February 2008 Summary

Summary of posts for February 2008

Posted by Chris on February 29th, 2008 in Update | Comments Off on February 2008 Summary

Rear Door Magnets

Now that WonderCon is over I’m hoping to go back and post details on the final few steps of my build – I’m probably going to post some things out of order, so you may see some things in the photos that I’ve not covered yet.

First up is the the rear panel/back door. I’d deliberated this for a while and tests a few different methods before finally settling on using the rare earth magnets.

I’d bought a bunch of different sizes, with the intent of using them on various spots on the droid.

One of my fears was the smaller magnets wouldn’t hold, and if I’d went with the larger magnets they’d get in the way of my movable electronics panel, or the door would be impossible to remove.

Frank Cerney had posted a few months ago about using 1/2 inch cylindrical magnets (NSN0818) from Magcraft successfully to hold the door on a wooden frame, so I decided to do something similar. Here’s Frank’s original implementation –

Frank Cerney Door Magnets

I don’t have the luxury of being able to drill holes in a wooden frame, so I needed to come up with something to hold the magnets to the skin. On hindsight maybe I should have gone with square or block magnets instead, but I was stuck with what I had on hand.

After a few experiments I ended up cutting some aluminum U channel into 1 inch chunks and bent them to clamp the magnets.

The gap is slightly narrower than the magnet, and I simply tapped the magnet in making sure they matched the opposite one.

I then took my CA glue and excellerant and glued them to the skins

I could have used epoxy, but I really wanted this to setup quick without worrying about clamps, movement etc. It seems to hold okay, but I still may still go back and re-enforce them with some epoxy at some point.

Here’s the skins/frame assembled showing the final location of the magnets

One of the issue of using the magnets to hold the door on from the sides is that the force pulls outward, instead of pulling or holding the door tight toward the frame/skin, like if I’d used screws to hold it in place.

You probably can’t tell from the photo, but this results in the door,which naturally curves a little tighter than frame, to bow out at the top.

To combat this I added a tab which will pull everything together and hopefully add a little more hold and reduce the strain on the magnets.

Again I used CA glue to hold it in place

I topped everything off by added some white tape to the inside line of the skins.

Remember I’d had a problem closing the gap at the bottom of the door once I’d cut it from the skins, so rather than fight with it – I simply masked the problem by covering the raw aluminum which blended the door into the skin. I have to thank my wife for this suggestion.

Due to the electronics panel having to swing out I had to either attach the rear power coupler to the door or make it removable from the frame. I opted for the latter as I didn’t want additional weight on the door.

I simply cut a chunk of metal (not aluminum) and secured it to the back of the power coupler. I then used a large magnet on a bracket on the frame to secure the power coupler and allow me to pull it off when needed

The good news is the door holds on great and I had zero problems with it at WonderCon – it even held on even when I did the R2 death spin 🙂

Posted by Chris on February 27th, 2008 in Body | Comments Off on Rear Door Magnets

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R2 Meets The Doctor

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Posted by Chris on February 26th, 2008 in Events | 1 Comment

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WonderCon 2008 Show Report

Thought I’d post a quick show report for WonderCon and our “R2 Droid Building Basics” panel.

I’m just about recovered after a real busy few weeks. It wouldn’t have been so bad if it was just the event, but I had a droid to finish which meant lots of late nights – but isn’t that always the way.

Luckily the day of the event went pretty smooth. With some help of some friends who showed up early to help us unload, Gerard and I were in and setup by 8:30am. Doors opened to the public at 9am, and the fun started. We spent the morning zipping around the convention entertaining the crowds.

We didn’t have a booth or anything as there’s too few of us to run it, but we were luckily to have access to the 501st break room to store our gear and charge our batteries.

People love the R2’s and were surprised to see one, then realized there were two of them running around.

I think Leia couldn’t decide which one to send on the secret mission!

Which one do I send on the secret mission?

The first glitch in our plan was the carpets – for some reason our droids didn’t like them at all. At C4 I didn’t have any issue with any of the floors, carpeted or not, but at WonderCon it seemed to sap our batteries really quickly. We’re both using JAG drive systems and NPC motors, and were getting around 60-90 minutes of runtime on about 21Ah worth of batteries. Compared to C4, my droid is a little heavier, but only by 20lbs, and I was getting closer to 3 hours off of the same battery system. [edit – see the following post for the diagnoses/fix]

My stand by set of batteries also had a problem which made me late for the Rebel Legion photo shoot, but Gerard made it.

At 1pm we started to get ready for our panel. People were already lying up outside anxious to get a seat – which surprised me. Turn out was great, with about 80 people in attendance and lots of questions were asked. Don made a brief appearance at the end too which was great.

R2 Panel

R2 Panel

Our panelists of local builders were –

Gerard Fajardo
Ryan Goff
Chinh Nguyen-Duc
David Calkins
Chris James

Panel Description –

R2-D2 Droid Building Basics Come meet local builders who will share their experiences and demonstrate working droids. Topics range from materials, tools needed, basic electronics and radio control information to make your own R2 come to life! This panel sponsored by the R2 Builders Club.

Thanks to Andy S for his slide deck which ours was based on. If anyone would like a copy of ours please let me know.

We did try and head into the dealer room in the afternoon, but it was way to busy and again the carpet was slowing us down. So we opted to stay closer to the main entrance on the tile floor. On the way out we did come across Doctor Who and a Dalek who was fascinated by our domed friends.


My photos from the event are here, and my favorite has got to be this one

Will you be my friend?

There’s also some photos on the Official Star Wars Blog Flickr pool

I’m hoping to be back next year, maybe with more droids in attendance (and bigger batteries)

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Posted by Chris on February 26th, 2008 in Events | 2 Comments

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Some more weight stats

R2 Weigh inAs I was reassembling Artoo last night I took the time to weigh some assembled pieces as they went on.

Remember my droid is almost all aluminum and steel, and there’s always a lot of debate among builders about material and saving weight, so I thought it maybe good to report in on how things break down.

I did a weigh in last summer on my partially completed, but functional droid, and he came in at 155lb with the dome. I was expecting a big increase but was pleasantly surprised.

Each leg, including the foot, motor, motor mount, wheel, caster, battery box, hoses, wiring and the detail pieces comes in at is 32lb. I didn’t have the horse shoe or booster cover, and I’m guessing I could add another 5-7lb per leg for those.

The body/frame with the skins, internal battery hold, center leg mount, electronics and the detail pieces comes in at 50lb. This does not include the batteries. I was surprised it wasn’t more considering a raw JAG 4 aluminum frame is roughly 30lb.

Center leg with casters and detail pieces was 14lb.

The body has three 12V 7Ah batteries, totaling 10.5lb.

Give a total of around 153lb for everything but the dome, which is unchanged at 17lb and includes a single 1lb 12V 2.2Ah battery.

So I’ve gone from a 155lb to a 170lb droid which isn’t bad. I’m going to double check with a bathroom scale tomorrow, as I’m really surprised it wasn’t more.

Posted by Chris on February 21st, 2008 in General | Comments Off on Some more weight stats

Back Together

Another quick post. It’s been a very long night but I’ve finally got Artoo’s back together and running around.

This is the first time he’s actually looked like R2-D2, I kinda miss the raw aluminum look but I’m super excited to finally get to this stage in the project.

I still need to fix and add a few minor things for WonderCon on Saturday, but if I had to do an event right now we’d be set to go.

I’m heading to bed to try and catch up on some sleep while R2 charges in the garage overnight.

Posted by Chris on February 21st, 2008 in General | Comments Off on Back Together

Mostly Armless

Another long weekend with late nights rushing to get R2 done for WonderCon.

I thought I’d take a break and post a few quick photos of where I’m at. I’m pretty sure I’ll have Artoo back together by Friday, it’s now down to deciding what do work on and what to leave out for now.

All the electronics and RC stuff have been upgraded and re-installed in the body with an all new wiring design. The charging system works a treat, and I can even run him off 120V when he’s parked up somewhere.

Legs and feet are also done waiting to be put back on, but before I can do that I need to finish up a few things inside the body.

Tonite I’m fighting the back door which is the last big annoyance that I need to work around. I was hoping to use magnets to secure it, but it’s not really working out too great. They hold it on fine, but it’s the alignment I’m not happy with, and there’s a balance between using strong magnets that take up a lot of space and block access to my swing out electronics panel (which lets me get at the batteries), or using smaller one’s that don’t quite hold well enough and don’t pull the door tight to the body or sags in spots that spoil everything.

I’ve got a feeling I may end up using screws or just leaving it off for the event.

Sorry for the lack of detail tonite, I promise to go back and cover all the work I’ve been doing the last few weeks 🙂

Posted by Chris on February 19th, 2008 in General | Comments Off on Mostly Armless

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Charging Jack LEDs

I’ve been busy most evenings this month getting ready for WonderCon, but thought I’d stop and post this new addition which I’ve been working on and off for a while now.

I’ve expanded my battery charging port to include some LEDs. The flashing pattern is based on the scene in ESB where Luke and Artoo meet Yoda for the first time.

The whole thing is driven by a 18X Picaxe board with some custom code. I’d originally planned on using some simple timer IC’s, but thought this would be a good project to experiment with Picaxe.

I’ve tried to capture the LED sequence the best I could, but it’s only shown straight on for 10 seconds, and even then it’s obscured by the door some of the time.

To get to this point I had to create a new acrylic mounting plate. I still need to wire in the new charging circuit Bob helped me redesign, but this was the first step in the process.

I went through several iterations and prototypes to get it to fit and work around the Robart hinges. Hence the slots on the left hand side.

I’m hoping to fix it to the 12V charging socket and use it to mount to the metal bracket I made a few weeks ago as part of the original charging circuit.

It’s also been a steep learning curve the as I’ve not really done any major thinking about complicated electronics in a very long time.

I’ll try and post more details in a few weeks, but here’s the completed circuit after a few late nights. I may switch to a smaller Picaxe, like the 08M, as the 18X is a little bit of an overkill for this project. But the price is negotiable in the grand scheme of building a droid. I’d have to guess the whole circuit costs less $35, but in the process I had to buy a bunch of stuff to figure out how to get it to work.

Here’s a a close up of the LED matrix connected to the PICAXE board.

I also had to create a voltage regulator circuit to power everything directly from the batteries as the main power distribution board will be isolated/turned off when the batteries are charging – and the whole point is for R2 to show some bling while he’s charging right?

I ended up using a LM7805 which will step down the 12V supply to the require 5V.

When I get a chance, the plan is to eventually make the LED’s display the current battery voltage when I press a button as the Picaxe 18X has a built in voltage reader.

Posted by Chris on February 13th, 2008 in Electronics | 9 Comments

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