BrickBear

I have succeeded in reducing the balancing issues by simply placing a 2x1 plate with rail underneath the innermost toe of each leg, this offsets the legs lean somewhat but it’s still precarious. Of course this means that the feet aren’t completely flat on the ground, it’s a cheap and easy fix, might have to place rubber pieces in the feet too as they tend to slip on smooth ground. I’ve also been working on the neck bending so it bends in two places, this is nearly finished and has significantly increased the rigidity of the head and assists with the balance. All that remains is to install the motors and place on the bodywork then hopefully it will work. The springs appear to be able to support the weight, let’s hope they can support some more.

I’ll order one (or a few) and see, if it turns out not to work I may just consider it an acceptable “loss” for the project. After all it still stands up and likely walks (once motors are in place) it just leans.

Ok so having worked on it some more I am being defeated by balance. Naturally it’s a little wobbly and when a leg lifts up it has a tendency to lean towards that direction. I’ve attempted to counteract that by experimenting with the head placement and so far landed on this angle as the way to support a lifted front leg. I was hoping to add a head movement mechanism which alternates the way the head is facing to shift the weight when one side has a leg lifted, unfortunately this angle is not ideal nor realistic. Note this problem is only a problem with either one of the front legs raised. A less extreme angle is enough for the back legs. the head The feet position.

From what I understand the 1x4 spring missile blocks are essentially just a spring held in the middle of a block, when you insert one of the long translucent projectiles they push against the spring and the little stopper built in to the projectile holds the spring in tension past a certain point, when you push down on the projectiles “tail” the stopper is moved downward away from whatever it is caught on and the spring expands again to shoot the projectile out. The mechanism i’ve made slides along three axles, one red at the bottom and two cream at the top, when i pull on a 4x2 technic L beam which is connected to the two cream axles, the mechanism is pulled backwards and the projectile is pushed into these https://brickset.com/parts/4630114/cross-block-form-2x2x2, specifically the slopes part which causes them to press down and shoot out. An elastic band pulls the mechanism back into place afterwards ready for reload.

I did it! It took a few days but it is compact and works well while also being nice and secure. The first iteration worked similarly but this version I moved a few things around to make room for the three minifigs I wanted to have inside the cockpit. Loaded: Pulled: (tried to include video but can’t get it to work)

Apologies for the late reply That’s something I hadn’t considered, I could have a play with that concept, though I wonder as it would be on a smaller scale that the pieces would have less flexibility due to being secured closer at each end (if i’m thinking of an axle for example). Like build the head around the mechanism? That’s a possibility, it would certainly provide a more secure connection.

I’m currently working on an AT-AT project using technic for a movie accurate walking mechanism and I also want to incorporate a somewhat movie accurate missile launcher. In the movie when an AT-AT fires it’s “chin weapons” the cannons recoil backwards (you can see this here): https://m.youtube.com/watch?v=wfuRpZAcTJk I’d like to see if I could implement that motion to trigger the smaller 4x1 brick spring loaded missile launchers which came in 75054 AT-AT (the set i’m working with). However as you can see the space below the head in this model (a recreation in bricklink studio by someone else) is fairly small: https://file.bricklink.info/19/797/797807.png I’ve been through a few iterations but nothing really any good and i’ve seen some wonders in compact mechanisms here so I thought i’d ask for some help.

I am nothing if not dedicated to my goal of destroying echo base.

Progress of today, finalised the connection of the gearbox, built the rear panelling around it for a more compact length, attached the legs and began adding the stoppers in a different position. Once I attach the head mechanism for balance, the xl motor and AAA battery box it should be ready for testing next weekend or possibly the one after that. Final stretch!

Thanks, I was motivated by the tedium of reconstruction :D I should add it has made the top of the structure a little wider but this is not a worry as it only 9 beams wide and does not affect leg movement or bodywork, in fact it actually provides more attachment points, hoping it makes things easier as a result

Okay so I added/am adding a feature that enhances the mechanism somewhat, this required removal of the legs but essentially makes calibration of the lego positions much easier: As i’m sure you’re all aware, working with worm gears requires keeping them strongly held within a tough frame, unfortunately however that means it’s a pain to adjust their position if you find something isn’t quite right. Now, with this small gearbox system allowing me to unite and separate the drive from one of the pairs of legs, I can freely rotate one pair to adjust their positions slightly and perfect the movement of the legs relative to each other without taking things apart to adjust things. Perfect. Secondly it has caused me to strengthen things even further and thirdly it does not take up much more vertical space. Win win.

It breaks up the monotony of redesigning the system each time I run into an obstacle. But also as the key problems have been fixed (the feet that are not raised being flush with each other on the floor, the strength of the springs to hold up the weight) it (the mechanism) is essentially finished, in the pic below you can see it was nearly there before I had to fix the aforementioned issues. I reckon i’ll get it walking next weekend. Balance ✅ Strength ✅ Bend ✅

It is great to finally be adding bodywork where the shape and design is somewhat a good compromise between accurate and possible (what with the gears and movement being quite limiting). Admittedly I did not work very much on it this weekend as I was working on another non lego project. So this much progress in such a short time is good.

Thanks, though i’m afraid from what I can tell the gait is the same as the other lego motorised AT-AT. But I have news. So I ran into a problem where the positions of the feet were not at an angle such that all feet that were supposed to be on the ground at a point in time were not flush. I have since changed that, the mechanism remains similar otherwise. I believe I am on the last stretch though to getting a moving machine. I intend to use the head turning left and right for balance too so that mechanism will have to be made. Progress though, is happening.

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…