622’s air pump and the end of detail castings

It strikes me that 622’s air pump will likely be one of the last detail castings I ever buy. Certainly, it will be the last brass air pump I buy. The next one will be printed, likely here at home.

It’s worth pausing here to enjoy the skill that went into the pattern for this little jewel. I suppose it must have been Bruce Bechtold who spaced those tiny bolts evenly around the cylinder heads, who assembled the minuscule valve glands and piston rod, who fashioned the cooling ribs on the air cylinder. I can only dream of being able to pull something like this together, and here we’ve been enjoying the fruits of his labour for 60 years. How many locomotives carry Cal-Scale air pumps like this one? What a legacy to consider that parts from his patterns are still carried with pride sixty years later!

Those great pattern makers and modellers at Cal-Scale, Kemtron and Precision Scale could not have predicted 3D printing. A printed part will enable me to tie the steam, exhaust and air pipes in without breaking any drill bits on age-hardened brass. I will design the supports into the part, and they will fit my boiler perfectly, without filing or filling. The space behind the piston rod will be space, and not filled in to enable casting. I may even create the part in multiple pieces to aid in painting and finishing. Oh yes, the 3D-printed air pump will offer many improvements.

But for now, I have enjoyed working with a tiny piece of art, and appreciating the ancient craft that went into it.

4 thoughts on “622’s air pump and the end of detail castings

  1. I largely agree, but the one thing i’m waiting for with 3d printing is a stronger material that remains capable of the detail. With frosted ultra detail, I’ve seen rivet heads rub off with the slightest touch (not a typical result, but it happens). Brass is harder to drill, and the creation of the masters is so much more dependent on honed shop skills, but once the job is done the material lasts without small surface details being at risk of breaking off. I’m only familiar with the properties of the materials Shapeways uses, so perhaps that day has already come for some home printers. Thanks to the help of other folks, I’ve found that using the printed part as a master and making a resin casting produces more solid part. But that too is an awkward process. So I am busy at it, but , , , waiting for the day.

    1. It’s a fair comment, Rob. I’ve seen the same, but we know that the technology is improving every year.
      The wonderful thing about 3D printing is the ability to create parts that can’t be cast at all. In the air pump, for example, there should be space behind the piston. On the casting, this is filled so the wax can be removed from its mold; with 3D printing, it should be possible to make this clear. Check out the printed Stephenson’s gear on 622, and imagine the complexity of the rubber required to cast something like that in resin or wax. Once we, as designers, come to embrace this capability (along with pre-assembled interlocking parts), there will be amazing changes.

  2. René As I read you very fitting “Ode to an air-pump” I thought about the new skill set that you as a practitioner of three-D printing have to learn, experiment with, and finally master in order to create a casting of this complexity. After the printing process is completed then you need the dexterity to remove this new three-dimensional print result safely from its base. A new and modern-day skill set is required to utilize this technology which I believe is acknowledged in the NMRA Achievement program rules. As a developer of the design for such a model it is an opportunity to see, plan and understand the components of a complex casting such as this. Thanks for sharing your thoughts in this matter.

    1. Thanks for your thoughts on this, John. Yes, the world is changing and the skills required are changing with it. It’s good that the NMRA is trying to acknowledge this.

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