Animatronic Eye - range of motion

Fxguy1 · Oct 14, 2017

I have designed and printed my animatronic eye mechanism following the Animatronic Eye course from Stan Winston School. However, I seem to have a bit of a problem and hoping someone can help.

I assembled the eye in my prop book and threaded the monofilament. If I pull on the filament by hand, I get decent movement out of it. Once I try to tie it down to the servo pulley and use the servo I get barely any movement at all.

So....what’s the issue? Is it that my filament isn’t strong enough and is stretching? My servos not powerful enough (they move the pulley fine, and it seems to be moving the filament but that doesn’t seem to be translating to the eye itself)?

Here are some pics of the setup:

Or maybe the acorn nut is limiting the range?

Been trying hard to finish this but it’s frustrating me to no end.

Thanks guys!
Tim

Sent from my iPhone using Tapatalk

propmaster2000 · Oct 15, 2017

Hey Fxguy1,

Do you have any links to the SW course you are following to see what the final build is suppose to do?

Looking at the pictures you posted, what are the two screws on the sides of the eye's purpose?
In order for the eye to move in all four directions, those screws should not be used.
I would think that after the eye is centered on the head of the acorn nut, all four lines must be tight, so
that any movement will be translated to the eye. Since the pulley is used in a pull-pull setup, there should be
no slack in the lines. In one direction the pulley pulls the line one way while relieving it in the other.
All four lines must hold the eye level and center when the servos are at "0" (home position).
Do you think that the four lines on the eye are too close to center?
I would think you would get more movement if they were closer to the outer edge of the eye,
further from center?
.

Fxguy1 · Oct 15, 2017

propmaster2000 said:
Do you have any links to the SW course you are following to see what the final build is suppose to do?

https://www.stanwinstonschool.com/t...an-eye-mechanism-design-3d-printing-assembly#

Granted I'm not making it EXACTLY as in the course since I only need one eye.

propmaster2000 said:
Looking at the pictures you posted, what are the two screws on the sides of the eye's purpose?

Those hold the eyelids for the blinking mechanism.

propmaster2000 said:
I would think that after the eye is centered on the head of the acorn nut, all four lines must be tight, so
that any movement will be translated to the eye. Since the pulley is used in a pull-pull setup, there should be
no slack in the lines. .

I think this is part of my struggle, keeping the eye centered WHILE tightening the lines. I noticed last night that I need to alter my screws on the pulley. I'm currently just wrapping the line around the screw and tightening down, but noticed in the course the line actually passes between two washers to hold it tight. I'm going to pick some up today and try that .

propmaster2000 said:
Do you think that the four lines on the eye are too close to center?
I would think you would get more movement if they were closer to the outer edge of the eye,
further from center?

Could be. In the course he does mention the specific placements to get more movement, but it was in reference to the holes in the bracket holding the eye. I can go back in and move those holes a bit and print another plate to try it out.

I'll let you know how my progress goes! Thanks!

propmaster2000 · Oct 15, 2017

.
You may need someone to hold the eye centered and held in place while you pull the line tight for both the x and y axis.
Avoid wrapping the line around the screw. It is best to use the washer to "clamp" the line. That way the head of the screw
is not pulling on the line or making it loose while you turn the screw.

.

Fxguy1 · Oct 15, 2017

propmaster2000 said:
.
You may need someone to hold the eye centered and held in place while you pull the line tight for both the x and y axis.
Avoid wrapping the line around the screw. It is best to use the washer to "clamp" the line. That way the head of the screw
is not pulling on the line or making it loose while you turn the screw.

.

Ok, I tried having someone hold the eye centered, pulled as tight as I possibly can, and clamped it down with the washers and still nothing. The servo moves (but not nearly as much as without the filament) but still not translating into movement. I'm stumped...... :angry I also tried with a braided fishing line instead of the plastic filament fishing line and still no difference. Best I can figure at this point is either the servo simply doesn't have enough torque or the run between the eyeball and the pulley is simply too long.

Wimismith · Oct 15, 2017

Unless there is some sort of friction causing tension, the servos should be able to move just fine. How smooth is the socket on the eye?

Sent from my iPhone using Tapatalk

propmaster2000 · Oct 15, 2017

Do your servo pulleys look like they are turning a fair amount to pull enough length of line to move the eye in it's full range?
I see you are useing an RC remote control. Can you tell if the servos are binding and struggling to move?
Can you adjust the range of movement?
If you can see the pulley move a sufficient amount, then you are loosing distance traveled somewhere else.
There should be no bidding at all.
If all moves well by hand, check the pulley travel (without the line attached) to verify the distance turned.
Your pulley should find it's center position then turn clockwise and counter clockwise the same distance for both
the X and Y axis.
The line would only need to move a small amount to pull the eye in one direction and then back again to center, then in the
opposite direction.

Fxguy1 · Oct 15, 2017

Wimismith said:
Unless there is some sort of friction causing tension, the servos should be able to move just fine. How smooth is the socket on the eye?

Sent from my iPhone using Tapatalk

Kind of hard to describe. Its pretty smooth in that it sits on the acorn nut and slides around it just fine. I'm starting to think its the almost 90 degree turn out of the piece holding the eye.

Fxguy1 · Oct 15, 2017

propmaster2000 said:
Do your servo pulleys look like they are turning a fair amount to pull enough length of line to move the eye in it's full range?
I see you are useing an RC remote control. Can you tell if the servos are binding and struggling to move?
Can you adjust the range of movement?

Well I tried fiddling some more only to discover even less movement than before. Turns out my battery is dead (Doh!). So I’m charging it up and going to give it another go fully charged.

When pulling by hand distance traveled wasn’t very far so hoping it’s just the battery as stupid as that would be.

Sent from my iPhone using Tapatalk

Fxguy1 · Oct 15, 2017

Propmaster2000, I think I figured it out. I think I'm loosing travel distance through the cable housing. I'm using some plastic tubing from a marble coaster but the inside diameter of the tube is far bigger than the monofilament I'm using and turns out its pulling the housing rather than the eye, so its not translating it properly to the eyeball. I'll have to stop by the hobby shop tomorrow for some Du-Bro 30 micro pushrod housing.

propmaster2000 · Oct 15, 2017

Like a brake cable on a bike, the outer cable cover is there to keep the ends of the cable the same distance apart as the cable is pulled.
If the brake lever was just free, the whole thing would just move closer to the brake (getting shorter) and there would be no pulling of the brake itself.
I think that the outer plastic covers you are using serve the same purpose. It holds the servo motors apart from the eye holder.
That way the monofilament inside gets pulled and the out cover stays put.
The servos must stay the same distance away from the eye holder allowing the inner filament to get shorter, pulling on the eyes.

(simple mockup without cable outer cover)
P.S. The "crunching sound" you hear in the video is the cable rubbing on my metal lever and not the PVC.

EDIT:

I see in your book you have some depth to work with so that the eye is at the correct height for the cover when closed.

I modified the eye mech. shown above to hold two servos on the same holder.
I think that I will use mono-filament instead of the steal wire which I mocked it up with.

I think once you get the cabling figured out you will have one cool build

Please post any updates and pics. on your progress when you get the time...

.

.

Fxguy1 · Oct 16, 2017

propmaster2000 said:
I see in your book you have some depth to work with so that the eye is at the correct height for the cover when closed.

I modified the eye mech. shown above to hold two servos on the same holder.
I think that I will use mono-filament instead of the steal wire which I mocked it up with.

View attachment 766493

I think once you get the cabling figured out you will have one cool build
Please post any updates and pics. on your progress when you get the time...
.

Propmaster I have to thank you! I hadn't thought about using steel wire (my wife has tons for her Jewelry making).

I went to try using it and I think I figured out at least part of the problem / issue. My servo pulley was off (not perfectly perpendicular) to the servo. I reprinted the servo horn and pulley and am finally getting some decent movement. I'm printing the corresponding one now and will hopefully have some time to post some pics later tonight. I think we a few more adjustments and I might have it.

Fxguy1 · Oct 16, 2017

Progress....

I’ve got a blink, up and down and a little side to side. My bracket snapped and so I need to reprint another one and do some fine tuning before I’ll be good with it.

Here’s the video:

And a couple pics

Sent from my iPhone using Tapatalk

Animatronic Eye - range of motion

Fxguy1

Well-Known Member

propmaster2000

Sr Member

Fxguy1

Well-Known Member

propmaster2000

Sr Member

Fxguy1

Well-Known Member

Wimismith

Active Member

propmaster2000

Sr Member

Fxguy1

Well-Known Member

Fxguy1

Well-Known Member

Fxguy1

Well-Known Member

propmaster2000

Sr Member

Fxguy1

Well-Known Member

Fxguy1

Well-Known Member

Attachments

Similar threads