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So you wanna make Samus Aran's arm cannon eh? Answered

Alright so I've decided this year for Halloween I want to be glorious Samus in her original suit glory. I'm just in the planning and blue print phase now. The bulk of the costume is going to be Eva foam. A stationary arm canon is cool and all, but what if I could get it to open up on the ends when i push a button? How cool would that be?

I won't need a really beefy motor to move foam, and hopefully that motor wont require a huge power source, something that will fit inside the arm cannon somewhere.

I can't find any video of HOW exactly the arm cannon opens up and functions but from this picture it could either

A. opens up where the 4 outside plates separate from the main cannon to better reveal the pew pew part, this would require something to push out all four plates at the same time from the main cannon at a fixed distance. Not very much maybe half inch to an inch and be able to retract back flush against the cannon.

B. the four plates simply rotate on a fixed axis.

Ive crudely drawn what I would like the arm to do so you can see what I'm talking about.

I've never dealt with motors before but I've seen amazing cosplays that have moving parts so I know it's possible. I'm more than willing to learn I just need to be pointed in the right direction.

Any help with how to go about this would be greatly appreciated! :)

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Jack A Lopez

4 weeks ago

A design that might be easier occurred to me:

It has each section held on by two struts, and the struts are two sides of a parallelogram, that can swing the section away, and towards, the central axis of the cannon.

I have attached a crude drawing of this, as well as a drawing of my previous idea that had the cylinder sections riding on two cones, for to move the sections away, or towards, the central axis of the cannon.

Also attached my previous drawing, from yesterday, of a view looking down the central axis of the cannon, as the sections move apart.

parallelogram-lift--closed-and-open.pngcones-lift--closed-and-open.pngexpanding-cylinder--closed-and-open.png
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MeonahH

4 weeks ago

I get what your saying. I was wondering about that as well. Some way to trigger this thing using the arm thats present in the cannon anyway.
So probably some sort of loop i can pull with my finger to make this happen. I could probably use a shower curtain hoop or something a little smaller. I have a chain fashion belt i kept for the pieces thats full of smaller metal loops i could use to put my fingers in to pull this mechanism into action. I'll definitely have to do some research and try to work it out in cardboard, string, and hot glue. got plenty of that laying around. I
ll definately post it!

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Jack A Lopez

4 weeks ago

Have you ever seen a tailpipe expander?

https://duckduckgo.com/?q=tailpipe+expander&iax=im...

It is this sort of fist-sized mass of steel wedges, approximating a cylinder. The important part is, this approximate cylinder has an outer diameter that can change, be made bigger or smaller, just by turning a bolt in the center.

The way it works is, turning the central bolt, draws two cone shaped pieces together, and the outer wedges ride on top of the cone shaped pieces.

Anyway, I think if you can get your head around the tailpipe expander mechanism, you will see a way to a mechanism to make these plates, or cylinder sections, of your big gun, so they can expand and contract radially.

tailpipe-expander.jpg
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MeonahHJack A Lopez

Reply 4 weeks ago

Thanks for your reply, Jack!
So using a servo to turn it so the four plates push out equally would work? How heavy are these expanders? You said they are steel so I worry they might be too heavy.

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Jack A LopezMeonahH

Reply 4 weeks ago

The pictures of the tailpipe expander are intended merely as inspiration, as a sort of koan to get your mind thinking about the problem of:

How do I make a cylinder that expands radially? Or rather, how do I make a cylinder broken into symmetric sections, which expand apart, and which can also be drawn back together again?

You are correct in thinking an actual tailpipe expander is too heavy, and moves too slowly, for it to work well as part of an arm-sized prop, for a Halloween costume.

Regarding the question of actuating the prop, making the sections open and close... I think this can be done without a motor. I mean, since you have your arm inside this thing anyway, that there can be some way to just move its parts, using the motion from your hand, like pulling something, or twisting something.

I have drawn some crude, 2D, pictures, attached to this reply, of how I am imagining this mechanism might work.

I started by drawing a small pipe, inside of a big pipe, with both cut into 4 symmetrical sections, and with some struts connecting small pipe to big pipe, with one strut per section. This is the drawing on the left labeled, "closed."

Then I just pulled these 4 pieces apart, to make the drawing on the right labeled, "open."

The mysterious blue circle, in the center of each drawing represents the mechanism that is pushing the sections apart, or allowing them to come back together. Notice this circle is changing size somehow. In the drawing on the left, sections together, the blue circle is small. In the drawing on the right, the blue circle is larger, and it is "pushing" the quadrant sections apart.

I am guessing the mysterious mechanism in the center will be two cone-shaped pieces, with the narrow parts of the cones pointed at each other. Pushing the cones together, pushes the sections apart. Pulling the cones apart, allows the sections to come back together.

I admit, it is maybe a little tricky to visualize how it works in 3D, just from this 2D drawing, and hand waving explanation.

For that reason I, or you, should probably try building one out of cardboard, or paperboard, and glue and rubber bands and stuff. That is: materials cheap and easy to work with, and just barely sturdy enough for the mechanism to work.

Regarding this notion of pushing two cones together, I found this animated gif,

https://en.wikipedia.org/wiki/File:GearBoxRotRotVa...

as part of the Wikipedia article for "Continuously variable transmission".

Essentially this is another koan. Something to demonstrate that pushing two cones together (or pulling them apart) makes a cylindrical surface, with a radius that expands and contracts.

expanding-cylinder--closed-and-open.png