# Another 3-axis skull



## dionicia (Nov 5, 2006)

Thank you for the huge pics. I will comment more when my monitor reaches the other side.


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## CaptnJackSparrow (Jul 5, 2007)

Vixen runs servos? I didnt know that, I only use it for lighting...


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## bonemanB (Sep 30, 2006)

I like the concept. Keep us posted with your progress.....


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## Dr Morbius (Jan 12, 2006)

Neat! How do you get the skull using that design to rotate on the pipe, ans also what servos are you using?


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## HomeyDaClown (Aug 27, 2007)

CaptnJackSparrow said:


> Vixen runs servos? I didnt know that, I only use it for lighting...


Captn,

Yes, but so-far only with the Efx-Tek boards or the build-it yourself 8 servo prop board that JohnnyMac designed for his Nut & Volts mag column. You have to keep an eye on the Vixen forums and check for new drivers, they keep addin em. It would be great to see a driver for the Lynx stuff.


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## evileyes (Oct 28, 2007)

Dr Morbius said:


> Neat! How do you get the skull using that design to rotate on the pipe, ans also what servos are you using?


they look like Hitec but i'm not for shure


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## dionicia (Nov 5, 2006)

I can't wait to see how those springs work. Thank you for making the pictures smaller.


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## Crypt Keeper (Jan 31, 2008)

Jeff, what servos are you using?

Can you get any pictures of your mechanism onthe inside? Would be great!


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## davisgraveyard (Mar 10, 2007)

The servo's are Hitec 425BB's I am using a cheap off-brand servo for the jaw. If it gives me any trouble I will grab another 425 for it.

I don't have all the linkages worked out yet and I still have to build the stationary rod for the head turn. Will post more picutures when I have more done.

Jeff


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## davisgraveyard (Mar 10, 2007)

Here are a few more pictures of the servos mounted. I used a servo bracket from Lynxmotion for the jaw servo. Still don't have the linkages worked out. Getting real close. though.


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## naberhoodhaunts (Mar 13, 2008)

That looks great! Please keep us informed on how thing work out.


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## Dr Morbius (Jan 12, 2006)

Video, dagnabbit! We want a video...because that's an excellent job you done so far!


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## davisgraveyard (Mar 10, 2007)

I have run into a HUGE roadblock on the design of this skull. It has to do with the turn motion. My plan was to have a small metal tab in a fixed postion on the rod with tightened nuts. The problem is that since the skull is setting on a nylon ball when the servo pushes on this fixed tab it doesn't turn the skull it tilts it to the side. The nylon ball can turn on the rod and I have even put a bearing under it to help the whole head turn. But I can't figure out the mechanism that will turn the head using the servo without the head tilting on the ball? I will post some detailed pictures if you guys want to see the problem. 

I really like the ball concept for tilt and nod and it works great. I also like the idea of the cut down and re-threaded rod from the bucky. But I can't get this turn movement to work right?


Any ideas?


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## Dr Morbius (Jan 12, 2006)

My guess would be to make sure you are using one of the side servos and not make the linkage too perpendicular for this one. It really should work, if you post a vid it would be easier to figure out.


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## indianaholmes (Feb 13, 2005)

Without having seen in detail, your setup, I would ask if your nod and tilt linkages are attached to the rod itself, not tabs. If they are solidly attached to the rod, then they should hold the skull in what ever position they are at, and the turn servo should only move the skull in that plane. I do not see any attachment to the rod itself. Some close up pictures of the linkages would help and even better, what the good Dr. requested, a video.


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## davisgraveyard (Mar 10, 2007)

Ok I took some video and did a voice over that might help.

YouTube - Animated Skull

Still didn't get much video of the linkages. The nod and tilt are attached to a nylon washer that is attached to the rod with a lock nut that gives it room to turn.


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## Death Master (Jul 20, 2007)

Your turning arm on the center axis rod might be to long, try to shorten it and see what happens, Oh by the way Fantasic JOB! I love it.


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## perdidoman (Nov 19, 2007)

*Great Job, Please keep us posted*


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## The_Caretaker (Sep 13, 2006)

I agree with DM shorten your turning arm, also I would add a second arm the is 180 apposed to the first and hook up the servo to push on this will you are pulling on the other. Both arms need to be the same length.


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## Lynn (Aug 23, 2005)

Gerat idea.... keep us posted. Anxious to see how this works out !


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## gym_ghost (Jul 6, 2006)

I agree, you need to trim that arm down... but I am trying like heck to figure out your spring setup???? Your spring load likes very heavy to what the servo can provide with regard to torque. 

If I can by so bold, I might make the suggestion of going with rubber bands instead of the springs, but make sure they work of three points... hint, hint, hint... remember, this is a 3-axis skull!

Joel


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## davisgraveyard (Mar 10, 2007)

If I get what you are saying you mean attach a double arm to the turn servo and attach 2 linkages to two fixed arms on the rod. So the servo is pushing and pulling at the same time?


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## davisgraveyard (Mar 10, 2007)

Rubber bands would work if they are attached to a ring connected to the rod so they can spin freely. The springs are really not that strong. In fact that is why I needed 2 to counter balance the skull. A slight push in either direction nods the skull. It really doesn't take much torque on the servo at all. The real problem with the springs (especially 2 of them) is it takes up too much room and gets in the way of the turn arms and linkages. It works but I might try something a little lower profile like rubber tubing or rubber bands?


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## The_Caretaker (Sep 13, 2006)

Yes a double arm on the servo and on the rod


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## Dr Morbius (Jan 12, 2006)

You said in the vid your linkages were loose. I agree, tighten them and the nod/tilt servos sould hold the skull in place. A shorter pan arm is a must, so the folcrum of the turn is closer to the main rod and reduce tilting. Also, a single stronger spring will create more space. Good job! Looks like you almost got it!


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## indianaholmes (Feb 13, 2005)

There was a post in the original thread titled "My 3 axis skull...in progress" by Halloweenbob on page 16. Here is the link... http://halloweenforum.com/props/62161-my-3-axis-skull-progress-16.html In this thread, KernelHappy was having a similar problem and it was discussed in detail. Perpendicular rods is what jumps out at me. Hope this may be of some help to your project.


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## The_Caretaker (Sep 13, 2006)

I was thinking more about this last night, if you do a push-pull arrangement then you side to side and front to back movement will be limited or hampered.


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## RBC (Mar 4, 2008)

I too was messing around with the ball joint method but I put it to one side for now to get other things done, Good Luck with yours, Hugs Blinky

always trying to build a better mouse trap, or skull trap in this case


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## davisgraveyard (Mar 10, 2007)

Latest video of my skull in progress. Still need to center my nod and tilt linkages. Found a 5/16" to 10-32 reducer that should work?

http://www.youtube.com/watch?v=idUfOeE9Gx0


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## gym_ghost (Jul 6, 2006)

Great job!!!

Joel


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## Joel (Aug 31, 2004)

You added a bearing to the connection point of the skull to the spine, but you need the same somewhere in the linkage to isolate the turning and nodding linkages. Watching your video, when you turn the skull, since all the linkages are connected to a common point, the stress is placed on the non-moving linkages which is causing the canting. If you separate the movements into at least 2 separate conection points and allow movement in at least one (preferably the rotation as that would be the easiest to attach a bearing) that should eliminate most, if not all of your canting.

My explaination may not be fully understandable with my description so if you need a better explaination I can draw something up - I've been thinking about this very thing for some time - more pully and counter pully based but has the same issues with isolating axises. Even have a web page dedicated to it (whenever I get a chance to start puting down my thoughts). I like the servo mounting system. May have to incorporate it.


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## davisgraveyard (Mar 10, 2007)

I added the bearing to the spine so the left/right turn would need little or no tourque. The nylon ball on top of the bearing allows the head to nod an tilt. The canting is happening because the linkages are not centered over the rod. they are connected to a nylon washer and are offset from the center. So when they push it causes the nod or tilt to angle. If I had a threaded rod coming out of the center so I could senter the linkages and connect them both to the center then I think that issue will be gone.

My main problem was I didn't want to weld something or drill and tap something into the top of the rod. I found a 5/16" to 10/32 reducer on McMaster Car that should work. I can thread it over the rod and it reduces down to a small threaded rod that the linkages will fit over. I am going to try it this week and see if it helps.

Thanks for your thoughts and I would interested to see what you have in mind with your concept.

Jeff
www.davisgraveyard.com


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## davisgraveyard (Mar 10, 2007)

It's been a couple of months since my last upate. I finally finished the skull and incorporated it into the bucky skeleton as the driver of our hearse. I have been mainly working on the programming for the show and have many threads at EFX-TEK about my progress. Here is a sneak peek at how he will look.

YouTube - Davis Graveyard Coachman 2008


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## Dr Morbius (Jan 12, 2006)

I am most impressed with what you got out of that prop2..I had no idea it was capable of controlling so many elements! It must have taken forever to code, I don't envy you that task, but I cannot deny the wonderful outcome. Is there a way to smooth out the motions and jaw sync? Or is the P2 at it's limit?


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## davisgraveyard (Mar 10, 2007)

Thanks! The only limit of the P2 is the amount of data I can store with the code. When I originally did the motion capture using a VEX transmitter and a Prop-SX I fed the data to a PC using it's serial port. The data was just under 3000 data elements of 20ms movements. I munged the data down removing duplicates down to just under 2000 data elements. I could only fit in about 425 data elements into the P2 so I had to get creative with the data. I ended up increasing the time between movements to about 240ms which creates the jerky motions. The P2 really isn't being taxed at all and I am only using about 7 of the 16 outputs. One of the biggest benefits was using an audio talker for the jaw movements. I tried forever to program the jaw movements to the audio but could never get it as close as the audio servo controler does. It took a huge burden off of me and it works better. 

Next year I am going to use the Prop-SX to do the show. It has a 32K EPROM that I can use to burn the data to and I should be able to easily get 2000 or more data points stored. Then the skull will be REAL smooth. It was a shame going from doing real smooth motion capture to the final jerky product but I'll get it working next year.

Jeff


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## Dr Morbius (Jan 12, 2006)

davisgraveyard said:


> Thanks! The only limit of the P2 is the amount of data I can store with the code. When I originally did the motion capture using a VEX transmitter and a Prop-SX I fed the data to a PC using it's serial port. The data was just under 3000 data elements of 20ms movements. I munged the data down removing duplicates down to just under 2000 data elements. I could only fit in about 425 data elements into the P2 so I had to get creative with the data. I ended up increasing the time between movements to about 240ms which creates the jerky motions. The P2 really isn't being taxed at all and I am only using about 7 of the 16 outputs. One of the biggest benefits was using an audio talker for the jaw movements. I tried forever to program the jaw movements to the audio but could never get it as close as the audio servo controler does. It took a huge burden off of me and it works better.
> 
> Next year I am going to use the Prop-SX to do the show. It has a 32K EPROM that I can use to burn the data to and I should be able to easily get 2000 or more data points stored. Then the skull will be REAL smooth. It was a shame going from doing real smooth motion capture to the final jerky product but I'll get it working next year.
> 
> Jeff


I see, so you were just using the propsx for data capture so you could upload it to the P2? If not, why not just stick with the SX? Why the switch to P2? 

On a side note, if you find the audio board still doesn't sync as well as you would like, try passing genereated tones through it silently (no speaker) on one stereo channel in sync to the dialogue, then play the dialogue through the speaker. Advantages: Perfect sync, total control, and you can have it talk over music without the music messing up the jaw movement. YOu can generate tones with Goldwave audio editor, it has a generously long full functional free trial. Just a thought.


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## davisgraveyard (Mar 10, 2007)

I originally intended to use the SX which is a better board and it can do interupt programming which means it can multi-task (sort of). You can dim LED's at the same time that servos are moving and your servos can all move at the same time instead of one right after each other. 

Problem was that the code to do all this is quite large and the program space for the SX is the same as the P2 which didn't leave much left for show data. I think it was somewhere around 200-300 statements. The idea of burning the data to an EPROM for a show hasn't been done before although it would work I was in uncharted territory. Also it was a pain to load separate programs over and over to get everything done. First load the program to capture the movements. Then load the program to burn the eprom data then load the show program. I just wasn't comfortable with it and I had already moved back to the P2 to get more data statements and the head looked pretty good so I just made a judgemet call for this year. It is still on my to-do list for after halloween.

In my case the audio we are playing has no music it is just a clean recording of the speech. The jaw moves pretty good along with the audio track. My problem was trying to do data capture of the jaw along with the had movements. I could never get it right. Even if I just did the jaw to the audio by itself. It also produces a LOT more data to move the jaw. The Audio-servo controller is the way to go for jaws in my opinion. With the jaw moving with the audio talker you are free to puppeteer the head which is MUCH easier to do and doesn't take as many data elements.


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## MsMeeple (Aug 21, 2004)

What happened to the pics in the beginning of the thread?
Final result looks great!

MsM


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## davisgraveyard (Mar 10, 2007)

Sorry about that. Switched hosting service this summer. I put them back. 

I should probably take a few of the new setup which has changed slightly.

Jeff


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## davisgraveyard (Mar 10, 2007)

Here is a photo of my final hardware assembly.

I used a 5/16 bearing. The nylon ball is 1 1/2". I used a 5/16 to 10/32 reducer female to male. I hand made the aluminum bracket. You can also see that I use a lock washer between the 5/16 nut and the reducer that holds the bracket in place tightly. The spring is on the nylon washer which moves freely and attaches to the inside of the forhead of the skull with an eye hook. The 2 link assemblies go to the tilt and nod servos and the turn servo linkage (not shown) attaches to the bracket hole. Thats it! Pretty simple really.


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## davisgraveyard (Mar 10, 2007)

here are the parts I bought from McMaster-Carr

Part #
92499A118  18-8 STAINLESS STEEL MALE-FEMALE THRD ADAPTER, 10-32 MALE END, 5/16"-18 FEMALE END

EA 4.95
6384K53 STEEL BALL BEARING, PLAIN DOUBLE SHIELDED FOR 5/16" SHAFT DIA, 7/8" OD 
EA 5.33

9614K39 WHITE DELRIN BALL, 1-1/2" DIAMETER (5 pak)
PK 13.25


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## davisgraveyard (Mar 10, 2007)

I couldn't figure out how to edit my previous older posts so here are the Youtube videos restored that I had deleted.

YouTube - Davis Graveyard Animated Skull How-to

YouTube - Davis Graveyard Animated Skull 2008


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## davisgraveyard (Mar 10, 2007)

I've been working on the 2nd generation of my 3-axis skull this month. I have thought of a couple in interesting ideas I wonder if anyone else has tried. 

I attached 60lb fishing line to the jaw instead of using piano wire or a rod. It gives the jaw a more organic movement and reduces the torque the jaw servo experiences with a fixed rod. And you can barely see it.

I am going to try using rare earth neodymium magnets epoxied to the inside of the skul and the plexi plate to secure the plate without using screws or tie wraps like my previous skull. I'm pretty sure 4 magnets will hold it fine.

I improved my spring for the bucky head. I had a couple of small ridgid short springs that I linked together to make a tiny rigid long spring. It is the perfect size for balancing the head. The pair of springs were in a package I bought at Home depot so they are easy to find.

I've come up with a fancy wiring scheme for the skull. I have mounted 2 RJ-45 jacks in the base of the skull and wired female servo connectors to them. You then just plug in the servos. The wiring is done so that a regular network cable can be used in the jacks. I can do 4 servos on one jack. I am using the other jack for power to the servos, LED's for eyes, and eye servos.


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## Sadler Vampire (Nov 2, 2007)

Jeff,

It was a pleasure meeting you at HauntCon in Milwaukee Sunday afternoon. It was too bad that I missed your seminar on Saturday, but you did mention getting my hands on one of your "handouts" from the seminar. PM me when you see this and we can discuss it further.

Bart a.k.a.


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## davisgraveyard (Mar 10, 2007)

The handouts for the seminar are now on our website.

www.davisgraveyard.com


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## bfrd22 (Oct 4, 2011)

Sorry I know this is old, but if anyone was looking for a 3 axis Bucky Skull like I was, I figured this needed a bump!
Andy


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