An ILM R2 Story

[Duncanator]

What's that gear? It looks to be for tensioning the chain, but it has no spokes/is hubless? Any details on that?

Good eyes Krest!

Yes, that is a chain tensioner. It is a custom 3D printed part. It's simply a ring with teeth around the rim. It rides between the upper and lower runs of the chain that connects the two wheels. It doesn't need a hub because the chains run in opposite directions, so it just merrily rolls in place. I didn't put spokes on it because I wanted it to be a little springy. It's super easy to install: just flex it a little, and pop it in. I had to play with the thickness a bit to get the springy-ness that I wanted.

I'd seen something like it in the McMaster Carr catalog and thought "Hey, why buy it when I could just print one?"
We'll see how well it holds up over time, but it works really well.


Here's a better pic (a bit dirty )

 

[Duncanator]

IT WORKS !!!

First test of the 2 to 3 leg transition. I'll tinker with the timing, but at least he doesn't fall over!

 

[protonpack]

WOW!!

 

[Duncanator]

WOW!!

Thanks! It was a a huge thrill when it worked.
But nerve-wracking the first time!

 

[nniebling]

So flipping awesome!! This has become one of my favorite threads!

 

[division 6]

Sweet.
That is so cool.

 

[Duncanator]

Sorry so long away. Work is still necessary to do, despite it taking me away from my fun.

So! Now that R2 could drive and dance, I need to get his head turning.

Here's an old pic of my buddy Fon Davis working on one of the R2s during the refurbishment.

I'm not sure what the original R2s back in 1975 used for rotating the dome; but by the time they arrived at the model shop in 1999 for refurbishing, they were sporting Tonegawa Seiko SSPS-105 servos to do the job. These are massive servos with over 5000 oz/inches of torque!
That's over 27 ft/lbs !!! (379 kg/cm for you metric folks) Those servos also come with a big price tag. They cost over $600 a piece!
A bit more than I was willing to shell out.

In this pic you can see the bottom of the SSPS-105 servo below Grant's elbow. This gives you an idea how big one is. (About the size of a can of Spam)

So I tried a different solution. I used a large Rockler ring bearing to support the dome, and glued a toothed belt to the inside of the bearing with contact cement. Then the plan was to use a gearmotor to drive the ring. This worked pretty well, but I had no control over where it stopped, and had a heck of a time trying to get his head to come back to center.
I found a servo circuit board from Australia to control the motor, which worked sort-of. I could get his head to spin both directions, and come back to "home", but it was always overshooting its position, and was constantly "hunting" back-and-forth rather than stopping. I think the motor was too fast and the inertia of the head too great, so it could never stop in the right place.

Frustrating.... what to do.....

 

[Duncanator]

..... along came eBay to my rescue!

Say what you want about eBay, but sometimes it turns up some awesome stuff. In my case, a used SSPS-105 with a damaged cable for $100.
I was able to get a replacement cable for about $12 - and I was all set! I could now get R2's dome moving properly - and for a price I was willing to pay.

Original R2s were only able to rotate their domes 180 degrees or so, which is the range of motion for these servos. If a scene needed R2 to spin his dome all the way around, it was done in two shots: The first shot would show R2's head start spinning around, then they would stop, take off his head and remount it backwards with the servo brought back to front. Then the next shot would continue the rotation from a different angle as if his head had come all the way. Movie Magic!



My plan is to mount a cross plate to the ring bearing with a center hub that the servo drives from below. The servo will mount on two aluminum angle iron (iron?) extrusions screwed to the body.

....And here she is mounted!

 

[DBoz]

I am really enjoying following this thread. You should cross post it to the R2 Builders forum at Astromech.net.

 

[joberg]

TFS with us John So cool to see the tuto and the familiar faces working on those R2 units.

 

[3Dsf]

>I'm not sure what the original R2s back in 1975 used for rotating the dome;

From what I can tell, the original droid domes relied on the advanced motive power provided by human fingers.

Very cool to see the hinged crossbar system in the Grant shot.

 

[Poikilotherm]

Love this thread!!!!

 

[Duncanator]

I am really enjoying following this thread. You should cross post it to the R2 Builders forum at Astromech.net.

I plan on it.
I've been a member at Astromech for a while too.

 

[Duncanator]

When our group was starting out on this project, one of the things that we all really wanted for our R2s were aluminum domes.
The New Hope droids were all aluminum, but there were also fibreglass domes on droids from later films. But nothing looks quite like real metal.
R2's head is actually two nested domes, with the panels cut out of the outer one. Unfortunately R2's dome is not a hemisphere.
It's actually kinda' bullet shaped. Not an off-the-shelf item. So we needed to get them custom spun.

Spinning domes is a cool technique where a flat disc of aluminum is pressed with a tool over a pattern while it spins on a lathe.
His dome was too big to spin on any of the lathes we had in the modelshop, and none of us had experience spinning domes anyway.
I would have loved to learn how to do it; 'cuz I love learning new skills, but the learning curve may have been expensive and wasteful.

We contacted several companies to get the domes spun. The price was pretty steep. The set-up cost was the killer - the making of the pattern and tooling. When amortized over a set of only 10 domes, was the price was north of $500 for a nested pair.

....what to do.... what to do.....


I think it was Don Bies who had the bright idea. All we needed was a larger order! The more domes in the order, the lower the per-dome cost would be. The beauty of amortization!

But who would order a bunch more domes? There were only 10 of us.
If only there was a large online group of R2 enthusiasts that also wanted to make droids.....

Don had connections in the R2 Builders Club over at Astromech.net , and through him we "leaked" the dome and panel dimensions to the Club so they could put together a larger order with ours included. Brilliant! We got our domes cheaper, and the fans got accurate domes for themselves. Wins for everyone!

An additional benefit of working with the R2 Club was acquiring the holoprojectors for the domes. They are some of the only "found" parts on an R2, and you need 3 of them per dome.
In real life they were reading lights from a Vickers Viscount airplane. A british airliner from the late 1940's and 50's. One of Don's friends had purchased a case of New Old Stock reading lamps, some of which he kindly sold to us. Mega-Score!!!

This is one of mine with the upper shroud removed. I've taken it apart to attach servos so R2 can look at people.

 

[joberg]

Yep, bonus for everyone involved with the pricing of those domes...very cool

 

[Duncanator]

>I'm not sure what the original R2s back in 1975 used for rotating the dome;

From what I can tell, the original droid domes relied on the advanced motive power provided by human fingers.

Very cool to see the hinged crossbar system in the Grant shot.

The old RC droids did have some way to rotate the dome remotely, but you are right - the heart and soul of R2's head performance came from Kenny Baker's hands.

The hinged crossbar makes it much easier to access the guts of R2. I thought about doing it for mine, but decided I didn't need the extra complexity. We'll see if I regret that later.
That picture is of the Uber R2 that the ILM modelshop built for Episode 1. You can tell by the black interior - it was made from carbon fibre instead of regular fibreglass. It has the distinction of being the only movie R2 built by the ILM modelshop. If I recall correctly, all the others were built in England.

 

[Duncanator]

More Dome Trivia!

In Episode 3, we needed a dome to be cut apart for the space dogfight scene were those weird plasma cutter droids cut the head off of an R2.
We REALLY didn't want to cut up an original droid dome, and a fibreglass one wouldn't look right, so Don Bies offered up his personal one to be cut up and used for the scene. SO NOW OUR DOMES ARE CANON!!! Suck it, accuracy!

 

[Stormy320]

Early member of the R2 Builders Club and fun to hear back story details about how the club got the inside info.

These were fun times gathering all the parts and building. I even did a couple part runs.

Used to drive me crazy the R2 Builders club was on an email Yahoo group instead of a forum board. For all I know it still is.

Thanks for the memories. Haha

 

[Duncanator]

Early member of the R2 Builders Club and fun to hear back story details about how the club got the inside info.

These were fun times gathering all the parts and building. I even did a couple part runs.

Used to drive me crazy the R2 Builders club was on an email Yahoo group instead of a forum board. For all I know it still is.

Thanks for the memories. Haha

Yup! I remember the old Yahoo group too. Several years back they finally got their own website.

 

[Pwrsrce]

Don had connections in the R2 Builders Club over at Astromech.net , and through him we "leaked" the dome and panel dimensions to the Club so they could put together a larger order with ours included. Brilliant! We got our domes cheaper, and the fans got accurate domes for themselves. Wins for everyone!

Hey John...It's great to read through your build thread. Since the cat is now out of the bag in regards to the domes, I thought I would fill in some of the blanks.

Don and I first started talking about the potential of a dome run in 2002, after the R2 Builders first group appearance at Celebration 2 in Indianapolis...(which I headed up)...Once I actually got the info and files, (which DIDN'T come directly from Don as I recall), I contacted my buddy Ron Barclay to help partner with me to make them a reality...Thus the R&J domes were born!

The very first batch was a small run that included the ones for you ILM guys, as well as a few close friends in the group to get them out there and make sure everything worked as designed. I can't remember how many Ron originally shipped out to ILM, but you got the first ones off the laser.

Interestingly enough, I bought one of them back from Grant earlier this year before his untimely passing...While bittersweet, that dome will be on my personal R2 when I finish it in a few months.

In regards to the dome in Ep3...

I'll never forget getting a very vague call from Don in 2004 asking if he could potentially get another dome later if need be...(to which I said "absolutely")...He wouldn't tell me what it was for, but I read between the lines...Fast forward to C3 in 2005, and he told me about the domes brief appearance as R4-P17 in the buzz droid scene. Since then, alu and/or fiberglass pulls from our RJ domes have appeared in TFA, SOLO, and Rogue One for sure...I'm not totally sure about TLJ or TROS.

And...The Viscount light HP's were found by John Sherrell. Once Jeremy Firth over in England tracked down the original part and part number, John was able to secure a fairly large cache of them. He bought all they had and had them shipped here to Texas. He then sold them to builders for what he paid for them...$30 each.

Again, thanks for sharing your pics and stories. I've been following the ILM guys builds for nearly 20 years. It's great to see and hear the back story.

Jason