http://www.instructables.com/id/DA-OTF-Hidden-Blade/

Food Living Outside Play Technology Workshop

DA OTF Hidden Bladeby LostRite on March 29, 2013

Table of Contents

DA OTF Hidden Blade . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

Intro: DA OTF Hidden Blade . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

Step 1: Materials & Costs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

Step 2: Assembly (case, paddles, and blade) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

Step 3: Assembly (shifter and sliders) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

Step 4: Assembly (wheel) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

Step 5: Completed . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

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http://www.instructables.com/id/DA-OTF-Hidden-Blade/

Intro: DA OTF Hidden BladeThis is the re-make of the hidden blase models from the Assassin's Creed video game. This version is a dual-action out-the-front model which means that it uses thesame finger motion to alternate between spring-launching and spring-retracting the blade. The majority of the pieces were 3D printed with the only exceptions beingthose I had to re-make due to my own failure to properly design the files on the first go. It was a good experience though as this is the first time I have used 3D printing. Ihave some experience with the software side, but I have never been able to afford the actual printing myself.

There are two videos included to help explain the mechanism. I would suggest building this out of balsa wood before 3D printing so that you better understand wherethings might go wrong and can adjust for them yourself if needed. It is a cool mechanism and fun to build.

Step 1: Materials & CostsThe materials used are minimal since most of this was 3D printed. However, some of the pieces are easier to use common items for. These are listed below:

2 Pins / needles / tiny nailsRubber bandBalsa wood (any modelling wood will do)X-acto bladesuper-glue (I used JET modeling glue)

Since the files that had printed were not 100% perfectly designed, I had to modify them a little bit with the balsa wood. This is what the extra modelling wood is for.

The total cost for the above-mentioned materials is fairly cheap if you have the blade already. It was about $4 for the glue, $2 for the wood, and I found the rubber bandsand pins sitting around my house.

The 3D printing was done through a friend of my family, so I cannot give an estimated cost using other vendors. Images of each of the CAD pieces is provided on this andother steps.

http://www.instructables.com/id/DA-OTF-Hidden-Blade/

http://www.instructables.com/id/DA-OTF-Hidden-Blade/

Step 2: Assembly (case, paddles, and blade)It is a lot easier to visualize the assembly with the pieces in front of you. They all fit together smoothly when done right. I have included a short video explanation of howthe mechanism works.

The first step to assembly is to pin in the paddles into the base case. The holes in the paddles is already printed into the piece. If they are too small for your pins, you mayneed to use a micro Dremel bit to bore them through. If you need to, it is easy to cut one out of the modeling wood. You will need to use 2 paddles; one for each end ofthe case.

Once the pins hold the paddles in place, slide the blade into the case as well. It should glide very smoothly (it should feel like it floats) through the track. If it doesn't feelthis smooth, use some very fine sandpaper to smooth it down.

Also, in case you are following my 3D printed parts, I must point out here that I printed the mirror image of the blade that I needed. To correct this, either mirror the blade Ihave shown or carve by hand the proper shape and build up and missing material by glueing an appropriately shaped piece of wood to the blade where you want to addmaterial.

Make sure the paddles fit snuggly against the blade with maybe 1-2 mm of open space between the paddle and the edges of the blade's butt. If they don't, you may haveto re-make the paddles. I give this advice in case you are making the mechanism by hand instead of using 3D printed parts.

I am going to break this step into multiple parts so the pictures appear more relevant.

Here is the video I mentioned above.

http://www.instructables.com/id/DA-OTF-Hidden-Blade/

Image Notes1. Ignore the rubber band here. It is best left out. (see later steps)2. Pin through paddle and case

Image Notes1. This piece is not attached to the paddle, it is glued to the case to prevent thepaddle from coming up ever. Not needed but helpful.

http://www.instructables.com/id/DA-OTF-Hidden-Blade/

Step 3: Assembly (shifter and sliders)This next step is the most important piece in the mechanism, it is what actuates the blade in and out.

Grab the two sliders (the pieces with what looks like shark-fins on it) and the shifter (that is what I am going to call the large piece in the pictures for this step). First off, cutout the little pieces that I have shown in the 3D printed model because they prevent us from inserting the sliders onto the track. We will have to re-glue the pieces thathold the sliders down later.

The two sliders fit in along the top of the shifter (along the track printed into the structure). See the second picture to see what this looks like. Finally, you must glue downthe wooden pieces seen in the second picture. These will keep the sliders in place as they are pulled back to launch the blade (to be explained in the video).

Place a rubber band between the shark fins on the sliders. This will tension them so that they can spring the blade into place when actuated.

Image Notes1. arrow points towards front of blade

Image Notes1. underside of shifter

http://www.instructables.com/id/DA-OTF-Hidden-Blade/

Image Notes1. slider

Step 4: Assembly (wheel)You should be able to slide the shifter forward and backwards along the tracks in the case at this point and tyhe blade should launch out and in smoothly. The finalmechanism now is to get the blade to actuate both in and out with the same movement. The natural action for this is to use a circle which rotates 180 degrees with eachpull of your finger. So each 180 degree rotation brings the shifter forwards and then the next actuation brings it backwards. In this piece of the mechanism, the circlepiece that I had printed has a knob on the bottom to shift the shifter with each 180 rotation. It is what converts the rotary motion into linear motion. On the top side of thewheel, there is an 's' shape (the two fins). As can be seen in the 2nd picture, the wheel has a layer cut out to allow the string to be pulled through the wheel to turn it. Thestring has a knot in it that catches with the teeth of the wheel. One end of the string is tied to a spring (could be replaced with a rubber band) and the spring is connectedto the case. The spring pulls the string back over the teeth of the wheel after each pull. The wheel acts as a ratchet. The other end of the string is then tied to the ring. Toaid in the ratchet ability, I modified it to include a tine (the longer stick) that gently brushes along the top of the wheel. The tine ratchets over 2 ramps spaced at 180degrees (see last few pictures). In this way, a rotation (looking down) clockwise is permitted, but counterclockwise rotation is stopped at the tine by the ramps.

http://www.instructables.com/id/DA-OTF-Hidden-Blade/

http://www.instructables.com/id/DA-OTF-Hidden-Blade/

http://www.instructables.com/id/DA-OTF-Hidden-Blade/

Step 5: CompletedHere is a video of the fully working mechanism. It could use a lot of beautification and could be improved with a re-work of the design files to make it longer overall. Thereason I kept it this length was so that it could fit on anyone's arm. Since the length of the blade is limited by the size of the casing, you can only make the extension ofthe blade so long without telescoping (which I am not using in this).

I aim to provide the printable CAD files or have them hosted online so that anyone can print a set, but as you may have noticed in this ible, there is much that needstweeking to make sure it all goes together right. So, to avoid having people print off incomplete files, I won't post the CAD files until I finish re-making them.

As always, post / comment with any questions you have or PM me!

http://www.instructables.com/id/DA-OTF-Hidden-Blade/

Image Notes1. just to give a size comparison

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