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3D CAD Modelling from the original drawings

A project log for Accurate Apollo DSKY Replica

Or how I try to create an exact mechanical (and functioning) replica of the Apollo Guidance Computer DSKY

mdasilvaM.daSilva 08/29/2020 at 07:450 Comments

Solidworks was the software used for this entire project. STEP files have been added to the VirtualAGC's repo, an each model has an accompanying .md file describing the eventual differences between the plans and the models, if any. If you need the original Solidworks files, send me a PM.

Reading American plans was a challenge for me, as I was trained and learned to create European plans. While the imperial units required little time to get adjusted to, the biggest change of conventions was how the faces were laid out. In Europe, we use the First Angle Projection (ISO standard), while US adopted the Third Angle Projection used on those plans. There's an interesting article on this matter here.

2004929-001: Front Cover

I started with this part, which will set most of the external dimensions for the front part of the DSKY. Several versions of the same plan existed in the NARA SW scans, which allowed to lift 99% of the uncertainties over some dimensions (overlapping traces due to the quality of some scans). For me, the most interesting face is the back one, with all the pockets to make this part as light as possible, while keeping maximum structural integrity. No expenses spared here!

2004900: Rear Cover

This is also a beautiful part. Stiffening ribs all over.

2004968: Front Housing

This housing holds the front parts of the DSKY: indicators plate, keypad, cover. It is pretty intricate, with a bunch of pockets and fillets that took me some time to figure out. I had to print several iterations of this plan to lift a few ambiguities.

2004919: Indicator adapter plate

It holds the two indicator modules and carries the pins for both connectors. This part was probably much easier to mill...

1006315: Indicator gasket

I didn't understand what this part was all about until I read a bit more about the DSKY. After the Apollo 1 disaster and the whole "pure oxygen" issue, the Command Module and LEM designers had to switch to a nitrogen/oxygen mix inside the vessels. In order to limit the risk even further, a bunch of the electronic modules (I don't exactly know which ones) were pressurized with 100% nitrogen. The DSKY was one of them. You can still remove the front cover and indicator modules without breaking the seal, hence those heavy gaskets.

2004699(000 and 001): alarm and display covers

Nothing too special about those. They're both very similar, only difference resides in the bottom blanking part. The LM version of the alarm cover has a taller opening as more status lights were used. Those parts mate with the respective modules with shouldered screws and C-clips.

1006387 and 1006315: alarm and display indicators

This is where it got tricky: I couldn't find much on those displays apart from the external dimensions. Those are thus dimensional models.

2004705: Main Housing

This is a behemoth. It holds the display driver, the keypad controller, the interface with the main AGC module.

The drawings are extremely hard to read, features constantly overlap and I only found a couple of schematics. This is why only the external features are finished for now. The internal features still have to be tackled with. I'll work on this someday, as for me this is vital to get a complete and accurate model for preservation purposes.

As for my replica, what I have here is plenty enough.

EDIT: I finally got around to finishing this thing. Took me 5 extra hours to get everything right. 

1005022: Keycap

There are 19 variants of this part, each for every key. It snaps onto the lower part of the switch assembly.

Misc parts

A few parts have not been described here: the connector plates for the indicators, screws, etc. Some of them have been modeled, others haven't. I'll update this section when (if) I ever add any others.

Complete assembly

Putting everything together on Solidworks was a simple matter of assembling the parts and mating the surfaces. This pictures shows all the before-mentioned parts, except the keypad and fasteners.

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