Iron Man Mk6 (or Mk4) forearm help - How do you do the mini rockets?

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DrCyanide

Active Member
Hello everyone! First post here, so sorry if I've missed some super obvious way to find what I'm looking for.

I'm taking my first steps at making an Iron Man cosplay, and I'm wanting to have as many moving parts as possible. I'm particularly enamored with the Mk 6's arm design, and would like to be able to re-create this scene from the first Avengers movie:

8252169213_4fa339546f_b.jpg

The rockets show up in Iron Man 2 as well:

IronManMiniWristRockets-IM2.png

I know that this can be done, thanks to some videos on YouTube uploaded here: https://www.youtube.com/user/pauloregini/videos
Specifically these demos:

What I like about his design is that it's very fluid (the door and the missiles move together) and that the missiles extend over the edge that the door was covering. Obviously I'd prefer to be able to trigger the extension and retraction electronically, but at this point I'm having a hard time piecing together how he got them to even fit inside that small of a space! It doesn't help that the fully assembled videos don't have the best lighting.

I doubt I'm the only one here who's been interested in this, I just can't seem to find any documentation from anyone else making it before. I'm hoping someone with more experience knows somewhere I can look.
 
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propmaster2000

Sr Member
I guess before anyone can really give you any advice, what skill set's do you have and what
materials are you comfortable working with?

The video below shows a bit more as to how the "outer door shell" works.
It appears to hold the door mechanisms and the inner shell holds the mini rockets.


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DrCyanide

Active Member
I guess before anyone can really give you any advice, what skill set's do you have and what
materials are you comfortable working with?

The video below shows a bit more as to how the "outer door shell" works.
It appears to hold the door mechanisms and the inner shell holds the mini rockets.

https://www.youtube.com/watch?v=NNqoMriAWnE

.

I'm a jack of all trades. A programmer by profession (planning on using a Raspberry Pi to control a lot of the suit), but I've got moderate electronics experience. My dad's a mechanical engineer, and I've learned a few things from him over the years. I consider myself "average" at 3D modeling, and have a 3D printer which I'm planning on using to at least prototype most of the moving parts. (As a wise man once said, "when all you've got's a hammer, every problem looks like a nail. Still, a 3D printer is a pretty decent hammer to have.") Other than the 3D printer my toolbox is pretty bare bones (only power tool is a cordless drill), as I've been in an apartment for the last 6 years or so. I know someone with saws and what not that I could use, but they live 2 hours away, so I don't think I can rely on that for the prototyping phase.

I've looked at that video, and I can tell they've got something running around from the button to all the doors (rubber bands?), but the camera never gets a good enough look at the mechanism for me to make sense of what I'm seeing. Because of the speed at which the doors open I know he's got a spring loaded hinge, and that there's a latch mechanism that holds it down until the button is pressed (which is what the something pulls on), but I don't see how that eventually translates into the missiles popping out. The missiles must also be spring loaded, held down by the door, but I'm having trouble visualizing how they would sit underneath it and travel in the path the other videos show.

I'm open to other implementations besides the one shown here, it's just that his are the only video's I've come across for this.
 

propmaster2000

Sr Member
I think if you want both the open and close function you could use the "pulley and cable" action using either
a small DC gear driven motor (for both open and close) or a "spring and solenoid function".
The spring could hold the doors closed while the solenoid/cable pulls them open.
Instead of the doors opening separately allowing the rockets to lift out, maybe the control action could be
on the rocket mechanism and each one pushes their door open.

Mini Wrist Mount rocket Launcher 1
The red is the mini rockets and the blue is the platform.
The colored part is the Launcher in the down position (closed door)
and the gray is showing the Launcher platform raised and level (open door).
The green is 2" wide and 2.5" long.
The orange is the pivot block(to be mounted to the inside of the box).

mini rocket launcher 1.jpg

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DrCyanide

Active Member

I've seen that video before. While they've got a lot of good stuff, they use the more standard Mk 3 arm rocket, which can use a much larger space at the end of the elbow. The Mk 6 is far slimmer, and I need to fit 5 of these mini rockets around each arm. (I might fit a larger rocket on top of each arm as well, but this thread is specifically about the small ones).

This is a quick video showing the 3D printed parts from the model shown in my last post:

https://youtu.be/TN1zpwmSCP0

.

I understood what you were suggesting from the diagram, but it is cleaner to see as a physical print. I do like your rocket slots, since that gives some flexibility for changing out the rockets with different designs later.

What did you do for your hinges? Mine feel too flimsy.

Here's my bare-bones version of your design for testing the proof of concept:
https://www.thingiverse.com/thing:2995785

What works:
* Very compact vertically
* Can lift the lid in the same motion (I also like that the lid over extends just a hair and gets pulled back in by the linkage)
* Space for a missile design

What doesn't work (yet):
* Lid gets stuck occasionally
* Hinges prone to cracking (too small)
* Too much force required to lift/lower it (might be worse with the lid connection)

If anyone knows what the technical name for that link I ended up using to connect the lid to the platform that would probably go a long way in making it work right.

PS: I am American, I just always use metric for 3D Printing so I didn't bother converting it for the video. My design is about half an inch smaller front-to-back than your design, and I wasn't trying to fit the width on this one. If the doors don't look as impressive when fully out then I'll probably lengthen the design to be closer to your size.

EDIT: I think I've figured out how to keep the door from locking in place on the way up. If I replace the arm that connects the lid with the platform with a triangular arm it'll push up against the lid before it can get into the angle that would jam it.
 
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propmaster2000

Sr Member
DrCyanide,

From the video. it seems like you are getting a handle on your design.
Have you made any progress since you last posted?


propmaster2000

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DrCyanide

Active Member
DrCyanide,

From the video. it seems like you are getting a handle on your design.
Have you made any progress since you last posted?


propmaster2000

.

A little bit. I printed out the piece I mentioned in the edit, and that did indeed fix the lid issue. Playing around with the physical model I now know that I'm going to want to move the platform by applying force to the center of the platform (as oppose to moving just the front or back arm. Front and back center, not absolute center). I'm going to need a hole for linkage wire to reach there, and move it similarly to how RC Planes use their servos.

I've had to make my design a little taller, since the servo arm was going to poke out over the top otherwise. The new design has a space to hold the servo built in, but I need to split that part of the model up into more parts so that it can be printed without tons of support. Lots of support on a print this small would just be asking for trouble. I'm also going to redesign how the lid connects so that it won't have as big of a seam at the back. That new lid hinge will be based on a video I saw from of some R2D2 makers, who were adding moving panels on R2's head. The combination of the servo and the hinge changes is going to make this a lot longer than the previous print, but for this prototype stage I think that's OK.

I'm going to be busy for the next few days, but I'll see if I can get some time to finish the modifications and post an update.
 
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DrCyanide

Active Member
propmaster2000

A WIP shot of the design changes so far.
opnK71n.png

What needs to be done before I can print it:

  • Need to split up the servo cover/connector (right now it's connected to the base plate, and that shape just won't do for printing)
  • Add the joint at the back for the lid hinge to connect to
  • Make a connection for the hinges to join to the lid (so I can print the hinges flat)
  • Add a new connection between the lid and the platform (the old one wouldn't work with the new motion)

It'll take a little while to work through all that, but at least you can see the idea. That last point will take a bit longer to work out, since I've got to find a new place that I can "anchor" my linkage arm to that won't get closer to the platform or further away.
 
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DrCyanide

Active Member
IMG_20180718_233424.jpg IMG_20180718_233402.jpg

Printed the updated prototype. It's too unstable to actually use the servo (too many parts broke and are replaced with hot glue right now), but it does show the general motion and gives me some clue how I'll need to modify the parts.

What works:
  • Servo mount holes are perfect. Able to hold the servo in place with some filament.
  • Modified hinge lifts up nicely, clearing the back

Changes to make:

  • My tolerances are a little tight on the servo mount, which caused it to snap while sliding the servo in place. Easy enough fix.
  • Long connectors look like a bad idea. They're harder to fit the filament rods through because variations in the print can render them nearly impossible to clean up.
  • The large, flat back panel on the base is also a bad idea. It snapped right at the base. I think the smaller pillars design lends more support to the overall structure.
  • I think I can try re-adding the platform-to-lid hinge design I had earlier. After playing around with the physical model i think it might work.
  • Tried to accommodate having the servo on either left side or right side, but since the servo only rotates 180 degrees and isn't semetric that's a waste of space. If someone ends up with a servo that rotates opposite of mine they can flip the part when they print it.

PS: sending this from my phone, I think my phone's auto correct is having issues with the text box. There may be some terrible typos.
 

propmaster2000

Sr Member
It seems like to make the mini rocket launcher fully automated (open and close) as well as be fairly compact will take a bit of design strategy.
It is a slow process of test and re-test to get a reliable set-up.

Since it will be used as a cosplay costume it doesn't have to be "movie CGI quality".
Looking forward to another update and possibly another "working mock-up" video.
 

DrCyanide

Active Member
IT'S ALIVE!!!


What works:
  • It opens and closes!
  • Servo moves without hitting it's arm on anything
  • The "Micro Pushrod" (RC Airplane part) fit the 3D Printed part decently well and was easy to bend into shape

Changes to make:
  • Prevent the pushrod from sliding out of the side
  • Change the 3D printed platform to prevent pushrod from rotating (currently managed with hot glue. (Might not be needed?)
  • Test different missile shapes/sizes (test version of that already on Thingiverse, I haven't had time to print and test it yet)

Seriously though, I thought I had just barely missed the mark. The first time I tried it I had the pushrod in the second hole from the top of the servo arm, because I thought that looked like it lined up better. Looks like it didn't have the leverage to do the job at that point. I'd actually recorded and uploaded my "it failed, time to try and make some tweaks" video before I tried the top hole and it worked!

Very happy with where this is going.

IMG_20180730_232738.jpg
 
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DrCyanide

Active Member
Thanks for the update video.
So far so good.

The Fun has only just Begun :)

.

I'm pretty pleased so far, but yeah, there's going to be a lot more work before this project is done. Still, it's at least at a "close enough" stage where I can see that this is going to work.

Once I get one mini launcher looking good I'll need to print out enough copies to go around a whole arm (while also leaving a slot for the main rocket - which I'll probably need to custom design to fit the same vertical space as these ones and to open the way I want). Then after I get a feel for how they'll work/fit on my arm I'll have to make a proper covering for them all, shaped to look like the armor.

The good news is that the forearms should have the most complicated mechanics, so I'll be a lot more confident in this working out when that's done. I want to try some different techniques with the helmet eyes (involving polarization), so that'll be another experimental phase, but a lot of the suit beyond that should be mostly shaping and painting foam.
 

DrCyanide

Active Member
Printing out some new parts right now. I also picked up a servo controller that will allow me to control all the servos I could possibly throw into this arm with very few wires from my Raspberry Pi. The trick is going to be where to place the servo controller, but I'll worry about that after I get the missile pod design down.
 

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