December 18, 20231 yr 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)
December 19, 20231 yr 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.
December 19, 20231 yr 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.
December 20, 20231 yr 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
January 11, 20241 yr 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, 20241 yr by R0Sch
January 12, 20241 yr 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...
January 12, 20241 yr @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€.
January 12, 20241 yr 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.
January 12, 20241 yr 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.
January 13, 20241 yr 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?
January 13, 20241 yr 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.
January 13, 20241 yr 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.
February 26, 20241 yr https://www.brothers-brick.com/2024/02/26/lego-technic-42179-planet-earth-and-moon-in-orbit-finally-an-orrery-review/
February 27, 20241 yr 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, 20241 yr by Frequenzberater
February 27, 2024Feb 27 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?
February 28, 2024Feb 28 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.
February 28, 2024Feb 28 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.
February 28, 2024Feb 28 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.
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.