My 3 axis skull...in progress

I see something that might help after viewing your videos. Try attaching the linkages to a hole closer to the center on the servo arm. The further out to the outside you go, the more turning takes place in addition to the straight out "pushing" you want to tilt or nod. By moving the linkage closer to the center, you get less of an arc motion. You may find that the linkages become a bit more lined up (90 degrees) as well, although yours are pretty good.

I would also try adjusting the height on your center rod of the rotate armature (move it up a bit if you have clearence). I see this has been discussed a bit already, but it shouldn't interfere with other motion. I know mine does not. Lowering the rotate servo is a viable option, but shouldn't be necessary.

It is also important that all linkage arms be as close to parallel to the plexi plate as possible.

Mine are still at a bit of an angle, but not as much as what I see on yours. That may be causing some trouble.

All in all it does seem to be working pretty well.

I should have shot video of that phase of my setup. Those videos are very helpful.

DrMorbius:

Yes, I have removed the rotation linkage and everything tilts perfectly. If you look at the design of the mechanism itself, the rotate and tilt servos are directly opposite of each other, only the rotation one is moved a hair towards the back of the skull so that it lines up with the rotation cam attached to the rod. The skull tilt motion works by shortening the distance between the center of the servo and the top of the rod, because the rotate servo is energized and holding it's position, the distance between the center of that servo and the rod does not change. Because the rotate servo is connected to a point that is not lined up perfectly with the tilt servo linkage, the plate rotates as it maintains the distance from the cam to the center of the rotation servo.

Eureka! As I'm writing this, I think I know what my problem might be! The problem may be the distance between the gimbal and either the connection point for on the top of the support rod, or the gimbal to the plate. If the distance is too long, the arc that the top of the rod sweeps through the skull on will be larger than if that distance was shortened up. A shorter sweep would mean less change in distance between the rotate cam and the center of the rotation servo which in turn means that when I tilt, the amount of unintentional rotation would be very minimal. When I created the metal bracket and through my initial setup, I figured a longer throw would be better, allowing me finer control by using more of the servos range of motion.

In an ideal world, the rotate servo would act on the gimbal itself minimizing the amount of movements from other motions it would have to deal with. I thought I had approximated what everyone else was doing, maybe the gimbal is too far down.


josemo:

I actually had a similar problem early on, the screw for the rotate linkage was rubbing against the nod linkage and when enough pressure was applied it would slip off to one side or the other. As it's adjusted now nothing rubs or touches through the motions except at the very far limits of the motions well after my the skull has rotated while tilting (the rubbing is easier to fix than my current issue).

As far as the angle of the rotation linkage: I intentionally moved the rotation cam further down the rod hoping that the extra angle in there would make it less susceptible to the rotation problem. I've actually moved that thing up and down a whole bunch, bringing it right to the top, and all the way down to the bottom. I also tried pushing the rotation servo further down to keep it on the same plane as the rotation cam, by making little stand offs. Based upon my current theory above I think I was on the right track, just didn't get far enough down.


I'm actually kind of hopeful that this will minimize the problem!!! It's the first thing that makes any kind of sense. If anyone still has their skull apart and cares to measure everything up (distances between all the linkages and connecting poitns) I'd appreciate it.

I just wish I had time to work on it tonight .

Bodies

I said I would post again as soon as I got these guys all dressed up.

Well, I have started the body-making.

The girl lead singer is a full bucky in a dress. She will also be wearing a wig.

I made a wooden stand that holds her up from the bolt that extends down in her pelvis. It is actually one long solid rod that goes the entire distance of the spine and holds everything together. I cut off the tailbone, and rested the end of that rod in a hole I made in the frame, and then bolted it down tight with oversized washers and nuts.

Here she is standing there:



Here is the frame I made to hold her up:



To attach the skull that I made, I cut off the bolt at the top. Slid a coupler over it, and tapped a couple holes in it to hold it tight. Now all I have to do is screw her head on right.



I left some of the vertibrae attached in front to hide the metal couplings.

For the guys, it was a different story. I had to make an entire body frame for each one. They will be fully dressed in a complete tuxedo. (I bought 3 of them) so nothing will show except for their heads and hands.

Here's how I started:



here's what it looked like from the back:



Then I started padding it out a bit. First I added shoulder pads:



You can also see where I added Chicken wire to build out the chest.

Continued in next post....

Next, I added padding to the Chest:



A couple of arms (Made from pool noodles, held together with those nylon tie-wraps. I'm not sure of the real name for them)



Then the hands....



Almost done now. I just had to get them dressed. I put the tuxes on them the same way I would put them on a real person except that I used a staple gun to hold things in place.



There he is!

So far, I have made 2 out of the 3 Background Singer bodies. I am purposely making them different heights because all people are not the same height. I wanted a little variety and it adds to each one's personality.

Here's the group so far with one background singer missing. (They will be displayed outdoors)




More as I get things finished up.