Wednesday, April 30, 2014

The Caretakers Redux

"Look, do you want the plutonium, or not?" asked Edward Hopper, the bronze robot's voice booming from fourteen feet above me.

"We do! We want it! I just don't understand why we have to wear these goofy suits when we are around them", I replied.

"It's for your protection. Besides, they poop out more of it when they are comfortable!"

"They're robots!"

"They're also animals. They have feelings like I do." 

"Yeah, but you programmed 'em that way!"

"I'm trying to help you guys out here! I'm starting to think you don't appreciate me".  

That's the extended caption that came into my head as I looked at the latest bronze, The Caretakers.

Yeah, it's finally done. I dicked around on this far too long. Fact is, I did learn some things this time out. The last bronzes, The Stockmen, which I rushed through production in order to submit them for a show they did not get in, had severe casting defects on the figures. These were corrected with proper feed runners. Almost corrected. The figures still had shrinkage porosity defects, aka "sucks", which I will take care of next time.
"sucks" in the same spot on both figures
But the Caretaker bugs were not vented properly. They ended up with some pretty severe gas porosity defects.

This has resulted in a new rule with the acronym ABV.
Gas Porosity from lack of vents
Always Be Venting.

The other big problems with casting, and ones that I should avoid and usually do, is turbulence and oxide inclusions.

This is all about skimming the bronze of shit before pouring, and proper rigging. Proper rigging meaning the obvious like, lots of runner and vents, but more importantly, I've found from experience to avoid right angles and make the rigging more organic and treelike or arterial*, so that a common sprue acts like a manifold and feeds everything rapidly and uniformly.

Surprisingly, or not so, some fluid dynamic studies back up my intuitive hunches and empirical observations:

So, one of these days, I may actually have a defect free casting... through luck. Here are some other pics of The Caretakers:

*Actually, I try and follow an old empirical law of circulation, in determining how many smaller diameter runners feed off a larger one, so that the number of runners needed is the sum of the cube of radius of the larger runner. In other words, the spherical volumes that can be fed from a smaller diameter runner tube sums up to the spherical volume of the larger runner tube.


  1. How big are these? I would love to see them life-sized, walk around them, become a part of their strange world for a bit.

  2. They are about 13" tall. Hmm. Life-sized, and hollow, they'd weigh a good half-ton apiece!

  3. Sure, they WOULD weigh a lot but I'd have to agree with Zina - those would be great to run in to downtown somewhere.