Introduction: The Electric Chair

This Electric chair has cams underneath the seat which make the skeleton go crazy!
Warning do not sit in this chair!

Step 1: Making the Chair

Cut list:

2 piece 2x4, 19" long for the front

2 piece 2X4, 16" long for the sides

4 piece 2x2, 14" long for the legs

4 piece 2x2, 6" long for the arm rest posts

2 piece 1x3, 16" long for the arm rests

1 piece 38" tall X 12-16 in wide for the back rest. (adjust if your skeleton is a different size)

screw the 16" pieces to the side of the 19" pieces to make a square. Screw the 14" pieces in the corner's for legs.
Attach the arm rest posts with nails. Nail the arm rests on top of the arm posts with a small air nail gun. The back is 38" tall but if your skeleton is taller make the back taller or wider as needed. I cut a 45 degree angle to make it look cool then just rounded it off with the sander. Paint it the color you want.

Step 2: Seat

Measure the inside where the seat goes. cut a piece of 1/4" plywood approximately 1/4" smaller in both directions and PLACE it there. Do not secure it down or it won't work, I added 2 to 3 nails or screws in front of it to hold it from falling off while still allowing it to move up and down. Paint the whole chair a color that works for your needs.

Step 3: Secure Legs and Pelvis

Sit your skeleton down and get him in the position you like, drill a small hole right inside and behind the front of the pelvis, then cut a wood dowel about 2 to 3" long. Screw the dowel to the seat in the middle of the pelvis to prevent it from rattling out of position. Mark the spot right at the front of the seat where the legs should be located and cut 2 blocks of wood tall enough to reach the bottom of the leg bone and about 3" long. Drill 2 holes for each block and screw them down and paint.

Step 4: Cams and Shaft

Items required:

5/16 or 8mm threaded rod.

several nuts and washers to fit threaded rod including 2 "T" nuts or threaded machined hubs to hold cams.

2Pc. 8mm ID bearing with flanged pillow block on Aliexpress or on Amazon Note: 5/16 threaded rod will work perfectly inside the 8mm bearing.

The heart of this project is the cam shaft that shakes the skeleton violently. This is accomplished by securing the threaded rod (shaft) under the seat in the flanged pillow blocks. Be sure that the shaft is installed low enough below the seat that the cam can be big and strong enough to not break. I suggest the cam shaft center to be 2" below the seat.


Drill a hole that is slightly bigger then the rod through the back seat rail at the bottom, put the rod through the hole. It should reach from just inside the front seat rail to at least 1.5" beyond the back seat rail. I added a piece of wood 3/4" thick to space the bearing away from the front seat rail but this was more because I accidentally cut the threaded rod a little too short.

On the outside end of the rod grind 3 flats at 120 degrees to tighten in a drill

Install one bearing on the rod where it will be right against the back of the chair rail. Tighten a nut on both the front and back of the bearing to keep it in place. When this bearing is screwed to the back side of the back seat rail the shaft should reach within approximately 1/16" or 1mm of the back side of the front seat rail, just enough that the front bearing can hold it but the shaft will not rub on the front seat rail.

Drill a 1/2" relief hole approximately 3/8" deep on the back side of the back seat rail so the rod can turn without the nut getting stuck against the wood. Screw a bearing to the back of the front seat rail after lining up the rod so that it turns freely. At this stage you should have a piece of threaded rod which can turn freely in the bearings mounted under the seat of the chair. Nuts tightened on both sides of the back bearing prevent the shaft from falling out. the shaft sticks out beyond the back of the seat approximately 1-1/2" where it can be secured in a drill chuck. You will remove the shaft and back bearing from the chair for the assembly step.


Now measure the distance from the rod to the bottom of the seat, which should be approximately 2", use that dimension to set a compass and draw a circle. My dimension was 2" so I drew a 4" circle. Add bumps to the circle, 2-3 bumps approximately 3/8" beyond the circle should be sufficient. Each bump will make the seat rise and then fall again. To make the action seem irregular and violent the bumps should not be all the same size or evenly spaced. Make two, one for the front and one for the back. Make the front and back cams different so the action is further randomized. Cams are most easily made of plywood but metal may be a good choice for some people. Drill a 5/16 hole in the center of the cam (which would be the center of the circle of the cam) if using a machined hub, or a hole to fit over the T nut if so using. Don't bother to paint the cams because they are not seen, and the paint would probably cause some sticking problems. Install the T nuts or machined hubs over the cam center hole and secure them in place.


Push the shaft through the hole in the back seat rail, thread a nut, a washer, the rear cam, another washer and another nut for the back. repeat for the front cam. This is a good time to install the shaft in a drill to spin the nuts into their correct positions quickly. Insert the shaft into the front bearing and screw the back bearing into position so the rod is secured in place. Position the cams in the spot you want near the back and the front of the chair (tip: I put my bigger crazier cam on the back because that is under the body of the skeleton). Back the nut out of position about the width of the nut and apply 2-3 drops of red locktite (Amazon) to the threaded shaft on both sides of both cams then screw the nuts over the locktite and tighten against the cam on both sides. Wait at least 20 minutes for it to cure before running it.

Rub some wax or grease on the cam lobes to minimize friction and damage.

Step 5: Helmet

Part list:

A plastic bowl that fits on your head will do. Spray paint it silver or a metallic color.

2 pieces 1X2 4"long

1 piece 1X2 9" long

1 piece 1X2 3" long (you can round the corners off if you want)

2 pieces 3X1.5" strips of 1/4" thick plywood

Several nuts and bolts.

Glue and screw or nail the 4" pieces centered on the back of the chair leaving enough space in the middle for for the 9"piece and standing above the top of the chair 1-1/2". Place the 9" between the two 4" pieces and drill a hole through all three pieces. insert a bolt and tighten a nut to secure it. leave it just loose enough to allow the arm some movement.

glue and clamp the two 3" strips of 1/4" plywood on both sides of the front of the 9" arm poking out about 1-1/2". Place the 3" piece in between the wood strips and drill a hole through them all and bolt them together, put a screw in through the middle of the helmet on the inside into the bottom of the 3" piece.

Drill 2 holes somewhere on the front of the helmet to put bolts through, get small gauge wire (16-22 gauge) approximately 36-48" long and wrap the wire around a pipe as shown in the picture. Remove the pipe and wrap one end around the bolt on the helmet and the other end on a small screw in the backside of the back rest.

Step 6: Secure the Skeleton

To secure the skeleton, I used white plumber's strap and screwed it to the blocks under the legs and arms. I selected a piece of cloth from my scraps (I used a darkish red) and cut a 3" strip. I measured it over the legs, arms, and neck. Staple it in on one side of each location and screw it on the other side so it can be removed easily when needed. (Staples are optional, you could just screw both sides.)

You have your self an ELECTRIC CHAIR!!

To operate the chair attach an electric drill to the shaft. Run the drill at a low RPM. The skeleton should shake violently like he's having the worst day ever!

Step 7: Add Lights

Lighting is beyond the scope of this instructable, BUT DON'T NEGLECT TO DO IT!

I'm not qualified to teach arduino programming and lighting techniques and there are plenty of resources available online. But I suggest you try adding some flashing white LEDs inside the helmet. Maybe a couple other lights to illuminate your decoration. A strobe light might be really neat too. The Arduino can also control the drill and sound effects.

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