To test your device, load the wire loop over the solenoid release system, turn off the room lights, and then connect the battery. Once the light switch is turned on, Harry the spider should lurch into action, making an arc between his hiding spot and your body to end his journey with a nice thump on your chest. As you will have noticed, the image of the spider becomes quite clear as it travels towards
you, but does not leave your mind enough time to process the image and get out of the way. If you are an unsuspecting victim at the light switch, by the time the spider is upon you, you are fully away of its hideous form and shear size, and can do nothing but scream or flee! Now you can see how tough your pals really are as they do battle with one of nature’s most feared creatures.
Figure 3-14 Harry the spider, ready for attack
Be aware of the motor voltage when looking for a suitable motor, since this unit is going to be battery powered, it would not be advisable to pull a 100-volt motor out of an appliance. The motor I used was taken from an old inkjet printer, and rated for 24 volts, although I found it to run at a good RPM and strength on a single 9-volt battery. A 12-volt battery pack would have been much better, but I wanted a small unit, and it only had to run once each time I planned to use it. You will also need a spool of thread, fishing line or wire fine enough not to be seen as it lays across the surface you plan to drag the beastie across. I like using a spool of thread because you can pick a color to match the floor or carpet, the spool is included, and it is fairly easy to “friction fit” the spool on to the motor shaft. As shown in Figure 3-16, the spool of thread can be forced over the gear that was included with the motor, and then placed in a box with a bolt to support the other end of the spool.
The bolt inside the box is smaller than the hole in the thread spool, but by only enough so that there is no friction. Since one end of the thread spool is friction fitted to the motor shaft, the other end needs to turn freely around the bolt which is used only for support. The motor will be mounted outside of the small box due to its size, so there will only be enough room in this box for a 9-volt battery and switch. If you plan to use this method,
ensure that the bolt center is aligned with the motor shaft center so that there is no friction between the bolt and thread spool. Figure 3-17 shows a close-up view of the spool mounted to the motor shaft and riding on the bolt. To replace the thread spool with a different color, the bolt is removed and then the thread spool is forced away from the motor shaft. If your motor did not have a gear attached that allows the thread spool to be fitted, then dig around your parts box for some small cylindrical object that can be forced onto the motor shaft that will also hold the thread spool. In a pinch, multiple layers of heat-shrink tubing over the motor shaft would do the job, but may make a vibrating noise from misalignment as the spool winds in the thread.
Project 7—Carpet Crawling Creature
Figure 3-15 Motor and thread spool Figure 3-16 Thread spool mounted to the motor
The schematic for this device is probably the simplest in this book so far: just a switch, a battery and the motor. However, when connecting the wiring, be mindful of the motor’s polarity so that your thread is wound into the spool, not the other way around. The thread is pulled out of the box by hand to the area where the critter will hide and then the motor will wind the thread back onto the spool when you press the button. The schematic is shown in Figure 3-18.
You don’t need to place the power switch in the actual box, and it may be easier to conceal the towing mechanism if the switch is remotely placed away from the box. For a living room scenario, place the towing box under the target couch,
table or chair with the switch remotely connected via wire so that you can press it inconspicuously as your pals stare at the TV. The critter would then come blasting out from whatever furniture it was hiding under right to the place they are sitting. I wanted the switch and box as a single unit so it would be easy to implant in a hurry in any location without having to worry about wiring, so this installation works well as long as I concealed the towing box. In Figure 3-19, you can see the completed towing box with a fresh spool of white thread installed ready to drag my furry monster across a kitchen floor with light-colored tiles. You will notice that the speed of the creature will depend on the power of your motor, size of battery, and friction between the load and the floor. My cat-sized critter moves at jogging speed across a tiled or wood floor, but slows down to a walk on a carpet. Of course, the fact that this blob of fur is coming straight at you is usually enough to scare at any speed.
The bigger the critter, the better. Of course, with a 9-volt battery and toy motor, you won’t be dragging a life-sized grizzly bear across your floor, so you have to do some testing to see how much weight your towing system can handle. I found that an empty 2-liter pop bottle made a perfect-sized lightweight body that would hide under various
Project 7—Carpet Crawling Creature
12 V
+
Motor
Switch
Figure 3-18 Motor, switch and battery schematic
furniture with legs, and once covered in fur, looked like a large rat, weasel or skunk. Some furry material from a fabric store or from an old coat was glued around the pop bottle so that no part of the bottle showed, except a tiny opening where the bottle lid could be removed to fasten the thread. The thread was tied around two small holes in the bottle lid and then the lid is screwed back into the bottle. Figure 3-20 shows the initial stage of my black furry beastie using a 2-liter pop bottle, a bit of furry cloth and some glue to hold it together.
The completed 2-liter critter is large enough to make an unsuspecting person run for cover, yet light enough to get some decent speed using the 9-volt towing system. If you want to make the
critter a bit more evil looking for well-lit
environments, then add some eyes or nasty looking fangs for a truly fear-provoking experience. Some other ideas for lightweight critter bodies might be: fur-covered balloons, a cardboard cylinder, stuffed animal with the stuffing replaced with a balloon or crumpled paper. If the victim is in a household that does not have pets, then obviously this critter is an uninvited guest.
The completed towing device and critter is shown in Figure 3-21. Sure, this beastie may not look that scary in this photo, but I guarantee that you will think otherwise if it came running out from underneath living-room furniture right at your feet when you were least expecting it! This joke can be made to last awhile if you let the beastie run all the way across a room to disappear under the couch or chair your victim is now cowering in. Everyone in the room will be standing on the furniture asking each other what the heck that thing was and where it went, so you can get in on the action and point around the room exclaiming that you thought you saw its fangs glisten as it moved again. “Dude, I think it’s a rabid weasel, and it’s right under your chair!” Yes indeed, this device is guaranteed to invoke the flight response in those unfortunate enough to fall victim to it.
Project 7—Carpet Crawling Creature
Figure 3-20 Two-liter pop bottle and fur covering
This version of the furry beast prank takes things to the limit, and will freak out even your most hardened, prank-resistant friends. When this prank is in action, your victim won’t have time to remember that you, the Evil Genius prankster, is likely behind it, nor will there be time to access the situation. In fact, your unsuspecting victims will only have time to duck, cover and scream with fear. Because the critter will lurch from the floor directly at the victim instantly when a light is switched on, the victim will only see the rough outline of whatever it was that is now heading directly at his or her face in a real hurry, so the effect is guaranteed to work. I call this the ‘universal critter launcher’ because you can set it up to hurl any small lightweight object into the air, and the mechanics can be made as large as you like. There are two parts to this system—a spring-activated hinge-launching system and an electromechanical releasing device. The two parts must be made to work together, so the amount of spring force you will be able to use will be
dependent upon how much force your mechanical- releasing mechanism can deliver. Unlike the previous solenoid projects, this one will demand some mechanical force from the solenoid, so running a 24-volt solenoid from a 9-volt battery is not going to cut it. Read the entire project before you start choosing parts so you will understand what will be necessary from the mechanics. The main part of this mechanical device is the spring- activated launch mechanism formed from one or more springs and a locking gate hinge as shown in Figure 3-22.
The hinge and springs can be found at most hardware stores and available in many sizes and shapes. For a small launcher capable of hurling a rat-sized beastie from the floor to about 5 feet in the air, a spring with a diameter of about half an inch and a length of about 3 inches should do
the trick. The hinge shown in Figure 3-22 is about 4 inches in total length just to give you an idea of how large my device was. The hinge will be bolted to a wooden base so that it functions in a similar way to a swinging gate. The hinge can be locked into position by placing an object between the hole in the latching part and the hinge body. The spring will then be placed under the hinge to create a pressure that will make the hinge fly open once released. This system is shown in Figure 3-23.
Drill a hole through the wooden base for the spring, which is fastened on the underside of the board using a piece of metal with holes drilled at each end. I used one of those 90 degree shelf brackets, and hammered it straight as shown in Figure 3-24. The spring could also be bolted directly to the wooden base without drilling the hole, but this would limit the amount of compression on the spring, reducing the amount of travel delivered to the hinge when the releasing mechanism is activated. The metal plate holds the spring in place so that it does not fly away from the board once the hinge has been flipped as far as it could go. The goal is to hurl a fuzzy critter at your victim, not metal shrapnel from your launching device, so it is best to secure the spring