BrickBear

So i’m using the 75054 AT-AT set. But i’m making adjustments to make it more accurate (more cockpit space for example). The goal is once i’ve finished the mechanism to isolate all the pieces that come with 75054 and then only use those for the body (i’ve made a more accurate version before just from said pieces). All the while making sure weight distribution is good

Akk I’ve just noticed, the weight at the front is a bit much for the position of the springs, gonna need to adjust that.

Ok I had to rework the gears of the legs, unfortunately the difference between the 20 tooth bevel gear and the 28 tooth bevel gear caused the legs to bend too far causing strain on the mechanism and knee stopper, so I changed it to 40 tooth straight gear and the 8 tooth straight gear but that was too little bend. I’ve now landed on 36 tooth and 12 tooth combination which is perfect and I sorted the balancing issue with the use of the head movement where it moves to the side of the body that does not have its leg lifted, this adds more weight to the limbs touching the ground.

All four legs added, Struggling a little with its balance despite it having three feet on ground

Update time, ordered some new bevel gears from bricklink. The good thing about these ones is they have three connecting points within them much like the old spur gears. This means I can connect it directly to the legs and simplify the bending mechanism greatly. The one downside is due to its size the gear has to be attached half a beam away, this allows the liftarm connected to the orange cam to not bump into it. However the connection remains strong which is great and the leg bends well.

Much better, as you can see the leg rotates on the centre beam and the mechanism for pushing and pulling the leg is placed inside, this has allowed me to bring the legs together, which i assume will make it more stable as the centre of gravity from a raised foot is closer to the other feet than it was before. The last remaining problem is stopping the knee from bending when the leg is pushed backwards and it succumbs to the weight of the walker, I plan to introduce a stopper at the top of the leg to prevent this from happening so that when the leg faces back, the beams that go up and down parallel to each other to cause the bending can only be straight. Incidentally I believe this new system where the leg is connected both inside and out will reduce wobble because it initially had a terrible lean towards whichever leg was lifted up. This has sacrificed my ability to hide stuff on the rear of the leg but for the most part it is possible to cover all this up.

Okay, that was not the final iteration, I discovered a mistake in the placement of the leg on the ankle, the leg is three beams wide and the connection should have been in the centre, however I hadn’t done that so when it came to testing all four legs, there was a point where a leg would be too long. Likewise I have to work on balancing it so it can be stable on just three legs.

Thanks! 10 years of working on walking mechanisms have led to this moment. Hoping that it’ll work!

Thanks! Hopefully it’ll work!

I think this is the final leg iteration, it bends adequately, the “hip” raises up and down completely and the connections are fairly strong, the final bonus features are that I managed to slim the leg down by a whole technic bar so now each leg will be the same thickness as the original 75054 Lego AT-AT, the dish at the top rotates and the grey bricks with technic holes move up down like in the actual actuators in the AT-AT walker. When the other three legs are attached it will be the day walking tests commence, hopefully due to the hard suspension used on the hips all four legs will be able to support the weight of a battery box and motor. I should be able to implement mild steering too and with plenty of space for mini figs owing to the compact gearing.

Latest update, made the knee bending mechanism better, this is not the latest image but essentially what i’m trying to achieve. My current setup has the white quarter circle liftarm replaced with a 2x1 cylinder attached to one of the beams which either gets pressed down or lifted up by a stopper, however this while working is unsatisfactory as its not as strong a connection. The problem with the white liftarm was that the rotation movement was ever so slightly too far for the leg to go down properly, so the quest continues…

Thanks! I’m going to release instructions when I’m done. I just have to figure out the best software to do that as I’ll need to compress the springs in the mechanism to show things accurately. It’s genuinely exciting to see it come to fruition and to hear positive feedback too!

I have got it to work and it has a kind of nice mechanical movement to it, I just need to refine the leg bending mechanism as you can see a simple yet fairly strong structure has been added to the top of the previously posted ankle mechanism, this joins one point of the leg with another and has a mechanism for forward and backward movement, as the ankle lifts up the leg bends due to the fact that one connection point is raised higher than the other and as it returns down it unbends (I do need to tweak things to male the leg bending a bit bendier), then it slides back, the solution turned out to be surprisingly simple and lightweight in the end however will need refinement to make it more compact and for the sliding part to be made more secure. Here is a gif as well:

Ankle Movement Mechanism, springs push beam down, cams push up, compact, simple, includes rotating middle to allow for gentle steering. Beige bevel gear on the right lower part of the mechanism is just me figuring out how to make legs move and not a required part of up down mechanism.

Kinda like this?