This is an interactive Halloween decoration/prop I made to spook Trick-or-Treaters. It's a skeleton that lays in a coffin, hooked up to a pulley system so you can make it sit up by pulling a string. It cost about $70 in materials and took 15 hours to build. The reactions to it popping up were priceless (see youtube video).

Step 1: Materials and Tools

Materials:

5-Foot Skeleton with hip joints (Home Depot or other Halloween store)
1 Drawer Slide
Plywood (4'x8' sheet)
Thin Rope / Paracord
Large Paint Stirring Stick
Small Hinge
Aluminum Brackets
Small Corner Braces
Pulley Wheel
Wood Screws
Double-Sided Tape
Black Cambric (or other thin fabric)
Plastic/Brass Grommet (optional)
Bluetooth Speaker (optional)

Tools:

Table / Circular / Band Saw
Drill

Step 2: Linkage Overview

The mechanism that allows the skeleton to sit up consists of 3 main pieces - a drawer slide, a linkage arm (paint stirrer), and the skeleton's torso. When the slide is pulled, the pivot point moves toward the skeleton's hips and makes it sit upright. Because I set a stop before the skeleton sits fully upright, it uses gravity to slowly lay back down after each pull. A pulley attached to the slide allowed me to control the speed at which it sits upright and lays back down.

Step 3: Skeleton Linkage Parts

There were a few small parts I needed to make for linkage connections. The first was the hip brackets. These components would hold the hips in place and allow the skeleton to pivot upwards. I cut and drilled them out of thin pieces of aluminum. The P shape was to avoid interference with the skeleton's hips when it was sitting fully upright.

Next up was the slider bracket. I made this out of plastic but it can be made out of aluminum as well if available. The flat bottom would attach to the slider and the hole would house a bolt.

The last small component is the linkage arm bracket. I made this out of an aluminum bracket with a band saw and drill. I threaded one of the holes so that the bolt could screw in and connect this piece with the slider bracket.

Step 4: Skeleton Linkage Assembly

I cut a 48" x 6" piece of plywood to mount all the parts to (A). I laid the skeleton on the plank so that its head was 4" from the end. I marked the location of the hip bolts and attached the brackets at that location (B). I screwed the drawer slide to the head end of the plank with the extension mechanism pointing toward the hip brackets (C). The slider bracket was attached to the slider with double sided tape (D). The linkage arm bracket was attached to the large paint stirrer with 2 wood screws (E). I ran a bolt through the two brackets to connect the linkage arm to the slider (F).

I cut down a scrap piece of 2x4 and screwed it to the plank to serve as a stop for the skeleton to rest against (G). The pulley wheel was attached to the plank on the opposite end of the hip brackets with a bolt (H). Two eye hooks were screwed into the plank - one to serve as a stop for the slider and another on the other side of pulley wheel to guide the string (I). Finally, I tied the string to the extension end of the drawer slider and fed it through the eye hooks, around the pulley wheel (J).

Step 5: Attaching the Skeleton

First I unscrewed the hip bolts and lined the hips up with the brackets on the linkage assembly. The bolts were then screwed back in, threading them through the holes in the brackets.

Laying the skeleton down, I marked where the end of the paint stirrer contacted the skeleton's back and then attached a small hinge at that location using wood screws. I screwed the other side of the hinge to the paint stirrer.

The skeleton came with a button that lights up the eyes and I wanted the eyes to light up when it sat up fully. Using double sided tape, I mounted the button to the underside of the paint stirrer so that it would come close to the skeleton when it sat up. I then put a single wood screw in the skeleton's back and adjusted the height so that it just barely pressed the button when it sat up fully.

Step 6: Building the Coffin

I first 3D modeled the coffin to make sure all the proportions were correct. This can be done by hand as well if you don't have access to modeling software. I made the internal dimension of the coffin 6" longer than the skeleton so it had some extra room. Using a table saw and band saw, I cut out all the pieces from a 4' x 8' sheet of plywood and connected them using small corner braces and wood screws. I drilled a hole in the vertical piece next to the pulley wheel for the string to exit the coffin. I decided to install a grommet in the hole to prevent the string from fraying against the wood as I repeatedly pulled it. The grommet is not necessary as long as you sand the hole smooth.

Step 7: Finishing Touches

I centered the skeleton linkage assembly in the coffin and attached it using wood screws. Now to hide all the mechanisms... Cambric is a black, cheap, thin fabric that is typically used under lounge furniture and works well in this case. Any thin black fabric can be substituted if you can't find cambric. I cut large pieces and laid them in the coffin, underneath the skeleton but above the mechanisms. This allows for a nice clean finish where you can see the skeleton but none of the inner workings. Using double-sided tape, I attached the cambric to the top inside edge of the coffin and cut off the excess. You'll want to ensure there is extra slack so it doesn't restrict the skeleton from sitting up. I left a small slit in the cambric by the skeleton's head so I could put a speaker in the coffin at showtime.

Step 8: Play Time!

With my pop-up skeleton complete, I was ready to scare some trick-or-treaters. I set the coffin up in my driveway with the string hole side facing the bushes. I put a bluetooth speaker in the coffin under the cambric next to the skeleton's head and paired it with my phone. You can play any sound effects you like through your phone but I used the "Center Stage" soundboard app which gave me some stock screams and allowed me to record my own sounds.

We put a bowl of candy in the skeleton's lap and my wife told kids, "If you're brave enough, you can take candy from the skeleton." I sat in the bushes waiting, and when kids reached for the candy, I pulled the string and hit a scream sound effect, making the skeleton jolt up right in their face. Of course for the very young kids, I made a ghost sound and slowly pulled the string so it sat up gradually. (Youtube link at the beginning of this Instructable.) Overall, the reactions were awesome. From screams, to jumps, to laughs, to head pats - it was clear that the pop-up skeleton was a Halloween success.

Introduction: Halloween Pop-Up Skeleton (In a Coffin)