Giant Spider Construction

Giant spiders sighted in Mirkwood Forest! Travelers, beware!

[photo] What's that up on the roof?

WARNING: If you are considering this project, read all Related Pages before you start!



[lots of PVC parts] The spider started with a skeleton for the body constructed of PVC pipe and fittings. The shape is a pair of octagons, squashed so that they are longer than they are wide. The lower octagon is structural - all of the legs hang off ot if. It is built of 3/4" PVC. The upper ring gives shape, thickness, and additional stability to the body. It is made from 1/2" PVC. The spider contains roughly $50 worth of PVC.

[gluing parts together] All of the parts are dry-fit. Only after everything is known to fit together properly is PVC cement used to permanently assemble the spider skeleton. The body will be glued up into a single unit. The legs are pinned into place, and can be removed and broken down for storage.

[the builders] The builders pose with the spider's skeletal body. Only the two front legs are installed, making them look more like antennae. The fellow in blue is David, Chief Architect of The Spider Project. The white bundle behind him consists of the additional PVC pipes that form the rest of the legs.

[dynamic testing on the ground] The spider is animated, because the only thing more terrifying than a giant spider is a giant spider lunging at you! The body is made to rock back and forth on a central pivot. Up front is an air cylinder that provides the motion. Although there is only one air cylinder in the spider, the rocking of the body causes all of the legs to move. When the spider lunges down at the victims, the front legs wave up and down.

The compressor in the photo is a small unit used only for testing.

The air cylinder is made from a screen door closer. This clever trick has been used for years by budget imagineers.

Also visible is the Haunt Air Manager (HAM) unit, consisting of air tank, pressure regulator, solenoid valve, and exhaust valve.

[constructing the base] Everything that touches the roof has a plywood base, with carpet scraps facing the roof. This is the main base for the spider body. It is upside-down, with carpet scraps being applied with hot-melt glue.

[fabric skin being painted] The fabric skin started out as plain muslin cloth - light and cheap. It also glowed blue-white under black light, whereas we wanted the spider to come close to blood-red. We used crimson Rit dye to give a red undercoat. It also killed the blue-white glow. Then we sprayed the skin with red tempra paint. We expected this to be a horribly messy job, but did it anyway. After all, haunters think horror is a good thing. It turned out that we did less damage than we thought we would.

Under black light, the spider glowed a vivid orange.

[leg layers] Each spider leg is constructed in layers. This photo shows one leg for each layer: inner skeleton of PVC pipe, meaty layer of foam pipe insulation, and fabric skin.

The photo also shows the nice red zebra stripes on the lawn. The lawn will get over it in time for next year's indignity.

[spider skeleton on the roof] The spider skeleton finally makes its first visit to the roof. The mechanical parts are completely set up, but it lacks skin, face, and paint on the base.

The large white and blue objects to right of center are bags of mulch, being used as counterweights. They keep the spider from tipping forward when activated.

To the right of the mulch bags, a slim silver line points up. That's the antenna for the X-10 radio receiver module. The spider is activated by remote control from a small hand-carried transmitter.

[constructing the base] Six of the spider's feet touch the roof. Those legs don't need to be terribly strong, because they are supported at both ends. This is a foot pad, which anchors the far end of the legs.

The pad is plywood, with carpet scraps glued to the back. The PVC pipe of the leg catches on a bolt, projecting up through the plywood. A small bungie cord holds the leg down to the plywood pad.

With a little black paint, the foot pad will be invisible on the roof.

[spider skeleton on the roof - testing and adjustment] Once on the roof, the spider undergoes dynamic testing: the air cylinder is actuated to make the spider rear up and drop down. Down below, David judges the effectiveness and offers advice, such as "Not threatening enough! Move his left leg a little closer to the porch!"

Note that the two front legs reach out over the edge of the roof - towards the Trick-Or-Treaters. Since these legs are only supported on one end, they are constructed to be light at the hanging end, and well-anchored at the body end.

[spider skeleton on the roof] Here is Master Haunter Dennis, posing with the spider to give you an idea of how big that thing really is. It might help to know that each leg is 10 feet long!

[spider eye] The spider was given a pair of eyes, made from faceted plastic "gems". Behind each gem was a pile of self-flashing LEDs, some yellow, some green. When activated, the LEDs twinkled, casting light through various facets.

The overall effect was a glowing, twinkling, moving kind of thing.

[spider face] Here's the spider's face, complete with glowing eyes.

Did we forget to mention that our little pet spits shaving cream at unwary visitors?

As we already mentioned, the spider jumps up and down by action of an air-powered piston. This, in turn, is remotely triggered via X-10. This means that the haunters can wander in and out of the house, up and down the street, and still make the spider jump up and down via radio-controlled Palm Pad.

We really liked the spider, and so did the neighbor kids. During setup, a van drove past and the driver slowed down to peek. A little girl stuck her head out the window, pointing up at our spider, yelling "There's a bug on the roof! There's a bug on the roof!"

My only regret is that the spider didn't make any sounds. The sounds didn't need to be authentic. Who knows what a spider sounds like, anyhow? But a bit of animal sound, when the spider reared up, would have vastly increased the threat component of the fear factor. Perhaps some kind of chittering sound...

We corrected the lack of sound in our year 2000 haunt.

[photo] The canned sound board is in the center. The trigger relay is lower right with the X-10 module just above it. The wire from the sound board terminates in a 1/8" socket that connects to the amplified speakers.


Related Pages

Make sure you visit all of the pages for the spider project:

Other projects that go into the giant spider:

Please check out the giant web:

General information in pneumatic effects:


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