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 almost finished the electronics and programming to control the new hinged pie panels. I’m using a small 18X PICAXE micro-controller coupled with a few buttons on the RF remote.

Check out the video of the panels in action.

I’m also in the process of replacing the veclro that attaches the servos to the dome with something a bit more permanent. The brackets are made from aluminum angle (1.5″x1.5″ and 1/16″ thick).

They’re attached to the top of the hinge and the bolts from the mounting plate that already fix to the dome.

As a side note, if I was doing this again I’d adjust the hinge position a tad. The pies open to the vertical position, but it would have been nice if they’d open a little further, and I figured out (too late) that the lower the hinge is on the pie panel the further it will open – but too far and the hinge will not clear the dome properly.

See Also:

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

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.

I’ve received several emails recently on where I got my 3″ wheel casters from. These are the exact one’s used by Mike Senna and Victor Franco, so I can’t take credit for finding them – but the question keeps coming up , so I thought it might be a good idea to post the information I have.

I have no idea why these seem to work better than others, I think it’s a combination of the dimensions and having a soft rubber wheel that works on variety of surfaces – and the price is right too.

My first set came from a friend in Southern California who bought them at the Arrow/Ace Hardware in Yorba Linda (714-524-1621) for $7 each. Once I had them in hand I was also able to get my local Ace Hardware to order me some spares.

Here’s a close up of the label that might help –

Manufacturer: Proctor Glove
Part Number: 3RS
Description: 3″ Rubber Swivel 125lb
UPC: 7 80272 000003 7

They’re made in Korean and sold by Proctor Glove Co. who are located in Santa Fe Springs CA, or more specifically:

11122 Shoemaker Ave
Santa Fe Springs, CA 90670
(562) 903-1320

I don’t think any builder has called them up directly to try and order, but if you are successful please let me know and I can add it to this post.

A builder contacted them a few years ago and did a run of these, including offering the rubber wheels in softer or harder variants.

Related:

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

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 had to find a better way to mount the RF remotes to my new Futaba transmitter. I’d originally had them mounted to the sides of Vex transmitter, but really didn’t want to go this route this time around.

I’m still toying with the idea of taking the electronics from the two RF remotes and installing it all in a custom box that would look similar to the Vantec HitchHiker /keycoder, but it’s been almost a year since I blogged something similar, and I’ve yet to do it 🙂

After some experimentation, I went with a very simple acrylic bracket to fix the main RF remote on the front of the Futaba, making it very easy to control with either hand. It does cover the screen, but to be honest it’s rarely used and the bracket is easily removed or lifted.

The bracket is only secured in one spot, the bottom of the Futaba with Velcro for easy removal.

I mounted the second RF remote sideways on the battery compartment on the back of the Futaba. Right now it only has functions that aren’t used often, so I don’t think it’ll be to inconvenient having it there.

The only real catch with this setup is the antennas, occasionally I’ve found it necessary to extend them if I get to far away from Artoo.

Summary of work and events for June 2008

• Futaba Setup and Tweaks
• Futaba 10C Arrived – It’s a 10 channel 2.4Ghz FASST spread spectrum capable receiver and a big step up from the Vex transmitter I’ve been using.
• RoboGames 2008 Report – the weekend was jammed packed full of interesting people and very cool things – like talking with the engineer who worked on the NPC motors many of us use in our droids, or hanging out with the Orb Swarm folks or Grant Imahara from Mythbusters, or getting some inside info from the engineer who maintains the machines that spin our aluminum domes. Artoo even got in on some battle bot action in the arena and lived to tell the tail.
• RoboGames 2008 – Day 1 Highlights
• Trip to Ace
• RoboGames 2008 This Weekend
• Dome Electronics Rewire
• New Larger Casters and Angles
• Center Foot Wedges
• JAG Center Foot Mod – Lip/Skirt
• We’re in Bantha Tracks this month
• Battery Terminals
• Caster Fix and Test