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This looks extremely useful! Thanks for putting in all this work.

I've now built this, and I regard it as one of the best sets ever. It's a pity there wasn't a bit more effort put into making it beautiful (especially the base), but the mechanics are outstanding, and it's a real pleasure to witness it IRL!

To be more precise, to a good approximation the Earth's axis points in a fixed direction relative to the stars (towards Polaris, in fact). This is what the model does, which requires that this part does rotate relative to the main sun-earth arm. This is achieved through gearing. Arguably the nicest feature of the model.

8480. Incredible blend of form and function. Every part is there for a reason. Some of them for more than one reason. Also some nostalgia as it was my first complex post dark age set.

I am far from a typical builder, but fwiw: Ideally I prefer to do things that have not been done before, so there is no actual mechanics to copy. Mechanics always comes first. If I can shape it into something elegant, that's a bonus. Whatever parts are needed (but in practice not much system). Dunno really - ideas from random sources, imagination, building on others ideas... Lots of trial and error. Start with the hardest bit. Lego has its own constraints. See above. Start with official sets. There is lots to learn from the designers!

Thanks for the enthusiasm! Indeed I had to do some prying to adjust it. There is actually a better way, which is to use clutch gears, like in the later "Pangolin" Surprisingly, they do not seem to gradually slip over time. Of course, it would need a redesign to incorporate them into Synchropods. I've been meaning to do this but have not got around to it. I also have the key parts collected for a 33 pod mega version....

Hopefully this will quiet down all the moaning! 😉 It looks quite useful. Even just for rigidly connecting two parallel liftarms it is quite handy, while the additional hole brings plenty of further possibilities.

Yeah I agree. I like the look of many parts of it - the rings, the core structures etc. But the base is just a mess. I guess some of it is colour coding to help with the build - the unsecured 3L blue liftarm matches the exposed blue axle pin (which I think should be 1/2 a unit lower btw), and there is probably a red one on the other side. But it would be so easy to tidy these things up at the end. Still, let's not lose sight of the many positives. It's a very clever piece of engineering, and completely unexpected as a set. We can hope that it heralds a new era of interesting mechanisms.

Wow! Brilliant! This is clearly it. I am quite surprised and impressed that they got it so accurate, and even more impressed with your powers of deduction. I had actually started to ponder the possibilities of 8t-36t, but I don't think I would ever have got it.

Oh yes, well spotted! Although I wonder whether that is a 20t or 36t (or even a turntable again). It is looking very much as if all the gears are horizontal, so really the task is to connect the 20t that turns the big turntable with the central vertical axle, with the correct spacing and ratio ... I've kind of got obsessed with this!

Cool - thanks for sharing. There are some tantalising clues in that last one. The teeth on the lower grey (16t?) gear appear more widely spaced than the black one above it, suggesting that we are looking at the former head-on while seeing the edge of the latter. Don't know whether that helps, but I still think there are probably gears not on the centre line of the handle. Is it possible that the black gear is another small turntable, not a 36t? Not that this would necessarily help with our difficulties! Clearly we need to track down the young lady in the photos and bribe her to spill the beans.

If you've got it, flaunt it?

Very impressive! Possibly taking the prize for [gears : other parts] ratio!

Can't have too many orreries! That's very nice and neat. I like the exposed gearing. Of course strictly speaking you need to offset the sun slightly to account for the orbit of Jupiter 😉

Yes, I see what you mean (although I don't know how to interpret it). And of course there is a clear shot of a 16t on the clearer images. Maybe that one is off centre? I now see that a 20t turning the turntable would not obstruct the support roller, so that indeed seems the most likely. I guess there is space for gearing hidden lower down in the base? Is that a possibility?

Ah, yes, you are quite right of course. It did sound a little too simple!

There seems no evidence of a new part here - the version we have works IRL and is consistent with the pictures. Good work. This part is mysterious to me too. Since the central axle below the sun turns the moon with a 1:3 ratio, we expect something like 1:4 between this axle and the main arm turntable. Possibly 1:3 or 1:5 after account for compounding rotation. 20t-60t would be 1:3, so potentially the 20t gear should be turning at the same speed as the central axle. A series of horizontal 16ts would do it, but seems to get us to the wrong hole. I am not seeing the large black gears, but perhaps you are better at spotting things! Also is there room for a 20t turning the turntable with the gold support runner for the arm? Could the turntable be driven by a smaller off-centre gear? Maybe 12t?

It's quite beautiful. We still need the gearing to control the sun-earth arm but I'm guessing R0Sch is on the case...

Cool! This looks very plausible now! I think the 28t turntable under the sun can now be fixed to the frame, and then the Earth will hold its axial tilt.

Yes, I agree that is (hopefully) how it should move. I just cannot see where the axle is connected on the sun side. Where is this fixed 28t gear? We seem to have a ratio of 3x3x3=27 for moon's orbit to earth's rotation, which is (fairly) good!

Ok, I understand, but it needs to be connected to the two turntables. Like this. The 5L axles go into the black half of the large turntable. (They might be pins rather than axles). Edit: the 28t turntable should be the other way up here.

Impressive work but I don't think this can be quite right. The Earth base with the tilt is not rotationally fixed to the Moon support - it needs to rotate independently. So its rotation needs to be powered by something. The only possibility I can see is that it is fixed to the top of the 28t turntable, presumably by two axles or pins running through the large turntable as I said above. So the tilt base and the small turntable top need to be rotationally aligned. I agree that the top of the small turntable must be fixed to the bottom of the large one, as you seem to have. But so far as I can see, the pair of them cannot be fixed to the frame - they must be free to rotate, presumably with the red liftarm (or something attached to it) fitting snuggly inside the ring. Unfortunately we can't compute anything unless we know how the lower axle is geared on the sun side, as I mentioned above.

Clever stuff. I'm sure we won't get differential-drives this in the model, but it will be a nice challenge to fix it!

I am not seeing anything that looks new here. This looks like a LBG pin with stop bush going through a blue 3L liftarm up into a white 3L perpendicular connector. Underneath some arrangement of pins and connectors (there are several possibilities) will connect that to the 28t turntable below, passing through the hole in the 60t turntable. There is second axle running along the bottom of the arm, which I think drives the 28t turntable in the Earth module, and is doubtless very important for the mechanics. But where is it geared to in the Sun module? It is at the level where two vertical 5x7 frames overlap, so there is not much room for gears. Perhaps there is a 12t bevel (single or double) that meshes with the *underside* of the horizontal 20t double bevel?

I suspect the rotation speeds will be of the correct order but perhaps not really accurate. E.g. I would not be all that surprised if there were only 120 days in the year. Happy to be proved wrong of course. The axis tilt is interesting too. Presumably it will retain its orientation during the Earth's orbit.