42179 Planet Earth and Moon in Orbit

[shroomzofdoom]

On 3/10/2024 at 10:37 AM, SJMarty said:

What a great build...I really enjoyed it.

Has anyone else toyed with the idea of motorizing this?

Quick and dirty for demonstration purposes. I used 88017... Not quite permanent.

I like the little crank. I sit here on video calls, cranking away, and everyone wonders what my left hand is up to. 

Edited March 11 by shroomzofdoom

[Davidz90]

I got the set. Very pleasant build. Unfortunately, my Earth prints are also slightly displaced, Africa experienced catastrophic tectonic shift.

After studying the gearing, I can confirm the earlier findings about gear ratios:

1 lunar month = 27 days (should be 29.53059 solar days)

1 sun rotation = 27 days (technically OK, some parts of the sun rotate at this speed)

1 hand crank rotation = 3 days

Regarding the year, earth is atached in such a way that without input, it will remain stationary in relation to the base (not the arm). So it will gain an extra solar day throughout the year (from the perspective of earth, sun will do 1 full rotation). This means that the year length is 364.5 sidereal days (2:729 gear ratio, rotations in relation to fixed base/stars) + 1 solar day. 

Since the earth rotations are in relation to the fixed base, all the days in calculations are sidereal days, which are shorter than solar days (they are 23 hours, 56 minutes long, so approx. 0.997222 of a solar day). Therefore, the final periods, in solar days, are:

1 lunar month = 26.9249 days (should be 29.53059 days)

1 year = 364.4874 days (should be 365.2425 days)

In short, year length is a little worse than the earlier calculations.

 

[Lego Tom]

18 minutes ago, Davidz90 said:

I got the set. Very pleasant build. Unfortunately, my Earth prints are also slightly displaced, Africa experienced catastrophic tectonic shift.

After studying the gearing, I can confirm the earlier findings about gear ratios:

1 lunar month = 27 days (should be 29.53059 solar days)

1 sun rotation = 27 days (technically OK, some parts of the sun rotate at this speed)

1 hand crank rotation = 3 days

Regarding the year, earth is atached in such a way that without input, it will remain stationary in relation to the base (not the arm). So it will gain an extra solar day throughout the year (from the perspective of earth, sun will do 1 full rotation). This means that the year length is 364.5 sidereal days (2:729 gear ratio, rotations in relation to fixed base/stars) + 1 solar day. 

Since the earth rotations are in relation to the fixed base, all the days in calculations are sidereal days, which are shorter than solar days (they are 23 hours, 56 minutes long, so approx. 0.997222 of a solar day). Therefore, the final periods, in solar days, are:

1 lunar month = 26.9249 days (should be 29.53059 days)

1 year = 364.4874 days (should be 365.2425 days)

In short, year length is a little worse than the earlier calculations.

 

While 'stickers' don't bother me, earth should have been painted on this model, in my opinion. As for the discrepancies, that is a total shame. The model teaches the principles OK but the accuracy (or lack thereof) ruins it. I haven't read through the entire thread, but if I remember correctly, I believe someone worked out the proper gearing needed. Too bad LEGO didn't follow that path.

[Davidz90]

4 minutes ago, Lego Tom said:

I believe someone worked out the proper gearing needed

Actually, I did XD In fairness, it is quite a bit more convoluted and makes use of multiple differentials, but for me that's a plus. The, moon is the most puzzling - a simple 1:28 would be better. I'l definitely make a mod implementing better gear ratios & limiting the color vomit on the model. 

Edited March 18 by Davidz90

[Davidz90]

One error in my previous post: everything is sidereal (rotations relative to fixed base), moon too. This means that we need the sidereal lunar month which is 27.32 days. So 27 is remarkably accurate after all!

Now if we want some serious accuracy, I've done some more calculations and here are the results:

calculations by David_Z1, on Flickr

 

Edited March 19 by Davidz90

[shroomzofdoom]

Any of my fellow North American Technic fans noticing the set doesn't quite line up for the April 8 eclipse?

Not complaining...but I just noticed this and was thinking I'd 'reset' it, assuming it to be related to the margin(s) of error mentioned above.

[Davidz90]

1 hour ago, shroomzofdoom said:

Any of my fellow North American Technic fans noticing the set doesn't quite line up for the April 8 eclipse?

I think that in the instructions, only the earth axis is lined up more or less properly, with proper seasons and equinoxes. I haven't checked but I believe that the initial moon position was whatever. In general, the set would benefit from some slip clutches allowing for easy correction of the relative positions.

[Jurss]

Bought today litllebit under 60EUR. Can't wait to build.

[ZENE]

We designed a very nice motorized kit for this set. Using customerized motor, with touch control speed, and showcase it at your preferred speed.

Need your comments, friends.

 

[BrickRally217]

Has anyone had success recoloring this thing yet? I just made a quick Bricklink wanted list for every non-black part included in this set that's available in black, except for the element used for the moon and a few dark bluish grey substitutions when black wasn't an option. I will have to go through the instructions and see how much non-black I can get away with, considering the rarity of some of these parts, but it's a start.

 

[JunkstyleGio]

Now this a set where I don't actually mind the "colours".

.

[DrJimbo]

On 4/1/2024 at 4:40 PM, BrickRally217 said:

Has anyone had success recoloring this thing yet? I just made a quick Bricklink wanted list for every non-black part included in this set that's available in black, except for the element used for the moon and a few dark bluish grey substitutions when black wasn't an option. I will have to go through the instructions and see how much non-black I can get away with, considering the rarity of some of these parts, but it's a start.

 

I replaced a bunch of the easily reached parts with black (or less bright) equivalents - looks good. I might tear it down fully to finish the job with parts I have. Would probably break out the black 3L pins in that case. 

I also did a number on the pointless white decorative elements. Local pick-a-brick wall had some gold parts that I bought at random without having this in mind. I am a few curly elements short so the other side is unfinished. 

Edited April 8 by DrJimbo
tidy up

[R0Sch]

@DrJimbo Looks good. The candle flames are a bit weird but gold and black looks good. I would just use a black marker to color the ends of the blue pins. Not worth the hassle to disassemble everything imo.

[Lego Tom]

4 hours ago, R0Sch said:

@DrJimbo Looks good. The candle flames are a bit weird but gold and black looks good. I would just use a black marker to color the ends of the blue pins. Not worth the hassle to disassemble everything imo.

They are there to warm up the sun!

[BrickRally217]

18 hours ago, DrJimbo said:

I replaced a bunch of the easily reached parts with black (or less bright) equivalents - looks good. I might tear it down fully to finish the job with parts I have. Would probably break out the black 3L pins in that case. 

I also did a number on the pointless white decorative elements. Local pick-a-brick wall had some gold parts that I bought at random without having this in mind. I am a few curly elements short so the other side is unfinished. 

WOW that looks amazing! I might have to steal your idea of using those gold Elves pieces for decorations because that makes me recall this really incredible brass orrery with the constellations that I saw when visiting the Frederiksborg Slot in Denmark. 

[DrJimbo]

On 4/9/2024 at 5:45 PM, BrickRally217 said:

WOW that looks amazing! I might have to steal your idea of using those gold Elves pieces for decorations because that makes me recall this really incredible brass orrery with the constellations that I saw when visiting the Frederiksborg Slot in Denmark. 

Thanks! Brass decorated orrery was the vibe I was going for. With the flames around the sun as a whimsical element. Saw some lovely instruments in Greenwich recently. 

[Jazzlw]

@Davidz90, @R0Sch, would one of you possibly mind making a diagram of the gear train / ratios? I would love to see how the whole thing works out. Just built it last night and it’s definitely one of my favorite sets. 

This YouTube video had a nice diagram but their numbers come out different than the ones here and they said something about missing the turntables that I didn’t understand…

 

[DrJimbo]

I finally finished my aesthetic upgrade:

• replaced where I could the more visible bits with black or non-yellow axles. I didn't do a full rebuild, but did some fairly extensive teardowns
• added more gold whirls
• removed the whimsical flames

I am tempted to drill the axle shape out a black double bevel 20T gear, so that I can replace the blue one - has anyone any experience of this?

[Davidz90]

21 hours ago, Jazzlw said:

This YouTube video had a nice diagram but their numbers come out different than the ones here and they said something about missing the turntables that I didn’t understand…

There is definitely something wrong with the numbers in this video. I'll try to make some diagram, but the numbers I posted on march 18 are correct ones.

Regarding the turntable stuff - he basically alluded to the whole solar/sidereal time issue. We are used to solar days/years, but all rotations in the orrery are in relation to the crank that is fixed to the base. So for judging accuracy, we need to compare the rotations to sidereal day and sidereal year (=true 360 degree rotation in relation to fixed stars).

[Jazzlw]

12 hours ago, Davidz90 said:

There is definitely something wrong with the numbers in this video. I'll try to make some diagram, but the numbers I posted on march 18 are correct ones.

Regarding the turntable stuff - he basically alluded to the whole solar/sidereal time issue. We are used to solar days/years, but all rotations in the orrery are in relation to the crank that is fixed to the base. So for judging accuracy, we need to compare the rotations to sidereal day and sidereal year (=true 360 degree rotation in relation to fixed stars).

Thanks, that would be awesome! Seeing everyone’s overall ratios / accuracy has been super cool, but I’d really like to see the way the gear trains achieve them etc. 

[Davidz90]

9 hours ago, Jazzlw said:

Thanks, that would be awesome! Seeing everyone’s overall ratios / accuracy has been super cool, but I’d really like to see the way the gear trains achieve them etc. 

Here's my schematic:

orrery_2 by David_Z1, on Flickr

Edited April 30 by Davidz90

[pleegwat]

And if I'm understanding things right, the number of sidereal days in a sidereal month is the same as the number of solar days in a solar month, correct?

[Davidz90]

1 hour ago, pleegwat said:

And if I'm understanding things right, the number of sidereal days in a sidereal month is the same as the number of solar days in a solar month, correct?

Not exactly.

Sidereal day is about 23 hours, 56 minutes - 4 minutes shorter than solar day.

Sidereal year, on the other hand, is about 20.5 minutes longer than solar year.

So:

solar year takes 365.2422 solar days, 366.2422 sidereal days.

sidereal year takes 365.2563 solar days, 366.2563 sidereal days.

 

[Jazzlw]

On 4/30/2024 at 6:07 AM, Davidz90 said:

Here's my schematic:

orrery_2 by David_Z1, on Flickr

Thanks a ton, this is great!!

[Frequenzberater]

Yesterday evening I had some time to build this nice set. From my point of view, this is more an adult display set than a playset. Because of that, the visual appealing was more important to me than usual. Therefore, I replaced all the miscoloured stuff as far as my spare part collections was allowing it. I think it looks much better than the official version now:

And here you can see the bunch of unicornvomit I have replaced  :

As you can see, I also added two small rubber tires to the main structure support roll in order to remove the slight sagging of the rotating arm. 

 

 

Edited Friday at 08:57 AM by Frequenzberater