Orcman

Yes the dials are moving at the same rate as their respective planet. To keep the dials sync'd, they each have a 16:140 reduction - same as the drive to outer ring. Although it looks ok, the outer arms already sag about brick. There is no way to support the arm from underneath. The Neptune arm is shown in both images below. The top image is just a single beam supported by the axle-hole. The bottom image is close to the final design. The further out you get, the worse the sag becomes. It was one of the compromise areas. So a more "in scale" arms would have sagged more than we desired. If you really re-enforce the arm, that weight then affects the movement and makes the whole thing much "heavier" looking. The other aspect is working area. It already needs a 76cm diameter circle to work in. We were aiming for something that could fit on a desk. If it was a purely Technic model, I'd probably agree, but I feel that with the design of the base and the planets being much more "Creator Expert" it should have a broader appeal. I would say that the model is almost a 50-50 blend between a Technic and Creator feels. So I am cautiously optimistic about our chances.

The view from above after removing the frame top and the sun The view from underneath Unfortunately the frame hides most of the gearing when viewed from the side. The end-points of the gear-train were fixed, so most of the gearing is mostly arranged in triangles.

I'd like to share our MOC and my experience building it, that I (Chris Orchard) and Brent Waller (yes, that Brent of Lego Ideas sets 21108 Ghostbusters and 21328 Seinfeld fame) have been collaborating on. Background During one of our Covid lock-down skype Brisbricks (our LUG) social nights. Brent was talking about something he would have liked to have made, but found he just couldn't get it to work. He elaborated that it was an geared model of the solar system or orrery (which I had always wanted to try, but never had), and he lacked the Technic know-how to complete, so I offered my help. We decided on dividing the work between the aesthetics and the technical, which worked well. Brent was responsible for the overall idea and look, as well as the base and planets, and I was responsible for the gearing and arms. We each gave feedback on the others work and I found that really helpful I had written a number of Technic articles for BrisBricks to help members get a grip on how to integrate and use Technic in their builds. So I was sure I could make it work, especially as I just had that "A-Ha moment" of using the big ring gear driven internally by smaller gears (that would also keep the ring centered). At first I thought it would be easy as the ring gear is a nice quarter circle, right? That piece turns out to have a little quirk - it is pinched in at the end cross-holes (or bowed out in the middle depending on how you look at it)! Check this video out to see what I mean. This meant that the standard Lego spacing would create far too much friction - it would slow down as the ring "tightened up", then it would speed up as it became looser. This wasn't what I wanted - I needed steady, constant speed. It took me around 90 hours of constant fiddling with various techniques to get a geometry that was slightly under a standard spacing. I found that a distance of less than 0.5mm would be the difference between it reliably turning, and gear slippage. Gearing Getting the gear ratios (planet orbit times) accurate was a key goal of ours. This is a small snippet of the design spreadsheet that I used. The original data is from https://space-facts.com/orbital-periods-planets/ and double checked with various NASA pages. Most solar system transit times are based on earth. Which would mean "gearing up" to make Venus and Mercury turn faster than Earth. I decided to turn that on its head, and base all the transit times on Mercury. So every planet would be "geared down" from Mercury, the idea was to make the movement as smooth as possible. In the spreadsheet this is represented by line 2. In the end every planet was less than 0.15% out, most being less than 0.09% It's really the introduction of the new 28 tooth gear that really enabled me to get the desired accuracy. Having a 7 in the ratios really helped. In the end I wrote a quick Perl program to help sift through the gear combinations. That program could handle up searches to 5 gears deep Early proof of concept video The physical model was created first, to ensure that it all fit correctly. The digital model was then created from that physical Moc. The planets are driven by a single M motor and turns Mercury at about 2s an orbit. We should have a video of that soon. Unfortunately for the physical model, I lacked the exact parts to make the planets just like the digital design, so an approximation of size and weight was used. Compromises Our goal was to create as accurate version of the planet's timings as possible, while still looking like attractive, but certain things had to be dropped. By introducing another ring, I did get a Moon to orbit Earth too as a prototype, but it was unwieldy and really threw the aesthetics out, so it was dropped. Pluto didn't make it, sorry. Although adding a ninth face in the base would be easy (as would adding another ring), constructing a nice looking, strong nonagon(?) on the base top just wasn't possible. MOC Stats: 2996 pieces 153 gears 15 months of collaboration 8 major revisions 2 completely different designs 3 gearing spreadsheets 1 custom written program to help work out the closest gear ratios Overall I am proud of what Brent and I have created, and we hope you like it too. More details, videos and images at our Lego Ideas Page.

Looks like the bottom beam doesn't stay perpendicular to the LA. How about this as fix? It doesn't eliminate the problem (one half can lead) but it sure limits it to a few mm difference. Also added the technic 1x bricks to stop the clams jamming open.

No problems buddy sometimes we can't see the trees for the forest. Nice idea with the connecting cable, should keep the skip firmly planted on its track too. I like Doug's idea too, as it avoids the need for a electrical switch (which can be a be costly). You could also use a clutch (slipping) gear instead of elastic, or have the timing spot on. I wanna see pictures (eventually) tho.

No, what I have is just an idea of what you have. The more information you give the easier it is to see a solution. However, Nico's reversing mechanism will still do what I think you need, if you simply put the output from the diff (8 tooth gear) to your original two-drum (on a single axle) approach. Providing the skip can drop under it's own weight as the cable is unwound. How it works: Once one skip reaches the top, it will encounter resistance from being against a stop. This forces the diff to turn, which reverses the motor. The other skip now moves up, while the first skip moves down - until the second skip reaches the top. Once the second skip hits it's stop, it will again forcing the diff to turn. This time in the opposite direction to it did first time. Cycle repeats. So it's really a reversing mechanism that activates under significant load. You don't need the second drum to force the movement of the skip, I believe Nico would have only used that because the incline is quite shallow and the skip wouldn't drop under its own weight. I hope you'll at least post a picture of the completed moc (as payment for my time )

Maybe your first idea then is more suitable. What about having some gears added to the drum that just add resistance to the drop? Thinking of something like a 24 tooth driving a 8 pinon. A similar mechanism is used for slow opening hinges. Don't take this the wrong way, but it sounds like this has a number of problems unique to your MOC, posting pictures will help people get a firm grip on your problem and help you solve it, rather than general hand waving.

Nice looking project. I am building something similar with a center pivot moved by two small LA's. I found that putting a differential between the two actuator inputs prevented binding, allowing the LA's to turn at the different speeds they needed to. YMMV with your design.

Is this what you're after? http://www.nico71.fr/gbc-tipper-trolley/