BrickBear

New version moving, lossy gif. No legs yet.

Ok so I’ve nearly finished modifying the frame. I’ve added the gearbox mechanism to adjust the front and back cams independently of each other, i’ve added an L-Motor and repositioned the grey technic frames one hole over as stated last time. one problem i’ve run into is the l motor isn’t really powerful enough with the resistance of the springs having increased. So i’m going to upgrade to the xl motor. Otherwise, the mechanism is now stronger and more polished than before and the positions of everything should be enough to support a battery box, steering motor and ir reciever as well as bodywork. That is very impressive. I’m guessing you’ll have to upgrade to a thicker gear if possible?

The real reason is much simpler, I have many black pins and fewer grey ones in my main technic boxes so I like to use them for things where it’s absolutely necessary for the frictionless stuff.

It’s not quite finished yet, I have to adjust some stuff for it to move but once done i’ll make a gif.

So this is what I worked on today: It’s essentially a redesign of my walker iteration’s chassis, reinforced and the suspension repositioned to take a heavier weight. The bend in the middle is also more stable than it was before. Few bits to finish adding and a tweak or two. But this should provide me with a better foundation going forward and has refreshed my mind on the project after being away from it. The previous one for comparison:

You’re doing gods work. Meanwhile i’ve finished my course and the house decorating is done so I should have a little time for development at the weekend. I’ll consider your discovery on the leg lifting situation when working on it.

Looks promising. Certainly try an xl motor. Do you think a medium + hard spring might be useful for push down? There’s also the question of linear actuators. They can do some interesting stuff: (note video not mine)

Sounds good 👍 As for the skateboard mechanism…well maybe something like this?

In a similar vein I was considering adding counterbalances that swing left and right. Basically you’d have the hips going up and down and then you’d have each hip attached to a see saw like mechanism and when one leg lifts up it would seesaw the weight away from it to the other leg. So left leg goes up, seesaw left side goes up, weight leans right. I also had another idea which was to make the legs move forward like a skateboard. Basically when the skateboard platform leans to the right, the front left part of the axle moves forward as if to steer to the right (but you could modify it so the leg stays straight) and as the body would be leaning right it would act as a counterbalance to the left leg moving forward.

@Nelson Unfortunately I don’t have a video of it yet due to balance. I could try powering it while holding it up just above a surface so that you can see it moving. Initially I did try to use cams keep the legs down, however it was before I had the linkage connection right so it seemed to not be stable enough and the timings made it not as smooth as I liked. However now I realise the linkage position had to be a certain way. if you can work out a way to do this successfully timed I’d be very interested as it may turn out to be more successful than initially thought.

Unfortunately haven’t got round to anything yet apart from some mental visualisation of necessary changes and bricklink scouring. We are having rooms painted this week so need to keep things tidy and stuff has to be moved about to accommodate. But I was looking at my model today and realised that while my front right leg is raised that the right back leg begins raising too at a certain point. So i’ve got a little configuration necessary to counteract that, speings I think in the leg where the feet connect, not enough to cancel out the feet being lifted clear off of the ground but enough to prevent unwated liftage.

This one would be pretty damn close if it weren’t for the awkward bar https://www.bricklink.com/v2/catalog/catalogitem.page?P=44810&name=Bionicle Matoran Torso, Gear 9 Tooth with 3 Axle Holes and 2 Pin Holes&category=[BIONICLE]#T=C edit: Now i look at it i’m not sure it’s a quarter?…

It might not have reached the state you wanted it to but it’s still very much alive and exciting to look at. Every attempt is also a page in our book of experiments.

I’ve seen a video where someone tried it with ev3 (or whatever the latest incarnation of mindstorms was) but I can’t find that video anymore and it walked in the same way as the official motorised AT-AT’s anyway. I think it could be done though. If you used smaller motors actually in the legs to bend them at the right timing which takes you to 4 connections (I think the limit is five or six per hub). Then you’d only need something to lift them up like a cam and move them forward and back like a piston which could probably be done with one motor. Maybe…I’m a powerfunctions guy myself and only ever made one walker with ev3

I remember mine was taking my technic arctic truck and making that walk with the mechanism from the official lego motorised AT-AT. It kinda worked but it wasn’t very attractive and I don’t think my m-motor was torquey enough to move it. Hopefully an xl will be enough for the current iteration.

Makes sense. Thankyou, very interesting. I’m very excited to get working on my version again eventually with all this inspiring talk. I probably need to order a few pieces first…

Mmm, I used a plate with rail to offset some of the lean. I’ve considered the inner rod as a point of support too, adjusting where the pins go too. If I may how exactly does yours work?

Mmm, I might redesign the main chassis. It’s beautifully compact but yes, it probably needs an adjustment to account for the weight.

Interestingly I learnt about tightrope walking through a novel which as part of the story explained how the physics of it works. Basically you can stay relatively stable if you place the weight further down which makes sense as a low centre of gravity is also what keeps double decker buses stable but it’s fascinating that it helps even on a thin wire. I figure if I experiment with boat weights towards the middle and slightly below the hips then it might help maintain the balance, it should provide a big help to the spindly legs.

I’m still here, life and educational has temporarily got in the way. I should be able to get back to it in a few weeks, in the meantime i’ve been having ideas. Believe me, I won’t stop working on this. As it stands right now my main concern is actually fragility, the 5L half beams that connect the legs to the cams are too fragile so i’m going to have to replace them with an alternative. Please also feel free to use this topic to discuss your own project and what got in the way and such. There may be designs that can come from the discussion.

This is exactly the video I’ve been referencing for the entire project it’s been a massive help.

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.