I was noticing when pouring aluminum in a mold, there was a rather quick transition from the mold being filled to when the casting sucks back the melt from the sprue. My reaction has been to reduce my pour rate at the moment I should be pouring faster. So, I was thinking I should make a pouring cup. I rounded up a few patterns. and then I cast this thing... slapped it in the lathe... and made this core mold. This is a baked pouring cup.
Using the new pouring cups, I prepared to cast a few things. and the yield ... Seems the sprues are a little small.
The cores look promising and maybe I can reuse them. The molds were baked at 275F for about the time it takes to make a corned beef brisket really tender. A couple of 4in. wheels and Mikes Thing.
The 4 in wheels are coming in closer to 3.5 " after machining and what not so, I need to make some 5" wheels with hubs. Ready to pour a 5" wheel and another Mikes Thing. Ummm..... seems I had a blow out on the corner of the drag. That's 5 lbs. of spilled aluminum. You can see the three places where the concrete spalled under the melt. And once again the petro bond caught fire. I've noticed if I shake out these heavy castings less than 20 minutes after pour, the alcohol ignites. The flames stay less than 6 inches.
Trying a few things different... The pattern sitting atop the core mold. . Ready for pour. Shake out aftermath. The yield. Ready for lathe work. The next few days will be cool enough outside to justify firing up the wood stove and just whittle away at these big slugs of aluminum.
I always use an extended riser and feeder comprising of a large soup can with the top and bottom cut out. I ram it with greensand with a short length of pvc pipe inside and form a funnel with a moulding tool. The extra height makes it easier to pour and give "head" to the metal to feed the casing. You can see it in this video for example.
I'm a little vague about what I'm building, all I know is I need to be able to cast 6" wheels. Right now though, I'm working on making 4" or better wheels that I need to rig up dad's chair so he can get out of it. The 5in chunk is the mold cavity pattern. The cones are the approximate shape of the sand cores I want to center in the mold cavity. The 4" wheel in the lathe will be another sand core.
I've watched many of your videos, thank you very much, and have often used the soup can. I was going for a larger reserve for the melt, which is what lead me down this path. I'm also experimenting with some ideas for further down the path. Speaking of paths, sometimes they are circular. I was working on 4" wheels a while back, don't remember what I was wanting to make but I had to stop when I realized I needed a 8" 3-jaw chuck. As I was turning the 5" slug, I got to the point were I needed a bigger chuck because the jaws of the smaller chuck were in the way. Deja Vu.
I got this wild idea... 11 minutes later This runs a little quieter than the other chunks of metal I've been using.
I've been bummed out the last few days after the last casting. My wonderful cores floated, messing up the casting. I think the problem, other than not anchoring them down, was the melt filled the vent paths and then the gases pushed the cores up. I think I have a solution to fix that problem. What I don't have a solution for is the new problem with the muller. My muller is a cement mixer in which I've put various chunks of metal to mix and mash the sand. All of a sudden, the sand just lies there. Whatever chunks of metal I put into the mixer just sits atop the sand which just stays at the bottom and slips and sands the drum of the mixer. Previously, the sand adhered to the drum of the mixer allowing the metal chunks to mash and mix as it turned. I'm wondering if it's time to add oil and alcohol. Meanwhile, it dawned on me that the 5" or greater disks and hubs I'm trying to cast won't fit into the crucible. I can't melt my failures without cutting them up. So, I had to replace the burned out metal bandsaw motor. Cross section of 6" disk, that poured short by the way, and the 4" wheel both of which had core float. The 2" hub on the bottom is supposed to be the vent chamber and not filled with aluminum. As you can see, the melt filled the 1/4" vent hole that led to the bottom of the drag. Same thing happened with the 4" wheel. With the vents plugged, the gases most likely built up and pushed the cores up.
Nice clean metal. You guys really impress me what can be done with dirt! I see some seriously THICK metal being successfully poured. Good on you for staying in the fight!
It sure looks like my casting sessions have ended until I do something about mulling my petrobond sand. I've been using a cement mixer with a steel ball but now the sand and ball just sits there in the rotating drum, no mixing or mulling action at all. Looking over the various threads on building mullers tells me this is a problem that won't be quick to fix.
I was casually looking, now I'm real interested. I'll have to shove the other projects aside to make room and time for a muller build.
My PB did that too with the oblong rock I tried as an experiment. I think what happens is the drum gets polished from the oil sand and just wants to slide. When I added more sand then it started tumbling again, so you have to fill the drum more. Find you a nice 8" piece of limestone that is pretty close to round. Look around where someone put rip-rap on a bank or ditch.
I was thinking of your rock tumbler, Fishbonz, and wondered if you had this problem. I've tried more and less PB but no matter, it just slides in the drum.
Tobbo Mott's video https://youtu.be/z4MYJhq6HQI inspired me to rethink my casting situation. He is using lost foam to make parts for a muller. I'm going to have to make a muller, too. In the meanwhile maybe I can do some lost foam to at least finish off my dad's chair alteration. I think I have everything I need. Can I cast these wheels with a 7/8" hole and maybe a keyway? I don't know yet how to proceed from here.
I recently cast some pulleys with a 1/2" hole so you certainly should be able to do so at/near 7/8". Even with care it's tough to keep them as concentric as you would like in the foam pattern but if you can mount them on a plug mandrel to turn OD feature your should be fine. Best, Kelly
Go for it! If it doesn't work, it should at least give you some ideas for getting the next attempt to work better. Since you have actual precise measurements you're shooting for, Kelly's methods will undoubtedly serve you better than mine. Jeff
