I printed Peter Van Den Berg's optimized J-tube

Scots John wrote:Looks cool, I can see the potential for casting intricate shapes but one would need a high frequency vibrating table to produce a good end product.
Are Dragon rocket stoves still being made?

R Scott wrote:It would be much easier to ship plastic pieces and bags of mortar than a delicate already cast core.

It would be easier if you had a big printer, but if you could find someone to help split the files (that only has to be done once) then anyone could print them locally.

Way beyond my abilities, but you have me thinking in a whole new direction!

Joshua Rimmer wrote:I do functional mechanical 3d modelling on a daily basis. If someone could send me the original model or drawing, I would be happy to split it up into pieces that could be printed on the typical 200x200x200 printer. Purple Moosage for email addy!

Solomon Parker wrote:

Scots John wrote:Looks cool, I can see the potential for casting intricate shapes but one would need a high frequency vibrating table to produce a good end product.
Are Dragon rocket stoves still being made?

Somewhere on Peter's site (or somewhere) is instructions on how to make a vibrating table. They are indispensable for casting cores.

Dragon stoves are still being made, but for the $1100 price tag, I can think of a lot of ways around buying one. That's just me though, I rarely buy something I can build. I can justify a lot of development costs and tooling to figure it out for myself for that price.

Scots John wrote:I am only guessing but, perhaps there would of been around $1500 2000 investment for a proper vibrating table, $5000 for the mold construction and $100 of refactory for each unit?

Scots John wrote:I did not say it would not work as I don’t actually know that but casting course dry mixes and expecting good results with fine detail would normally require a high frequency vibrating table?

Solomon Parker wrote:I don't think that's quite the next step. What I'm suggesting is not people building their own printers or CNC machines, I'm just talking about printing molds on standard off the shelf printers that are already all over the market.

This is certainly an option, especially if someone is using EPS or XPS foam. But I think building a CNC machine is going to be a bit daunting for most people interested in casting their own core.

Glenn Herbert wrote:I made a styrofoam cavity model to cast my 8" refractory J-tube core, with top and bottom sections instead of left-right to minimize differential expansion and stresses between areas. It has served well for four and a half heating seasons so far. Both sections have cracked in several places, but are still locked in place and not in danger of failing. Notably, the burn tunnel roof with trip wire molded in is still unbroken and almost perfect. I do see a difference between the bottom which I cast first with cement that had started to set and was honeycombed in spite of vibrating, and the top which cast perfectly. The top is largely still smooth from the plastic bag mold release material, while the bottom (patched solidly where honeycombed) has spalled to a rough surface in a number of places.


Just curious where the cracks actually end up?

Solomon Parker wrote:I printed Peter's 3d Model of his optimized cast rocket core.

I'm a visual thinker so I had to see it in person, even if at 25% size.

Thomas Tipton wrote:I have considered the potential for using the water soluble material used for biodegradable packing peanuts to cast pieces for a "lost wax" "Lost styrofoam" type of casting.  Except in this case you would let the casting set and then dissolve the mold with water.  Though admittedly, I have not yet done any research on the composition of said biodegradable packing peanuts.

Chris Kott wrote:Wouldn't doing a "lost wax" casting with polystyrene produce dioxins, especially if you do a low-temperature degradation in oxygen?

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-CK