Photos of the Portland Furnaces.

[Pete VanderLaan]

This is the element protruding thru a soft brick. The shank is 7/16th inch diameter and fifteen inches long.. The outer two inches is the connection section for the electric strap. The next nine inches is in the brick and then it enters the crown. the very last half inch of the shank has to be inside of the furnace.. The thinner port, which isn't in this picture is the heating portion. Jons was 18 inch, Steve's was 12 inch.

[Pete VanderLaan]

These are the elements entering Steves' crown. The straps are bringing the power from the transformer. You can get either stainless steel or aluminum straps. The aluminum ones come with the elements at no extra charge. I got the stainless ones. They have to be tight.( torque them down)
Note the plastic tubes that are pumping air at the connectors. Cool connectors are happy connectors. Good idea Steve.

[Pete VanderLaan]

This is a shot of the full element ( almost) going thru the brick. Note on the left where it has gotten thinner. Thats the business end. The hand is Steves'.

[Pete VanderLaan]

This is a sideways shot of the transformer with the cover off. We'll have to wait til my daughter gets home to rotate it. These are seriously heavy little buggers. This one was about 2x2x3 feet and weighed about 600 lbs. Used they can cost whatever you can pay, as little as $200 dollars. New its a 1500 dollar item. Hard to re-sell at garage sales.

[Pete VanderLaan]

This is Jons' transformer in place. Note how it is much cleaner than Steves was. Note that it cost much more since it was new. Both work fine.

[Pete VanderLaan]

This is Jon's transformer next to the panel that contains the silicon Controlled rectifier ( SCR) It gives you an idea of how much space this junk actually takes up. ( not much)

[Pete VanderLaan]

Here is the Watlow 150 AMP SCR on its side. I have no idea what I will do when the kids leave home.

[Pete VanderLaan]

This is the relay which controls the on/off function from the controller to the SCR.

[Pete VanderLaan]

This is a shot of the top of Jons' furnace. Everyone is supposed to gasp at the exposed fiber. I preferred to gasp at how easy it was to stick your hand in there and get killed by the exposed connectors. It has a cover and it should have been in place. I'll bet the farm that it isn't in place right now. This is seriously dangerous.
You can see the straps going from element to element. Jons furnace had six eighteen inch ones. He never really turns it up high which I though he should do for the visiting clowns. He didn't.

[Pete VanderLaan]

This is a shot of the door "kill" switch. ( What an appropriate name). It doesn't show well but it is a little momentary switch from Graingers that opens the circuit when you swing the door open. I didn't like their doors. If they had fit better you would not have known that these furnaces were on and were melting batch. It was very strange.

[Pete VanderLaan]

This really shows what the connector straps and the element tops look like.

[Dan Buchacher]

Is it intended that these element units complete with supporting soft bricks are easily removed like a plug, and replaced when they fail?

Do these elements extend down around the sides of the crucible or is this all top fired?

I've been looking at these pictures again recently and a few questions also came to mind of the makers of this design..Jon, Steve and now Pete

From the posted pics and text from Pete we have the following dimensions -
the thicker connecting shank is 15" long, 2" at top of the brick for connections, 9" in the brick, leaving 4" protruding from the brick on the furnace side, the last 1/2" of whick needs to be inside the furnace

So. how thick are we casting these crowns, of what castable, and are the holes in the crown and the soft bricks tapered or not? Are these flat crowns or slightly domed?

The dimensions posted above would indicate that at least 3" of the shank portion of the element are sitting in a small ' well ' in the castable...is this the most healthy configuration for the shank area...would it be better if just the required last 1/2" of the shank was exposed to the heat of the chamber?

Further, if Pete looks at this, what castable did you finally decide on for the floor and main heating chamber of the new furnace, and did you go with the front of the heating chamber and gathering port being detachable from the rest for cleanout and pot changes as you have described for your gas furnaces?

Lots of questions, but I'm hoping to start my 150# furnace once the frigid weather warms up here on the edge of the North Atlantic

thanks

Bryan

[Pete VanderLaan]

This does presume a three inch thick crown and I do think thicker might be better, by one inch. Mass is important in electric furnaces although it is a tradeoff with strength. The brick does just sit in the well.

My castable will be Morocast 99 % alumina. II was really impressed with the Morocast 95 and Tom suggested I try this stuff too. I will be using 18 inch by eighteen inch by one inch paver tile from Engineered ceramics as well.

This furnace will open from the side with a giant refrigerator door to remove the pots.

and the paver tile goes....where?

Bryan

"Note the plastic tubes that are pumping air at the connectors. Cool connectors are happy connectors. Good idea"
Sure but the air is their to keep the crappy fumes inside the furnace from condensating on your elements lead-through the bricks.
Element failure in no time for sure.
Been building these furnaces since the 80th, with the expensive kanthal elements, one thing, they did publish excellent guidebooks.