Andy,
It’s common to put a thick piece of wire, like from a coat hanger, in a long slender core like that. Think about the rebar they put in concrete. You are almost there man!
Rindert
Rindert, thanks for the input. I can always count on a response from you in this subject.
I actually put a wire in the middle and pulled it out to make a vent hole. Maybe i should put some glue on and slide it back in once the core is hardened.
I also considered the possibility that i didnt compact the sand consistantly.
The fins are pretty thin, its a tall order to keep them strong enough.
I just thought with your concrete analogy, maybe I could add a little fiber to hold it together better.
By the way, looking back on previous posts, i noticed on your molding flask you use crossway dowels to hold the screws. Thats a good trick I dont see uses often.
2 Likes
Maybe you could put two in and pull one out to make the vent. The vent is necessary too. I want to see this nozzle working. I think you have a good idea
It’s cheap and strong. That’s why I do it. But its doesn’t look nice, in a fine woodworking sense, so you don’t see it around often. Furniture makers used to do it when one side would be hidden. They didn’t drill all the way through. Then manufacturers started making dowel nuts, and you know the rest of the story…
5 Likes
Here is a foundry/forge using a waste oil burner. It looks like it needs some adjustments to make it more viable. Like when it is tilted in forge mode, it looks too low, but it is about right for casting, so it needs a height adjustment. I think it could be modified slightly to use propane and/or wood/char gas as well. It also looks like it needs wheels. but that is all nitpicking, it seems pretty solid.
4 Likes
I never knew there was such as thing as a jewelers charcoal block until today. Apparently, they are used for soldering jewelry like silver/gold/platinum, and they use them for melting small bits back together like a kiln.
They make a compressed charcoal block but I have no idea what they use for a binder.
“Specially compressed charcoal delivers a super-hard, reflective surface with a much longer life than soft charcoal blocks. Charcoal blocks reflect heat efficiently while creating a reducing atmosphere around the pieces you’re soldering or fusing, which helps to reduce oxides.”
It makes sense but I never knew.
2 Likes
I would form a pleated shape somehow with aluminum flashing, and pack it full of sodium-silicated sand (or even just greensand) for the core. The aluminum flashing will keep a little strength during the pour, and weld itself to the molten aluminum.
Also, I used to putz around with baking soda and vinegar, and even dry ice, till I discovered how inexpensive it is to just get co2 from a gas supplier. I suppose for a tiny one-off project you might not want the overhead of tank rental, but I wish you success and hope you do many more cores and casts so that cost is justified after all.
1 Like
My 2 cents on the metal casting topic. Aluminum bronze is a popular marine alloy. I got the copper from a local scrap yard in the form of copper wire. Firing the oil burner this hot usually destroys the intake tube of my furnace.
6 Likes
I’ve really wanted to attempt an aluminum bronze nozzle for a cross draft or a downdraft. Maybe print it with a wax type filament and do Lost Wax casting to have NPT threads.
5 Likes
Would be very interesting to see how that would work. The melting point could be an issue, but it might be overcome by the thermal conductivity of the alloy if there was enough heat dissipated back through, it to the outside.
3 Likes
I would probably do as little preheating as possible ie fresh air coming in to cool the nozzles, and moistened charcoal to keep the reaction a bit lower if it’s in a downdraft.
Making them very thick would likely help as well.
2 Likes
You can do lost PLA casting.
I think there was a method to do it in the microwave as well but don’t use a microwave used for food. And you can actually melt the material in the microwave.
If you have a model say made of clay or whatever. They sell a reusable, pourable material called Alumilite. It is like jello. then you can pour it in to get the reverse, cast a low melt wax into it. then do the lost wax casting.
You can do a homemade version of it, without looking up the recipe, it is glycerin, gelatin, and water.
5 Likes
I think that would work. Or if you have the ability to melt copper, straight copper would maybe transfer heat a bit better.I had limited success with my aluminum nozzle. See it in the charcoal nozzle thread.
4 Likes
That’s an idea worth trying! The weather is getting warmer, I think the foundry will have to wake up soon.
3 Likes
Lost PLA works but they make a wax type filament to burn away easier.
In the slicer program I use you can actually create a negative, a mould type of the 3D image.
1 Like
true, but the last time I looked it was fairly expensive, and it requires different heat settings which of course means time dialing the printer in.
I suggested the other way because it might be faster if you already have the nozzle design you want, but you just want to switch materials.
2 Likes
Do you guys know a cheap/easy way to make ceramic molds for lost wax?
Rindert
I haven’t seen much on using ceramic molds, more plaster or silicon/gelatin because of the odd shapes used.
You could probably use a clay slurry like you would for slip casting.
2 Likes
I used ceramic shell molds for decades, not sure it was ever cheap. However, both Ransom and Randolf, and Remet warehouse shell materials in the Denver metro area, (Aurora). I would order with the companies and by the time it took to drive to the warehouse it was ready. You might also get a small sample from one of the art foundries in the area.
Kent
1 Like
If I remember correctly the slurry uses ethel-silicate, sort of like making a clay slurry with alcohol. The solids are fused silica, re-melted glass allowed to form a crystalline structure, fused silica has an extremely low coefficient of thermal expansion so the mold does not expand or crack when heated. but when melting the wax out you need to quickly heat the molds to get the surface of the wax to melt before the wax expands with heating and cracks the molds. de-waxing and flash firing can be done with a cheap weed burner if needed. Rather than aluminum bronze, Silicone bronze has a similar melting temp and is a beautiful alloy to pour.
Kent
2 Likes
Most of my experience is with green sand. You can see one of my projects on post 3 of this thread.
Also I made one lost foam casting. https://forum.driveonwood.com/t/spiral-path-heat-exchangers/3657/117
Are Ransom and Randolf, and Remet warehouse shell materials still around here?
Rindert