Maker Faire is just a day away, and I’ve had a busy time getting ready. This is probably my favorite event of the year, and we will have a good showing, with 4 droids and 6 builders in attendance. Bonnie Burton from SW.com will also be there running a kids workshop on Star Wars Puppet Craft.

Over the long Memorial Day weekend I stripped Artoo down for some long needed repairs and upgrades I’d been putting off.

I’ve replaced the center foot with the a new one from JAG with the taller skirt. Here’s a comparison shot with the new foot on the right

Sadly, with extra tapper of the foot skirt, the “Special” 3 inch Ace casters are too big and had to be re-worked. To be honest, they were a bit of a squeeze in the old foot, so I was on the hunt for some nice 2.5″ casters! I searched and searched locally, but couldn’t find anything suitable, I had three options, order something online, hack what I had, or just install one caster.

Long story short, I tried the last option, and even went as far as creating a new mounting bracket for one 3″ caster, but when I was done I then had to redo my ankle locks as there was now a backward tipping as well as the forward tipping. Hard to explain, but bottom inline I needed to redo my locks, which meant drilling more holes in the ankle that I wasn’t prepared to do….. back to the drawing board.

Because of time, and on Gerard’s suggestion, I resorted to trimming down the 3″ casters I already had. I mounted them in my drill press and filled them down.  It took forever, there was rubber dust everywhere, and it’s not something I want to do again.

What I’ve also realized is that never trust a label, the original casters were labeled 3 inches, but they were closer to 2 7/8th. Here’s a before and after comparison

After some finegaling, and making a new mounting plate,  I got them installed in the new foot – nice and level, unlike when I had the 3″ wheels.

Getting the right caster for the center foot can be tricky, it’s a balancing acts. You want the biggest wheel you can get fit, but because space is tight, the deeper you recess them to get things level the less space you have for a bigger wheel.

oh! and just as I was done with trimming the wheels, I went back and looked at one of the online stores I’d found earlier in the weekend, and what do I find – they’re LOCAL, or almost. They’re called California Caster and based in San Francisco, and had 100’s if not 1000’s of caster products in stock. I just had to make a trip up there. This was just a small selection of casters they had on display

Even though my new center foot was running again, I picked up these replacement 2.5″ wheel for the next round of maintenance.

I also replaced the radar eye with one I picked up from Dave Shaw many moons ago, luckily the old hole placement didn’t screw anything up. It doesn’t look too much different, and the wife thinks I’m crazy for swapping it out. I had the hardest time matching the Kryder blue, and it’s way to clean, but none of my panels match anyway 🙂

I can’t remember exactly what else I worked on, this was my droid on Sunday morning, all stripped down.

There’s been a long list of things I wanted to re-work, like shortening and re-routing some wires that were bugging me, to tweaking the front vents. I almost added servos to the utility arms, but that would require me filling them down and repaint – which I didn’t have time for.

But I did hinge manage to hing some doors in the body. I made some little aluminum brackets to help mount the servos to the frame

I know I worked on more stuff for Makers, but I can’t remember exactly what 🙂

oh! I remember, I’ve also been working on a small wireless controller based on a iPAQ Mobile phone, but more on that later.

Related:

• Proctor Glove Wheel Casters
• New Larger Casters and Angles
• Caster Fix and Test
• New Wheel Casters
• Fitting Casters for R2’s Center Foot

I replaced the original drawer slider bracket with something a little bigger. It’s cut from a piece of alu angle and makes the whole setup a lot more solid. You can see the original bracket in the background.

The slots make it easy to align on the dome ring

I still need to work on the riser below the periscope assembly and fix it to the lifter.

I’ve been busy prototyping a new periscope lift mechanism for Artoo.

Some of you may remember my earlier posts and videos demonstrating a mechanism I’d purchased from Daniel, unfortunately I gave up on it a very long time ago. In my opinion the design was flawed from the start and I never did get it to work well, but not for the lack of trying on my part.

Now that I’ve finished adding servos to the dome I was anxious to get the periscope working. I remembered seeing photos of Wayne Orr’s lift mech and thought I’d try and do something similar. Rather than fabricate something new he uses a drawer slide as the basis for the design and a small motor to hoist the periscope up on a platform.

The only catch with Wayne’s implementation is that the periscope and life form scanner mechanisms extend deep into the droids body. I don’t have this luxury as I’ve left the top ring cross bar in place to support the slip ring. So anything I come up with would have to fit within the approximate 10″ height restriction of the dome. The periscope assembly itself is around 6″ tall, so that would be the minimum requirement but if I could get more height that would be a plus as I could add an additional riser or have room for a servo to rotate the periscope once extended.

I’d shopped around and bought a selection of drawer slides, but couldn’t find anything shorter than 16 inches locally. Once I had them on the workbench I realized that it really didn’t matter because whatever extended out would need to be hacked off anyway. In the end I picked a 20 inch slider made by KV because it’s two sliding components worked in lock step, which was important to my design.

I removed the stops and hacked it down to just over 10 inches and cut a small section of the inner slider that would run up and down on the sliding bearing, which itself ran inside main track.

This is the start point with the slider on the right

And it extended all the way to the left. Notice the two part slider has moved and not just one piece.

Unfortunately I have to jump a few steps as I didn’t take many photos of my late night tinkering with the lift platform and various iterations of how I tried to move it.

I’d originally added a roller to the top (similar to Wayne’s) which would guide the rope, but in the final design it wasn’t really needed – and currently acts as the end stop.

Right now I have a fixed motor on the lift platform that pulls itself up with a piece of string attached to the top of the slider. It uses gravity to lower itself back down as the motor unwinds the string.

I’m using a small Vex motor, but basically it’s a servo that can continuously rotate, so I can plug it directly into my receiver without the need for a speed controller.

It looks like the platform is sloping in this photo, but I’m hoping it’s just the angle of the shot 🙂

Here’s a short video of it in action

I have a lot more work to do on this and not sure how well it will work inside Artoo, especially at an angle. My short list of things to work are:

• Add support to help stop the drawer slide shaking.
• Extra weight to the platform to help it lower.
• Make sure it’s all level
• Limit switches to stop the motor
• Possibly automate with the PICAXE micro-controller, rather than control it manually via the Futaba transmitter.

In closing I also wanted to mention that I’d experimenting with having a spring loaded wheel on the motor (same position as it is now) that would run along the side of the drawer slide to pull the platform along. I still like the idea and may give it another try later. It definitely had a smoother action and having a wheel on the motor made the lift a little faster – Unfortunately I couldn’t get the spring mechanism to work right.

I’ve finished re-installing the pie panels using hinges and servos, so now I’m starting to think again about the gadgets that pop out, like the Life Form Scanner as seen in ESB.

Yesterday at Ace, I found some perforated brass sheet that’s close to the screen material used in the movie. It was $25 and probably big enough to make at least 6 screens. According to the label the product is distributed by K&S Engineering, Stock No. 6412, UPC 6 76116 06412 2.

I’ll have to paint it silver, and the perforated design is not totally accurate but it’s close enough for me.

I’ve also been researching mini/compact power antennas for the Life Form Scanner lift mechanism.

Spent the last few evenings working on the dome pie panels, and after some tweaking I think I have a setup I’m happy with.

I ended up keeping the extra plate on the inside of the pie panel. It adds some detail and I like the sound the panels makes because of the extra weight. I left the hinges in the default configuration with no tweaks apart from drilling some holes to attach the servos.

I glued the hinges in place using CA glue, which sounds like it may not work so well, but I used the same glue on the hinges on the body and they’ve held up well.

Notice how the hinges are angled slightly to follow the curve of the dome.

I could have just glue the hinges directly to the dome, but I wanted to make the panels removable, so I created a small plate that glues to the dome and then then the hinges are screwed to it.

For the front Holo projector I’d purchased some push rod assemblies to attach the servos, but they were pretty expensive for something so simple, and I thought I could do better – this is what I ended up with.

It’s made up of some very cheap and readily available parts you’ll find at any hardware store. It basically some #4-40 and #6-32 screws in varying lengths, and short length of aluminum tubing that I cut up to make some linkages. I think it cost me less than $4 to make four push rod assemblies.

The long push rod is a #6-32 screw which attaches to the hinges via a piece of the aluminum tube that’s tapped at one end for the screw.

A long #4-40 screw passes through it horizontally to fix it to the hinges.

On the servo end I tap a small section of the tube on each side, and drilled a hole in the middle that allows the long screw to freely pass thru until I lock it on the side.

The servo is currently attached to the dome with some heavy-duty Velcro, which works fine right now, but I know it will eventually fail so I’ll be making a mounting brackets next.

Here’s a short video showing the setup in action

The next step is to wire all 4 servos into a PICAXE processor and tie it all together with some software to trigger sequences from the RF remote.

See Also:

• Dome Pie Panel Control
• Dome Pie Panel Hinge Experiments
• Discussion of my Pie Panel setup on Astromech.net – some really cool suggestions.

Adding hinges to anything on Artoo is tricky, with so many curves and often located in tight spaces it’s really hard to get things just right. I’d bought a bunch of the Robart “350” bomber door hinges a long time ago, and successfully added some to the power charging panel. They’re not cheap, but if you shop around you can find them for around $7 a pair.

There are other options that are cheaper, like the McMaster Carr steal hinges or the plastic one’s Calvin found for 30c. But the consensus seems to be that the Robart hinges are the way to go.

Some builders have had to reverse and trim part of the hinge to get them to work, but I’m not convinced it’s necessary for the dome pie panels. Here’s Keith’s explanation on how he uses them.

Most people seem to use epoxy to secure the hinges, but I also like how Calvin uses nuts and bolts for easy removal.

For my experiments I temporarily used adhesive foam tape, and played with several configurations.

I started off with Keith’s method of trimming and doubling up the hinges. I also added back the cut out from the inner dome to the pie panel to give it more weight and substance.

I found that by reversing and trimming the hinge, it has to sit right on the edge of the dome cut out – making it really easy to align – this is probably the only advantage I can see for flipping the mounting.

But I’m not crazy about how it look so close to the edge.

I also had to slightly file the inside bottom edge of the pie panel to get it to open cleanly.

For my next test I went the minimalistic route, and used a single hinge, configured the ‘correct’ way with it extending further into the dome. I also did not attach the extra cut out to the pie panel.

It was a snap to align and worked surprisingly well and opened just as easy as the first, if not easier. I suspect a servo would like the setup a bit better, being lighter and only having to move one joint. However, it felt more flimsy (obviously) and it would be super important to keep the single screw tight – which is hard to do on anything Artoo.

In summary – I like the heavy feel of the first option and how it sounds when it closes, but I also like the simplicity and cost saving of the second. I’m going to sleep on it tonite and get a second opinion tomorrow before permanently affixing anything to the dome.

Related:

• George Lucks Robart hinge page
• Calvin’s pie panel setup and servo attachment
• Robart website
  
• Google search best deal on the Robart 350 Hinges

I’m definitely getting into the fun part of the project. I spent part of the evening trying to add a servo to the front holo projector. It was a little more tricky than I thought it was going to be. I’d seen photos and vaguely remember a setup on one of the tables at C4, but until tonight I didn’t understood the nuances of the angles and forces need to move something with a servo, so it was frustrating and fun at the same time.

Most people seem to use the same basic method to move pie panels, doors, holo projectors etc. And that’s to convert servo rotation into a linear movement using a push rod attached to the servo horn.

I’d bought some random mini servos from Tower Hobbies a while ago (Hi-Tec HS-55), and a push rod/linkage assembly from ebay. Problem was the servo was too small to fit the rod attachments. I managed to improvise and this is what I finally came up with

Please ignore the kinks in the rod, it really should be straight, but I’d tried to copy what I’d seen at C4 and got it totally wrong 😀

If I was to do this again I’d probably skip the pre-made assemble and make something in acrylic and parts from the local hardware store.

I also created a short video to summaries and demo the new setup.

As I explain in the video it’s not perfect, and I need to affix the servo more permantely to the dome rather than using velcro and I’m not entirely confident the linkage to the back of the HP will last very long.

The good news the Hi-Tec servo is definitely powerful enough to move the HP and will probably work for the pie panels as well.

I also need to decide if I’m going to add some code to my micro-controller to automate random movement.

See Also:

• Slip Ring Servo Test

I replaced the failed Pittman dome motor last night, and thought I’d post some pictures of the failed gearbox.

The pen tip is pointing to the failed gear in the center of the picture. The teeth are almost stripped flat.

And this is the new motor opened up and how the gearbox should look. Again the gear in question is in the center of the shot. Notice the teeth!

I’m not confident that it will not fail again, and I may need to look at an alternative. I’m hoping the issue was my failed attempt to use batting tape to line the dome bearing to help with traction, but the gear may have been slowly failing with the constant harsh stop/starts on such a small gear. I know of at least one other builder that had a Pittman dome motor fail in the exact same spot.