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Interesting! I imagine alignment with the racks will be tricky. Perhaps it needs some sort of horizontal guides.

Nice. Can we see some close up photos?

+1 for Prusa. I have a MINI and love it. And they come across as a really thoughtful company that cares about its customers (including novices).

I suspect the more crucial thing here is that they are easier to align correctly.

For the weights, I think the best arrangement is a continuous loop of chain, with a self-winding mechanism in the weight: the weight consists of a battery box and motor and switch, which crawls up the chain to the top when it hits the ground... Like in this one: https://ideas.lego.com/projects/5f13f0c2-284c-4cb2-b649-f554f29e1514 https://flic.kr/p/H9Wvnk

Brilliant!

Looks like a very neat and capable build!

From the pictures of 42157 it looks as if the distance between the holes is 5 *along the diagonal* because there is an alternating liftarm running along there, so that they would not be in-grid. It would be pretty difficult to distinguish 5 and sqrt(5*5+1*1)=5.1 from the picture.

There is a tapered slot on the underside made with two bionicle teeth. When the lever is moved into turn-in-place mode, the slot captures a connector on the bottom of the lever, forcing the knob into its central orientation. It's a beautiful mechanism! The only other set I'm aware of with such a sophisticated steering mechanism was 42054. I think this one is in some ways even better.

The more I see the more I like! This looks like a great set. It's clear from the labels that the two steering modes are indeed controlled from the same lever, by pushing it back and forward and by rotating it. I can't tell whether there is some mechanism to lock the rotation into the central position when in turn on the spot mode (which would be cool). It also looks as if the two axes of movement of the arm are both controlled remotely via some mechanism. And finally the suspension looks very interesting. The bar on the top seems to link the two sides, while two of the three wheels on each side have their own additional pivot. And nice wheels, and lots of new or rare parts in white as well!

Yes, this looks like a very useful part.

One way to increase the torque it can handle is to trap the wheels between two discs which are held together.

Right. So perhaps "rocking" the lever into one position forces the two sides into their extreme positions for turn-in-place mode, with no rotation of the gear possible, while with the lever in the other position we can rotate the gear for normal steering. That would be a nice control mechanism!

No idea, but on the plus side, if you want motorized wipers....

Great job. There really was a lot of empty space in that model!

Why not just attach the ring rigidly to the axle and forget about the two 28t gears? Any technic gear will mesh with the ring gear, but the spacing needs to be correct. A simple case would be the 12t gear, which will work 1 unit closer to the ring gear than what you currently have.

Very interesting! I'm amazed the the gyro holds its orientation for so long.

This looks like a good idea. As a variation, the chain itself could be built out of liftarms (in various ways), potentially providing a stronger basis to attach the discs to. Thanks for the post. It would be nice to see more discussions like this. Someone asks an interesting technical question, then lots of people chip in with ideas. I feel like there was more of this in the past (OK "good old days" rant over!)

Thank you for the kind remarks and the suggestion. I'll look into that. Sometimes I find I miss things when they are in such a thread, though, because I don't realise there is a new model. Perhaps the solution is to have a general thread and also one for each model, but perhaps that is too much duplication?

Thank you for all the kind words folks! Mindstorms would be cheating! (Just kidding - I'm very impressed by the things people do with it, but I am obsessed with doing everything mechanically). Many thanks! I'm curious what you mean by "reduced the motion to a minimum"? My general philosophy is to make everything as simple as it can be, and no simpler (while achieving the intended goal), but I'm not sure whether that's what you are referring to...

About 5 years ago I made the first version of this model, which used a combination of pneumatic and mechanical control. I was never completely satisfied with this - according my own particular ideas of purity it would be better for it to be either 100% pneumatic or 100% mechanical. Moreover, it was not completely reliable at shows, since the pneumatic elements tend to dry out and develop leaks over time. The new version is entirely mechanical, and just works from one motor. I have taken inspiration from the recent mechanical Container Transport GBC modules and put the control system out in front where it is visible to an audience. The Tower of Hanoi puzzle is to move a stack of "discs" (here 5 of them, not really disc shaped) from one peg to another, making use of a third peg, with the rules that only one disc can be moved at a time, and a larger disc can never go on top of a smaller one. It required 2^5 - 1 = 31 moves to complete. The solution is ususally described recursively, but here (as in the previous version of the model), it is implemented by a repeating sequence of moves between pegs A and B, B and C, C and A, etc, where in each case the smaller of the two discs on top is the one that moves. The main challenge with such models is to provide a precisley timed control mechanism for the various functions that is reliable and capable of supplying sufficient torque. After trying various options, I did this using a chain drive (similar to the Loop Coaster, but with controlled lowering as well as raising), and two Tomy Armatron mechanisms, one with feedback to advance by a precise amount, and the other using a slipping clutch in combination with end stops.

Yes, I think you are right. So quite a bit of stretching of the rubber for it to bend.

To me Train GBC means GBC that involves trains in some way. GBC is ultimately about variety - time to think outside the hopper! Anyway, no worries - glad you've got your inspiration back!

Maybe this could provide a starting point: https://www.eurobricks.com/forum/index.php?/forums/topic/49988-tomaszajacs-lego-mindstorms-caterpillar/ Although to be honest I'm not sure exactly how the tracks are constructed. The designer gives a remarkably large number of pictures while somehow not giving much clue about this crucial detail! Perhaps some of our reverse engineering experts can help...

1. Pass balls directly from one train to another. E.g. one goes over a bridge and opens a hatch dropping them into another waiting below. 2. A linear GBC module situated on the cars of the train itself, which passes the balls along from the back car to the front car in sequence while the train is in motion. 3. Something along the lines of Akiyuki's "Stuck Ball" module but for trains, where the train can only move if it contains enough balls, and the choice is made mechanically. 4. A module that requires sequencing, e.g. like Container Transport or a Pick and Place device, but the sequencing is done mechanically by a train. It goes continuously around a loop (not carrying any balls itself), and attached gear racks provide power to a sequence of gears situated along the track, powering the various actions. That should keep you busy for starters. I expect to see working prototypes by next week. 😉