Halloween is coming up and it happens to be my favorite holiday. I always try to have some type of display in my front yard. The past few years, I've had “Lawnmower Man”, which is a madman running over a body with his lawnmower. It’s a static display, but it gets attention. This year on Halloween night, Lawnmower Man will be using his new tool, a chainsaw, to cut a zombie in half. It will be motion activated so that when someone walks by, the chainsaw starts up and the skeleton sits up in pain. The chainsaw sound is provided by a loud compressor that inflates a bladder behind the skeleton, which raises him to seating position. I hope you enjoy this Instructable.
Here's a test run in the basement (very messy since Hurricane Irene)
And here it is set up with the rest of my mini-haunt.
Step 1: Step 1: Materials
I had almost everything I needed for this project lying around my shop. Here’s the list.
1” PVC pipe – sizes below
3 – 1” PVC Tee’s
4 – 1” PVC Elbows
1 – 1 ½” PVC 45° slip/hub (male one side, female other side)
1 – Bladder from a wine box (yes, a wine box)
1 – ½” Copper pipe – 2” long
2 – Shelf brackets
Screws to mount shelf brackets
1 – Threaded rod approximately 21” long
2 – Nuts for threaded rod
3 – Set screws (whatever ½” – 1” long screws you have on hand should work)
1 – Plastic skull
Scrap wood for the base – 1 piece a little longer than the threaded rod, and 1 piece about 24 inches or so. These are mounted together to form a T (see photos).
Air line for compressor
Tubing for exhaust blower (optional)
Chainsaw (I had an old electric one in the basement that doesn’t work. Perfect!)
Mannequin to hold chainsaw (I built one with scrap 2x4’s and a severed head prop, but be creative)
Clothes and newspaper to dress and stuff these guys
String or wire to attach the bladder to the skeleton
Motion activated light fixture (around $8.00 or so)
Lamp holder to outlet adapter (to plug the compressor into the light socket)
Ground lift (3 prong to 2 prong converter so you don’t have to destroy the compressor power cord)
PVC pipe sizes:
Spine – 18”
Shoulders – 7” (x2)
Upper Arms – 6” (x2)
Forearms – 7” (x2)
Neck – 4”
Coupler – 2”
Step 2: Step 2: Skeleton Preparation
Cut all pieces to the sizes above. You can modify any of these sizes for your needs, but this worked well for me.
The 4” long neck piece needs to be drilled for set screws. Drill 3 holes equally around, about 1” down from the top of the neck. These holes should be a little smaller than the set screw diameter so that the screws are tight at all times.
Now you can build the skeleton by following the pictures. Don’t use any glue at this point. You have to remove some pieces now and then.
The skull has a small hole in the base that a ½” copper pipe fit in tightly. If your skull doesn’t have this, then modify your mounting design to work for you. Insert the 2” piece of pipe into the hole. Now insert this into the neck and tighten the set screws. This will hold the head in place.
Step 3: Step 3: Mounting to the Base
Once the skeleton is assembled (no glue), insert the threaded rod through the hinge base. Place the unit on the base and mark where the brackets will be installed. Make sure you leave room for the unit to move freely. The brackets I used were shelf brackets that I cut down and drilled to fit the pieces I had on hand. I’m sure you can find something that will work just as well for you. Once you mount the brackets, insert the threaded rod through the brackets and hinge base. Install 1 nut on each end of the rod to secure it in place.
Step 4: Step 4: Bladder Prep
Drink a box of wine. Remove the bladder from inside the box and rinse it out. Now take the tool end of your air hose and insert it into the bladder a few inches. Using electrical tape, secure the hose in place while leaving a small opening for the air to escape (or travel through the optional auxiliary blower line for super scary blowing effect). I then used a piece of duct tape along the top of the bladder. I folded if over and taped it back onto itself so I could have some room to make 2 holes in the top for the wire. Run a length of wire through these holes and secure it to the neck (see picture). If no auxiliary blower is needed, this part is done. If you want to blow air on unsuspecting trick-or-treaters, you can tape an air hose to the opening you left before. Use enough tape so that all escaping air goes into this hose.
Step 5: 5: Bladder Mount
I found a 1 ½” PVC 45° slip/hub that has been in my shop for years. The slip end fit the taped bladder opening and the hub end was perfect for drilling to mount to the base. I used a band saw to cut a notch for the air hoses to fit through. Slip the air hose(s) through the slip end of the elbow and tape it securely to the bladder opening. Now you can screw the elbow to the base. Mount it so that when the bladder is fully inflated, the skeleton sits up and when it's deflated, it lies down flat.
Step 6: Step 6: Motion Activation
I found a motion activated light fixture for about $8.00. I’m sure you can find a similar deal near you. I mounted an electrical box to a stake and wired the light to a power cord. This makes the whole thing very portable. The only modification I made was screwing in a lamp holder to outlet adapter into one of the light sockets. I then plugged my compressor into the adapter (via a ground lift) and now it is motion activated!
Step 7: Step 7: Set Up the Display
This is where you can use your imagination and find ways to use the sound of the compressor to intensify the effect. I decided that an old chainsaw would be perfect for this. I set up 2 saw horses with a board across them for the torture table. The skeleton (now fully dressed) sits on the table with stuffed jeans laying across the hinge base. I laid the chainsaw just below this point and stood the mannequin against the table holding the saw. The auxiliary blower line is run to the edge of the chainsaw blade causing a blast of wind making it seem like the saw is running.