Compact pushback spring missiles for AT-AT

[BrickBear]

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.  

Edited June 14, 2024 by BrickBear
Edit title

[Carsten Svendsen]

I don't know how the spring loaded missile launchers work, but the arm mechanism seems simple enough. Unless you want it to be motorized, then I don't know how you would fit anything in there.

You also didn't specify a scale for the head. It seems you are building the head with studs facing forwards. That could be quite a challenge.
If all you need is a little movement, and there's no space for springs or rubber bands, I suggest using the very nature of the plastic pieces as a spring. 

See my battery drill from 2 minutes in, I used a long axle as a spring for the lever button. It works amazingly.

 

[Stereo]

Maybe you can approach it the other way around?  Build a mechanism that only fires the missiles, and use their natural recoil to overcome a centering spring (which could just be the 1x2 rubber piece on an axle in the linkage that lets them pivot, though maybe there's something with more damping on the 'return to center').

Edited June 15, 2024 by Stereo

[BrickBear]

On 6/14/2024 at 7:09 PM, Carsten Svendsen said:

I don't know how the spring loaded missile launchers work, but the arm mechanism seems simple enough. Unless you want it to be motorized, then I don't know how you would fit anything in there.

You also didn't specify a scale for the head. It seems you are building the head with studs facing forwards. That could be quite a challenge.
If all you need is a little movement, and there's no space for springs or rubber bands, I suggest using the very nature of the plastic pieces as a spring. 

See my battery drill from 2 minutes in, I used a long axle as a spring for the lever button. It works amazingly.

 

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). 

 

On 6/15/2024 at 5:19 AM, Stereo said:

Maybe you can approach it the other way around?  Build a mechanism that only fires the missiles, and use their natural recoil to overcome a centering spring (which could just be the 1x2 rubber piece on an axle in the linkage that lets them pivot, though maybe there's something with more damping on the 'return to center').

Like build the head around the mechanism? That’s a possibility, it would certainly provide a more secure connection. 

[Carsten Svendsen]

5 hours ago, BrickBear said:

  On 6/15/2024 at 6:19 AM, Stereo said: Maybe you can approach it the other way around?  Build a mechanism that only fires the missiles, and use their natural recoil to overcome a centering spring (which could just be the 1x2 rubber piece on an axle in the linkage that lets them pivot, though maybe there's something with more damping on the 'return to center').

Like build the head around the mechanism? That’s a possibility, it would certainly provide a more secure connection. 

I agree with this, it seems like the better idea. Iterate the mechanism a couple of times and then see if you can scale it down with smaller parts. The rubber part is also way better than flexing the axles themselves.

[BrickBear]

On 6/18/2024 at 7:08 PM, Carsten Svendsen said:

I agree with this, it seems like the better idea. Iterate the mechanism a couple of times and then see if you can scale it down with smaller parts. The rubber part is also way better than flexing the axles themselves.

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)

Edited July 6, 2024 by BrickBear

[Carsten Svendsen]

39 minutes ago, BrickBear said:

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. 
(tried to include video but  can’t get it to work)

Very nice, it does like compact, but I'm not entirely sure how it works, probably because I don't know how the spring missile block works in the first place. A video would be nice.
Usually, just upload to youtube or something and post the direct link here. Eurobricks will auto-embed the video

[BrickBear]

35 minutes ago, Carsten Svendsen said:

Very nice, it does like compact, but I'm not entirely sure how it works, probably because I don't know how the spring missile block works in the first place. A video would be nice.
Usually, just upload to youtube or something and post the direct link here. Eurobricks will auto-embed the video

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.