Next year will be my 10th year haunting and hanging out on the forums, and this is my first tutorial. It's not so much an exact step-by-step of what you should do but, rather, how I approached this prop. I do a great job of copying others work, and not so much creating my own, so your mileage will certainly vary. I'm more lucky than skilled (LOL) but I hope I can help somebody out there to do an even better job on something like this.
My inspiration was the Zombie Guard Dog animatronic. It's available from thehorrordome.com for $1200. I don't have that kind of scratch so I had to be creative. The original prop is much more animated and scary, I suggest you check it out!
I started out with the animated buck reindeer from Kmart, bought on clearance after last Christmas. I removed the motor, but kept the rod that moved the head. I also removed the stops on the back legs so the legs would have the full range of motion for a lunging movement.
For the lunging mech I had to google various sites and found something close on frightprops.com in their pneumatic section. It's called "attack mech" so I fiddled with the length of the arms until it was perfect to hold my dog in a level, standing position and still give a good range of motion for the lunge. The base is scrap wood, the bottom mount is 2x4 scrap and the arms are 1x2 scrap. The mounting arm is 1x2 turned horizontal to give a mounting surface. The lengths of the arms will vary depending on the size and position of the frame you use and what kind of movement you want. It took me maybe three hours of tinkering to come up with the final build that worked for me.
I attached a mounting board to the frame and then screwed down the reindeer frame.
I wanted to use an air cylinder to move the head side to side and the arm is perfect for that, so I built a bracket out of a steel bar to hold the cylinder and fiddled around until I found the perfect spot to mount it.
If anybody remembers the surplus buy of box movers that was here a few years ago, that is the cylinder I used for the head. I think the throw is something like 5 inches which is perfect for maximum head turn without the neck hitting the framework. Here is the cylinder mounted and attached.
I had to shorten the neck of the reindeer frame to look more dog-like. I just snipped out one section of the framework in the middle of the neck, slipped the remainder of the head form down inside the remainder of the neck form, bent the remaining framing to connect and wrapped duct tape around the connections. It was pretty sturdy.
Here is how I ran the air hoses to the solenoids
What helps to sell the whole thing is the dog skin. I got hella lucky at the last yard sale of the year when I found this lifelike stuffed pooch for $5!
I am no sculptor and I'm not sure how I would have created a dog head that didn't look sh*tty so I want to thank the woman who sold me her stuffed dog. Honestly, this prop would not have been finished if I hadn't found this stuffy!
So I cut up the stuffy. I cut his head and neck as one piece to help cover the open movement area. The head had a styrofoam form inside that fit right down over the reindeer head frame pretty well. I used zip ties to secure it down as well as the neck (loosely) to the neck framework. The dog feet went on the feet, the butt end on the back and the stomach trimmings on the underside.
What was left of the exposed white framework I wrapped in black plastic and melted with a heat gun. Loose edges were zip-tied to the framework. Remember to leave the belly of your creation wide open for the mech to move.
Then I took Great Stuff and, with gloves on, smoothed it over the plastic. Yes, it's messy but it gives a rough, infected skin type look. I smeared silicone throughout the dog hair to mat it down and hit the 'skin' with flat black paint and red spray blotches.
I used tstraub's 4-button learning controller for the programming and after a lot of trial and error I got the thing to run great on about 25 psi.
FUTURE UPGRADES: I plan on rebuilding this for next season and adding teeth, blood and hopefully a chomping mouth animation.
DURABILITY: It's not as sturdy as store-bought folks! But that's why we are here. You can expect to lose pieces of great stuff 'skin' and some plastic just from the violent shaking. The first night of the haunt it probably triggered 150 times and the head looked funny. I took it home and found that a section of the neck frame right above where the movement-arm connects had snapped. I don't know if that was from stress or when a kid punched the dog (seriously!)
I used JB Weld on the break and wrapped it over and over with duct tape. On the second night it triggered maybe 220 times. The JB Weld repair broke but the duct tape held tight and we survived. One more night to go so I'm letting it ride.
That's all I have for now. Feel free to ask any questions you might have, and give me a 'like' if you like my tut.