Brutkey

smells of bikes
@smellsofbikes@mastodon.social

So I trundled out the foundry furnace, set up the propane, and put the crucible in. Sometimes it's hard to get this homemade burner to fire. It needs a diverging cone at the end to hold the flame better. Plus I had low gas pressure because the propane was approximately freezing. But it did start.

Metal bucket lined with refractory clay The depths of the furnace with a flame visible and some shiny aluminum in the crucible
smells of bikes
@smellsofbikes@mastodon.social

It takes about 15 minutes for any aluminum to melt because the heat transfer is just radiant. Once some is melted and touching the crucible side conformally, heat transfer skyrockets and everything starts happening quickly. I put the two investment molds in greensand. One mold had a crack so I put weights on it so it wouldn't float during the pour. I got to try out my diy carbon tip thermocouple thermometer for the first time.

Investment molds in greensand with steel weights (splitting wedges) Down in hell with a big gob of molten aluminum and the temp gauge down in the crucible Almost pouring temperature. I pour as cold as possible to minimize shrinkage Some aluminum scrap preheating on the foundry exhaust because heat transfer is vastly better here than in a crucible where nothing has yet melted, and this raises efficiency anyway
smells of bikes
@smellsofbikes@mastodon.social

As I said once it's hot things happen quickly so I didn't take a pic of dumping in boric acid or the actual pour. I'm very busy right then. But I did get both molds filled and dumped the excess (I melt way more than needed in case I miss the pour basin and waste some) into a muffin tin. The aluminum is still very molten here so it has a mirror reflection aside from a bit of dross.

Poured molds Aluminum reflecting the sky and clouds
smells of bikes
@smellsofbikes@mastodon.social

One mold had a blowout and lost about 300ml of aluminum out the bottom into the sand but both filled well. I have not finished cleaning them yet so the inner passages are still full of investment.
The tapered helical spiral sprue and pouring basin worked really well. It choked and remained full the whole pour, not entraining any air. That was the main point of this. There was some grubby stuff in the pour visible in one mounting boss and one lip of the intake didn't fill entirely. Still ok.

Rubbish in the aluminum including ash from the PLA burnout Little lacunae in the edge of the intake pipe. I could weld this. Both sides, one with the helical sprue very obvious and the almost empty pour basin above it
smells of bikes
@smellsofbikes@mastodon.social

Here's a video of one intake cut loose from the gate system and the other as cleaned up but still gated to show how the gating worked. I'm very happy with this.
I do have to figure out how to make the gating easier to remove. Long flat contact is really frustrating to cut loose.