# Acid Spitting Demon Rat



## Haunted Neurons (Jun 23, 2006)

Acid Spitting Demon Rat! PART 1

I am posting this "how to" in eight parts in this thread.

Here is a "how I did it" post with pictures on the creation of my acid spitting demon rat. I did not take pictures as I created it but since several people here wanted to know more and I have seen how everyone is eager to share all their great tips with everyone I took the prop apart and rebuilt it to get pictures, from now on I will take pictures as I go. I tried to keep the image file sizes small to help out the dialup users. (are there any out there still?).



















Here are links to videos of the rat in action. 
There is no sound with them and are about 1minute each. They are low rez and low framerate for dialup help so look a little jerky. The first video the rat looks a little floppy since I forgot to pack the stuffing back in when I shot the video.

Rat in action Animatronic Rat :: Motion example with skin on video by HauntedNeurons - [email protected]@[email protected]@http://vid69.photobucket.com/player.swf?file=http://vid69.photobucket.com/albums/i58/HauntedNeurons/Animatronic%20Rat/[email protected]@[email protected]@[email protected]@[email protected]@[email protected]@[email protected]@i58/HauntedNeurons/Animatronic%20Rat/motion1
Rat talking to child	Animatronic Rat :: Talking to child video by HauntedNeurons - [email protected]@[email protected]@http://vid69.photobucket.com/player.swf?file=http://vid69.photobucket.com/albums/i58/HauntedNeurons/Animatronic%20Rat/[email protected]@[email protected]@[email protected]@[email protected]@[email protected]@[email protected]@i58/HauntedNeurons/Animatronic%20Rat/Talking1
Rat frame in action	Animatronic Rat :: Internal frame assembly motion video by HauntedNeurons - [email protected]@[email protected]@http://vid69.photobucket.com/player.swf?file=http://vid69.photobucket.com/albums/i58/HauntedNeurons/Animatronic%20Rat/[email protected]@[email protected]@[email protected]@[email protected]@[email protected]@[email protected]@i58/HauntedNeurons/Animatronic%20Rat/Frame1
Rat being skinned	Animatronic Rat :: Putting skin over frame video by HauntedNeurons - [email protected]@[email protected]@http://vid69.photobucket.com/player.swf?file=http://vid69.photobucket.com/albums/i58/HauntedNeurons/Animatronic%20Rat/[email protected]@[email protected]@[email protected]@[email protected]@[email protected]@[email protected]@i58/HauntedNeurons/Animatronic%20Rat/Skin1

I had no plans drawn up for this project and created it as I went with stuff I scrounged up around the house and at home improvement stores. This is a crudely built prop with rusted bits and popsicle sticks, but hey it actually works! You will have to use your imagination to come up with substitutions if needed.

My parts list is not all encompassing; you can substitute your own variations to accomplish the same tasks.

Radio with receiver and 3 servos you could probably get away with only two
(Pulled out of old airplane, can find on EBay or cannibalize something)
Water pump
(Pulled out of old leaking battery operated squirt gun, you could buy a new gun and pull it out or use some other pump)
Aluminum U channel and L channel and flat stock various small sizes
Bits of thin sheet metal
Popsicle sticks (really)
Small wood scraps
Thick music wire (get at some hardware stores or hobby store)
Red leds
Vinyl tubing
Copper tubing
Micro roller switch
Battery Holder
Sports water bottle
Velcro strips
On off switch
Empty 8oz soda bottle
Silicone sealant
R/C steering horn
R/C servo connectors
Part from old 1980s era VCR
Screws, wire, ect....

The star of the show is a latex rubber rat I found at Wal-Mart for $7. It's about 14" tall and was filled with some kind of poly stuffing. The goal is to build a movable skeleton that conforms to the inside of the latex rat. You don't have to use a rat; any kind of hollow latex creature that is flexible can be used like cat, gargoyle, and bat ect...


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## Haunted Neurons (Jun 23, 2006)

Acid Spitting Demon Rat! PART 2

I cut the tail off and slit the rodent up the back to behind the head and halfway across the bottom. I removed the stuffing but didn't throw it away as it was needed latter to pad out the arms, head and some of the body. The internal metal skeleton doesn't support the latex and it droops horribly if not supported.



































The base was made out of some wood scraps to make an 12"x15"x4" box with an open ended bottom. I located the center and drilled a hole to provide a pass though for the skeleton of the rat, more on that later. I also cut a small arc in the top to allow the tubing and wires to slide around when rotating the rat.










You need to find or make something that will allow the prop to rotate freely about 45 degrees.The bottom part of the metal frame is attached to that. I used a flywheel from an old VCR but you can make something similar with a circular peace of thin wood or hard plastic and a thin bolt passed through and some washers. This provides a rotating platform with center bolt that can be used to rotate it from below, with a servo. The picture below shows the bottom part of the frame already attached to the rotating part and passed through the top of the box.


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## Haunted Neurons (Jun 23, 2006)

Acid Spitting Demon Rat! PART 3

I added two pieces of L bracket to the rotating part to make up the lower half of the body. I kind of gauged where the rat would bend at the waist and drilled a hole between the two brackets and passed a bolt through to make a pivot point.



















I cut a piece of U channel to reach from the pivot point to the head of the rat. I passed the bolt through the two L channel and U channel holes creating the basic frame. The upper part can pivot forward and back.


















To make the mouth open and close I made a beak like contraption that would fit inside the head and into the snout. It's easier to look at the picture below. I formed some wood and attached some manipulated thin metal to make a pivot point, the top part moves up and down and the bottom is stationary. Then it was pop riveted to the upper U channel at the level of the mouth. The bracket looks sloppy with some extra protrusions that can be cut off. I left them to be used as attachment points for future improvements I am thinking of.


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## Haunted Neurons (Jun 23, 2006)

Acid Spitting Demon Rat! PART 4

Now I have all the moveable parts. Left and right on the bottom rotating part, forward and back bending at the waist and the mouth can open and close. This would allow me to aim it in just about any direction.



















Now comes mounting the servos. I mounted the mouth servo on the upper U channel so it will move with the upper body and can open the mouth at the same time. I attached the servo linkage as shown and mounted the servo using a scrap of wood.


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## Haunted Neurons (Jun 23, 2006)

Acid Spitting Demon Rat! PART 5

The body servo is mounted to the lower body L channel and connected to the bottom of the upper body U channel with a music wire connecting rod and linkage connector. The forward and back travel does not need to be extreme. You only need it to help you aim up and down about 45 degrees, if that much. The servo travel was extended by adding a cut down popsicle stick to the servo arm.



































To rotate the rat side to side the servo is mounted in the bottom box. An R/C steering horn is attached to the rod or bolt that passes through the top of the box and linked to the servo. If you don't have something similar you can cut a control arm out of a piece of metal and jam two nuts on both sides. On the servo end I added a popsicle stick and metal strip to it to increase the servo arm travel. They are connected together with music wire. You only get 45 degrees of travel side to side, that's the limit of the servo travel. That means you can't squirt someone directly to the side of the prop but if you arrange your rat so people can't go behind it or directly to the side then it's not a problem. You could probably come up with improvements to let it rotate in a greater arc.


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## Haunted Neurons (Jun 23, 2006)

Acid Spitting Demon Rat! PART 6

The water pump was pulled out of a battery operated squirt gun. The pump is attached inside the bottom and vinyl tubing was run from the water reservoir to the pump and up through the frame to the mouth area. I used copper tubing velcro'd to the frame to try and control the placement of the exit end of the tubing. There is probably a better way to do it. The water reservoir is just a sports water bottle. I cut a hole in the top and attached the top of a soda bottle with cap to provide a water refill hole. (make sure you drill a small pinhole in the top of the cap to avoid a vacuum lock) This passes through the top of the box so I don't have to turn it over to refill. I used the nozzle end of the squirt gun where the water comes out and attached it to the end of the copper tubing in the mouth area with a short piece of vinyl tubing so it's flexible. This will shoot water just like the squirt gun did. You can use any cap\plug type thing with a pinhole in it to the same effect.











































The pump is activated with a 3rd servo mounted to a piece of wood. I cut the servo disc into a cam shape to activate the micro switch which feeds 6 volts to the pump motor and at the same time lights up the red led eyes. This setup allows me to operate the mouth independent of the water pump so I can open and close the mouth without squirting people. If you want you can eliminate the 3rd servo and activate the pump using the servo for the mouth. Just add some linkage to activate a switch at the same time the mouth is all the way open.


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## grapegrl (Jan 3, 2006)

Awesome, HauntedNeurons! It's amazing what you did with an inexpensive Wal-Mart prop!


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## Haunted Neurons (Jun 23, 2006)

Acid Spitting Demon Rat! PART 7

The image below shows the routing of the water tubing and how it is mounted to the mouth. You can also see the led eyes on the ends of the wires.


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## Haunted Neurons (Jun 23, 2006)

Acid Spitting Demon Rat! PART 8 (Finished with all parts)

The latex shell is then pulled over the frame and some stuffing re-added to fill out the droopy parts, making sure the stuffing doesn't cause the servos to bind. The red leds are just poked through pin holes in the eyes just enough to see the light. The squirting end is poked through the tongue. The back can be taped shut with black tape or use Velcro.



















I mounted the water bottle, pump, rotate servo, battery packs, and receiver in the bottom with a on off switch. Everything is battery operated so the prop can be put anywhere in the yard without having to attach a power cord. For longer run times a wall wart would be better. I used a separate battery packs for the water pump and receiver only because it was convenient. The receiver came with its own battery pack with a special connector. The receiver battery is too small to power the water pump by itself. You could combine the two if you want, just make sure your voltage doesn't exceed what the receiver takes or you might blow it up.


























It's ready to go. Put some kind of decorations around it so it fits in and maybe hides the bottom box some. I just used a black cloth draped around it last year but plan on making some kind of small stage or façade for it this year. Put a pitcher of water near it for refills. You can move it around and follow people, actuate the mouth, get people to look closer at it then&#8230;wham you squirt them. I have never had so much fun; you can control it completely and even keep squirting people as they try to move out of the way. My only suggestion is to not squirt the very young as they tend to cry and their mothers tend to want to beat you.

Next year I plan to make the mouth servo actuated by audio input like I have seen on some skulls on the net. I will use a voice changer to try and get as close to creepy rat sound as I can, that way I can talk to and insult people (in a fun way) walking by.

Here is a link to the album of all the images on photobucket, there are a few extra pictures not in this thread.
Animatronic Rat pictures by HauntedNeurons - [email protected]@[email protected]@http://static.photobucket.com/player.swf?file=http://vid69.photobucket.com/albums/i58/HauntedNeurons/Animatronic%20Rat/[email protected]@[email protected]@[email protected]@[email protected]@[email protected]@[email protected]@i58/HauntedNeurons/Animatronic%20Rat/RatInstru

I hope this was in depth enouph for everyone, have fun and good luck if you want to build something like this of your own.

[email protected]


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## Haunted Neurons (Jun 23, 2006)

grapegrl said:


> Awesome, HauntedNeurons! It's amazing what you did with an inexpensive Wal-Mart prop!


Thanks, The Wal-Mart prop was very inexpensive, its the radio that would cost a lot if you bought a new one. I had to buy the rat because I am not talented enouph to sculpt one and cast it in latex.


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## Ugly Joe (Jul 13, 2006)

Outstanding!
For being "thrown together", as you claim, that is one concise package - you have a massive round of applause from me!!!

Very creative with the "spitting" idea, BTW...I thought the X/Y axis movement was pretty impressive, and then an animated mouth was bonus...but adding the squirt gun pump is brilliant.


What kind of voice were you thinking of? Something squeaky?


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## Sickie Ickie (Jun 20, 2006)

I have no training in electronics. This has been a huge help!!!! Thank you!!!


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## Sickie Ickie (Jun 20, 2006)

Quick question...How are the servos plugged in? Did I miss that?


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## Hellrazor (Jun 18, 2006)

HOLY ! WOW ! NEATO! Way to go! Great Job. I love it!


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## Haunted Neurons (Jun 23, 2006)

Sickie Ickie said:


> Quick question...How are the servos plugged in? Did I miss that?


I guess I glazed over the servo connection part. You can see in the picture the empty radio reciever and the servo connector. The servo just plugs into the reciever. Each lever axis on the transmitter activates a different port on this reciever. You can see I could put 7 servos on this type reciever. The 2nd picture show where each one is plugged in at.



























I need to correct the "how to" in this thread. This project actually uses 4 servos total not 3, but you could get away with 3 or even two.


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## Haunted Neurons (Jun 23, 2006)

Ugly Joe said:


> Outstanding!
> For being "thrown together", as you claim, that is one concise package - you have a massive round of applause from me!!!
> 
> Very creative with the "spitting" idea, BTW...I thought the X/Y axis movement was pretty impressive, and then an animated mouth was bonus...but adding the squirt gun pump is brilliant.
> ...


Hey thanks for all the great accolades, it helps make it all worthwhile.

As far as the voice goes, I am thinking of a combination of squeaky and gravaley. Something close to Gilbert Gotfried. It has to fit the small size but sound insulting. lol, dont know where to start on something like that though.


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## Sickie Ickie (Jun 20, 2006)

Simple, e-mail me and I'll do a voice over! ;-D


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## Sickie Ickie (Jun 20, 2006)

I get it now!!! I get it now!!! *Dance of joy*

I've been trying so hard to understand servos! Now I think I finally do!!!!!


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