Glaysche

I would like to hear some basics about the part development process. How was it decided to build these specific parts? What were the biggest challenges in designing them? What were the tradeoffs in the design? Any regrets about the final design? Anything you would do differently next time?

My collection is not as old as some here but I have not seen parts breaking nearly as much as is being reported here. I have a couple ideas. Maybe different manufacturing plants are producing different quality parts? Some people (or even whole regions of the world) are unlucky and getting poorer quality parts? Another thought I have is that exposure to sunlight might cause the plastic to get more brittle. If models are on the shelf in the sun, could that cause the parts to degrade and break more often?

This is hilarious. I love it.

To follow up on my own post, this is what I am working on. I’ve done most of my testing with Powered Up hubs and app. The Spike Prime / RI hubs are much nicer and I would vastly prefer using those. This robotic arm has a large angular motor for rotation which seems to work fine. The XL motor is on the bottom tilt axis. 5 L motors control the other axes. Oh, I should mention the Spike Prime hubs have 51515 firmware and I’m using the 51515 iPad app. I’m using these because I think the yellow looks better than the teal in this application. I suspect the RI hub will have the same behavior.

I did a test of Powered Up L and XL motors on the 51515. The basic functions work like start and stop motor. Some more advanced functions seem to work like “move to relative position” and “move 2 rotations”. Reading the current position or relative position seems to always return zero. This seems strange that encoder would work for some things but not others. Anyone else see this? I just reported to Lego support but I’m sure a response will take a while. Have any of you reported this?

I have tried to build my MOCs with only parts available from Lego Bricks and Pieces. In fact, I often have used the newest parts available like the 15x11 frame or the new differential. It’s nice to see what the new parts can do. That being said, I will buy rare parts to get a specific color, especially on the pins and axles. That way, if someone else doesn’t want to buy the rare parts, they can can use a common part in a different color.

An option that would be pretty nice would be if they included a 51515 hub instead of two Technic hubs. That would allow 6 motors with a single hub and be rechargeable. To follow the pattern before of Mindstorms components going to technic, they would probably recolor the hub to be LBG/DBG just like the large angular motor that went into 42114. I suspect it would be a relatively simple software change to make the 51515 hub work with the PoweredUp and Control+ apps.

If you look around, it seems most other themes are largely sold out as well. (I'm also in the USA.) Maybe they are focusing all manufacturing capacity on the 2021 sets?

This MOC is just stunningly good. This is one of my favorite things I have ever seen in Lego.

I have loved following this series. Applying theory to lego mechanics is very interesting.

I've been working on a robotic arm that went through many of these same challenges. I actually tried a 60t turntable with 1L worm gear, 56t turntable with 2L worm gear, and a variety of other things. I was not happy with any of the solutions. What I eventually ended up doing was to have 2 12t gears driving a 60t turntable. This ended up reliably rotating in both directions and was a pretty reasonable amount of structure needed to make it all work. Here are some pics: This is the robotic arm. The joint of interest here is the rotating joint at the top. Zooming in on that, I have two 12t gears driving the turntable: Here's a pic with the arm removed: These 2 12t gears are attached to 28t gears which are driven by an 8t gear seen at the top middle. This localizes all the high torque to just those two axles and the rest of the gear train is relatively low torque and easier to deal with. These two axles needed really good axle support but once that was built, it worked pretty well.

I think the one you are looking for may be the second video on this Akiyuki blog post. https://akiyuki.jp/en/1548

The original post in this thread was complaining about not having many original MOCs. I see that too but I assumed it’s because people aren’t interested. I’ve made a few posts on EB about a robotic arm I’m working on. My specific design is quite original but I suppose the theme has certainly been done before. I received no replies or other interest. I’ve actually made a lot of improvements since my last post but I wasn’t going to bother posting again because there’s no interest. I don’t think I’m alone. The topics that get the most replies and discussion seem to be mods of TLG sets and scale models as previously mentioned. I hope my experience here is just a fluke because I would love to see more original designs.

Very interesting. I'm wondering if there is a way to use the motors as servos using this app. That is, calibrate to find the end of travel and have a slider move proportionally between the endpoints. In some setups, there could be many rotations of the motor between endpoints.

This is amazing. I'm excited to see this as it progresses.

I made many updates over the last few months. Here is the big picture: I designed new jaws, made a cleaner way of transferring an axle through the turntables at the wrist joint, completely redesigned the arm rotation gear train, made the inclination joint much more robust, added "spring balance" shock absorbers inspired by Akiyuki's robotic arm, redesigned the gearing for the whole arm tilt to no longer have worm gears, switched to the Spike Prime angular motor for rotation, and designed a brand new base that is much more solid. It's been a lot of fun. Here are a few more pictures: I think this is right at the edge of what Lego Technic can do. In particular, the bottom tilt joint is a lot of stress on the parts. In order to minimize this as much as possible, I drive each of the 60t turntables with 2 12t gears which get geared down a few more times so that the XL motor can drive it. The axles are very well supported in this gear train. Some of my intermediate designs permanently damaged some axles in operation. As always, I'm sure there are more improvements to come.

I was inspired by this series of posts and decided to build my own 6 DOF robotic arm. I did things quite a bit differently than this one and had newer parts available to me. I used the newer Control+ motors and battery boxes. They are more compact than the Mindstorms parts. I didn't end up using pneumatics. I'm sure this is just the beginning of my Lego MOCs.

There is a new thread detailing my latest version of the robotic arm: Update: Here is version 2 of the arm: Studio model available for free on Rebrickable: https://rebrickable.com/mocs/MOC-109607/glaysche/6-axis-robotic-arm-mk-2/#details Original post starting here: This is my first MOC and first time posting on Eurobricks. A few months ago, I got back into Technic by buying the Liebherr set (42100). I decided to design my own 6 degree of freedom robot. In doing research and experiments for this project, I was inspired by this post I found here on Eurobricks: I ended up making a lot of different choices in my model. Here is the big picture: I wanted to optimize for three things: It should work Maximum range of motion -- the wrist axes should be able to turn indefinitely and other axes should have as much range as is possible Built as compact as possible Here's the video with poor production values (and using a simple BuWizz profile to control it): https://www.flickr.com/photos/188456966@N07/49900167801/in/datetaken/ This was quite challenging to optimize it in this way. First of all, in order for the wrist joints to spin, they needed to be axle driven -- pneumatics won't work. In the example of the grabber at the end, I put an axle through the turntable to control the LA for the grabber. When the grabber turntable is spun, however, the grabber will open or close in an undesired way. To counter this, I used a differential and the correct gearing to compensate. Here's a picture of that: This is difficult to see in there. There is a new 2 piece differential (65413 / 65414) inside the turntable. The gears turn the differential at half the speed as the turntable which makes it so the grabber doesn't move when the turntable moves. The control for the turntable and grabber are axles on both sides that go through the next set of turntables seen here: The axle turns the perpendicular axle that goes through the turntable and is driven by another axle in the next stage. The stage has the same problem as the previous one where flexing the wrist will cause the grabber to turn and open or close. This is compensated with an additional two differentials and another set of gears. This one is particularly compact. Here's a picture of that stage: The lage gear there is a 28 tooth double bevel which is needed to get the correct gear ratio to the 28 tooth differentials. Pulling the side off of that, we see: There are three L motors (22169) here to control the grabber and first two degrees of freedom. I particularly like the gearing in the front of this section for the compensating differentials: As noted by Hanso in his series of posts, the end of this arm is actually quite heavy. I would have preferred to send all three functions though the next turntable but I could not find a solution that sturdy or compact enough. This weight caused trouble for the next turntable. To make this work, I used two turntables, one in compression and one in tension. There is a beam that goes through the center of the turntables that takes some of the load here. The next stage is a another stage that I would like to be able to turn forever so I don't want the wires to get twisted. In order to accomplish this, I also put the battery box on a turntable that turns with the rest of the arm. The wires go through this stage and don't get twisted. The humerus (in LBG) is very small (5x5) and it was a bit challenging to get the gears in there. The motors (XL 22172) for those next two axes very neatly attach there. The base has the last two degrees of freedom. The spin axis here uses a mechanism very similar to the Rough Terrain Crain (42082). The final axis uses worm gears to drive the turntables. There's a lot of force on this axis and I experimented with a variety of different gearing. The thing that worked best is displayed above. The center piece is driven and it gets geared down symmetrically to the axles that have the worm gears. Axle support was a bit tricky here: (Still waiting for the remaining black 7x11 frames to clean up the look here.) The 2nd battery box fits pretty nicely here: In conclusion, I think this works pretty well. I haven't explored the software at all yet -- just used BuWizz as a proof of concept. Many of the motors would work much better configured as servos. I wish Lego would release an SDK for Control+ so I could write an app similar to the Liebherr controls. My day job is actually a software developer so it would be pretty fun to build a full featured app to control this.