Hello builders.
This is my first instructable, I am 12. Over spring break, I built a hydraulically powered arcade claw. This is my first attempt so I made some errors and mistakes. This project allows creativity and freedom for the builder. My directions are specific, but different designs can be used; a different number of joints can be used to fit a bigger or smaller box, etc. I highly recommend arcade claw #2 for its design and weight. Also, on arm #2, the pictures can get confusing because I used only 2 joints instead of the 3 joints that the instructions tell you to make.Before you start building, scroll through my pictures of different joints, arm, and claw designs.

Ps, Please vote for me in the robot challenge. Heres the link https://www.instructables.com/contest/robot2012/?show=ENTRIES

Warning: Some of the materials and tools are capable of hurting the operator, so please be careful. Any injuries resulting from this project cannot be blamed on me.

Step 1: Tools and Materials

Please note: Not all of the tools and materials listed are needed for this project. Something similar or different that works can be used with success.

Tools

*Band saw
*Table saw
*Side cutters
*Pliers
*Drill Press and bits
*Belt sander
*Sand paper
*Clamps
*Hot glue gun
*Hot Knife
*Box cutter

Materials

*About 50 popsicle (craft) sticks
*Wood skewers
*About 20 3/4'' by 3/4" wood cubes rounded on one side with a hole that fits the wooden skewers (about 3/16 drill bit) drilled through one side (see picture)
*A big box
*Only for claw #1. Three 2" diameter thin wood circles (I used these to reinforce the arm's hinges)
*Ten 10ml syringes
*Thick vinyl tubing that fits your syringe tightly
*Various wood scraps for a base and brace
*Hot glue
*Water
*Cable ties
*Duct tape
*Masking tape
*Spray paint and cardboard stencil for decoration
*Only for arm #1. I think this is called a flex fold 2 hinge but I know it is found at Tap Plastics. (I called it a flexible joint in the picture)

Step 2: The Arm

The first step is to build your jointed arm. Below are two possible ways to build your arm, I recommend claw #2's basic arm design because it is lighter, which will help the hydraulic system out. To check if a popsicle stick is strong, put it up to your ear and gently twist opposite ends of one in opposite directions. If you hear lots of crackling (little fibers breaking) this is not a strong popsicle stick; if you hear only a little crackling, it is probably a strong popsicle stick. If you're confused about one of the steps, look at the series of pictures below the text (not all steps are shown).

Claw #1
Arm building

1. Hot glue together 16 pairs of popsicle sticks.
2. Slowly drill a 3/16 hole through the middle of both ends of 6 of the 16 pairs
3. Glue together 4 pairs of popsicle stick pairs in a box shape so that you have 4 of these boxes of popsicle sticks (these will be the arm segments). Make sure that two of the popsicle pairs with holes drilled through them are in each box and that the holes are lined up. I recommend that you use some method of reinforcing these boxes by either bracing the inside of the prism/box with short cut-off pieces of popsicle stick or using small pieces of popsicle stick, placing them across every side of the prism.
4. Using a band saw, cut 3 half-inch pieces of the flexible joint (they should fit in the hole in your popsicle stick boxes).
5. Using a hot knife, cut off the top part of the flexible hinge's clip.
6. Glue the plastic joints into the inside of your popsicle stick prisms (two arm segments for each joint) so that the arm segments are all connected.

Claw #2
Arm Building
1. Using a cable tie, bind 10 popsicle sticks together and using a drill press, drill one hole on one side of the bundle really close to the edge. Make sure that the hole fits your wood skewer. Drill the holes slowly to prevent splitting. Clamps can be used to position a piece of wood to help with the drilling.
2. Using a pair of side cutters, cut the cable tie off of the popsicle sticks. This is where the steps start to get hard.
3. Stack 3 of the drilled popsicle sticks and push the middle on out past the other 2. Using another group of popsicle sticks lined up like this, line it up with the hole of either the 2 popsicle sticks or the one that is sticking out. Using the side cutters, cut off a piece of skewer that when placed through the hole in the lined up popsicle sticks will overhang just a little.
4. This is how one of the joints of your arm is going to look, make sure that there is a little gap between the two top popsicle sticks to reduce friction, this makes the arm move easily. Now, using hot glue, glue together the stacked popsicle sticks and once it has cooled, put the bit of skewer into the lined up holes, and hot glue the ends of the skewer to stop it from falling out. MAKE SURE THAT YOU DO NOT GLUE TOGETHER THE HINGES. CHECK TO MAKE SURE IT CAN PIVOT BEFORE THE GLUE COOLS COMPLETELY.
5. Create two more joints like the first one. When you are are done, you should have 3 hinges (places where the arm can move), and 4 segments.

Step 3: Building the Claw

Claw design For Claw #1 and #2

1. For the claw's fingers, break 4 popsicle sticks as close to the middle as you can (I recommend measuring) but leave a few fibers to allow it to bend slightly one way or another.
2. Using side cutters, cut 4 pieces of popsicle stick (about an inch) from a piece of scrap popsicle stick and straighten out the sides with the side cutters or even a belt sander to take away any curves.
3. Hot glue the broken popsicle sticks where they have splintered from the break to keep them from moving and to stop you from getting splinters (optional).
4. Hot glue the one-inch piece of popsicle stick to the inside of the broken popsicle stick and, before it cools, position the piece so that this section of the claw forms about a 90 degree angle.
5. Again, draw a line at the exact center of a popsicle stick and this time, use the side cutters to cut it in half. Before, in step1, I broke it with my hands to create a kind of temporary hinge to create the 90 degree angle of the claw so that I had 2 pieces to arrange instead of 3 (if I had cut it in half all the way through).
6. Finger hinges: I had scraps of cable ties lying around but you might want to sacrifice one to do this step. Using side cutters, cut 4 one inch pieces of a cable tie and using a generous amount of hot glue, glue one side (half) of the piece of cable tie on to one of the half popsicle sticks that you previously cut. Once the glue has cooled, glue the other half of the popsicle stick on to the other half of the cable tie (see pictures); repeat steps 3-6 3 more times. When the glue has fully cooled you should be able to bend the hinge toward the side with the glue.
7. Take about a 1" by 1.5" rectangular piece of duct tape off and wrap it around one end of the hinge you just made and then flatten it. Do this to both sides of all 4 hinges.
8. Glue one of the duct tape hinges to the top of the syringe body (not the plunger). Glue the other duct tape hinge on the same popsicle stick to the inside of the plunger. Repeat this for each popsicle hinge and make sure they are equally spaced along the plunger.
9. This step can get tricky, so you can use a dab of hot glue or some masking tape to position the claw. Using one of these positioning methods, attach one of your popsicle stick claws to the bottom part of the popsicle hinge so that it doesn't fall when turned upside down but can be moved slightly (repeat this with the other three).
10. BEFORE YOU GLUE, YOU WANT TO HAVE THE PLUNGER OF THE SYRINGE PUSHED DOWN ALL THE WAY SO THAT THE CLAW SHOULD BE CLOSED WHEN THE GLUE IS COOL. A GOOD WAY TO KEEP THE ANGLE CORRECT IS TO QUICKLY GLUE ALL OF THE CLAWS ON SO THAT YOU CAN POSITION THEM BEFORE THE GLUE COOLS. Using side cutters, cut 4 one-inch pieces of popsicle stick and glue each one against one of the popsicle stick fingers and hinge so that it supports and braces it (repeat this with the other three). Now, take off the tape (or leave the dab of glue) on the somewhat stationary hinge and permanently glue that end of the popsicle stick down to where it was before. When all of this dries, test the claw by moving the plunger up and down. This should open and close the claw.
11. Position the claw tips where you want them when the syringe plunger is all the way down. This is a tricky step because you have to do it one handed. Keep holding the tips in place with one hand and with the other, glue a scrap of cable tie onto each pair of the claw tips bases. (see picture).

Step 4: Syringe Positioning

This is not usually a hard step because there are many ways to position syringes. First, hot glue one drilled, rounded wooden cube onto the end of one of the syringes. For this step, you want to label one side of your arm front and one back (it doesn't matter which if your arm is symmetrical). You can also label your arms first, second, third, and fourth segment, starting from the back. The two syringe positioning instructions are basically identical but some extra steps need to be used on arcade claw #1.

Syringe positioning for arcade claw #1
1. The first syringe placed is the hardest one, it is the one that lifts the entire weight of the arm (which for arcade claw #1 was a problem because it was too heavy). Using duct tape, position the syringe on the first segment of your arm. The rounded cube on the plunger of the syringe should be resting on the second segment of the arm. Test its movement by pushing the plunger in and out--the arm should move up and down. Please note that not all the syringes may have to be pushed all the way out to get a full range of the arm up and down. Next, thread a cable tie through the drilled hole in the cube and through the hole in the popsicle prism in the segment of the arm that you are working on, and tighten it just enough so that it can slide along the arm a bit.
2. To attach the second syringe, hot glue 2 of the cubes to the second segment of the arm about an inch a part, and then hot glue a third cube to a place a bit more than a third of the way up the 3rd segment of the arm (should be closer to the 2 cubes you just placed than the other end). Now, duct tape another syringe with a cube on the end to the 2, inch apart cubes so that the end that squirts water is basically touching the syringe you placed earlier and that when the plunger is about halfway pushed out, the end should touch the cube you glued to the third segment. Now, using a cable tie, make a loop through the hole in the cube on the plunger and the cube on the third segment of the arm and tighten it securely.
3. Glue a popsicle stick on to the fourth segment of the arm so that it overhangs about 1/2 an inch. Next, rip off about an inch of duct tape and fold it in half sticky side in. Then, glue one side of the duct tape to a plunger of a syringe without a cube on it and then the other side of the duct tape to the overhanging side of the popsicle stick you just glued to the fourth segment of the arm. Next, straighten out the whole arm, put hot glue on the bottom of the syringe you were just working on, then set down the syringe on the arm. You might want to duct tape the syringe to the arm instead of glueing it so that you can reposition it if needed.
4. The easiest syringe to place is the one that has the claw on it. Position the syringe claw-down on your last segment and then wrap duct tape around it.
5. I happened to have wooden disks lying around which I used for this step, but you can drill these with a special drill bit or just use 2 squares for this step. Find or make 2 one-inch tall circles or squares (at most three inches across for diameter or width), and cut a 2 inch piece of dowel about 1/4 inch in diameter. If there isn't a hole through both of your circles or squares, drill a hole that fits the size of dowel you are using. Use wood glue to glue half of the piece of dowel you are using, and push it through the hole in one of the circles or squares you have. While waiting for the wood glue to dry, find a big box (I used a box 12'' tall, by 24" long, by 16" wide) and cut a piece of wood about 1'' thick, by about 3'' wide, by the width of your box. Lay the piece of wood across the width on end of the box and hot glue it there, this will hold the base that holds the arm up. Once the wood glue is dry enough to work with, hot glue the arm onto the square or circle with the dowel so that when you are done, the dowel points down, not towards the syringe. Now, hot glue the square or circle without the dowel glued in it to the very center of the plank you glued to the box and stick the dowel on the other circle or square in the hole you drilled in the one you just glued. Hot glue a cube to one side of the first segment of the arm, making sure that it is above the plank, not off the box. Stack several cubes on the plank that your arm is attached to and then place a syringe on top, making sure that the syringe is level with your arcade claws arm. Hot glue the cubes you stacked together and then hot glue a drilled, rounded cube onto your syringes plunger. Position the cubes with the syringe on top so that when the plunger of the syringe is all the way pushed out, the arm is all the way to one side of the box and when it is all the way pushed in (pretend that the arm is connected to the plunger) that the arm is all the way to the other side; this can take a little while so be patient. When the cubes and plunger are positioned, glue the stack of cubes to the plank, and then glue the syringe to the top of the cube stack. Finally, cable tie the cube on the plunger to the cube on the arm together.
Cut three 2'' diameter thin plywood circles (about a 1/4 inch thin), a hole. Carefully hot glue the circles alongside the hinge joints so that the arm does not twist when moving up and down. This makes it easier for the hydraulics to function, otherwise, your arm won't have as big of a range of movement.

Syringe positioning for claw #2

1. This syringe lifts whole arm. Using duct tape, position the syringe on the first segment of the arm with the rounded cube resting on the second segment of the arm. Test its movement by pushing the plunger in and out; the arm should move up and down. Please note that not all the syringes may have to be pushed all the way out to get a full range of the arm up and down. Next, thread a cable tie through the drilled hole in the cube and over the segment of the arm that you are working on, and tighten it just enough so that it can slide along the arm a bit.
2. Glue a popsicle stick on to the third segment of the arm so that it overhangs about 1/2 an inch. Next, rip off about an inch of duct tape and fold it in half, sticky side in. Then, glue one side of the duct tape to a plunger of a syringe without a cube on it and then the other side of the duct tape to the overhanging side of the popsicle stick you just glued to the fourth segment of the arm. Next, straighten out the whole arm, put hot glue on the bottom of the syringe you were just working on, then set down the syringe on the arm. You might want to duct-tape the syringe to the arm instead of glueing it so that you can reposition it if needed.
3. Flip a syringe so that the end that squirts faces the front of the arm and place it like you did the first one, only flipped.
4. This is the easiest syringe to place, its the one that has the claw on it. Position the syringe claw down on your last segment and then wrap duct tape around it.
5. I happened to have wood circles lying around which I used for this step, but you can drill these with a special drill bit or just use 2 squares for this step. Find or make 2 one inch tall circles or squares (at most three inches across for diameter or width), and cut a 2 inch piece of dowel about 1/4 inch in diameter. If there isn't a hole through both of your circles or squares, drill a hole that fits the size of dowel you are using. Use wood glue to glue half of the piece of dowel you are using, and push it through the hole in one of the circles or squares you have. While waiting for the wood glue to dry, find a big box (I used a box 12'' tall, by 24" long, by 16" wide) and cut a piece of wood about 1'' thick, by about 3'' wide, by the width of your box. Lay the piece of wood across the width on end of the box and hot glue it there, this will hold the base that holds the arm. Once the wood glue is dry enough to work with, hot glue the arm onto the square or circle with the dowel so that when you are done, the dowel points down, not towards the syringe. Now, hot glue the square or circle without the dowel glued in it to the very center of the plank you glued to the box and stick the dowel on the other circle or square in the hole you drilled in the one you just glued. Hot glue a cube to one side of the first segment of the arm, make sure it is above the plank, not off the box. Stack several cubes on the plank that your arm is attached to and then place a syringe on top, make sure that the syringe is level with your arcade claws arm. Hot glue the cubes you stacked together and then hot glue a drilled, rounded cube onto your syringes plunger. Position the cubes with the syringe on top so that when the plunger of the syringe is all the way pushed out, the arm is all the way to one side of the box and when it is all the way pushed in (pretend that the arm is connected to the plunger) that the arm is all the way to the other side; this can take a little while so be patient. When the cubes and plunger are positioned, Glue the stack of cubes to the plank, and then glue the syringe to the top of the cube stack. Finally, cable tie the cube on the plunger to the cube on the arm together.

Step 5: Hydraulics

The hydraulics concept is simple but cool. When you push down a controlling syringe, the syringes that you just so carefully placed move out, and vice-versa. With this concept, you can move the arm up, down, and side-to-side.

Hydraulics

1. Push the syringes on the arm all the way down or as far as they can go without being forced.
2. A bigger (35ml) syringe will be helpful to use to fill, and get air out of, the vinyl tubing. Fill a medium sized bowl with water.
3. Cut the vinyl tubing into pieces a bit more than 2 feet (I had 30" for each piece).
4. Screw a piece of vinyl tubing all the way into the big syringe, submerge the end of the tubing in water and pull out the plunger of the syringe.
5. Submerge the end of a 10 ml syringe (not connected to vinyl) and pull out the plunger until the syringe is full.
6. Attach the syringe to the other side of the vinyl tubing on the big syringe.
7. Take off the big syringe and attach the open end of the vinyl tubing to any syringe on the arm that is pushed all the way down.
8. Repeat this until every syringe on the arm is attached.

The next few steps will tell you how to make a clamp to hold your syringes in place while you use them

Control Board

1. Cut a piece of wood 3'' (width), by about 1'' (height), by about 10'' (length). Use a drill gauge to test the bit needed to drill a hole that matches the diameter of the 10 ml syringes and lay the piece of wood you just cut down flat and drill 5 equally spaced holes.
2. Find a screw that when lined up with the wood on edge will go through a bit past half of the width, then use the drill gauge again to find what drill bit to use to drill a hole the size of the screw you are going to use. Drill 4 holes with the size of drill bit you just measured, one hole in-between 2 of the syringe size holes.
3.Using a table saw, cut the piece of wood in half length wise so that you have 2 pieces of wood 10'', by 1.5'', by 1'', and they should have half circles along one side.
4. Line the syringes up along a half of the wood in the half circles and then place the other half of the wood on top and, using a screw driver, screw the screws into the screw sized holes enough so that when you move the plungers and down, the syringe bodies don't move. DON'T TIGHTEN THE SCREWS TOO MUCH OR YOU COULD BREAK THE SYRINGES AND YOU WILL HAVE TO DO THE HYDRAULICS ALL OVER AGAIN.

Step 6: Prize Drop System

This step is pretty easy, but you want to get it right the first time.

The Prize Drop System

1. Mess around with your finished arcade claw and find a spot that is easy to reach (not too close or too far away). I recommend a spot in the middle, and to the left or the right.
2. Cut about a 5" by 5" hole there with a box cutter (I used a 4" by 7" box to fit my claw).
3. Hot-glue a 4"-high cardboard wall around the square hole to stop the prizes from falling in without the claws help.
4. Glue a 4''-tall tin can to each corner of your box as legs.
5. Just to make the instructions less complicated, I will call the side of the cut out square hole not touching the side of the box (see the picture) V.I.P side because it is special and key to steps 5 and 6. Cut a cardboard chute with a width the same as the V.I.P side, and a length of about 10''. The length needs to hang out from under the box with about 3'' extra.
6. Hot glue one of the shorter sides of the chute (the width) to the V.I.P side and test the chute with a medium-sized toy. If the toy gets stuck, bend the chute down to give it room to slide out.

I hope you have fun with your finished arcade claw, (go for the big prize).

-TheBuildingGuy