EPILOG:
FWIW. Our
build of the TechIngredients pea souper was not very successful. We managed to get it going
in one scene
in one show but the quantity of
fog was insufficient due to our implementation of the
unit. We got a thin coat roughly 100 square feet. We're going to evolve our prototype to do better but here's some of the issues we had to deal with:
1) Small size is an advantage to the design but water proofing the
PVC board cabinet seams and heater mounts was problematic. The right
epoxy must be used on the seams. Also, water heater elements have a slight curve for mounting to water heater tanks. So sealing them to a
flat flange was difficult.
2) The hinges and clasps are not the right design for
practical use. They are good for getting a good seal to prevent
fog leakage but not speed of opening and closing. Also, when the top is opened, all the condensation on it runs down and drips outside the box onto the floor and the electrical boxes on the back side of the
unit. It doesn't really hold itself in any
practical way when open so you end up sliding it off the hinges. It is extremely fiddly to get it back on and utterly impractical for a dark back
stage environment. The clasps are good for getting a tight fit but way too fiddly.
3) The parts
basket for holding the dry ice load needs to have small openings. We could not find one. We ended up with one whose openings were too large. This resulted in losing small dry ice crumbs directly into the hot water.
4) Use of a water tank
element requires adding a thermostat to regulate the temperature. To handle the case of water boiling off, we added a float valve to shut off the heater if a low water situation occurred (think
unit being left on accidentally). The thermostat needs
power, it needs a hefty
relay big enough to handle the heater
element, the float valve also needs a hefty
relay and
power for the coil. Lacking time, we ended up with a hodge podge of low
voltage power supplies for pumps, wireless pump
switch receiver, thermostat and float valve coil all sealed from water intrusion.
5) After getting all the mechanicals and electricals to work, the crux of the design comes down to how well you distribute the water onto the ice. The amount of
fog you get depends on how much dry ice comes in contact with hot water. The TechIngredients implementation used rice shaped dry ice to maximize ice surface area and a meticulously constructed water dispersion pan to maximize gentle water spread. We only had access to
block ice so by definition, we would not get high efficiency. Add to that the ice crumbs created by smashing up the ice lost through the
basket openings and our ice utilization suffered. Lastly, the pumps in the specs are quiet but do not develop enough pressure to spray the water on the ice in spite of best efforts with physical stream disruption. This is why the TechIngredients
build used a dispersion tray.
6) Ergonomics: The compact form is a winner when it comes to hiding it on
stage. The spec'd handles are too small for the
unit's weight. The pumps and other things stick out rather precariously on the back and
unit needs a drain valve. When striking the set, one of our
stage hands inadvertently side-swiped another set piece. In the set piece vs pump collision, the pump broke away and created an instant drain of the water.
7) Heater: I expected dual 1000
watt heaters but the
unit came in with dual 2000
watt heaters. That spec ripples to the the thermostat
relay, float valve
relay, wiring and facility. Fortunately we had 20amp receptacles and 12ga extension. I only used one heater and it heated 5 gallons of room temperature water to 150 F in 25 minutes. Plenty for our use. Due to lack of testing, I can't evaluate the water heating recycle performance but I have ideas on how to maximize it.
Summary,
on opening night with my student builder's Dad in attendance, everything was set with pans and towels to control leaks and condensation: the thermostat failed. Next show I hot wired it and we got our first and only use of it. I'm committed to the move-water-to-ice design over the move-ice-to-water design and will rebuild the whole thing over the summer with the lessons learned from our prototype and some new ideas. There WILL be a sequel!
Wind in the Willows: Spring