Giant King Kong Arm Puppet

A little while ago, an old friend of mine that occasionally directs plays at my hometown's community theater asked me if I could build him a puppet of a giant gorilla arm. I immediately said yes without asking questions or considering if I could.

He then filled me in on the "Why?"...he would be directing a production of Kong's Night Out by Jack Neary, and the show stopper for the play is King Kong's arm crashing into the set and terrorizing the actors onstage. Fast forward to about 3 months before opening night when I really started trying to figure out how to do this. I quickly found out that there was little evidence online of previous productions of this play, and among what I could find, there were no good examples of this stage effect. I've been trying to push myself to write Instructables after years of reading them, so I tried to document this project to have a resource for future productions of this show. I hope it might also be useful as a template for anything requiring a giant puppet arm appendage.

This Instructable will not be a clean path from well-planned blueprint to finished product that was exactly the plan from the get-go. I had things in mind at the start that absolutely did not work out, especially due to production timeline and limited time that I could access a woodshop to finish it up. Concessions were made, and I trusted that the magic of a stage would carry my shortcomings on this. I'll do my best to document what I planned vs what I had to scrap and how I recovered the design along the way. I'll also note things that I definitely would have done differently if I had the chance to do it again. Also, I did not do the costuming of the arm, so I have little detail on that part.

Before I get going, I want to credit this older Instructable. When I was first figuring out the hand, I was working from this design to get the basic mechanics.

There's quite a lot of hardware you'll see pictured that didn't make it into the final build. For sake of simplicity, I'll list what I ended up using in the final build and not worry about the pieces that ended up being taken out.

Lumber

1. 23/32" 2'x2' Plywood project panel (2x)
2. 8' 2x4 (7-8x)
3. Several bits of lumber from the scrap pile

Hardware

1. 12" diameter, 1000 lb-rated lazy Susan bracket
2. 8:1 lifting power, 2200 lb work load, 1/4" rope block and tackle pulley
3. ~ 6' 1.5" slotted steel angle, 14 gauge
4. 1/2", 12"-long carriage bolt w/ 2 nuts and 2 washers
5. 1/2", 8"-long carriage bolt w/ 1 nut and washer
6. 1/2", 8"-long carriage bolt w/ 2 nuts and 3 washers
7. Scrap 1/2" steel and plastic pipe
8. 4 shelving brackets (like these)
9. 1 1/2" rigid single pulley (like this)
10. 6x 2" fixed pulleys (like this)
11. 2x large eye bolts (at least 3/8", 5-7" long) with nuts
12. 2x 3/8", 8" lag screws
13. 5x 5/8"x6.5" extension springs
14. 10 small carabiners
15. A ~2" welded ring, 1/4" or thicker
16. 10 1.5" hinges for finger joints (try to buy stainless...brass will warp and bend with repeated use)
17. A rope cleat
18. Several 1/2" pipe straps
19. Good supply of screws, small screw eye hooks, hammered metal staples, and washers

Plastics

1. A small HDPE plastic block (maybe ~2"x4"x1.5" starting size)
2. ~ 10 ft 1/2" PEX pipe
3. Semi-slit pipe insulation

Miscellaneous

1. A good roll of black 550 paracord
2. Several light duty bungee cords, a cheap variety pack will do
3. Black electrical tape

The first image is just of initial sketches as I was coming up with ideas. The design as 4 main parts:

1. The platform, which is anchored to the floor in place and rotates on a large lazy Susan bracket
2. The mast, which sits centered on the platform and pulls together all of the controls for the puppeteer
3. The arm, a simple wooden frame with lighter-weight PEX around it to bulk it up
4. The hand, which can be clenched into a fist and released to an open hand

My first note on design choices I'd change: I wish I had made this mainly out of aluminum rather than wood. I was just working with what I knew, and I haven't done much work with aluminum framing. In hindsight, I could have made something significantly lighter and probably not spent much more on material if I'd gone with an aluminum frame.

To get overall dimensions (see image 2), I literally pulled up images of gorilla skeletons and used a seamstress tape against the screen to figure out relative dimensions of parts of a gorilla's forearm.

I started with the hand, as that's what I could manage to work on in my apartment floor. All of this was done with 2x4s. First cut the three segments of each digit. See picture 1.

1. Index/Pointer: 9.5", 7" & 4.5"
2. Middle: 10", 8" & 6"
3. Ring: 10", 7.5" & 5.5"
4. Pinky: 8", 6.5" & 4"

Next, frame out the hand. The knuckle board is 22", and the wrist is 18". Fingers are equally spaced across the knuckle board, with about 2 2/3" between each finger. Make marks for where the fingers go on the knuckle board. You'll need 3x 15" boards for the braces on the pinky side of the palm and the two that line up with where the middle and ring finger attach to the knuckle. See picture 3.

For the thumb side of the knuckle board, you'll need to make both cuts on an angle. See picture 4. It's an awkward angle, so it's easiest to set the board against the already framed piece, mark your lines for the cut on both ends, and cut against your lines with a handsaw or skillsaw.

Next, you'll need a very long drill bit with a diameter wide enough to allow paracord to be threaded through it. For each finger, you'll need to drill 2 holes through the board of each segment, as seen in picture 7. Likewise, you'll need to drill holes through the knuckle board for where the fingers will attach (picture 6). For the holes on the sides of the hand (to the outside of the index and pinky finger), you'll need to angle the hole so that the bit exits to the inside of the hand, relative to the boards making up the sides of the hand. The fingers attach to the knuckle board such that they would be flush with the floor if the hands frame is laid with the "back of the hand" to the floor. See picture 5. Make sure that the spacing between the two holes in the fingers work with the spacing of the holes on the finger hinges. You don't want hinge screws coming through perpendicular to these holes. Do not attach the fingers to the hand frame yet.

Next, you'll thread paracord through the fingers to be able to place tension on the fingers from inside of the hand. It works like a set of tendons in the fingers. Install an eye hooks on the tips of each finger (picture 1). The cord will cross through the hooks, and having the cord lifted up off of the board helps a little with friction.

For each finger, you want to start from the point of attachment to the hand, thread cord through one of the holes on that end, and then through each segment working to the fingertip. Cross the cord through the eye hook at the end, and then back down the set of holes on the other side of the finger. You'll likely need a thin rod and some tape to thread the cord through the holes (see pictures 2-5). Leave plenty of slack line on each end (~2'; picture 6). At this point, you can attach the fingers to the knuckle board with a hinge and thread the slack through the holes drilled in the knuckle board. See picture 7.

Now, you'll install the extension springs. The spring for the middle and ring finger will go between the two center posts in the hand, and the spring for the other two fingers will go directly in line with the finger inside the hand. See picture 8. Attach eye hooks to anchor the extension springs to the inside of the wrist board. Then, start tying. You probably don't want to tie permanent knots at this point. As the whole arm takes shape and you start messing with mechanisms, you might want to adjust how taught each pair of ropes are on the spring to adjust how much force is needed for movement and how fluidly the fist re-opens.

At this point, I'll point to pictures 9-10. In picture 9, the you'll see there are eye hooks on the backside of each finger segment. These are needed, but this is a point where the design changed on the fly. In picture 10, you'll see that I originally used extension springs to apply tension on ropes threaded along the backside of the fingers. While that tension around the backside of the fingers is absolutely necessary, the extension springs here were a mistake. I later replaced them with extension cords.

Finally, in picture 11, this is a good time to shave down the corners on the finger joints. Possibly, a better time to do it would have been before attaching all the finger segments together, but I didn't have that foresight. Also, I didn't end up doing this til the very end, but now would be a good time to also lay down some electrical tape over the shaved corners to drop friction even more.

Making the thumb is much like making the other four fingers. The thumb just has two segments, 8" & 6". In the same way that you prepped the fingers with two drilled holes down the length of the segments, an eye hook in the digit tip, and paracord threaded through, you'll do the same here with the thumb.

Before mounting the thumb on the hand, add another board across the width of the hand (see picture 1). It should sit about 4-5 inches down the hand from the wrist (the same spot where the thumb will rest). Use the frame to mark the board for the angle cut. Now, you can mount the thumb with it set back a bit from the palm and angled in the direction of the wrist. While this isn't anatomically like a hand, it will give the illusion of a real hand's shape when the puppet has a clenched fist.

Last, you'll route the tension cables and the extension spring (pictures 2-5). For the middle post in the palm that is under the ring finger, use a spade bit to drill a hole just a little larger in diameter than the extension spring. Mount an eye hook on the inside of the post making the pinky side of the hand to anchor the spring (picture 3). Drill holes in the post under the index finger and the middle finger to route the thumb tension cords through (picture 2). Finally, tighten up the two tension cords on the extension spring to apply tension through the thumb.

I'll point to picture 6 real quick. You'll notice in some pictures of the hand from this point on, there's also a board fixed over the knuckle board. That ended up being taken off later to drop weight from the hand.

Later on, I added bungee cords around the back side of each finger, with the bungee cords laced through eye hooks on each segment, and the cord was stapled down on the knuckles (pictures 7-8). If I could go back, I would have spent more time rounding over and sanding the edges of each segment of the digits. In a pinch, we later covered them with electrical tape to keep from fraying the bungee cords too much.

Another thing that got added layer was a spacer between the thumb and the hand (picture 9). The thumb took a little more encouragement to fall, and it didn't hurt with the look of the thumb to not have it default to jutting straight up from the hand. I just cut some scrap HDPE to make a wafer that sat under it to tilt it towards the palm just a bit.

The platform will be made with the two 2'x2' plywood panels. You'll want to find the center of each panel with regard to both x and y dimensions and lay some marks down for the lazy Susan bracket (picture 1). Use a spade bit to predrill holes so that you can access the screw holes to attach the second panel to the bracket (picture 2). Last, secure some scrap 2x4s around the perimeter of the bottom to lift the platform up off the ground (picture 3). These will be needed to eventually anchor the platform in place.

You may choose to wait until after the next step before fixing the second panel onto the bracket, but personally I think it is easier to build the whole platform first to make sure you have it right, then remove the second panel for this next step.

Make the mast by fastening two 8' 2x4s against each other, effectively making a 3"x3.5" 8' post (picture 1). Originally I meant to do this with a 4x4, but I could only find as long as 6' and pressure treated. I talked with my dad about this, and he said two 2x4s bound together actually make a stronger and often straighter mast than the one 4x4 would. Get them secured together and just work your way down with 2.5" screws, fastening every 6" or so and alternating sides.

Use the two lag screws with washers (picture 2) to fasten the mast to the top panel of the platform (picture 3). You'll need to predrill your holes for this but still leave plenty for the screws to bite into. Then fasten the platform back together.

Finally, fasten the shelving brackets on each side of the mast to reinforce it (picture 4). You'll see that when I did this, it was after a later step, but it will be easier to go ahead and do this now.

Originally, the arm was meant to be a 54" long rectangle with 18" width (picture 1). There were 3 boards to frame along the length, roughly 11 15/8" apart. This design counted on the wrist of the arm bending, which would allow a longer arm to still clear the doorway needed to enter the set for the play. In practice, the hand was way too heavy have on a hinge, so I ended up having to shorten the arm by one segment (as seen in picture 2). The hand was just attached to the end board by several screws with a rigid wrist.

First, make the pivot that will function as the arm's elbow. You'll take the 12" carriage bolt and 1/2" pipe (about 3.5" length; picture 1), and first thread the carriage bolt through the segment of pipe a few times to make sure it is a snug but workable fit. Set up a couple of pipe straps as pictured in picture 2, and do a quick spot weld to fix the straps in place on the pipe (picture 3-4). Fix the pivot onto the end of the arm and at the center of the width as pictured in picture 5.

Next, you'll want to slightly drill out a ~3.5" segment of 1/2" plastic pipe (pictures 6-7). This will act as a spacer to hold the pivot off of the mast. Then, drill out a hole on the mast for the pivot to attach. You will want to go around 11-12" above the base of the mast. This will give 9" for half the width of the arm plus a little extra for clearance (pictures 8-9). Thread a nut and washer up to the spacer on the pivot bolt, place into the mast and secure with another nut and washer (picture 10).

The elbow's side to side rotation is handled by the the rotating platform, but the up and down of the arm at the elbow joint is controlled by a block and tackle pulley (picture 1). Fix one of the large eye bolts at the top of the mast, pointed towards the side that the arm is attached on. Attached the end of the block and tackle that has the pull rope coming from it to this eye bolt (pictures 2-3).

Fix a couple of layers of scrap 2x4 on the side of the mast (picture 4). This should be centered about 35-40" up from the ground. You want to give enough room to the top that the block and tackle has plenty of travel. The two layers of 2x4 position the control rope coming off the block and tackle at less of an angle to the arm, making the controls smoother. Run an 8" eye bolt through the now 4 layers of 2x4 (counting the mast) and fix the 1/2" rigid pulley in place, pointed towards the arm (pictures 5-6).

Next, make a plastic guard from the HDPE block. I just did this on a jig saw by eye. This guard prevents the arm from getting stuck on the rigid pulley when you pull the arm up all the way. You just want to make a sled that the arm can slide up against (picture 7).

Finally, install the other large eye bolt in the bottom of the arm, just behind the third joist counting out from the elbow (see picture 8). Tie some paracord to this eye bolt, run it up through the rigid pulley, and secure the other end to the lower portion of the block and tackle (picture 9). Try it out and see how the arm motion works.

Rigging the hand to properly open and close a fist was probably the hardest part of this to get right. I'm not convinced that I found the best way to scale this up for the puppet, but I found a way that worked...especially when viewed from stage.

Refer mainly to picture 1 for rigging the fingers. Because I couldn't predict what might happen after I turned the puppet over to the stage crew, I thought it best to attach with carabiners in case repairs needed to be done on the fly. Attach a carabiner to the eye hook in the tip of each finger, tie with paracord, and lace through an eye hook for each digit placed on the palm-side board below the thumb. The cord for the thumb shared an eye hook for the one for the middle finger. This setup of puppetry strings for the fingers works pretty well. We did later find that including a fixed pulley (attached with an eye hook) on the inside of the segment of each digit closest to the knuckle helped smooth out this motion of the puppet and make it behave a little more predictably. I'm sorry to say that I don't have good pictures of this, but you can kind of make it out on the pinky in picture 2. No fixed pulley was needed for the thumb.

Next, you want to get the lengths right for joining the ropes into one control rope. The main thing here is that you'll need to give more slack to the thumb since it will have less travel than the rest of the fingers. This will also prevent the thumb from getting stuck in the index finger when the fist closes. I fiddled with this as I got it right by just tying the 5 ropes at different lengths to the welded ring (picture 3), but eventually this was also hooked up with carabiners (picture 4).

Connect a new segment of paracord to the other side of the welded ring and run the ropes towards the mast. As seen in picture 5, install a couple of fixed pulleys, one at the base of the arm and another near the bottom of the mast. Fix them with an eye hook in the wood and then an S hook to give them a little range of movement.

This next part isn't really part of the hand controls, but it needs to be installed before continuing. It's very helpful to have a plank coming perpendicular off the mast and pointed away from the arm (to the "back" of the puppet; picture 6). You want to put it at about chest high for the puppeteer, so that this plank can sit between their upper arm and torso.

Up to this point, I haven't really explained the design for this puppet in terms of puppeteer interface, so this is a good point to do it. Look to picture 7. This puppet has 3 main movements and controls: left to right of the arm, up and down of the arm, and clenching/unclenching of the fist. This was made to be controlled by one puppeteer if needed, though you could use two if flush with stage hands. For one puppeteer, this plank coming off of the back of the mast can sit under the puppeteer's left armpit so that they can use their body to control the left/right motion of the arm. That leaves the left forearm free to control the lever (about to be discussed) for fist clenching/unclenching and the whole right arm to make small adjustments to the up/down of the arm once it enters the stage. You will need two people or both hands of one person free if you want to make full up/down movements of the arm while also controlling the fist.

For the lever to control the fist, we used a piece of scrap 1x1. Take the other 8" carriage bolt, drill a 1/2" hole through the mast, left/right control plank, and the 1x1. In terms of how long the 1x1 should be and how far in front of the mast it should jut out, play with the rope lead on the fist controls to see how much travel you need on that lever in order to comfortably get the fist to clench and unclench. I think about 1.5' forward from the mast worked for my build. Fix the carriage bolt through the mast and left/right control, place 2 washers, then the lever, 1 more washer, and then two nuts to lock all in place so that the lever can move fluidly but isn't loose (picture 8). Finally, put an eye hook at the front end of the lever, on the bottom side and tie off your control rope at the right length to get the fist to clench when the back end of the lever is in line with the left/right control.

At this point, I also added some chocks under the hand to make sure that the fingers never collided with the ground (picture 9).

Cut your slotted steel into four 6-12" segments. I just used a jigsaw for this (picture 1). Several screws and washers with these brackets, and the platform was very secure to the stage (picture 2). Later on, the set designer decided to add a lighter weight lazy susan bracket to the top of the mast to cut down on it wiggling. I wasn't around to grab pictures of that later addition, but they just attached the bracket to one piece of scrap board that capped off the mast and then another that was attached to some supports coming off the back of the facade of the set (picture 3).

A simple quality of life thing we added: Drill a hole through both panels of the platform, out near one of the corners. If you drop a bolt in that hole, it'll keep the platform from rotating when the puppet is not in use (picture 4).

Also at this point, we added a rope cleat to be able to store the arm in an upright position when not in use (picture 5).

This is another one that I don't have great pictures of. Segments of pipe insulation were used to add bulk to the figures. We just cut it to length for each segment of the fingers and attached it to each side of each digit using screws with a big wide washer to keep from cutting through the foam (picture 1).

To add bulk to the arm, segments of PEX were used and fixed to the arm with pipe straps, as you can somewhat see on the backside from the view in picture 1. We put electrical tape around the ends of the segments of PEX to make sure the pipe straps clamped down tightly on each segment, and we also lashed any crossings of PEX together with electrical tape to make somewhat of a cage. You can also kind of see it in the attached video.

A costume designer took over from here. I know that from there, it was just a lot of black shag material to give it the gorilla look, and they hit all of the exposed wood with some good ol' backstage flat black paint.

Sadly, I don't have a good video of the final product, but I'm sharing the one video I have of it operating before all the fabric went on. It's a little rough, because we ended up having to work on the finger tension shortly after this video was taken.

All in all, this was one of my most fun builds, and it was easily the coolest prop I've built. Every part of it was exciting and the right level of challenge for me. I hope that the details I figured out (and mistakes I made) can help someone else with a very niche need like this, whether it be for a production of Kong's Night Out or anything else.