The "ORIENTAL"

[Dave Otto]

Thanks Maury,

The base is a casting, Marvin cut a mold for them and Roland had them investment cast. I ended up making quite a few of them. I even did some for the Lightning Hay Press engine. I had a couple set aside for me and I let someone talk me out of them. Now when the time comes I will need to make some more. It would not be that much more work to just CNC the body, because there was a ton of work finishing the castings.
Roland found a source for the glass tubing and perfected way to cut them in the lathe, using a tool post grinder and diamond wheel. He found that using a metal collet they would always break when the blade broke through, after trying a Nylon collet he had much better luck.

Dave

[Jasonb]

I find that Micro-Mesh is good for polishing the acrylic, you can buy small sets with a range of "grits" and the final polish.

After machining



After Micro-mesh

[maury]

Nice oiler Jason. I've beem using a similar buffing setup with fine abrasive and rouge. I get about the same finish
as your oiler. I was just looking for a bit more clarity. Guess with oil in there it probably doesn't matter much.

Thanks, Dave for the info. If you have more of these cast, I'd like to add a few to the order. I was currently working
on the cylinder oiler. Just happens many moons ago I bought one of these at a show and scaled it. I made some sand
castings, but the oiler is too big for this model. I'm scaling and tweaking to get it about right, but when I do, I'll
also have the delima whether to investment cast or CNC. Investment casting has the advantage that allows me
to share with others.

[maury]

Just trying it on for size.

[CI]

 

[maury]

Y'all, the design has progressed with enough detail that I think it's safe
to start making some patterns for the castings. I'll start with the right hand
valve cage. There is a right hand and a left hand cage. The valve cages are
swiss cheese parts, so It's best to start out with the most difficult part.
These will eventually need to be gray iron, but I can cast them more quickly
at home in my foundry in aluminum. OK for just machining and design verification.

[CI]

Nice pattern work !
We need casting photos.
.

[maury]

Ok I have done the core box for the RH Valve Cage casting.
I have been using sodium silicate to bind the cores, but have had some
trouble with thin and small cores breaking. I have some investment
casting plaster, and thought I might give it a try. Has anyone made cores
using this plaster? I'd be interested in your comments. The castings
will be in aluminum.

[vtsteam]

I have not, but generally you want cores to give since the metal shrinks, and they do that by burning the core binder. Aluminum seems to put up with all kinds of abuse, but best practice is to use a normal core type.

[vtsteam]

If you cast your lower corebox itself as an aluminum part, you can use a classic sand, molasses-water, and corn starch core mix. Remove the plastic top after the core is rammed, and leave it in the lower aluminum corebox as a half-shell to bake in the oven. That way you don't have to handle it until it's hardened.

Run a couple fine wires in the core if it needs strengthening when ramming up.

Also:

Not sure how you plan to add the core mix.

It's easier if the ends of the channels/core prints end at the ends of the corebox so you can pack it through those, from the ends.

Maybe this is the reason yours have been breaking if you're trying to load it like a sandwich into a closed mold -- cores need to be rammed some -- and that takes place from the ends, where possible.

In a split corebox with no ramming, they are made as halves, hardened, and later cemented together with core cement.

[CI]

I have not tried plaster cores, but I suspect they may hold moisture or water.

Some things you could consider:
1. Use small steel wire in the core, either straight pieces, a loop, etc.
The ends of the wire should terminate in the coreprint.

2. I have used blue painter's tape on the interior of coreboxes, to help with release.
I wax the tape before and after every core is made.

3. I tried a variety of percentages of sodium silicate for cores, using CO2 to harden the core.
I thought that "more is better" when it comes to CO2, but my cores were very weak, and were breaking up.
I increased the percentage of sodium silicate, and the cores had a bit more strength, but did not want to break up after the pour due to hardness.
I finally found out that SS cores should be gassed for 5 seconds only, and while I did not believe that, I tried it.
The cores I made using the normal percentage of SS (I forget if it was 3% or 5%, but per the manufacturer's recommendation) that were gassed for 5 seconds remained usable for over a year sitting out on the open shelf.
Cores gassed for more than 5 seconds started breaking up on their own within 30 minutes.

4. Moisture in the sand may affect the binder.
Resin-bound sand has to be oven-baked dry.

SS bound cores should work without having to resort to something exotic.
Good luck.

Edit:
Perhaps drill two small holes on the opposite side of the coreprint, so you can blow CO2 into the coreprint area, and it will go through the core and out the holes on the other side.

The heavier percentages of SS seem to block the movement of CO2 through the sand.
Sticking to the recommended SS percentage gives good permeability.
I use fine sand, and that is not a problem with SS cores.


.

[maury]

Y'all, thanks for the suggestions.
The core boxes I made are for the iron foundry. They use air set sand. Their method is to make the cores in
halves and glue them together. I have made core boxes for them with open ends, but they pull out the pins
and make the cores in halves. Over the years I have learned not to try to influence the way a foundry does
their thing.

I have often thought about making molasis baked cores the way you have described. I used to use a foundry
that used that process, and it works very well with iron, suppose non-ferrous too. I'd like to try it, do you have
a recipe for the sand mix? All the of foundry guys I worked with for years are gone now.

I'm good using SS for many of my cores, and have had a lot of good luck. I just have trouble with the thin ones.
I have also tried using different mixes and have used wires with some success. Might end up going this way.
I just haven't stopped being curious about trying to improve my work- or actually just being successful.

Guess I forgot to mention baking the investment plaster. It requires slow moister removal, but I have the time.
I was going to bake cure it per the instructions, so moisture should not be a problem. Raw plaster would
probably explode in the mold

Shown are the left and right head patterns. I toyed with the idea of coring out the combustion passage,
but there is no good way of supporting the core on both ends. It'll just be more fun to mill out the cavity.

[CI]

I know people use the methods that work for them in the foundry world, but if there are better methods, then using dated methods seems counterproductive.
The best cores (in my opinion) are made from resin bound OK85 sand.
They are very strong, and have a long shelf life.
You can carve and shape these cores after making them to fine tune the size/shape.

I don't see the need to make two-piece cores.
I do have core adhesive, and while it works well to secure mold halves together, it would have to be an extremely complex core to require adhering multiple parts together (such as automotive engine block work).

The core print area of a corebox can be left open, and the mold mostly filled before closing the two halves.
Then you can final fill and ram through the coreprint area.
Makes a nice one-piece core.

The old-school foundries use to work wonders with linseed oil cores, but I don't know exactly how to use that material, and I think it requires baking.

Sodium silicate cores are pretty good material, but the cat's meow is resin-bound cores.

.

[vtsteam]

Hi @maury, this is my most recent recipe and it worked very well. Formerly I used a recipe from the Gingery books, which used wheat wallpaper paste as the starch. But I liked the corn starch as binder as just as well, and all ingredients are available in a normal kitchen (except sand). Sand shouldn't be super fine as that makes it weaker actually.

https://www.modelenginemaker.com/index.php/topic,12658.msg301085.html#msg301085

I was not suggesting a core cement, btw earlier, but just saying that closed coreboxes (ie without openings at the print ends) the normal foundry practice was to ram the halves, harden or bake them, and then cement them.

I was not suggesting that you do that. but that you supply openings at the ends of your core to allow ramming through the ends with the corebox assembled. You can do this possibly with your existing 3D prints by sawing them off flush with the extension cavity's ends -- depending on the internal fill -- I guess.

I disagree that one method is "better" than another, if results are satisfactory in either case to the person who chooses that method. I don't see hobby casting as a competition. Nor "new" as necessarily better than "old". I try to be open minded, and am in it for the enjoyment. I find the smell of baked molasses cores in the kitchen more pleasant than exotic resins, and the satisfaction of using what's avaiable, inexpensive and non-toxic to be a pleasure personally, but that's my own set of choices, not everyone's.

I hope if you try it, the cores work for you by whatever method.

[vtsteam]

Oh, and if you do bake your cores as I do, don't forget to grease the pan, so to speak! A wipe of salad oil beforehand would have made my baked sand cookies release properly, last time.