.
I empathise! It’s taken me forever to get all this togethor and working… Still gotta make a curing “oven”, but I have done them (albeit a bit smaller) before so it’s not such a big deal.
Check out the EPS Hotwire Setup Pix thread for plenty of good/cheap/easy (all depends on which you choose) ways of getting a decent hotwire setup togethor.
Thanks Doug. I didn’t realize you were talking about the link previously supplied. I did browse that info. For me, I have to look at stuff a couple of times before it clicks. But that’s not going to stop me from screwing something up. Ha.
Had a moment of “I’m getting this done today” over the weekend. Without overthinking too much, I slapped this together. I really liked the way it worked. Every time I go to Lowes, I grab a handful of paint stir sticks, both large and small. Work nice for ding repair, reusable, and they are free. Anyway, when the wire gets hot and stretches, just squeeze your hand together to get the tension you want. Didn’t even burn anything down. I did burn through the tape I had laid up for rail bands however. Doubled up after that and no problems there. More come on that…
