42179 Planet Earth and Moon in Orbit

[Davidz90]

1 hour ago, Zerobricks said:

Don't forget if the gear ratio is 364,5 the Earth does one additional revolution going around, so the end gear ratio is actually 365,5.

I don't think this is the case here. Earth is locked to the input axle/hand crank, which is not rotating and instead it is locked to the stationary base. If we would disconnect and lock the earth input, then over the year the earth would remain stationary and not do one rotation. 

But thanks for bringing up an interesting video - Veritasium is a good channel (even though he sometimes makes some minor mistakes in physics-related content)

[wissamms]

Very interesting video, thank you

[Jockos]

Thank you for the video. Obi-Wan would like it (from a certain point of view)

[allanp]

This is referring to a sidereal day vs a solar day:

 

[Davidz90]

 

2 hours ago, allanp said:

This is referring to a sidereal day vs a solar day:

Exactly. To quote Wikipedia: 

The Gregorian calendar improves the approximation made by the Julian calendar by skipping three Julian leap days in every 400 years, giving an average year of 365.2425 mean solar days long.

As of 2008, a mean solar day is about 86,400.002 SI seconds, i.e., about 24.0000006 hours

 

So yes, my bad, in this orrery the earth is not gaining additional rotation during the year, but one full rotation of earth, relative to the base, is not a solar day - its a sidereral day. So indeed, Zerobricks had it correct.

[Davidz90]

I decided to dig into this a bit more. Assuming that everything is geared from the crankshaft on a fixed base, so that all the rotations are completely separate and counted in relation to fixed base, we need to use sidereal day and sidereal years (rotations in relation to fixed stars).

According to this:

https://multiverse.ssl.berkeley.edu/Portals/0/CalendarInTheSky/Resources/Presentations/HowLongIsAYear.pdf?ver=Wt-kX9xEaM0fZve8OXxBfg%3d%3d

the proper gear ratio for the earth is 366.2564. So 364.5 is a little worse than I thought. I'll make a mockup to test if the rotations are really completely separate and run my program with the new target value.

[Davidz90]

I'm back with results. As expected, the earth stays still as long as it is connected with the central gear with 1:1 total gear ratio, with even number of gear ratios. Only then the two motions are fully separate.

To quote the presentation in the last post ": take the sidereal year (in seconds) and divide by the sidereal day (in seconds) to compute the number of spins Earth makes in one orbit…366.2564".

For 366.2564 target, I get (among others):

1/60*12/40*(16/28-1/40)=1/366.0131
1/24*1/20*(8/40+40/36)=1/366.1017
1/16*1/24*(40/36-1/16)=1/366.1987
8/140*1/24*(1/28+40/36)=1/366.2284
1/16*1/28*(36/28-1/16)=1/366.2482
8/60*8/140*(1/40+8/24)=1/366.2791
1/20*8/140*(8/20+20/36)=1/366.2791
8/140*1/16*(1/20+20/28)=1/366.3551

[R0Sch]

The 360° animation is available and as expected the gearing is exactly as I predicted
https://www.lego.com/cdn/cs/set/assets/blt0262e384b8de7bdf/42179_360.mp4

Also, high res images are available on lego.com. I really hope the prints on the Earth hemispheres will align perfectly as advertised below, even though I consider these two part designs mediocre for something that's supposed to be a sphere.

Edited January 11, 2024 by R0Sch

[howitzer]

Is it just me or is this set really expensive? Here's a screenshot from my go-to Lego retailer:

Especially the Airbus seems a bargain compared to the orrery, considering you get battery box, motor and almost 4 times the parts for little over twice the price. Of course the orrery has some expensive parts like the hemispheres, hoops and some frames and many gears but still...

[R0Sch]

@howitzer It hasn't even come out yet. So how can you expect a good price now? Just wait a few month until it drops below 60€.

[howitzer]

33 minutes ago, R0Sch said:

@howitzer It hasn't even come out yet. So how can you expect a good price now? Just wait a few month until it drops below 60€.

I'm not talking about discounted prices, those in my screenshot are normal prices at that particular shop.

[langko]

5 hours ago, howitzer said:

Is it just me or is this set really expensive? Here's a screenshot from my go-to Lego retailer:

For comparison, over hear at Lego AU this set is $99 and the Airbus is $329.

[Jurss]

On lego.com for LV 95eur. Not yet in local stores. But could be around 70 also.

[howitzer]

Lego.com rrp for myself is ~100€ for the orrery and 210€ for the Airbus. So about the same relative difference as my local retailer.

I'm still baffled about the pricing, what makes it so expensive?

[Jockos]

5 hours ago, howitzer said:

Lego.com rrp for myself is ~100€ for the orrery and 210€ for the Airbus. So about the same relative difference as my local retailer.

I'm still baffled about the pricing, what makes it so expensive?

I think firstly the globes, and maybe the rings and wheels. They are the only uncommon parts.

[thurd]

On 12/7/2023 at 7:27 PM, allanp said:

There's also yellow gears in the forage harvester. JCB (specifically a 3CX or 4CX) confirmed!

I'd buy 2 or 3 if they made them in some proper scale. 

[SNIPE]

 

[R0Sch]

https://www.brothers-brick.com/2024/02/26/lego-technic-42179-planet-earth-and-moon-in-orbit-finally-an-orrery-review/

 

 

[R0Sch]

And as feared, the two hemisphere prints do not line up well at all :(

[Maaboo the Witch]

There's continental drift, and then there's whatever the f*ck that is.

[Frequenzberater]

 

Does this thing also rotate? As far as I know the rotating achsle of the earth is not fixed

 

Edit: Apparently it does. Pretty cool 

Edited February 27, 2024 by Frequenzberater

[Davidz90]

3 hours ago, Frequenzberater said:

As far as I know the rotating achsle of the earth is not fixed

If you are talking about Earth's axis precession, it is 1 rotation in 26000 years so basically stationary for all intents and purposes. So the part does rotate, but in the sense that it remains fixed in relation to the base, properly demonstrating seasons.

 

I'm eager to get this set and do some improvements. Too bad about the print mismatch, and I don't understand why there are pins at all - axle going all the way through would hold two hemispheres just fine?

[howitzer]

On 2/26/2024 at 10:34 PM, R0Sch said:

And as feared, the two hemisphere prints do not line up well at all :(
 

This is awful. For such a parts they really ought to do better quality control.

[R0Sch]

1 hour ago, howitzer said:

This is awful. For such a parts they really ought to do better quality control.

Exactly. They even have 2 alignment pin holes for this and still messed up.

[Jockos]

1 hour ago, howitzer said:

This is awful. For such a parts they really ought to do better quality control.

 

34 minutes ago, R0Sch said:

Exactly. They even have 2 alignment pin holes for this and still messed up.

It's funny they photoshop it on official pictures, but can't make it in real life properly.. if only they released less sets but with higher quality.