Glaysche

Lego is a challenging but satisfying medium in which to build robotics. There is a lot of backlash in Lego gears which can reduce precision but there are techniques to counteract that. When you gear down, the effects of backlash are reduced. You can take advantage of this in some circumstances. You can gear up before going though a long chain of gears and gear back down at the end. You can create two parallel gear trains that are built with a slight tension. That can almost entirely eliminate backlash for those gears. You can reduce slop by using connectors in place of bare cross axles that twist a lot less. You can use multiple motors on the same joint for more power and less slop. All Lego flexes under stress which reduces precision. You can compensate by building structures with reinforcing in multiple directions. You find a way to incorporate triangles into the structures. Sometimes you can use interlocking frames to make something very strong and rigid. Finding creative solutions to the shortcomings of Lego is part of the challenge and part of the fun.

I love this! I am a sucker for all things robotic. I've only used the absolute positioning on the angular motors (https://rebrickable.com/parts/69730/motor-large-angular-position-light-bluish-gray-housing-black-wire/ and the medium and small versions as well). With those, you are able to access the absolute position. I at least used it from Mindstorms software -- I haven't used PyBricks. The angular motors also have a printed mark on them for the 0 position. That helps lining things up when you build it.

This is really nicely done and well presented. I think the counterweight is a really nice touch. One question, did you try gearing it to move faster? Was this the fastest it could reliably move using the XL motor? One thing to try is to use the large anglular motor (https://rebrickable.com/parts/69730/motor-large-angular-position-light-bluish-gray-housing-black-wire/). It is more powerful and may be able to support faster movement.

@Unbrickme's video is content relevant to this discussion. It is completely appropriate for him to post it here. I would not have seen it if he hadn't posted and I found it useful. Even if he doesn't make any other posts except for a link to his video, it is still useful, relevant, and appropriate.

For what it is worth, I thought the title was fine. I enjoyed watching the interview. Nothing mentioned was particularly new to the EB community but it was still good for me. I suspect people at TLG will watch the interview and it’ll be another data point for them to understand the AFOL Technic community which is a good thing.

This is some more detail about the new truss part from New Elementary:

Very cool. I love this!

New Elementary write up for the March wave of Technic parts: https://www.newelementary.com/2023/02/lego-technic-parts-review-42152-42153.html?m=1

I’m pretty sad about this. I really like the PoweredUp ecosystem, particularly when using the RI or Spike Prime hubs. The hardware is great and the software is bad but has been steadily improving and is certainly usable now. I’ve made it a point to use the Mindstorms software for all of my creations because I thought it was more accessible than something like PyBricks. I want other people to be able to build and program the things I publish on Rebrickable. The Spike Prime software does not have the features I need. Now it seems like there is no platform to build on that is accessible by everyone. I wonder if the logistical hassles related to shipping rechargeable batteries has anything to do with this? Lego Education charges way more for shipping and is probably more tolerant of these sorts of issues. TLG may be trying to streamline their main business.

Well, here are some pictures of the new turntable compared with the old. The new one is on the left. The most interesting change to me is that they are now using 6 clips to hold the two halve together rather than just 4. Will this make it stronger in certain applications? It does appear to work with a chain.

New Elementary review: https://www.newelementary.com/2022/07/lego-technic-review-42145-airbus-h175.html

The Ideas submission was not approved in review. It has been resubmitted here: https://ideas.lego.com/projects/bf7068e7-bd0e-42ae-afe5-dc867b8479d4

I also have 4 ports used for sensors that are only used during calibration. Well, actually, the force sensor is also used as a kill switch. If I make a mistake in the programming, I can hit the kill switch before it damages itself. The axis 2 in particular is geared such that it could break plastic parts if it runs against the end of travel. If I eliminated the 3D part, I’d probably end up with two 6 port hubs and one 2 port hub for the full robot. The 3D printed part is cheaper but it’s not pure Lego. in fact, with reasonable software, I’d probably use one of two Essentials hubs on the 6 axis remote control as well. That would make it easier to add gripper control to the remote. Thank you. I’m never sure if people are getting much value out of these posts and my Rebrickable MOCs. They are complicated and expensive enough that I doubt anyone else will ever build them. I’m hoping that by providing Studio models, people will be able to borrow some of my ideas and use them in their own MOCs.

Thank you for the kind words. Backlash was probably the trickiest problem to solve in this whole project. The differentials definitely add some backlash but try to mitigate it with different techniques. The five gear red differentials are definitely better so I started by using those. Being 28 tooth gears made it a bit challenging to get the proper gear ratio to cancel out the rotation through the axes but was worth it. The most effective technique is to gear up before going through the differential and gear down at the end as close to the load as possible. This makes higher speed and lower torque through the differentials. This works really well with the gripper and sixth axis. The fifth axis (bending of the wrist) still has too much backlash for my taste. I couldn’t find a way to gear down enough at the end of that gear train without making the structure too big or too weak. Maybe you were looking at my first version on Rebrickable? My second version is already up at: https://rebrickable.com/mocs/MOC-109607/glaysche/6-axis-robotic-arm-mk-2/ In that version I re-designed axes 1,2, and 3. I don’t have plans to eliminate the 3D printed part. If you look at my very first version I posted in this thread, it was pure Lego. I had put the motors for the gripper and axes 5 and 6 out in the wrist. This ended up being really heavy and stressed the axis 4 turntable too much. Adding the 3D printed part and moving the motors to the elbow dramatically improved axis 4. I haven’t found a way to as good of results with pure Lego. The 3D printed part is actually quite generic and useful for many designs. Maybe someday TLG will produce something like it. One idea that is plausible would but the use the new Spike Essential hub and small angular motors out in the wrist. This might be light enough to not stress the turntable too much. Or maybe TLG will come out with a more robust turntable? The Spike Essential hub has the additional challenge that it only supports “streaming” mode and only the Spike Prime software. I am currently using Mindstorms software and downloading to the hubs.

Good overview of the new parts in the Ferrari: https://www.newelementary.com/2022/05/lego-technic-parts-review-42143-ferrari.html?m=1