Warning : This is my first project here at instructables, so I'll apologize if there might be mistakes, typos or other faults. In the end this is a FREE, good for nothing, fun project that intoduces you to basic kinematics with stuff that can be found in any place where there is a shaving guy, some cd/rack with old CD:s and time to burn.
( If the above video doesn't show you can watch it at http://www.youtube.com/watch?v=jTUqKATp2eM )
Teachers! Did you use this instructable in your classroom?
Add a Teacher Note to share how you incorporated it into your lesson.
Step 1: Parts.
Parts and tool for this project:
What you need for this project if you would like to follow my lead is:
4 BIC razors (minimum)
A scavanged watch. Naturally you'll need some kind of body, and a blastic housing for a watch is the choise for this project.
A small saw. I actually used a lazer-cut bred-knife without problems.
Drills or a hot needle . All the joints are wire-connected which makes it essential with holes roughly the size of the wire. A hot needle (keep it over a flame) will do, but it's messy as the plastic evaporates with ridges and the needle easily gets stucked as it cools. Use a drill if you have one.
Metal wires. A myst for joints. You can actually use tooth-pics or similar as alternatives as long as there are no serious friction or too loose joints (this is the main job; finding that right looseness of joints and yet keep them sturdy). I also used brass-wire (quite flexible) for the connection of the arm-to-leg movement.
A good glue-gun. If you want all the parts to stick this is a must. Super-glue or similar will also do it, but plastic has a tendency to flex and crack the glue-points over time.
A CD, a big CD-case and a felt-pen hat or similar as an axle . The spider is attached to the central column of a CD-spindle (one of those where you have like 50 CD-R records from the store. Through the column I used a wooden flower-pin as an axle. The axle is then attached to the CD which is locked to wheels from a toy-car . The wheels are connected to a lever that you turn to move the whole thing. I also attached an axle under the cd which have two toy-wheels attached to secure the position of the CD-record.
I also used square pearl that I found in my daughers playpen which elimitaded the need for some drilling in the casing, but I don't think they are needed. Yet you'll need some kind of extension between the upper and lower case to created enough space for the mechanics.
Step 2: Basic Cutting.
If you only have four razors (I had a whole bag of them) you have to be very careful while cutting the joints! Those razors are made from a quite low-grade plastic and can crack if you have a blunt or highly ridged saw, or knife. Take your time and 'measure twice, cut once'.
The front and back legs were cut to fit over the bracelet-columns (those four black extensions in the picture) and then drilled. You should cut the BIC-handles similar to what is shown in the piture so that those legs are flexible in the right direction. This is a good excersize in creation of certain kind of DOS (Degrees Of Freedom) for your future advanced projects.
Step 3: Assembly.
This is the fun part if you did the previous step right and a hustle if you didn't. For looks I attached one of the bracelet-sleeves as a tail together with the hind legs (there is just a long wire through the whole thing). The movement of the legs is acheived with a single arm that rotates in the center of the housing. At this arm there are a very thin wire attached to each leg that follows the rotation of the arm. This is actually NOT the right way to do it if you would like a natural movement of the legs as they should move in opposite directions and therefor act with opposite-moving circles/cogwheels. But this is a very simple project in which I settled with a bsaic movement of four of the eight legs, so...
The brightly colored parts are square pearls that was glued to the housing. They were pre-drilled and a simple way to avoid drilling of the case itself. You actually need clearance enough for the arm that will pull the wires. I glued it all together as shown in the picture.
Step 4: The Mechanics.
Now to the fine-tuning. I created an axle from a small needle (very stiff metal) that I heated and inserted through a short piece of plastic pin. The pin was then drilled and glued to the long axle (a wooden flower-stick in this case). The lid shown in the previous picture are glued to the central column of the CD-box after it's been drilled through and the axle inserted into this.
The trick is to add the wires between the legs and attach them around the needle without creating neither to much traction or slack.
When you are able to turn the unit with axle, wires and legs without problems it's time to lower the axle through the central column. Find a good height for the placement of the CD and cut the axle at that height.
Step 5: Final Assembly.
You probably got a good overview in the drawing. I glued the hat of a permanent marker in the center of the CD, drilled a proper hole through it and attached the axle. Then I got another BBQ-stick on which I attached two wheels from a small toy-car. Those are needed as there are a lot of pressure and friction needed for the top-wheel that will turn the whole thing. The top-wheel with an axle from the same toy are then attached though a hole in the plastic casing of the CD-box (naturally you turn the casing upside down this time).
The plastic are not enough to keep the wheel-axle in the right position, so I drilled another BIC-razor that act both as a lid-lock and a support-column for the axle as seen in the picture. The trick is to attache the CD to the central axle and thread the toy-wheel though the hole of the casing and supporting razor while you're closing the whole thing. It feels similar to building a bottle-ship.
Finally, when you feel that the machinery turns without to much hustle, you can add a lever at the toy-car axle to your own liking. I used yet another BIC for this and plenty of glue-gun plastic. Then, when I was sure the configuration did what it should I sealed the razor which act as a support-column for the axle and another one on opposite side.
Well, as always there are a million different ways to create things like this from junk. I built this project as a way to show my kids some simple mechanics but also as an example of DIY-kinematics and a way to join the Instructables community. Thank you for reading this far, and good luck with your own projects!