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 where things might go wrong and can adjust for them yourself if needed. It is a cool mechanism and fun to build.
Step 1: Materials & Costs
- 2 Pins / needles / tiny nails
- Rubber band
- Balsa wood (any modelling wood will do)
- X-acto blade
- super-glue (I used JET modeling glue)
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 bands and 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 and other steps.
Step 2: Assembly (case, Paddles, and Blade)
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 may need 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 of the 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 feel this 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 I have 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 add material.
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 have to 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.
Step 3: Assembly (shifter and Sliders)
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, cut out 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 that hold 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 down the 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.
Step 4: Assembly (wheel)
Step 5: Completed
Here 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. The reason 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 of the 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 needs tweeking 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!
UPDATE: The CAD files can be found here. Note that they have yet to be fixed and are exactly the same as those shown in this ible.