NiChrome questions

or a heat gun... you can bend plexi almost double with a good heat gun and patience... wouldn't your light sabre be more effective??

(posted only to the REC to hopefully slow down this dumb ass cross posting)

Tons if info at this website:

400F is pretty dark, as an example - look in your oven set to 450F - it doesn't glow (visible) red. 35V would have tried to drive lots more than 3A through the wire - more like 12 if I remember your numbers (in the bit bucket now) that would fry a 3A supply.

mike

400F is pretty dark, as an example - look in your oven set to 450F - it doesn't glow (visible) red. 35V would have tried to drive lots more than 3A through the wire - more like 12 if I remember your numbers (in the bit bucket now) that would fry a 3A supply.

mike

400F is pretty dark, as an example - look in your oven set to 450F - it doesn't glow (visible) red. 35V would have tried to drive lots more than 3A through the wire - more like 12 if I remember your numbers (in the bit bucket now) that would fry a 3A supply.

mike

Thanks Mike.

I think I solved the mystery yesterday. I picked up a cheap switching PSU at the surplus store to continue my experimenting. But I still wasn't getting much heating. So I decided to check the resistance of my test wire and it was 3+ x what I expected. It turns out that the vendor shipped me the wrong wire, 3.5 ohms/ft, not the 1 ohm/ft I ordered. They're shipping the correct wire, so this should solve my problem.

Thanks, good site.

Thanks Ken. Did you make your own coils of buy then ready made? Do you remember the gauge/resistance? Did you use an insulator on the coil or let it hang free in the channel?

How did you construct your channel? I was thinking of MDF base, reflective aluminum, masonite (channel sides), covered with some heat resistant material, perhap fiberglass.

Thanks again Ken, useful info.

Bill, the way I made my bender jig I wouldn't recommend doing it the same way to you, it was pretty cobbled up and not very safe.

I would use a ready-made coiled element or take one out of a milkhouse heater whose element might be broken, but at least half of it's length usable. The dimmer will take care of having a shorter length (I think--see disclaimer below).

Make a U-shape from steel sheet (NOT aluminum) and get some ceramic insulators from an appliance store to hold the element in the channel. I think the old Maytag dryers used ceramic thimbles that the element threaded through, that might be just the thing.

A quartz heater element would be even better, it's self-supporting so you don't have to worry about shorting a coiled element to the sheet metal.

Won't go too much further into the design, except to recommend that the channel be a seperate piece from the top surface where you lay the acrylic--you only want heat to come out of the slot. I would not use any flamable material, but fabricate the whole thing from sheet metal probably pop-riveted together, with an enclosed box at one end to hold the dimmer and protect the connections from fingers (and vis versa!) I am NOT an electrical engineer, so I don't wanna tell you how to wire it and get blamed for your demise--just be safe and find the correct way to do it! If for some reason the dimmer is not appropriate, you could use a limiter control from an electric stove, one of the burner controls which cycles the heater on and off in short periods. Think I'd better stop here before I *really* get into trouble from those who ARE electrical engineers!

Ken Grunke

Good thinking, I wouldn't use flammable materials like lacquer thinner or gasoline to build the thing either. Come to think of it, I wouldn't use any combustible materials like wood, either. ;)

Get your ceramic grommets at:

Dan