Dyne's Treadwell

[Dyne]

As I mentioned in the edit to my next-to-last post, I was tinkering with an eye mechanism prototype while Fusion 360 was down, mostly to sort out what I need to know to design the real thing.  There are plenty of eye mechanism videos on Youtube, including a few free videos from the Stan Winston school, so if anything that follows is confusing, those may help.  

I know that Treadwell doesn't really have internal eye mechanisms, but I think it'll be fun to add one.  The entire setup will be hidden behind/distorted by the normal Paterson style lens.  It's mostly just to give an impression that something is going on in there.  Probably mostly painted black, with a few dim red LEDs somewhere in the murky depths.  It shouldn't be obvious unless you are specifically looking into his eyes.

Treadwell's head design complicates these mechanisms a little (since each eye is in a different box) but luckily, fitting servos into this space isn't a huge issue.






Here is the assembly for my initial mockup ...


Note that each eye consists of a double gimbal setup: the light blue outer ring pivots on a horizontal axis (you can glimpse part of it where the leftmost ring touches the leftmost arm of the yellow frame).  The grey inner disc is attached to that ring with a vertical pivot.  The outer ring can therefore tilt up or down on its pivot, tilting the inner disc in the process, while the inner disc can independently tilt left or right on its own pivot.

Now, imagine that one of the taller dark blue spindles is a servo, and one of the shorter spindles is another servo.  These turn their respective discs, or servo horns.  This leaves the other disc/horn at each height unpowered and spinning freely.

Now connect the horns at each height with a tie rod, like so:


These ensure that the unpowered horn at each height moves in sync with its powered sibling.  As you can see from the pair in the foreground, when either low horn rotates clockwise, the tie rod between them goes right, forcing the other horn clockwise as well.  (The angle of those two discs would be identical if the length of the tie rod was exactly the distance between each spindle, but my little wire mockups are only rough approximations.)

Now consider either of the upper horns.  If you use a similar tie rod to connect it to the the outer ring of the eye that's in front of it (in CAD, not the photo), then the upper horn can tilt that eye up (by pulling) or down (by pushing).  Now do the other upper horn the same way to the other outer ring.  Since both upper horns are moving together, as the upper servo moves, that means the upper servo will make both eyes tilt up or down in sync.

If you then do a similar arrangement with the lower horns (tying them to the attachment point on the right side of the inner disc of each eye) then the lower servo makes both eyes look left (by pushing) or right (by pulling) in sync.

I did print the eye gimbals and their frame, but these parts were so small that my print-in-place hinges weren't very effective and the frame is too flexible, so they pop loose.  It doesn't matter much, because the point ohere is just to explain how the servos drive each axis and keep the two eyes in sync.  

I am considering another method of articulating the eyes, anyway.  If you take away the gimbal setup and put a ball joint (or u-joint) at each eye's center of rotation instead, the eye piece can be a single part and -- in spite of having only one point mounting it to the frame -- it can freely tilt both up-down and left-right.  The mechanism in this video has extra servos in back for eyelids, but it demonstrates the idea with u-joints starting at about 35 seconds:





The drawback to this variant is that the prop eye must surround the pivot.  That's fine for a human-style eyeball, but Treadwell's eyes will be more like mechanical camera parts.  Having a ball joint in the center limits the design a bit.  With the gimbal I originally described, the pivots are on the outside of the eye, leaving the center free.

So that's what I've been up to on Treadwell recently.


Non-Treadwell tangent time.  (I did mention yesterday in another thread that I have the attention span of a goldfish...)

Whenever I do something like these droids, my urge to put my own stamp on them always starts getting twitchy.  That's one reason why I'm doing a Treadwell AND an R2 unit ...  I want R2 to be as close to screen accurate as I can manage, but I'm always fighting the urge to incorporate my own ideas, so I'm not trying for the same accuracy with Treadwell.  (The other reason for doing both droids is that R2 will take much longer.)

Another manifestation of that urge is that I'm getting tempted to eventually do a non-canon BB-8 style droid at some point.  I came across David Scott's BaBy-8 build over on the BB-8 builder's club and started looking into the concept art it was based on.  That's when I spotted this other piece of concept art (apparently) by ILM's Christian Alzmann:



If I were to build a roller style droid, I'd be tempted to base mine on that.  It's similar to BaBy-8 (and BB-8), but clearly represents a distinct design.

The one thing I dislike about BB-8 is how that type of locomotion just seemingly sprang from nowhere (in-setting), at least insofar as Astromechs are concerned.  There are other spherical droids (Droideka, Buzz droids, etc.), but unlike BB-8, those droids aren't exactly similar in purpose or style to Industrial Automation's products.  I realize that decades have passed, but Star Wars technology has never really seemed to change all that quickly.  Unless it is WMD technology created by Sith fanboys, I suppose.

So one reason I'm tempted to do that droid is to imply that it's an earlier model in the same design lineage that BB-8 is from, back before they sorted out the whole "floating head" thing.  I'd hesitate to call it BB-5 or whatever, because if that whole thing is the model, there's nothing left to identify the individual droids.  (It's bad enough that naming one of millions of R2 units "R2-D2" is roughly equivalent to calling your car "Mustang #64".  Star Wars naming conventions can be illogical sometimes. )

Anyway, the Ralph McQuarrie "ball mounted" concept for R2-D2 could've been the earliest model in this family, stylistically tying it to the R-series.



Various other designs like BaBy-8 could also go in there somewhere.  I like the one on the lower right here; it just looks so happy.  (I'm not sure that the others really look like BB-8 relatives.  The top one looks like a cross between a Viper probe droid and a LIN droid.)



Well, that's a project for the future.