Intro

You get a lot of motion from a single pneumatic cylinder:

• The cylinder pushes up the front of the spider.
• The spider body pivots at the "hip".
• The front legs are only attached to the body. When the body moves, the front legs wave.
• The other legs are attached to the body via pivots, and have pivit points on the toe pads. When the spider body moves, the legs do, too!

Notes

• The PVC pipe and numerous couplers are the most expensive part of the project.

• Some of the other parts can be scavenged from scrap bins, and are amenable to substitution. For example, the toe pads are documented as being assembled from #10-32 flat head machine screws. But the base uses #10-24 stove bolts. If you don't have some screws and bolts already lying around, you might want to buy a single package and use the same fasteners for both.

• Several of our choices were driven by the setting in which the spider is to be displayed. Our spider was to go on a black roof. Covering her with black fake fur would have caused her to vanish into the night. Your setting - and choices - may be different.

• None of the drawings are to scale. They were produced two years after construction from old notes, and might have errors.

CAUTIONS

• We aren't mechanical engineers. We built something that seems to work well for us, but might not work for you. We are merely documenting what we did. Use your own judgement in building something like this.

• The animated spider throws a lot of weight around, and might not be stable on your roof if the pitch is steep. In our situation, she was solid when reared up, but in the relaxed position showed a slight tendency to tip forwards. We solved this with a counterweight on the back of the base, consisting of a bag of mulch.

• Watch the weather! The spider skeleton won't be harmed by rain. The electronics and pneumatics can be protected from foul weather with a bit of work. The biggest rain worry that we have is that the fabric covering will absorb water and get heavy. This will strain the skeleton in the areas that are marginally designed.

• Know your materials and tools; use them properly and safely.

Special procedures

Pinned coupler

One side of the coupler is permanently attached to the coupler.

The other side is held into the socket with a pin.

Notes:

• We bought a box of "concrete nails" for use as pins. The length was perfect to go all the way through PVC and coupler without sticking too much out the other side.
• Once the pin is in place, put a piece of masking tape all the way around it to keep the pin from falling out.
• Mark the pieces that are pinned together so that you can easily figure them out next year.
• Make sure the PVC pipe is driven all the way into the socket before drilling and pinning. When we took apart the spider after the first use, we discovered some joints that were weak, because the pin didn't go through enough pipe.

These are the nails we used for the pins.

Bored tee

In some cases, we need to run a single length of pipe all the way through a tee. Think of using the pipe as an axel, with the tee rotating on it.

This requires that the material in gray be bored out.

Notes:

• This is probably something you can't do with a drill bit!
• We used a small lathe. Ask friends and neighbors if they work with power tools as a hobby.
• Reader Thanh Quach used a different method. "Instead of boring out a 3/4' tee, I just used a 1 inch tee with step down sizers to connect to the legs."

Base

The PVC pipe provides attachment points for the spider and pneumatic cylinder. It also starts spreading the weight around. The safety rope is passed through the uphill PVC pipe. The spider spitter is attached to the downhill PVC.

The plywood finishes the job of spreading out the weight, protects the roof, stabilizes the spider by providing a larger footprint, and gives you something to put counterweights on, in the event that the spider is unstable.

Materials:

1	plywood rectangle, 32"x48", 3/8" thick
1	carpet scraps, 32"x48"
4	pipe straps, for 3/4" pipe
8	fender washers, 3/16"x1 1/4"
8	bolts, #10-24x3/4"
8	nuts, #10-24
	PVC pipe, 3/4", sched 40
7	PVC tee, 3/4", sched 40

You will also need some cheap black paint (or something that matches your roof), and a 13/64" drill.

PVC pipe layout and dimensions.

Directions:

Body

Body - lower ring

Green tees are 3/4" tees with a 1/2" side. They point up, and are used to attach to the top ring via 6" spacers. The two front spacers are special, with tees built into them so the face can be attached. If you want, you could do something similar at the back to attach an abdomen.

Red tees are all bored through, and rotate on a piece of PVC tubing.

The yellow elbows are colored just so I can point out that they don't quite aim the way they look on the diagram. They all point up, and are used to attach legs.

The piston connector points straight down.

Materials:

3	cross, 3/4" PVC, sched 40
14	tee, 3/4" PVC, sched 40
8	tee, 3/4" PVC, sched 40 - BORED THROUGH
10	tee, 3/4" PVC with 1/2" side, sched 40
8	45-degree elbow, 3/4" PVC, sched 40
8	90-degree elbow, 3/4" PVC, sched 40
	pipe, 3/4" PVC, sched 40

Notes:

• When everything is dry-fit together, each of the tees shown in red should be able to swivel.
• Note that the two front legs have legs fixed in position, but the others swivel.
• The ring may seem a little wobbly. It will become remarkably solid when the top and bottom rings are joined together.

Body - upper ring

Green tees point down, and are used to attach to the lower ring.

Pink tees point up, and attach to the hoops.

Red tees are special: 3/4" tee, with 1/2" side. The 3/4" section is bored out so that a piece of 3/4" PVC pipe can slide all the way through.

Materials:

3	cross, 1/2" PVC, sched 40
26	tee, 1/2" PVC, sched 40
8	45-degree elbow, 1/2" PVC, sched 40
2	tee, 3/4" PVC with 1/2" side, sched 40 - BORED THROUGH
	pipe, 1/2" PVC, sched 40

Interestingly enough, the old parts list that I'm transcribing calls for more tees than the old diagram that I'm transcribing. So I'll just transcribe them and let you figure it out. In addition, the old parts list said

middle 1/2" tee 2*2

The number of tees is somewhat academic anyway, because you probably want to buy them in the big "contractor pack" to save some money.

Body - spacers

And using them is simple, too - the lower ring has connectors facing up; the upper ring has connectors facing down; the spacers go in between.

There is a minor exception to the simplicity of the spacers: two of the spacers are lengths of 1/2" PVC with a tee near the middle. [We actually used a 2" and a 3" piece with the tee between.] The overall length is still 6". These special spacers go in the front of the spider, and are used to attach the face.

If I count them right, we need 8 regular spacers, and 2 of the specials.

Body - hoops

We chose to have a pair of semicircular "hoops" arcing over the spider, from side to side. When covered by a fabric "skin", the spider looks much larger and more organic. But if you look too close, it has somewhat of a "covered wagon" effect - especially from the side.

You could solve this with more hoops; a layer over the hoops to support the cloth; or more rigid and/or textured body.

We chose to limit the view of the spider to the front - where it looks very good.

The hoops are formed by cutting a "Hula Hoop" in half.

Legs

Legs - front

The leg section nearest the body is 3/4" PVC. The outer sections are 1/2" PVC.

The front legs use 45-degree bends everywhere. Their setup is:

  body coupling | 3/4" pipe | 45-degree | reducer | 1/2" pipe | 45-degree | 1/2" pipe

  3/4" pipe | 45-degree
  reducer | 1/2" pipe
  45-degree | 1/2" pipe

Legs - others

• Use a mix of 90-degree bends and 45, in order to get some random leg positions.
• Are supported at both ends (spider body and toe pad).

This yields the following three assemblies per leg:

  3/4" pipe | 45-degree (or maybe 90)
  reducer | 1/2" pipe
  45-degree (or maybe 90) | 1/2" pipe

Toe pads

Materials:

1	plywood rectangle, 12"x12", 3/8" thick
1	carpet scraps, 12"x12"
1	machine screw, flat head, #10-32x1 1/4
1	nut, #10-32
1	S-hook, 1"
1	cut washer, 1/4"
1	lock washer, #10
1	fender washer, 1/4"x1 1/4"
1	bungie cord, small

You will also need some cheap black paint (or something that matches your roof), and a 13/64" drill.

Directions:

• Dang! That's a lot of washers! Did we really use all of those?
• Start by drilling a hole in the middle of the plywood.
• Put the fender washer on the machine screw and put it through the hole.
• Using a pair of pliars, squeeze the S-hook on each side, closing up the ends. It's now more of a figure 8.
• Then start adding other things on the protruding end of the screw: cut washer; S-hook; lock washer; nut.
• Tighten down this mess and put a dab of thread-lock on it.
• Bend the S hook up from the board a little. Put the bungie on it. Crimp that end of the bungie so it won't fall off.

Ridgeline protector

Materials for each one (we built two):

2	plywood rectangle, 12"x6", 3/8" thick
1	carpet scraps, 12"x12"
	wood scraps, 1x2"

You will also need some cheap black paint (or something that matches your roof).

Directions:

• We put these together entirely using hot-melt glue.
• One of the guides came off one of the pads during storage, and was easily replaced with more hot glue. It would probably be a better idea to use whatever screws you have lying around the house to hold these together.

Covering

Covering - material and color

What I really really wanted was a big black hairy spider. Perhaps covered with fake fur, which is available in just about any color - natural and otherwise - that you can imagine.

But my roof is a very dark gray, almost black. A black spider up there would be almost invisible.

David wanted a blood-red spider, so we did that instead. We still could have used fake fur, and doing so would have given the spider a texture that hides wrinkles and structural elements like the hoops on the top of the body. But fake fur can be expensive. We settled on $.99/yard muslin, dyed in scarlet RIT fabric dye.

The red spider is quite impressive, and brightly colored spiders can be found in nature. But sometimes I still wish he could have been black. If I reroof with something lighter, I can always recover the spider.

You should also consider how the spider is to be lit. We wanted that spider to glow red. Naturally, this brings to mind black light.

The muslin, from the store, glowed under black light with the standard blue/white of optical brighteners. The scarlet RIT didn't glow under black light. We intended the scarlet dye to do two things: kill some of the blue/white glow; and make the spider red. Then we planned a top-coat of a paint that did have a red glow.

The scarlet dye was much more effective than we had planned. It killed every bit of glow. In retrospect, if we could have just killed some of the blue/white, that which remained might be colored by the scarlet dye. But we never had a chance to try that.

The other problem, and we knew it going in, is that it is extremely difficult to find a paint or dye that glows an honest red under black light. Oh, there are plenty of glow paints that look red in normal light. Some are even marked "red", and sold as red fluorescent paint. But when the black light goes on, they glow orange.

We wound up using a top-coat of a day-glow tempera paint mix. It looks very nice under white light, but certainly looks more orange under black light.

Which brings up yet another topic - Don't use black light unless you have adjacent objects that you don't want to glow. Think about it for a minute. We put that spider on a nearly black roof. Even if we hit him with a halogen light, or a spotlight, the dark color and rough texture of the shingles would drink up any spilled light! Only the spider would be visible! The place to use black light is where you want to illuminate an object that is near other light colored objects or backgrounds, such as a Flying Crank Ghost in front of a red brick wall. In that case, use of a white light would illuminate ghost and red bricks, but black light would only pick up the fluorescent ghost. This is a cost-saving tip, because even the cheapest black light costs more than a white light.

Covering - structure

There are several pieces, each to suit a different part of the spider. But you can think of each as a cloth bag.

• body - This bag even has a drawstring sewn into the hem! Pulling on it tightens the bag around the PVC framework of the body and encloses all but a small area on the bottom, where the risers connect the body to the base.
• 6 legs - Just cylinders.
• 2 front legs - Cylinders with one end sewn shut.
• "face" - This is a bag with a roughly oval shape (more human than spider), with "fangs" sewn in.

Pneumatic assembly

Face

The face unit contains a minor structure thrown together from scrap pieces of PVC pipe. Most of the shape comes from the covering bag, which encloses the PVC pieces and is itself stuffed with light bulky stuff, like fiberfill or crumpled paper.

Two pieces of PVC pipe protrude from the back of the face assembly. These are inserted into sockets in the front of the body and pinned into place.

It helps if the spider has some kind of readily visible eyes. These can be as simple as brightly colored pieces of paper or cloth, or scavenged pieces of automobile tail-light reflectors.

Sound system

The next year we added a simple sound system. It used a 20-second digital sound recorder, played into self-amplified computer speakers. The "play" switch on the digital sound recorder was "pressed" by the N.O. contacts of a 110 VAC relay, which was run by the same X-10 module that animated the spider.

Every time you pressed the "spider" button on the wireless X-10 remote, the spider would rear up and the sounds would play.

I was hoping to find a nasty rustling sound to record for the spider, but came up empty. I eventually found a sound track of "thousands of tiny frogs peeping". It's very strange and erie, and a good fit for the spider.

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