My 3 axis skull...in progress

HalloweenBob · #1 (**permalink**) 07-01-2007, 05:14 PM

I have a couple of pictures of my prototype. I will take a bunch of new pictures as I make the other three skulls, but this should give you an idea of what I am doing.

I am making a singing quartet based on (That means idea stolen from) Mike C's Graveyard Quartet. Ever since I saw his video I couldn't get it out of my head.

A neighbor of mine with a machine shop has helped me with the prototype, machining some of the parts I needed, and helping with the design.

I have been using the prototype to do some programming to make sure it all works with Brookshire's VSA software. So far, so good. I will post detailed pics of every step as I start making more skulls, but for now, here's a couple of basic shots with labels on them.

The Jaw servo was not mounted yet in this pic. It is in now. You can see the mounting screws and the linkage wire in the pic. The servo mounts standing up on end. I will add pictures of that later. The eyelid servo is mounted under the plexi-glass. That one is not hooked up yet, but when it is, it will be attached to one of the eyeballs...I am using wooden balls for eyes. It will move it up and down, not side to side. The purpose is to make it appear that it is blinking. I have large fake eyelases that will be attached to the eyeballs. When the eye is moved down, it appears to be closing as the top eyelid moves down with it. In the pic below, you can see the slot cut in the eye socket where the armature will go to move the eyeball. Don't worry, I will post pictures of that as well. I am using a 3/16 rod end as the gimbal which allows movement in all directions. When I build the next one, I will have clear shots of that as well.

Feel free to ask questions, and I will answer as best I can. I now have it hooked up to VSA and it is working very well. I am using the lightweight Pirate Skull and so I do not need springs, elastics or counterweights.

Dusza Beben · #2 (**permalink**) 07-01-2007, 05:49 PM

No questions, just WOW!

DB

Dr Morbius · #3 (**permalink**) 07-01-2007, 06:04 PM

I agree...I was thinking why doesn't somebody doing the gimble thng use those rotating socket bolts? I see someone has! nice work. Got a vid? I'd love to see it in action!

HalloweenBob · #4 (**permalink**) 07-02-2007, 01:43 AM

No video yet....I don't have a video camera. I'll have to try setting up my webcam to capture something.

I'll get something up as soon as I can.

cruizer · #5 (**permalink**) 07-02-2007, 04:54 AM

Very ingenious!

How is the rod end attached to the skull?

HalloweenBob · #6 (**permalink**) 07-02-2007, 05:02 AM

If memory serves me right, the rod ends I purchased were part number 2458K111 fom http://www.mcmaster.com

The exact specs really aren't that important. Anything even close to this will work fine. The only thing is that the rod you slip through it must be the same diameter as the opening of the rod end.

The main piece that I had machined for me was the rod that sticks up through the ball joint rod end. I don't have a good picture of it yet, as the only one I have is mounted in the prototype skull at the moment, but here is a drawing I made and a description:

I don't have the exact dimentions, but as long as you make it to fit whatever coupler you are using and whatever rod-end you are using it will work fine. The actual dimentions should be something close, but are not that important.

The rod starts out thicker, somewhere around 1/4 20 bolt size at the bottom with threads cut into it so that it will fit in the threaded rod coupler I bought at the hardware store. The shaft extends up for about 3" or so and is then shaved down with a flare so as not to restrict movement as it goes into the rod end, but it keeps the rod end from moving any lower onto the shaft.

Above the rod end I have a thin spacer made of nylon. At that point, the shaft is threaded again. The threads match the two nuts that are attached here.

The portion of the shaft going through the rod end is not threaded. It probably wouldn't make any difference, however.

The first nut is tightened down over the spacer and holds the rod end tightly in place. Then a small aluminum arm is placed on the shaft with another nut on top to hold it in place. This arm sticks out towards the back of the skull and is for the servo which controls Rotation (left right movement) to attach to.

The very top of this rod has a small hole drilled in it in the center and it is threaded (inside threads) for a 4/40 screw. This screw can be seen in the picture in my first post. It holds the two armatures from the other two servos in place. They control the nod movement (up and Down) and the tilt movement of the skull. So there are your 3 axis'

I will post another picture of the skull mech including the jaw servo shortly.

HalloweenBob · #7 (**permalink**) 07-02-2007, 05:08 AM

To answer the question posted above, the shape of the Pirate Skull by Lindberg (http://www.lindberg-models.com/71302_pirate_skull.htm) allows me to drill a small hole behind the jaw and extend the rod end male threads through that hole, attaching a nut on the either side.

I had to bend the threaded end of the rod end slightly to acieve the correct angle. This was done by putting it in a vice, heating it up a bit placing a steel tube approximatley the same diameter around it and banging it gently with a hammer. Be careful not to damage the threads or snap them off. I would buy a couple extra rod ends for practice. I didn't need much of an angle, maybe 10 or 15 degrees. I didn't measure, I just did it by eye.

In that last picture, you can also see where and how I mounted the Jaw servo into the plexi plate and attached the jaw wire through a hole drilled in the skull. Exact location of the hole is not important. just find a spot that doesn't show too much and allows you to hook up to the lower jaw.

twistedvisions68 · #8 (**permalink**) 07-02-2007, 11:17 AM

sweet bob you are the man, thanks for showing us this. and email more when you can
if you could show us a picture of the rod and neck mec with out the skull on it that would be great. Is the neck rod all one peice that runs up into the rod end? if so then I get the point.

thanks again