Setup is 2@ TC's in lead pot, one at 1/2" from bottom and side of pot and one immersed 1" into the melt. Object is to observe temperatures of the melt and to time from a cold start how long before things stabilize. Lee 10# Production controlled by Rex C100 PID unit. Also used another Rex C100 to read the 2nd TC. Also used a VOM hooked to a flat surface TC to monitor the mold temperature after the mold sat on a hot plate controlled by a PID set at 400°. Object of this was to see if any value was added by comparing twixt use of a covering over the mold or notl. The "hut" is insulated with 1/8" cement board on all 4 sides and top. Inside dimensions are roughly 4.5x4.5x4.5 inches.
11-2-18 Shop temperature 90° F
Just used the bottom TC on this run. About 7 lbs in the pot, set at 365° C (689° F) Placed "hut" and mold on hot plate and turned everything on. Pot reached set temperature about 20 minutes. Had an interruption so didn't measure mold temperature till 26 minutes. After shutdown placed and left in melt the 2nd TC about 1" into the melt.
Mold temperature after 26 minutes using the "hut" about 340° F
11-3-18 Shop temperature 90° F
Turned on with same settings as before. This time without the insulated hut. While pot was coming up to temperature the top TC was 40-50° C lower than the one on bottom of the melt. That gap narrowed a bit as bottom got closer to 365°.
Set temperature of 365° reached ub 19:35 minutes.
Top TC hit 365° in 19:45 minutes.
Hot plate set at 400° on PID read about 390° across the disk.
Mold was 330° F at both 23 & 26 minutes elapsed time.
My thought had been a cover over the mold was not worth the bother and think this confirmed that. Possibly would help in a breeze but I cast inside.so it's not needed for me. The gizmo in the one photo enables various molds and handles to sit flat on the hot plate and I think that's prudent. And as a recent post pointed out once you're up to temperature it is pretty consistent throughout the melt unless you add sprue's, etc. Using a feeder pot set 1° hotter I''ve never noticed temperature drop of more than a degree or two.
quote "popper
not much difference from bottom to top of the melt. The thermal conductivity of liquid lead is such that there is effectively NO difference in temp, top to bottom."
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