Back when TLC actually was a place where you could watch educational programming, they would occasionally run a BBC production entitled Connections. In it, presenter James Burke explored the often unlikely connections linking the technological advances that make modern life possible. I make no claim that my connections are as life changing, just that it is interesting how work on one thing can lead to another.
I said in the last entry that I was putting the burner project on hiatus. And at the time, I meant it. But things don’t always work out as planned. Last week I was troubleshooting my little problem with the Harbor Freight heat gun. Still haven’t figured it out, but in taking apart the donor hair drier it occurred to me to test the resistance of its heating coils. This particular model had three separate strands of heating wire. Lo and behold, the resistance of the two smaller wires put them in the range I needed for ramping up the power of my crock pot heater. Just to review, the first crock pot heater drew about 40 watts. The upper limit for the new and improved model has to come in at under 400W since that is the rating on my car’s DC to AC inverter which will be keeping the unit hot during transport. Using the electrical equations P=VI and V=IR, we input our knowns. 400W=120V x I. Solving for I gives us. 3.33 amps. Then we put that into the second equation and solve for R to get 36 Ohms. I set a target of 40 Ohms for a safety factor. The final product ended up in the 50-55 Ohm range. Here is a picture of the windings on the crock.
The grey electrical tape was there to hold the insulator strip as I did the winding. The strip allows you to have the connections to a cord be right next to one another. I really like this setup instead of my original idea of buying 28ga steel wire as it accomplishes more resistance in 12 windings than the steel could in 60 (which I was having trouble fitting onto a crock anyway). By the way, this operation was not without casualties. That wire is wavy because it was coiled up like a spring and needed straightening. Evidently, too much of this kind of activity is hard on the fingers:
Only that long one going from top right to bottom left cut deep enough to hurt. Think paper cut only more efficient.
After placing the windings, they needed better contact for heat transfer. That waviness of the wires not only went up and down, but also in and out so not all the wire was touching the crock. My initial plan was to just put a coat of thin set mortar over the wire and call it good. This would fully bury the wire to prevent shorts. But as I was nearly done with that, I found that I had a good deal of mixed up mortar left over. So I thought, aw, what the heck. I’ll fill the entire cavity between the crock and outer shell with mortar.
In this photo we are looking at the underside of the unit minus the bottom plate. I only filled in the space around the sides where the heating elements are. After that cures, I’ll likely stuff some fiberglass batting into the bottom to minimize heat loss there.
Well, that is the extent of my progress. I look forward to sharing more with you all later.
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