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Elegant!

Looks interesting, would be nice to see it actually driving!

Congratulations - this is a very nice and interesting piece of work. Impressive that you managed to get it so accurate. Some might question the fact that getting on for half the time is spent (auto) winding! But this seems a perfectly reasonable compromise, of the kind that every Lego model inevitably involves.

Sorry that you don't think you'll make the deadline, but I for one very much hope you will continue to pursue this. It looks really interesting, and especially noteworthy that you are aiming for maximum realism.

Thanks everyone! Indeed, you have exactly identified the central challenge here. Due in part to quite a lot of good luck, I think I have managed to solve it...

I think it's finished! Video coming soon...

About the friction from the sliding gear: I think it might be possible to use the very clever method here instead (also check out the linked earlier videos by the same GBC builder). The basic idea is that the two screws (or chains in the earlier version) turn at different speeds in order to control the second degree of motion. I wouldn't want to do it in 2 weeks though!

Final BL order...

What a pity. It's a really interesting idea. I hope you will eventually find a way to make it work even if it's not in time for the competition. So it seems like the horizontal reversing is getting triggered too easily, if I understand correctly? Perhaps it could instead be triggered by physically reaching the end stop?

Thanks! Sorry for all the teasers! Getting the stickers on correctly is a delicate business that requires a fair bit of disassembly...

Working on a taller window for the day drum to display the result more prominently. Some tolerances are incredibly tight, and it is really lucky that they work out. The drum cannot fit beside the middle hole of the thin red left arm - there is only enough room at the two ends. And the clearance between the drum and the grey (soon to be red) engine crank part is so small that the paper sticker cannot go on this bit! Also the liftarm sandwich at the bottom needs a gap to accommodate the crank part.

Right. Everything is now assembled. Not completely surprisingly there was still a bit of a problem with gear lash, meaning that the output day of week indicator would not be reliably centered on the day. Acceptable, but not ideal. I have therefore added a further detent mechanism for the output drum. This one is a much less aggressive gravity driven one, compared with the strong spring driven ones for the inputs. Astonishingly the gear ratios work perfectly for this, and there was just exactly enough space to fit it in, one of many examples of tight tolerances in this model. It turns out to work really well! One drawback is that if you want to calculate the day of the week on the space station, it may not be so reliable! Remaining task is the stickers...

Exciting to see this shaping up!

Yes pneumatics are good. In principle one can use it for arbitrary logic or calculation! One long term goal is a fully pneumatic Babbage difference engine, but using binary rather than decimal. One disadvantage is that constant running tends to dry out the cylinders, so it is not so good for shows. Case in point: https://youtu.be/qsW5xmd9XCY

Thanks! Pity the trans blue is all going to get covered! Many thanks for the encouragement!

Pieces: no idea - maybe 2000? Gold springs https://www.bricklink.com/v2/catalog/catalogitem.page?id=236062&idColor=11&ccName=6472027#T=C&C=11 I'm quite pleased how the colour scheme is turning out. At first I was disappointed that the most neutral colour for the 14t splat gears is medium nougat, but then I realised it is quite a good steampunk colour, especially combined with some pearl gold.

The side panels are really tricky. They need to be strong enough to accommodate the springs for the detent mechanisms, while allowing the various axles and gears to pass through. Curiously, I have not used any frames or panels, and it is likely to stay this way...

It will do Gregorian calendar 1601 - 2399. This could be extended by adding more entries to the century dial.

OK, major updates. I think it is close to being finished apart from the "programming" of the drums. Basically all these bits just need sticking together. It was *much* harder than I anticipated. Getting the necessary bracing to fit around the bulky cylinders was a real challenge. However I am now somewhat confident that it will work, and quite excited!

Very interesting data! Can comparing the sound traces of the anomalous periods (perhaps averaged somehow) provide any clues? Or perhaps a slowmo video? (I assume you have ruled out the rewind). Also, very cool creation (of course)! The hanging face is very neat. Really enjoying the artistry as well as the cleverness.

Personally I kind of like the (humourous?) contrast that the whip (or wishbone) is the only organic looking part. That's what reminded me. Yours is indeed less creepy!

It's simpler than it looks. Basically 3 diffs sum the inputs to the 4 bottom drums and output the result to the top (day of week) one. The 4 inputs have very strong and precise detent mechanisms. Finally, the year drum also controls the sliding (alternating) leap year window on the month drum. It is crucial that 7 and 2 are coprime. The "offloading" is not really my idea. This is how the existing tabular day-of-week methods work. The devil is in the details. Currently the devil is finding plenty of details to occupy himself with.

Some progress. Getting the overall size and shape pinned down. MLCad is proving invaluable. The monster cylinder at the bottom is needed for the final two digits of the year, which will need up to 12 options per row.

In particular I am reminded of this: Steampunk colours: yes! I am thinking similarly for my calendar, and I think we are not the only ones. This may turn into a de facto steampunk contest!