Working on a project with @Uglydog, 2.25" diameter x 3/4" bore x 11.25" to be lost foam cast in Alu. Parts to be turned down and threaded before use. -does the 1 x 1.25" sprue look feasible for a near vertical or vertical pour? -any merit in packing the centers with loose sand or Petrobond in case compaction is less than ideal? Hoping to coat today and cast tomorrow, thanks!
You may need a weight on top of the sand to overcome the buoyancy of the sand in the middle/core as it'll tend to float.
Thanks Mark, we had not considered that. We have some cast iron brake parts at our disposal for weights.
I only know of this secondhand from a guy who cast tons of bronze tube: He used these hollow shell cores and filled them with steel shot to keep them from floating and had some wire to keep it centered in position. he used to add a few extra inches to the length as the bronze would have shrink defects up the top but that didn't matter as they cut it off and remelted it.
We are going to wait on coating until tomorrow, so still very open to ideas. I had not considered shrink defects.
Buoyancy is less of an issue with aluminum versus bronze because silica sand and aluminum are fairly close in density. I cast 1.375"D x .25" wall hollow tubes with elbows all the time and have very good core stability. Automotive Water Neck | The Home Foundry Casting tubes gets more challenging as the tube and core diameter decrease. This is true for any casting method because the cores become weak and the core prints small. -It's not a linear world. In lost foam the diameter and location of the tube opening are analogous to core prints in conventional open cavity casting. I'd suggest at least 6" of sand depth above the pattern so that would mean >6" of combined sprue and cup height assuming you burry the exterior of cup near the top, which you should, and of course, good vibratory packing will be important.......don't rely on just tapping on the flask. Sand float should not be a problem under these conditions for Aluminum. I'd position it at ~20-30 degrees from vertical and feed the top half of the tubular cross section. You don't have to coat the interior, but if you do, you will have to move air through it to get it to dry or it will take days to dry. If you don't coat the interior, you will likely have some imbedded sand in the internal casting surface, which could be an issue if you intended to machine/bore the ID. Best, Kelly
Thanks Kelly, we appreciate the information. Rainy weather is pushing the casting date into the future.
