Sunday, April 14, 2013

Halloween in April

I've got exciting news!
A neighbor of mine wants me to build him a Halloween animatronic!!!!!
Crazy right?

Let me introduce my friend the Wolf Spider.

 When you think of freaky-scary spiders is this not the picture that comes to mind?
These things are great. Big, hairy, they don't build webs. They use those long legs to run really fast and jump on their prey to grab em. Now imagine one of these things with a two foot long body running along the ground and leaping up to grab you! Yep, nightmare machines.

The plan is to make a spider that leaps up from the ground and moves forward toward the trick or treaters while making a horrible sound and clacking its 'fangs' together.

The prop has to fit the space which is a bit tight (see below).

Scaled Haunt Map
That's about as big as I can make the spider and have it fit the parameters. The idea is to have it leap up to just above the level of the hand rail on the stairs while not intruding into the six inch safety buffer.

How am I going to do this?
With what's called a 4-bar lifter.
That would be the tower and the two diagonal lines in the below diagram.
 When in the resting position the spider will actually be 6" off the ground so it will look like it is standing on its legs.

Up Position
 Boo! c'mon that's gonna be a pants wetter right?

 Yes, I can not sketch artfully.....and the 1' should say 6".

Just about everything in this project I have built before for myself. There are two things that I don't instantly know how to do best.
1. My neighbor would like me to make the legs wiggle when its up in the air. We need to keep the spider itself as light as possible. I thinking of some kind of spring loaded leg assembly as shown horribly below.
2. How to best make the moving jaws effect which is also sketched out horribly below.
 I'd appreciate any helpful suggestions on these last two points.
This is going to be an interesting build as the spider needs to be as light as possible but also stiff enough that it doesn't flop around on the end of the nearly 4' long arm.

Some clever folks suggested some ideas on how to give the legs some movement.
I've distilled the ideas into the following two sketches.

Hope that makes sense to someone.
I'm going to try to build a prototype ASAP.


1 comment:

Joel said...

How would a set of counterbalanced legs and fangs do for this? Kind of like those little insects-in-the-walnut toys. You pop the top and the legs wiggle because they're neutrally balanced on a pivot point. Neutrally balance the legs on your spider, and then when you lift it up, the inertia will make the legs wiggle on their own.