Post by: vtsteam on May 06, 2025, 02:23:47 PM
Yeah sure, anything is better than sitting around picking up and putting down the same set of patterns over and over and griping about the weather. If I can cast both in the same flask, and if I start melting while I'm packing the mold, I should be able to do it right? I know I have in the past, just a little rusty at the moment So to speak.
So I take the patterns outside to the molding area, which is just an extension of the roof of my tiny workshop shed. I move the propane melter out from under, hook up the propane tank grab a bunch of aluminum muffin ingots, shove em in the pot, drop that inside the furnace, grab the mapp torch and turn on the furnace gas. Light her, and let it rip full blast.
Oh, no, greensand is drier than Death Valley during a drought! I keep my sand in a plastic storage box, which for some reason never seems to keep the moisture in. Run back into the house, grab a spray bottle full of water, and run back out to frantically condition the sand. Squirt squirt squirt, trowel trowel trowel, squirt squirt squirt, trowel trowel trowel, etc. for a good fifteen minutes of my allotted hour. No I don't use a motorized sand muller. That's for sissies! Squeeze some sand, holding shape, feels okay. Drop the lump, trowel trowel trowel. Meanwhile I'm starting to worry: am I overheating the aluminum? Give it a check, but, good it's still not melted yet. But it is looking kind of like it wants to. Turn down the burner, but it doesn't like that very much and starts to sputter, back up a little. What time is it?
Back to molding. Oh yeah, I need a little facing sand too. Grab a handful put it in a quart yogurt container, squirt, squirt, squirt, mash it together with an old spoon, repeat, etc. Okay find a wooden flask set that isn't burnt to a crisp on the edges from melting iron. Find two that actually fit together. Lay down the patterns, dust, sprinkle all over with strained facing sand. Dump some greensand in, press in place by hand, more sand, pack around edges, then pound center, repeat all the way to top. What about the aluminum is it overheating? What time is it? Are the clouds darker?
Roll mold, lift off board, looks good place sprue and riser to leave impressions, lift them out again, cut runners carefully. Wait, no that's wrong! Cut runners AFTER you make up the cope. Okay fill those back in, scrape it off with a ruler flat again. What about the aluminum? MELTED! How long? What time is it. Looks hot. Add more ingots, that will cool it! Plop plop.
Back to molding. Sprinkle parting dust over remade face. Add cope. Add facing sand, add greensand, pound pound, etc. Separate cope. Wait a minute.....you forgot to replace the sprue and riser! You idiot! Break up the cope again, add sprue and riser dowels to the drag, make up a cope again, pull sprue and riser dowels, lift off, cut runners, reassemble. At last a functional mold!
Only I didn't say "functional." What time is it? Move mold to sand base under the ever darkening clouds. Please remember to pour in the sprue hole, not the riser.... Check metal with stir rod, plenty hot! Cut the gas, pull the cover off the furnace set on firebricks. Grab the pot of hot metal with my big grabber for aluminum, and pour, keeping the sprue choked, yes the sprue not the riser. The riser fills properly. Is that it? Did I do it? Did I manage? Wait, where's the muffin tin to pour off the remaining metal? Oh man, set down the pot, find the tin, then pour out 3 ingots plus some. Replace pot in furnace, and cover.
Everything is quiet now. No furnace roar. No rain. Metal looks shiny in sprue and riser, it's shrinking down the riser. Shiny ingots in the tin. I can relax. I did it!
Half an hour later, tea, toast with jelly indoors, it starts to rain again outside the window. I don't mind. Everything is put away, the mold is broken out. Greensand Casting in the Rain. The title of a song.
Post by: kayzed1 on May 06, 2025, 04:47:22 PM
Post by: tom osselton on May 06, 2025, 05:36:57 PM
lol I hate it when things go that way but usually it works out, the casting looks good despite the rest of the show well done.
Post by: John Rudd on May 07, 2025, 06:40:28 AM
I hope all the remaining work for your engine works out just as well... :thumbup:
Post by: vtsteam on May 07, 2025, 08:21:28 PM
I thought it might be of interest to hear what REALLY happens at metal pouring time for me, rather than just the results. I gotta say I lucked out on these two, in many ways. In fact, I think they are probably the nicest aluminum castings I've ever done. Go figure!
FYI details: it was just plain fireclay and local sand type greensand, not Petrobond, and not even Bentonite for the clay. And it's probably ten year old stuff.
I think really important factors in getting that kind of fine detail and finish with aluminum are three things: Use a fine facing sand, sieve it onto the pattern when molding, and use a riser between the sprue and the pattern.
My facing sand was made from a bag of fine mason's sand, which when mixed with clay proved too impermeable to use for regular casting.
But in a thin layer as facing, I was able to use that sand/clay mix anyway instead of throwing it out. The backing of regular greensand provides the permeability, and the facing sand picks up the detail.
The three things above are not original to me, but were gleaned from Ironman's videos after watching them over the years, like a hundred times.
I'm a slow learner.
Post by: shipto on May 09, 2025, 11:38:07 AM