Nelson

If I could create more organically-shaped cams, that type of balance shifting might be possible. Unfortunately, I've yet to find a way to pull that off. I'm going to try stretching the length of the chassis out a bit to see if getting the legs closer to the front and rear will help. I'm also going to experiment with reducing the camber on the feet, making them more perpendicular to the legs rather than pitched slightly. I may let it all sit for a week while I catch up on some other projects. I have to portion out my obsession in metered doses!

I completed my goals for the weekend: test the model on various substrates and see how it deals with weight. Mixed results in both departments. I really love how the side panels look, but man... they need to lose some weight. The chassis and legs alone are 1.25kg. The side panels bring it up to 1.38kg. That's over 3 pounds. I can't imagine how heavy this thing's going to be once I add the top and end panels along with the head! I just hacked together a method for attaching the sides, so you see them gracefully falling apart in the video. Aside from the idea I mention about angling the legs out a bit toward the front and rear, I wonder if reducing the camber on the ankles/feet might help it not pitch around so much. Here lies the next challenge! Honestly, it performed better than I expected. I didn't think the feet would even get off the ground.

@BrickBear Crank Ankle. "Crankle"

Some tests on various substrates. I didn't notice the upper leg on the right rear had separated while I was setting up. It may have altered the motion slightly, but is probably not responsible for the mechanical failure at 1:00, even though it's on that leg. The loose terry cloth really bound things up. I think if it had been pulled tight, it wouldn't have been a problem. Still. This baby won't be tackling any loose dirt or gravel any time soon. Watch the rod on the right rear flex like crazy before finally breaking the crank ankle.

I will study this image a bit. As for reaching goals, I try not to think of this as a competition (although that can be motivating). My idea of success is different than yours. A model with true bending legs is integral to your vision, while I'm bypassing that feature. I would not be where I'm at in this process without your contributions in this forum. The current concept #2 design is a direct offshoot of this conversation. I only hope my contributions are helping you reach your goal. I had a sizable head start on this project, two years at least if not three.

Thanks for the lighting tip @BrickBear! I will investigate. And I think I'm following you a bit better now. I'll have to look at some video to see about your observations with the gate. If you feel it would be useful, draw up a image like the one I recently posted with naming conventions for the mechanics of your model. Perhaps we can even agree on some names for portions of our models that are similar or serve the same purpose.

@BrickBear I'm not quite following your post, but it seems like you feel your current leg motion isn't as close to the ideal line as you'd like. I'll look forward to seeing updates when you get back on the project! I love how differently we think about the same challenge and how we utilize different tools to assist us in our quest. I imagine Lord Vader and General Veers hanging out in a conference room hashing out the AT-AT's design. Vader is pushing the intimidation features of the vehicle while Veers is concerned about its fuel economy. I'm "satisfied" with the gate of the version in the video below. This concept design will always have a bit of shuffle from the feet on the ground. It's just the way the geometry works. I've minified it as much as possible. I could go back to concept #1 (and may someday), but I think #2 is more stable, robust, predictable, and will be more conducive to creating instructions for laypeople to build. I've got clearance between the toes now! (Barely!) No hang ups. That may change as weight is added. I've attached the aesthetic "shoulder" pieces and love how the look is coming together. (I'll worry about articulating the upper legs later.) I'm going to try to get the side cladding on this weekend and see how it handles that weight. @BrickBear One issue I've noticed in this thread is that we don't have adequate language to describe our model's mechanical features. I created this image and will use the terms shown in it moving forward. And here's the latest video:

I did do a bit of "cheating" early on in development, using non-lego springs, rubber bands, etc. But at this point, I'm down to two general model concepts (currently working with concept #2), so I typically start with a test mechanism that's all Lego. It's just one leg or quadrant stuck on a 19x11-stud technique panel (https://www.bricklink.com/v2/catalog/catalogitem.page?P=39369#T=C). It's kind of a pegboard where I can try out different geometries and timing. Unfortunately at this point, there's no replacement for actually putting it all together and firing it up. The concept is fairly proven, but it's really touchy in the overall build. IE: Last night I found out that kicking the timing of the rear legs forward one gear tooth caused total failure of the entire system! I admit that I still don't fully understand what makes one model work while another almost identical one fails even though I've been at this over four years now! Heck, NASA sent men to the moon only eight years after Kennedy's speech!

I'm trying my best to keep the model pure, using only genuine Lego parts that are "currently" available. I'd like to eventually sell the instructions on various platforms and that usually means not using non-Lego or out of production parts.

So much for taking time off. I woke up with a few ideas to try out. I was perusing BrickLink yesterday and ran across part #28974. (https://www.bricklink.com/v2/catalog/catalogitem.page?P=28974#T=C) A quick test with a minifig backpack confirmed this is a great part to shim various areas where you need just the tiniest bit of spacing. For my model, it will help get a touch more lift height in the legs. Obviously, I won't use the brown minifig backpack shown in the photo once I get the more appropriate parts, but you get the idea. There was just a touch of un-utilized gap at the peak of the leg lift cycle, but it was too small to add even a thin bushing. Now the crank can get that little extra lift it was missing before. That tiny shim gains me about 2/3 stud in height once the distance is amplified at the end of the liftarm raising the leg.

Here's the latest. It's been torturously frustrating trying out several time-consuming concepts only to discover the model runs worse than before. Each iteration takes most of a day to redesign, tear down, rebuild, and test. I'd say this version is about as good as the last video I posted. It's really tricky getting the legs to not interfere with each other as they flex from their own weight. I'm going to take a few weeks off and see if diffuse thinking offers any revelations. Abridged-Terrain Awkward-Transport

I'm still ironing out some issues with the mechanics, but thought I'd share this building technique using bars and round plates. It doesn't look as nice (or as screen-accurate) as the inverted tile pieces I had cladding the legs previously, but it's seriously tough. If you use this technique, get it right the first time because it's quite difficult to deconstruct!

Lots of progress over the weekend! I made some planned adjustments and encountered some happy accidents. I hope to have video up shortly. The timing has been corrected. The pronounced shuffle of the non-lifting legs has been tempered, and I have a building technique for the legs that is almost indestructible.

That limited ankle range can be beneficial. I found it critical to control that range of motion in my design. Too much ankle flex, and the model can end up on its bum.,

I like the action of that mechanism. Sort of a dual cam.