Wednesday, July 30, 2014

Time to re-think R2-D2 Blue!

Back in 2012, many of us R2 Builders thought we had found the perfect blue!  We stumbled onto Dykem, a metal dye that was used on the original R2-D2s in STAR WARS A New Hope.  It appears the crew were doing a fair amount of touch ups during filming since the Dykem blue goes to all purple after a while, so to stay blue, frequent touch ups and re-do's are needed.

We thought we had it nailed down to a decent formula.  Polish the aluminum pieces (plastic pieces need a shiny silver base coat), apply the Dykem, apply a coat of DupliColor Metalcast Blue Anodized and a few coats of a UV clear coat.  However getting Dykem to go on well was a challenge with my airbrush.  Then, there was how those purplish-blue pieces look a year later.  Based on pictures other builders posted, it was an eventual failure.  

I painted several of the pieces in my 2012 post.  Any some of the pieces came out really good, despite a very laborious process.  However, close to two years later, the color has changed.  Now that I have a new 300 mm dome ready to be un-boxed, prepped and painted, its very important all the "blue paint" matches!

Currently I am testing some formulas/recipes that other builders have used and are pleased with.  Some are rattle-can formulas, as I used on the first R2.  The blue I have on the first R2-D2 is what we call "Krider Blue", but the Rustoleum Metallic Purple has been discontinued.  I'll post pictures of the tests later on!

That said, today was all about removing the paint.  I figured out a low tech way to do this...used two paint roller trays and an old paint brush.  I filled one with water and the other I filled with enough acetone to work the part around in.  (SAFETY REMINDER - I did this outdoors with plenty of ventilation, eye protection and gloves!)

In went the utility arms and using the paint brush, I just kept slowly applying acetone to the part.  The paint and dye quickly started to peel off the part.  So much so that it was clogging the brush bristles and the acetone was full of chunks of paint.  After the part was pretty much free of paint, into the water it went.

Now my method is hardly the best, in hindsight.  I wound up using a cloth with acetone on it it to wipe off those stubborn specks.  The resin eye is going to take some more work since the silver base-coat will require some light sanding to completely remove all the paint and primer.

The aluminum arms have cut outs to make them lighter, which also means you can still see paint in side those holes.  Those will require a bit more labor to be completely free of paint and dye!

Many more parts to remove paint from!

Next up will be modifying the aluminum utility arms so they can travel in and out of the body skins.  More soon....

Wednesday, February 19, 2014

Lifter mechanism motor work

Work continues on the lifter mechanism!

The challenge this time is the motor shaft to gear connection.

The original design uses metric pieces, which are available in Europe but not locally!

The design uses a Module 1.0 rack with the 12 tooth gear.  You don't appreciate how tight those tolerances are until you order a few "I think this will work" pieces from eBay and wind up with a stack of parts that won't work!

Add to this a 12 volt, 300 RPM motor with a metric shaft diameter of 6 mm.

So, we jump into our arithmetic (that's "math" for you kids!) and determine that 6 mm is  0.23622 inches.  This number comes in handy in a moment.

The solution to not being able to purchase the Module 1.0 brand rack and gear was to buy something similar from McMaster Carr.  I purchased the 20 degree steel rack and two 15 tooth gears to go with it.  I shipped the steel rack to a local machine shop to cut them down to specified lengths and have the holes and grooves cut.  Once back, those were attached to the brackets.

The gear bore has a 3/8" diameter and the motor shaft is 0.23"  I was able to find a bearing that has the outside diameter of 3/8" and an inside diameter of 1/4 inch.  Which is really close, 0.25" versus 0.23"

My approach is this...drill and tap a 10-24 thread hole into the gear, drill a slightly large hole in the bushing, then use a set screw to screw the set screw into the flat side of the motor shaft.  That should help tighten up some of the 0.02" difference

And here's it is in action..

Sunday, January 26, 2014

Working on the Lifter and more computer work

The Lifter Mechanism

This week I started working on the lifter mechanism that will give R2 the ability to show off the Life Form Scanner and Periscope.  Another builder in Sweden has a very clever design that has great potential.  

The trick is in Sweden everything in metric.  Replicating the parts in a non-metric country is a bit of a challenge!

Since he was kind enough to give me the files in STL format, my Ultimaker 3D printer and its CURA software can print most of the parts with ease.  However for something like this, I am not sure plastic is the best material.

To make the parts in aluminum, we had to work a bit harder.  Lars was kind enough to make the plans in DXF format, even though he had them all in Solid Works format.  Solid Works, which I have the Academic Version, does not allow you to have the latest Service Packs.  So, I could not view his files since he had a newer version.  Anyways, asides Solid Works proving to be more an obstacle than an effective CAD tool, we switched programs to keep making progress.

Then it was math word problems.  In the USA, all of our materials are in Imperial.  We can't go to the metal supply store and buy 5 mm thick material.  The closest I had was 1/4 inch, which when measured, turned out to be 0.24 inch thick.  That converts to 6.096 mm.  For each part, I would have to mill away 1.096 mm of material.  Sounds easy now but at the time, making all the tweaks in vCarve Pro and remembering to convert to metric...busy day of math problems!  

The bracket pieces are currently bent but I want my welding friend to touch that up a bit.  

The remaining parts are hard to source in the USA.  The gear I found, but the Module 1.0 15 mm x 15 mm rack is proving to be a bit more of a challenge.  Once I do get hold of the rack piece, I believe that will need some additional machining too.  Since that is steel, the equipment I have access too will not be able to cut it.  I'll need to recruit some help from a local shop for that.  The servo, shaft adapter and motor are all ordered and en route!

More Intel NUC progress!

The new power converter was put to the test this week!  Thanks to Intel replacing the NUC with a newer model that had the power connector, I tried it out.  

The HDMI to VGA adapter that went bad was replaced under warranty (despite having to email incessantly to C2G and Tiger Direct to get them to SHIP THE REPLACEMENT.  I can't give either high marks for customer service on this one.)  

I ran on battery power for 25 minutes before shutting down, happy that there were no hiccups with the converter.  According to the technical specs, the NUC will draw 13 watts at idle, 27 watts at load.  I've been consulting with some electronic minds to get an idea on the best battery and size to consider for powering this PC.

Sunday, January 12, 2014

3D printing an adapter piece

Tonight I finally got around to printing the part I needed to provide airflow to the NUC's power converter.

I own SolidWorks (Academic) 2013 and despite going thru many wonderful tutorials on, I could not create the piece to my satisfaction.

Here's the plan:  Take an old CPU cooling fan from an old Pentium Pro server and create an adapter piece so it can sit on top of the power converter enclosure.

It sounds simple!  The fan is a 50mm square and the enclosure is 43mm wide.  I had several ideas on how to do this and I settled on one where two tabs would extend out from below the piece, so it could straddle the enclosure and be attached from outside.  I'd leave the outside tabs intact, without a mounting hole, since I was not sure the best place for it to rest.

Several of my Ultimaker printer friends mentioned how quickly and easily they create things in SketchUp 2013.  After viewing the video tutorials on (a fantastic resource!), I started working on my drawing...

The biggest complaint I have with SketchUp is when creating circles, you can key in the distance you want.  The small holes are 4mm each, however the software, for whatever reason, enters in radius.  Also, resizing an existing object is a bit less intuitive, requiring you to "rescale" it, and if the object has been extruded (thickness added), you have to make sure both sides of the hole are selected.

In short, I struggled to make my simple part despite the "easy" interface.  In both SolidWorks and SketchUp.  Why?  I think while watching the tutorials, I had my mindset on what I needed to make versus learning the principals well.  In short, the impatient learner.

Once I had the part made, I had to Export it into a format the printer's slicing program, CURA, could use.  The only modification I had to do was flip the part upside down.

Just over an hour later, I have the part completed.

Next up is to see how the fan fits on it.  It fits perfectly.

Now I can drill and mount this piece as needed!  

The Ultimaker 3D printer is proving to be a very useful tool in droid building.