Small world! I met a local 'one of us', and damned if it didn't happen through YouTube of all places. He did get signed up (thanks Dave & Kelly). I'll leave it for him to come out of lurker mode to reveal his forum handle and really dox himself if he chooses, but meanwhile here's a page about his work in sculpture that I found online which he's ok with me linking here: https://oenogallery.com/artists/david-perrett/#Bio Popped by his new foundry this past weekend, it's a nice 1h drive from here out into cottage country. Hooked him up with one of my POUND SAND'ers and we spent a couple days making a big mess and some big molds. (I bet it gets turned into a floor rammer before the project is done...) Loosely described, he's got this big rock, that he's cut up into cubes, which he's made plaster backed rubber molds of, which he's pulled plaster patterns from, which will be sand cast in aluminum. The cut surfaces will be done with plate. Then if I understand correctly, 2 identical yet opposite complete sculptures of checkerboarded half-rock / half-aluminum boulders will be assembled. Some of the patterns had to be cut in two to get around undercuts. I imagine he will have to do a lot of welding and chasing to hide those seams... Others he (we if I can be there) plan(s) to try molding up whole. This one's the biggest, and the main reason why the rammer will probably be reconfigured: He has a 55 gallon drum furnace lined with rigidized inswool and an A25 crucible. Real nice 2-man tongs and shank custom made by a local blacksmith, loosely based on reference pics of the ones I got from Bill Jurgenson a couple years back. More to come in the next post or 2, still gotta sort and crop more pics. Molds were made and rock parts were cast though. When was a 20h work weekend ever this much fun?! Jeff
Day 1 we built flasks, figured out some logistics, then rammed up and poured the first big mold. I think it was 18 x 18 with a 2x4 cope and 2x6 drag. There's a couple flasks around that size so I'm not sure if it was the 18x18 or the other one. Plenty of A356 on hand... Day 2 pics coming. I went back for more yesterday, so same goes for day 3... Jeff
Day 2, here's the first mold, first the cope then the drag with the pattern still in it. This is one of those ~18x18 flasks again. I don't believe petrobond can support itself over that far of a span. Especially when the copes protrude so deep into the drag. We should really be using what CW Ammen called bars in the cope to support the sand, I think. But since all the patterns are each so different, different areas will need that support on every pour. Rather than keep reconfiguring bars in the cope, we've been turning the molds up on their side to open them instead of risking having the cope drop out into the drag. It worked well enough for these first 2 molds. Third one was less cooperative. Rammed this beast up twice, only to have the patterns slip when we cracked it open... Because the day was growing short and we wanted to get at least a couple more pieces poured, I rammed up just the smaller and flatter of the two patterns in a 12x12 flask that has never felt so light, and we poured. Got them both. Welllll... The bigger one is missing a bit of one of its corners, unfortunately. But David believes he can fix it with welding and chasing. Fingers crossed! The smaller one is actually the mating piece for the casting from day 1, so now David can start welding and chasing them too. More to come. Jeff
Day 3. By the time I got back there a cement mixer boulder muller had been built and the second pattern that kept jumping out of the mold on day 2 had been molded up on its own in a 12x22 flask. I got to work on another big pattern in an 18x18 flask while David welded up some ingot molds and did some test TIG welds on some gating material, which seemed to be working well. Surface finish on these wasn't bright like the castings from the earlier pours, kind of a dull grey look to it. Maybe when it all gets blasted that'll go away? I didn't think we had overheated it, but maybe... Could be some kind of contaminant (plaster sawdust?) got into the little bucket of facing sand I used on the 18x18 too, not sure. Though I'm pretty sure the other mold was faced with all new clean petrobond straight out of the bag. Who knows, I've been trying to figure out what happened there for a couple days now. Anyone have thoughts on this? The gating was bright however, it was just dull looking where the pattern touched the facing sand. Also there was some unfortunate surface porosity on the bigger casting, guessing some sand washed loose or maybe it 2as just turbulence from the gating not acting how I planned, or something. Time will tell if it gets repaired or recast. The new petrobond is so much better than my old sand, mine is pretty thrashed I guess. I've probably asked too much of a mere 300# of it over the years. Oil and catalyst aren't cutting it anymore. And the never ending search for petrobond powder or organoclay continues. Now we can't even seem to find it premulled. David is working on getting us both more petrobond too, running down many leads including reaching out to petrobondforsale (waiting on a reply about shipping 50# bags) and others. The new supplier in Ontario that replaced Smelko Foundry Products won't have any in stock until sometime next month!? Jeff Ps. Bonus pic: assembly begins...
Update on the sand situation. We heard back from chasft aka petrobondforsale. David placed an order for the two of us for a few hundred pounds. We're going to need it to fill the huge flask with the drag that's two 2x6's tall (see post 1) ... He has a guy on the US side of the border to receive and transport it the rest of the way. All in, looks like it's going to be cheaper than Foundry Supply Source's (replacement Smelko's) sand. And we don't have to drive 11+ hours to Milton and back to get it in our hands. And I believe chasft uses a finer sand ingredient as well ("140 mesh" vs. GFN 130 from the supplier). I'm already impressed and we haven't even got the sand yet. It never occurred to me that it could be imported from a small operator across the border cheaper or faster or easier than buying from a big supplier in my own province! Too early to say for sure but so far it's looking like all 3. Kudos to petrobondforsale. FSS got back to us less than an hour and a half later saying their shipment expected in May arrived "early" so they're back in stock. I've had good dealings with Foundry Supply Source and their "OBB sand" petrobond but in this case I'm not unhappy the replies came back in the order they did... Jeff
Working on these big molds and using the 2 man tongs and shank are a new experience for me too. So far no big surprises though, everything's just a little bigger. Jeff
Jeff, I'd like to ask; once you took the rubber/plaster casting, how did you create the "back side" of the pattern taken from the r/p mould? Was a thick plaster made (rather than pourable) and just rubbed in?
That was something the artist (David) did. I think it must have been done something like that though. I wasn't there but it's a hard plaster (might be hydrocal?) reinforced with burlap. He embedded some small wooden blocks in the plaster on the back side of several of the pieces to drill out for rapping and for draw screws. Jeff
Some of the patterns are quite thick in places though. Aside from the metal and fuel involved, that may complicate the welding process. If there wasn't a deadline looming we might have talked about trying to thin down some of the patterns in places somehow. Though being beefy probably does make them a little sturdier. I had to rap on some of the ones I molded up pretty hard to get them to pull out... Jeff
