Ever since I decided to do a giant monster costume, I knew that proportionally I would need to extend my hands. I also knew it would be way cooler if those hands moved. This instructable is the result of that thinking.
I did research on line as I didn't want to completely reinvent the wheel and found that there are many different tutorials and varieties online. The one that inspired my project the most was found here (Mechanical Hand) on instructables.
I have made some modifications (which proved to make it a more challenging project) that gave it more of a wooden puppet look to it. I am quite pleased with the result.
Here is the link to the final costume: 7' Monster Costume
Step 1: Materials
I tried to make this project with as much simplicity as possible, using things I had around my house already. Some of the Hardware I had to buy.
2x4 (I cut this into 1.5x1.5 for the fingers. Then the length of each segment was cut from this.) (Also used for the arm.)
2x6 (This was for the palm)
Eye Hooks (stainless steel ones worked way better than the zinc ones) x60
Wall hanging wire (about 10 ft.)
4" finish nails x16
Elastic cord (about 12 ft.)
1" Key Ring x6
Needle Nose Pliers
Step 2: Cut Wood
I wanted these hands to be large and 3 fingered. I drew out a basic design and figured out the lengths for each segment of finger. I had to factor in an extra 1/2" for each segment due to the joint system I had set up. With that in mind, these are the measurements for each segment;
Fingers: Bottom - 5" (x4) Middle - 4" (x4) Top - 2.5" (x4)
Thumb: Bottom - 4.5" (x2) Middle - 3.5 (x2)
Having cut my 2x4 into 1.5x1.5 size, I was then able to cut those portions out. Next comes cutting the slots for the joints. We rigged up the table saw with a .5" cut to run through the center of the wood as shown. This was cut 3/4" in. This is the female end. Each piece would need a male and a female end, so only one side was cut. (we had some variations in this process.
Then, with the drill press, use a 1" drill bit to make the male end. This should be drilled down .5" on both sides leaving a .5" round disc in the middle. Then, with the band saw, shape a rounded end on each side of the segment (except the top one).
Once the full finger is pieced together, they will need to be shaped further. On the band saw, cut the shape of the finger. This will allow the to swivel more and provide a more natural shape for each finger.
Step 3: Pin Fingers Together
Fit the pieces together and then drill guide holes for the finish nail. Make sure to then redrill the center piece with a thicker drill bit than the finish nail as it will need to spin smoothly on this. Once the pieces are fitted and drilled, then carefully hammer the finish nail through, connecting the segments. There will be extra nail sticking through. With the grinder, cut off the nail fairly close to the wood. I then hammered that end flat (giving the nail two heads).
Step 4: Cut Tracks for Springs and Wires
Once the fingers are all together and shaped, the will still need trenches on each side for the wires and bands to sit down in. This is a rather simple process, but needs to be done carefully.
Set the table saw blade to the right height. Mine was only about 1/4" deep, just enough for the eye hooks to sit down in. Set the guard so it runs down the middle of the finger. Then just cut your trench on each side.
Step 5: Eye Hooks in Tracks
The eye hooks are really what allows the manipulation of the finger. On the back of the finger, the hold the bands in place for the fingers to snap back erect. On the inside of the finger, it holds the wire which, when pulled, curls the finger.
On the backs, a hook is placed on either side of the joint. On the inside, a hook is placed toward the top of each segment. This creates maximum leverage.
Step 6: Add Arm Attachment
In order to have the hand be attached to my arm and be able to manipulate the fingers I needed to have an arm extension. For this, I cut the palm to lock with a 2x4. the were then glued together using a good wood glue on every surface and then clamped together until dry. Screws can be added for additional support.
Make sure the length of the 2x4 is long enough from elbow to ends of fingers while still allowing space for your hand to be hidden from view of the mechanical hand.
Step 7: Cut Tracks for Palm and Wrist
In order for the pull wires to not stick out and to run where I wanted them, I cut tracks into the palm. I used the dremmel tool for this. I had them run from the finger down to the wrist where my hand would be to manipulate the wires. Hooks will need to be placed in these track through the palm to guide the wires down to the wrist and arm.
Step 8: Carve/Shaping Fingers
This is where artistry meets functionality. I wanted the fingers to look more natural while also providing maximum mobility. I used my dremmel tool for this. This took the fingers from looking really blocky to be more like actual fingers. This took quite a bit of time.
Step 9: Pin Fingers Into Palm
I don't have any pictures of this, but it is a precocious step. The challenge here is getting the right angle of the pin, and not being able to use the drill press. I had to draw onto the palm a line of angle as well as point of entry. It is also a challenge as the nail wont come out the other side. Pinning the fingers in also has to be done in the right order. Do the thumb last, otherwise, you won't ever get the index finger in.
If the angle of the nail is off, it will mess up the pivoting of the finger. Be very careful with drilling the guide holes and with nailing in the nail. Take your time and do it right. Make sure you have the right finger in the right slot. Once that nail start to go in, it isn't coming back out. This is a permanent process.
Once the pins are in, there will most likely need to be some adjustments made. I really panicked when the fingers wouldn't move well and kept getting stuck. Fortunately, with some careful observations and carvings, I was able to fix all the problems.
Step 10: Wire and Bungee and Gloves
Now with everything put together, the mechanics are ready to be put in. I started with the wires. I ran the wire through the eye hooks and then tied it to the top hook. The bottom of the wire is tied to the key ring. The measurement of this needs to be right for where the hand is to get the right amount of finger curl with your own finger.
On the back side, I basically did the same with the elastic cord. However, I also ran a second cord up to the second to top hook to improve the strength of the snap back. Make sure the elastic is tight, but not so tight the finger wont curl.
I then screwed the glove into place. I used 5 screws and washers to prevent the glove from easily washing off. This also is what helps the whole apparatus to be connected to your hand/arm, so secure is good. Then, because the screws digging into the back of my hand were uncomfortable, I hot glued some foam padding over the screws for comfort. This also gave the glove a tighter fit.
Step 11: Arm Straps
To have the mechanical hands be more secure to my arm, a belt was put in for around my forearm. I screwed this into the 2x4. I cut the belt so it would be able to tighten securely. Each half was measured to have the buckle in the middle, then screwed in.