Rider Ericsson Homemade Castings

[raveney]

All good ideas and images. I have a plan now. Thank you all very much.

Please expound on the "retracts" and "cement and clamp the mould pieces" together. I think you are saying to cement the flasks together, and not the as cast pieces, right?

I love learning about casting things. I read a previous post made and used the reference you posted from the archives about core patterns and core prints.

 

[GreenTwin]

Here is an example of retracts (retractable pieces) by the light pole manufacturer "Spring City".

Everyone who does hobby casting has to figure out how complex they want to get with their patterns and molding.
There is no "right" or "wrong" way in the hobby.
The "right way" is what gives you the cast part that you desire, with the quality you desire, using the methods and materials that you prefer.

Bound sand, such as with sodium silicate, opens up a lot of possibilities, and you can make entire molds from sodium-silicate bound molds, not just cores. SS molds can be form-fittted closely around a pattern, sort of like how a crankcase cover on a motorcycle closely covers the flywheel.
This saves a lot of sand and sodium silicate.
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I started playing around with making twinned sodium silicate molds with a small pattern that was a cylinder support, and the intent was to avoid having to create two of the same patterns (photos attached).
Obviously you can make two separate molds, and pour them individually, but if you cement the molds together, and clamp them, you can use one pattern to make two molds, and pour two castings at the same time.

Retracts were used to make molds for large flywheels, where they would only make a pattern for one spoke, with a small pie-shaped section of rim and hub, and then they would use a retractable spoke section, and make the flywheel mold on the floor, one pie-shaped section at a time, thus saving a huge amound of pattern making effort, not to mention the space savings of only having to store a single spoke/hub/rim section instead of a huge flywheel pattern.

I only had one finished cylinder pattern on the green twin engine, and used it to cast two cylinders at a time. (photos attached)

A little creativity goes a long way in the casting world.

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[Jasonb]

I simply did not draw them as it was not needed for the example. I would have thought it was obvious they they would pull out the sand OK with the position of the split line as mentioned. I also did not show draft

But as Crest says they will all cast with the method we show and no risk of a foundry loosing the loose piece (retract). Yes it happens and I have made replcements for people where the foundry has lost them.

I don't really see the advantage of sticking those two cylinder moulds together unless you only have one flask. At least it is in a position where alignment of the joint does not matter, you would have to get it right if this yoke were cast as two moulds to avoid a step in the finished part

 

[Jasonb]

here is one half with the bosses added

And the mould that can be taken from it. Just drop a simple core into the space left by the core prints on the pattern and you are good to go

 

[GreenTwin]

Yes, I see it now.
Very clever setup.

For my cylinder, yes, only one snap flask, and only one cylinder pattern too.

And so I assume crest set his mold up about the same way.

I like your arrangement much better than my cemented molds (for this part), but cemented molds do have their uses.

And I prefer a pattern without retracts, but sometimes those are also necessary.
I would screw the loose part(s) to the main pattern when the pattern is being stored.

The wishbone pattern could also be made in one piece, and a crude follower formed up to allow the two mold halves to be made.
I have noticed that most patterns I have seen at commercial foundries (old and new foundries) are generally one-piece, with the exception of something like matchplates.

All of the Cretors original patterns I saw where one-piece.

So I guess I was thinking a one-piece approach.
Small patterns with thin parts like spoke halves can be fragile, and I have gotten into the habit of making mostly one-piece patterns.
I actually shattered one of the green twin flywheel pattern halves, but was able to glue it back together.
That pretty much cured me of two-piece patterns, but in many cases two piece patterns are not optional, but instead a necessity.
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Edit:
For 3D printed patterns, often you get forced into printing pattern halves, just to have a flat side to start the print with.

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