Plexitube Owl Clock

April 4, 2016 by Kurt

For Christmas I designed and built six steam-punk owl clocks that have a novel faux Nixie Tube display. Nixie tubes are wonderful with their glass tube bodies and brightly glowing numerals, but think how wonderful a solid-state low-power any color “Nixie Tube” would be!

The basic idea is that you position an LED at the edge of a piece of acrylic that has a pattern laser-etched into its surface, and the LED lights up the pattern. Long ago I’d realized that a stack of 10 laser-etched digits with an LED to light up each digit might have the same visual charm as a Nixie Tube, and the Plexitube was born.

I’m pleased with the way the project turned out. I’ve put the software, circuit designs, and illustrator files up on github. I even made a short video of one of the clocks in action. The project has even gotten some attention from Hackaday and won this Reddit unconventional clock competition. Thanks a lot guys!

At the time it was unclear if light bleed between the layers would make the digits hard to read, so I sat on the Plexitube idea for a long time waiting for a project that could use that kind of display.

Then I went to work at a new company, and I had to spend an entire day listening to benefits summaries and corporate on-boarding. To pass the time, I started to do some sketches of an owl made from only two pieces of wood. I used my Swiss army knife to cut my co-workers’ name tags into owl prototypes. I really liked the design, and I thought it would be perfect for an owl-shaped clock with Plexitube eyes. Would this be this year’s Christmas Project?

I can’t really start a Christmas Project until after the Halloween Costume builds are done, but this project couldn’t really take shape until I’d at least tested the viability of the Plexitube. I figured if I just spent one evening laser-etching a digit stack and holding it over an LED, I could figure out if the displays were going to be an unreadable mess. If it failed, I could pull the plug on the owl idea before they got out of the paper prototype stage. So I spent one of my Wednesday nights making a prototype stack.

The prototype stack had a lot of issues. The back digits where hard to read, there was a lot of inter-digit light bleed. I really couldn’t say for sure whether this was going to work. That’s pretty much the worst-case scenario for a make-or-break prototype. Really, I should have just stopped then, but I couldn’t stop thinking about the nice owl shapes.

The Impossible Project

Halloween came and went and I needed to decide. I even went so far as to do some prototypes of an alternative project that was much simpler, but I could tell that the owls were the ones that wanted to be made. I’m usually pretty careful planning one of these projects, and never before had I taken on one that had so many BIG unknowns. I’d never worked with surface mount electronics, never bent wood to such small radii, never designed a PCB with a lot of exact physical layout constraints, and never used an in-circuit programmer. I decided to go for it, but I knew I’d have to get first-time-success-lucky on a number of things, and I told my coworkers that I did not expect to succeed.

Two months and counting

Time to make a lot of quick choices and order stuff from China. I chose the popular Neopixel surface mount LED as my light source. They could be any color and all 40 of them could be controlled using just one pin from my controller. I decided to go with the ATMEGA328p, which is the same chip in an Arduino UNO. I was building 6 clocks, so I’d need 240 LEDs. I ordered a reel of 500 from China, along with some surface mount capacitor and resistor assortments, photo resistors, and some DS3231 real-time clock modules with battery backup. Ordering things from China is very cheap, but it can take a few weeks for the stuff to show up, so I had to get that moving quickly.

Now ordering printed circuit boards from OSH Park takes something like 10 days, so I really needed to get that in the pipe. If the first set of boards were a complete blowout, I could still get a second order in, but I had to hurry.

The LEDs I was using are much fatter than that 1/16″ acrylic layers I was using, so each layer needed to have a sort of integrated light guide leg that would stick out and sit directly above the 3 tiny color chips inside the LED. The alignment had to be exact. So I measured an 10-layer alternating stack of acrylic and black card stock to get the exact spacing, and then I had enough info to begin laying out the PCB.

I used Eagle CAD and finally had to spring for the non-free version so I could work with more than one page of circuit. I had to use some tricks with the Grid to get all the LEDs laid out in the exact right locations. After a full weekend of fighting with Eagle, I had something I could send off to OSH Park. I also quickly ripped one eye segment out into another file and ordered 3 small “test boards,” so I wouldn’t have to do my first attempt at reflowing a surface mount board with one of my giant and owl boards.

Then it was back to working in Illustrator on the design for the acrylic digit layers, black card stock separators, etc. I customized the digits of a font to make them slimmer. All the digits obstruct one another, so I wanted something that was lovely, but was mostly empty space so other digits could shine though. I also did some tricks like make the zero (which is in the back) a bit bigger/bolder so it would still read well though all the other digits.

Secret Symbols

Now on a clock there are 4 digits, but not every digit needs all 10 numerals. Heck, the tens of hours digit only really needs a 1. That leaves 9 layers for other special non-digit things. I could, in theory, have put some extra digits in the back of the tens of minute digit since it only goes 0-5, but I decided if I was going to be showing other info in those lower digits, it would be better to have all the digits there. I also decided to keep the 2 in the hour-tens digit so I could support 24-hour time in the future, and show a full year like 2016, etc.

I wanted to show the phases of the moon, sunrise and sunset times, moon rise and moon set times, etc. I used 6 of my 8 free digits doing the arcs of the moon. Because all the layers are at different depths, I staggered them so the arcs actually make a 3D sphere shape with the middle most arcs at the front. That left me with 2 layers. I used one for a sun outline that could be used along with the arcs to show things like the equinoxes/solstices.

The Magic Eye

That left me with only one free layer, which I used to add the outline of an eye. I realized that the arcs could be used to animate a slit-pupil eye looking back and forth. Of course I needed that! My owls eyes have eyes?! Yes … yes they do.

Plexitube Assembly

Each eye element can display two digits, and they are laboriously assembled by stacking 20 digit layers and 20 paper masks on 4 brass pins in careful sequence. Thankfully, the digit layers were fairly easy to keep track of because they already had digits etched into them! Each acrylic layer has to have its protective plastic peeled away, and its etching scraped and dusted. Because the pins are press-fit, I had to carefully push them down on the pins without cracking the 1/16″ acrylic. The first stack took me 2 hours to assemble. My finger nails were frayed from all the plastic peeling and I had 11 more elements to make. What had I gotten myself into?!

First Reflow

Finally the owl boards came! I had also ordered a solder stencil from OSH Stencils. When making a board like this, the basic process is a bit like silk screen printing. You position the PCB under a stencil and squeegee solder paste though the stencil holes onto the board. Then you place all the itty-bitty components onto the board with tweezers. Finally you oh-so-carefully put the board in an oven and heat it up until the solder paste melts and the parts all snuggle down exactly into place via surface tension. A while ago, I had built a special computer-controlled toaster oven in order to do just this process, but I had never used it!

I kept waiting for my test boards to show up, but eventually I gave up and decided to do my first reflow on one of my giant and indispensable owl boards. I populated the board, put it in the oven, and pushed the button. Then I held my breath as the oven went though its 3-minute cycle. Success! The board came out looking perfect! It looked like something totally commercial, not something I’d made with tweezers and a toaster oven. MAGIC! Surface mount is awesome. I’m never going back!

Ok, so the board looked like it was all soldered up, but would it work? I hooked the LED chain on the board up to an Arduino UNO (remember how those NeoPixels can be driven by just 1 LED?) and some quick code showed that all the LEDs were working! I blinked each one red-green-blue to test and they passed with flying colors! *phew*

Now for the real question: would the digit display actually look good or was the whole thing going be two months of work for an unreadable mess? I wrote some code to cycle though the numbers and positioned the eye module over the LEDs. It sort of worked, but it wasn’t great.There was quite a bit of cross lighting between digits, especially between digits 1 and 2.

I was extra sad I’d left that 2 in the hour tens digit. No one wants to look at a clock and not be able to tell if it’s 11:14 or 22:14. Something really needed to be changed. But what? I did, however, decide to get my second round of PCBs made. OSH Park sends out 3x boards, so if I wanted 6 by Christmas, I’d have to order the second round pronto.

I spent an evening designing a nice owl icon to put on the second round of boards, added two regulator bypass pins, and then sent the thing off. No time for anything fancy. It turns out the icon was a fail. Even though I followed OSH Park’s guide lines it did not render properly.

Eerie Is Good

One thing I did notice while I was running that test is that although the digits were not yet crystal clear, the whole thing had a very eerie feel to it. It was almost as if I couldn’t quite tell what the heck kind of technology I was looking at. It sure didn’t look like LEDs. The layers of acrylic have a wonder full “hall of mirrors” effect on the lit segments. I also noticed that the light bleeding off the tops/sides of the eye element were kind of hypnotic to watch go through their sequence. I had originally planned to cover the elements with a ridged copper cylinder segment, which would have looked steam punk, but not as strange/cool as that bleeding light. I decided to leave them uncovered.

Back To Body Work

Now that the boards and the eye element design were mostly settled, I had to get back to figuring out how to design the bent body of the owl. I did a second pass of designing the body in cardboard. I knew that trying to bend 1/8 plywood into a loop maybe 3 inches in diameter was going to be tricky and might be impossible. In a recent build, I’d used laser “kerf bending” to make it easier to bend curves in thicker plywood. Could I take that to an extreme? MicroKerf Bending™? I tried spacing the kerf cuts .1″ apart, cutting almost all the way though the plywood. The results where a satisfyingly bendy piece of wood. Still the owl has some very wide sections at the top of his eye arches and those were still quite stiff. Too much variation to be able to bend into a loop.It would have been nice to write some sort of script that would space the kerfs closer/wider based on the overall width of the piece, but I had to settle for just doing a few different spacings by hand.

The brows above the eye were delaminating when I’d apply the bend. That was bad. I fixed it by pre-sanding the upper layer thin in those areas and by putting a few little spring clamps on those edges during the bend. That solved the problem, but all these iterations on the body design were burning up time at a crazy rate. Would I make the Christmas deadline!? Here I’d been thinking I was saving time by having most of the owl form come from just one piece. So wrong.

Steaming and Clamping

I built a clamping jig out of a big board and carved away clearance for the owl feet. I’d steam an owl body in a pot on the stove and then bend it with my gloved hands whilst racing out to the garage to clamp the body around the face in my special jig. The first time I did this the face of the owl split in two! Yes, when the body is looped back on itself and clipped tail to feet the forces on the face are nice and balanced, but while you’re bending that around the forces on the face are actually pretty big. So I changed my clamping jig so it would support the face during the bend. Finally, it worked!

I had a lot of other little issues. I had to add some “foot prop” pieces so I could have a way of evening out feet after the main clamping was done. I thought I’d be able to adjust the owls stance by adjusting the tail angle, but a sort of scissoring action made it so any amount I pushed up the tail also pushed up the feet, canceling out the adjustment. So the owls look down a little bit more then I’d like. That’s okay though because they like to nest up high.

I wish I could have used 1/8″ mahogany plywood. Then I wouldn’t have had to deal with staining the outer body. However, that’s not something I can get locally so I was stuck with stain. I hate stain. I tired pre-staining, which gave nice crisp edges at the stain boundaries, but that made the gluing a lot weaker. I tried post staining with with pre-clear coating areas to try to reduce bleeding over, but it still bled some and required lots of awkward sanding to fix. If I had it to do again, I’d try to get hardwood ply. I did eventually get them all glued and stained.

The Secret Sauce

I’d been thinking about my eye element problems. How could I improve the contrast? I already had black card stock all over the place blocking as much light as I could. I realized that as tight as the fit was around the card stock, there were still micro gaps, and the light leaks I was seeing were probably coming right up from the LEDs and into the clear bottoms of the other segments. I decided to use a small brush to paint some black acrylic into those areas! EUREKA! That fixed the problem entirely and now the displays looked great.

Christmas Eve

It was Christmas Eve, and I was still clear-coating owl bodies. Applying wood finish on Christmas Eve is par for the course for me. The big issue was that I was still driving the displays from a separate Arduino and hadn’t fired up the on-board computer at all. I spent a while reading about fuse bits and fighting with boot loaders, and fiddling with Arduino IDE config files. Had I made some mistake with as-yet-untested parts of the PCB? Could I get lucky one last time on this “impossible” project? Yes! At last, I was able to program the chip on the clock board, get the real time clock synced with Greenwich Mean Time, and put enough code in the clock that it could actually display the time! The clock could go under the tree.

Software in the New Year

Early on I had decided to punt on all but the most basic software until after Christmas. I had pages of ideas on fancy software features, and I knew I’d have enough trouble just getting the things physically built by Christmas. This was going to be a Christmas gift with an eventual “firmware upgrade” gift chaser.

I knew there was going to be a lot of software, so I wrote a iPhone owl clock simulator to give me an easier platform to develop some of the code. I had been reading Jean Meesus’ Astronomical Algorithms, and I wanted to have the clock not only show the phases of the moon, but be able to display sunrise/set times and moon rise/set times.

I had included a light sensor on top of the clock so the clock could dim a bit when it was in the dark, but it could also tell if your hand waved over the clock and maybe then it would cycle though showing the sun going though sunrise colors while showing the sunrise time and the show the sunset time while cycle though the sunset colors.

Color Picking the Old Fashioned Way

I really wanted to use nice colors in the clock, but just choosing 3 numbers for Red/Green/Blue doesn’t tell you what those are going to look like in the final display. I needed a way to search for good colors. So I made a super simple color picker by hot gluing three potentiometers to a board. I used an Arduino UNO to read the three RGB values and display the color on a jury rigged LED + acrylic digit. Go Go gadget gaffer’s tape! The program would print the values out to the serial monitor. That way I could find just the right pink by fiddling with the knobs and then write down that RGB triple from the screen. I used that to make a whole pallet of colors I liked.

The Trouble With Doubles

The big problem was that most of the Astronomical Algorithms need double precision math. The solar system is big and you need the precision, but the Arduino tool chain doesn’t have real double precision math. I spent a while (stupidly) writing a math lib that did approximate double precision math using two single precision float values based on this paper targeted at GPU computation with floats. I did get the math working, but to my horror, I discovered that the code it produced to compute the equinoxes/solstices was so huge that it didn’t fit into the 32k of memory on the ATMeg328p. That was a huge waste of time. I did, however, use the code to generate the next 100 years of solstices and equinoxes and compress them down into just 100 bytes of Progmem, but the sunset/sunrise times were doomed. I went back to some still usable moon calculation code so the clock can show the current phase of the moon.

Then I wrote a lot of silly features. On the clock recipient’s birthday, it displays in their favorite colors. (And on their kids’ birthdays, their kid’s favorite color, etc)

I wrote all the code to set the time/date/gmt offset with nice auto repeat ramp ups and useful icons. (When you’re setting the month a sliver of moon shows, when you’re setting the day there’s a sun icon, etc) I even used the right arc of the circle to show AM and the left arc for PM like they were the first and second parts of a 24 hour clock face. Not that I expect people have to set the time/date much, but a clock needs to do that.

The clock counts down to midnight on New Year’s Eve and shows fireworks and a spinning golden globe at midnight. On JRR Tolkien’s birthday, the the eye of Sauron looks around and sometimes a golden ring spins and the digits are red and fade up and down like like a breathing beast. etc. I don’t want to give to many surprises away.

Needless to say, there are a year’s worth of Easter Eggs in the clock code, even on Easter.

Two Words “Optical Theremin”

When I was working on the auto-dimming feature, I wanted to have a direct readout of the light sensor, so I could fine tune a mass/spring system for the dimming rates. When I first hooked it up, I realized that with a much stiffer spring it was pretty neat to play with. You’d wave your hand over the clock and the digits would smoothly go up and down. It was kind of mesmerizing.

I was showing it to a friend, and when I started waving my hand around he said, “Wait, it has a Theremin too!?” and the Optical Theremin was born. I hooked that code up to the hue of an hsv conversion and now when you press the down button, you get one minute of “Optical Theremin” where waving your hands around changes the colors and numbers in a soothing and lovely display of Plexitube awesomeness.

It’s hard to stop writing code for the clock, but after the “Optical Theremin” feature, I started getting close to the memory limits and I decided to call it quits. It was time to give out festive springtime firmware upgrades! I had been trying super hard to have the code all done before the spring Daylight Savings Time change because people had clocks they couldn’t set! I only missed that deadline by a week. I blame double precision!

Clarence was starting to think that perhaps this hazing ritual was going a bit too far…

Angels and Devils: Making A Smoking Man Candle Holder

January 31, 2014 by Kurt

Every year is build a big Christmas project. Usually I get started on those projects right after Halloween, but this year I started way late. At Thanksgiving, I was sitting out on my sister’s porch and finally managed to sketch something that I liked enough to build. The problem with such a late start was that I kept thinking, “I need to keep it simple, and depend more on excellent design rather than absurd complexity.” This would have been great if I hadn’t eventually let the “keep it simple” part fall to the floor.

In Germany, they have Räuchermänner (smoking men), which are little wooden figurines that have a small compartment to hold an incense cone. The burning incense smoke comes out of figure’s mouth. I’ve always wanted to make one. I considered traditional figures like a hunter, and wackier ones like a dragon, but eventually I decided it might be fun to make a devil with smoke coming out of his mouth. A lot of German Christmas decorations have angels on them, so I thought a candle-holding angel and a smoking devil would make a nice contrasting pair. I started some sketches and paper cut-outs, and I finally started designing the thing in earnest on Dec. 5th. That was an epically late start.

I still had some 1/4″ mahogany plywood left over from the Egyptian labyrinth project, so I decided to use that for the devil. This turned out to be a big mistake. The devil wing design had very thin spars that would have been trivial to cut out of 1/8″ plywood. If I had used 1/8″, the laser could’ve been cutting quickly enough that I wouldn’t have problems with the wood heating and catching fire. Since I had committed to 1/4″, I had to develop an entirely new technique where I cut the devils in three passes, using a syringe to put water into the cuts at each wing tip and pointy corners that would otherwise smolder during the subsequent laser passes.

This worked, and it gave the devil an interesting burned look, but having to develop this technique burned a lot of my laser time. Christmas was fast approaching, and every minute on the laser was precious. I found myself sprinting back and forth to the bathroom with syringes of water. Not good. I also discovered that if you’re cutting multiple passes in wood, it’s best to orient the cuts so they are perpendicular to the direction of the compressed air blast at the cutting head. Otherwise the compressed air can blow along the cut and fan any sort of smoldering wood you may have left in your wake.

I really do not like multi-pass cutting. The wooden bases for the project were thicker than the devil wood, and I was able to cut them very, very cleanly in a single pass. It’s oak, and the tiny holes you see are vessels that form in the spring. You can see how they’re not blocked by sawdust and the radial rays are clearly visible radiating out from the center of the tree like spokes on a wheel. I cut this at 300 pulses per second, and you can see the tiny grooves left by the pulses. There is no charring or need to sand the edges. It’s lovely, but I was careful not to have any thin sections or sharp points in the outline of the base.

The devil was hard to cut, and he turned out to be somewhat tricky to assemble as well. I had to hand miter the top edge of the curved side pieces. I also had to glue a paper smoke dam into his neck since the top of the devil’s body had to be airtight to prevent leakage of incense smoke from his neck. The first two devils that I assembled still leaked a thin stream of smoke from that seam. In later versions, I suspended the assembled devils upside down and dabbed white glue down into the peak with a long stick to make sure the seam was sealed.

Another way that the devil was much harder to assemble than the angel was the slanted back. The angle forced me to hand sand a bevel on the base. The curved sides made it tricky to attach the front since I needed to push the sides out to get them into the curved groove on the front face, but without disturbing the anchor pieces, and without knocking the bottom plate out of whack. So it was an exercise in white glue octopus wrestling. If I applied too much clamping force, the slanted back would cause the base to come squirting out and whole process would begin again.

By the sixth devil, I was quite adept at this, but the first few had some unenviable gaps, which thankfully were not visible from the outside. I like the way the devil’s beards came out. They’re the hidden shape of a swooshing bat. I did some hand wood burning on the horn segments to make them a bit more interesting. The biggest disappointment with the devils was that when I finally applied the clear coat, the contrast between their faces and the facial hair dropped unexpectedly, and by then it was far too late to switch to black walnut or something else.

I like the way their gnarled little fists came out. Complete with thumbs! They’re made from three stacked segments glued together and then glued to the devil’s front. Here you can see the pieces ready for some dabs of glue.

The first two devils I cut had some burning on the inside corners of the belly door. This was because I hadn’t realized those corners also needed some water injection. Later devils didn’t have that problem, but to cover the first two I hastily designed some little feet I could glue on over that area. This design change is why you don’t see any feet in my original sketches.

I also had to punt on having a tiny flame theme around the incense holder because there simply wasn’t enough room, so I switched to a simple ring. The copper pan that the incense sits in was cut from a 1/2″ copper tube cap. I used these both for the incense cup and the candle holder.

I chucked a piece of 1/2″ copper pipe in the lathe and used that to hold the end caps so I could cut them off at two different depths with a parting tool. The only annoyance was that removing the remaining ring of metal from the 1/2″ was hard to do. The parting operation squeezed the copper rings so they were hanging onto that pipe for dear life, and I had to pry them loose with a giant flat-head screwdriver and a lot of elbow grease. Good thing I only had to do that twelve times.

Once the feet were on and the door was done, the only thing left to glue on the devil was the head of the pitchfork. I always glued that on last because it’s cut from thin sheet, and there’s no way to orient the grain of the wood to make them strong along their whole length, so they’re quite fragile between the tines where the grain cuts directly across those narrow sections.

The angels were comparatively simple to assemble. I carefully positioned them on the maple board so the maple’s figure would form the folds of her skirt and sleeves. I used different wood for her face, neck, and hands. I used a layering effect with the hair to try and keep her head from looking too much like 2D extrusion. I was going to try layering the area with her ear back one layer to make it even more 3D, but that would have required some more hair fragments, and a bit of iterating on the laser to get the ear size just right. Eventually I punted on that plan. So her head is a bit more of an extrusion than I would have liked. Oh, well.

I did have to have a slightly tricky clamping rig to glue on the top wing mounting bracket. I used a laser-cut scrap to match the shape of the bracket and make the clamping possible. Then I used some clothes pins to keep the scrap aligned while I tightened up the other clamps.

The only materials disaster I had with the angels was that the 1/8″ plywood I used to make the wing spars was defective, and some of the spars had their topmost layer of wood just fall off. I had to re-cut a bunch of them. I’d never had that happen before. I used clothes pins to provide even clamping force when gluing the spar to the feather veneer.

I had originally thought about using white paper angel wing feathers and black paper wing membranes for the devils, but when I was shopping for the figured maple board I used for the angels, I found some lovely dark figured veneer. I realized it would look SO much better than black paper on the devil. I already had the veneer I needed for the angels, so after I’d sprung for the devil veneer, I switched the angel over and never looked back. I’m glad I did.

I did end up having to sand a slight bevel onto the very bottom point of the wings to keep them from clonking into the angels bustle, but other than that they were really easy to put together. The wings are glued to the top bracket, but they are just slid into the bottom bracket. That keeps them from getting pried off by differential wood expansion of the body and wings.

The only serious annoyance I had with the angels were their faces. A face is so important, and I’d really sweated the design. I ended up trying to keep it super simple. Just a few lines. However, as I was assembling the angels, I realized that from a lot of angles the laser-etched faces were very hard to see.

Faceless angels are a bit creepy, so I knew I had to do something. For the first two, I used black acrylic and a fine paint brush to darken the lines after the clear coat had been applied. That was a pretty ticklish operation to do on otherwise finished pieces. It was no fun at all. After that, I simply highlighted the face details with a mechanical pencil. That was nice and easy, but when I used a brushed on clear coat the graphite ran and gave their expressions a somewhat haunted look. I spray coated the last two angels, and their faces came out the best. Nice clear details from any angle.

One of the design details I’m proud of is that I wanted a little cleavage V in the front aligned with her hands, but I knew that would look weird on the back. So I positioned the wing mounting bracket so it neatly trims that off, making it look more like a normal dress back.

I wanted to make halos for the angels. I went wandering through the hardware store to see what kind of rings or loops I could find. I purchased a few different kinds, but eventually settled on some straight knurled brass lock nuts. As the giant monolith of Christmas rolled inexorably toward me across my calendar, I decided to punt on the halos. No one would miss them.

However, during the Christmas break, I had a change of heart (and a bit more time), so I decided to make the halos even though that meant giving out a few “halo retrofit” kits. The alignment holes for the halos were in the original design, so adding them was just an insertion and a dab of E6000. Simple pimple. To make the halos, I used a boring bar on the lathe to machine the threads out. No self-respecting angel goes out in public with a halo that looks like it screws on. I then had to drill a tiny hole part way through the halo to mount a piece of piano wire.

Luckily, I already had the tiny center drill for the job, and I set up a depth stop on the drill press. Then it was just a matter of clamping and drilling the six golden rings. Four calling birds, Three french hens, Two turtle doves… Wait where was I?

I used a bit of JB weld to glue lengths of piano wire into the holes. I glued each wire to the halo at a jaunty angle so the angel would not look like she was balancing a book on her head at Angel Finishing School.

The piano wire feeds down through holes in both the upper and lower brackets on the back of the angel, and a dab of E6000 cements the wire to the bottom bracket in a slightly springy but tenacious way. Then it was just a matter of mounting each angel on a base, and adding a candle cup made from another 1/2″ copper pipe cap.

The devil is mounted using T-shaped pins that pass through his floor plate and into matching holes in the base. The angel is simpler. She just has two pins on her bustle that align with slots in the board.

I managed to have two sets completely done by Christmas Day, and I finished up the other four sets a bit into the new year. Overall I’m very happy with the way this year’s Big Christmas Project turned out, especially considering the late start. I’m marking it down as a success.

Making a Egyptian Retro Technology Labyrinth Game

January 8, 2011 by Kurt

When I was young we used to spend time at my Grandparent’s house. It was a farm house with a porch swing and there were lots of fun things to do. My Grandfather would tell the story of my first trip around the yard on the go-cart. I was very young and when I came back around I told him I’d “never operated a motor vehicle before!” and he thought that was hilarious coming from such a little kid. There was a mini bike (until we broke the front fork doing jumps) we played Jarts, yes all sorts of “dangerous” distractions.

One of the fun things we’d do is play an old wooden Labyrinth Game that they had. We played it so much that we could run the ball all the way though and all the way back. We played it so much that we tried playing it with our feet. One day one of the control strings broke and although Grandpa “fixed” it he wrapped the string around the wrong way. Reversing that control, and permanently invalidating all our muscle memory for that game.

The Idea

Though TechShop I have access to a laser cutter. Each year I build some sort of crazy Christmas Project, and this year I decided that a Labyrinth Game would be an awesome thing to make with the laser. I decided on a Egyptian with a retro-technology flavor. (To fit in with the Secret Society theme I’d been following for a few years.) I went with the kiddo’s to the local Rosicrucian Museum to do some first hand research. I went to Toys R Us to see if they had one of those games. I talked to 4 people there and non of them had any idea what I was talking about. I then went to a smaller local toy store and the guy knew at once what I was talking about, and he had them in stock. This more modern instance of the labyrinth had the same design (same hole pattern/course) but had been cheapened in a number of ways. The metal balls were smaller, but the course had not been fully adjusted for that size change, which made some shortcuts/cheats possible. I was able to finish the maze on the third try though, so my muscle memory from 25 years ago seemed good. It was only $21, so you can’t expect much at that price point.

The Design

I started in on the design, I wanted to make a lid for the maze so it would come as a decorative wooden box. I was originally going to put brass clasps on the lid, but eventually had to abandon that plan because of time constraints. It would both cost a lot and I’d have to strip/age the brass fittings, and I was planning to build 6 of these things so it was better to keep it simple. I did some sketches, and looked at Egyptian Art. I noticed that the Scarab was a nice fit thematically since he’s such a famous ball roller. (Although this project didn’t involve any dung.)

I had bought a lot of very thin wood from Minton’s in Mountain View when they went out of business, so I decided to do an inlaid wood Winged Scarab on the box lid.

Normally with these projects I do 4 of them by Christmas Day, but then have 2 others I finish up before New Years. (For out of town folks where the timing isn’t as critical.) However when I started working on this one I realized that the physical size of the project was going to require more laser time then I was used to using. It takes a full hour to etch the scarab on the lid. So I quickly realized I wasn’t going to be able to schedule enough laser time before Christmas to cut/etch all the parts needed for all 6, so for the first time I limited much of my part cutting to the basics I’d need for the first 3 and then I’d cut the rest after Christmas when laser time is a lot easier to schedule.

The 60watt laser deep etching the scarab into the lid.

The laser etched ball glued into the lid

This is how I organized the parts. They are laser cut, but I tape them down to the surrounding wood before I take them out of the laser. That way the uncut material acts as the parts organizer, then I can just slip them into these three ring binder page protectors. Using this system one three ring binder can keep track of all 8 zillion parts. As long as you never EVER pick up the binder upside down and dump everything out! I put a big orange arrow on the front of my binder to help keep that from happening.

The main body being glued.

There are 88 pieces for the wing segments alone, so it takes a while to glue up. After the parts go in I clamp them down to dry. The pieces aren’t a super tight fit, so hopefully that’ll leave enough room for expansion/contraction of the wood.

It is ready to clamp, but I didn’t clamp this first one. It’s always a learning experience, so this one was never fully flat/level. Later ones were better in that regard. I had 3 mistakes in the wing segments. (two parts were swapped, and two were actually the wrong shape) So I had to figure that out, and cut extras. Once all that was ironed out things went more smoothly.

A shot of the very first prototype in normal plywood, and two of the final ones in the 1/4″ Mahogany Ply that I got for the project.

The lid after being glued to the sides and with it’s first coat of Linseed Oil.

The inside of the lid before finishing. I wasn’t too happy with these two corners. They align the lid to the base, but don’t look that great. Later I tried a bit fancier shape/look. the little right angle brackets with the holes are nice and fancy looking, and quite simple to do. Of course that’s 8 more things you have to glue in (two on each side of the lid.)

The lid sitting on one of the sides just to show how the wings will work. this is before I started the Linseed Oil finish work.

This is one of the sides laid out with one of the knobs. Above you can see the zip lock bags I used to organize thick knob segments. I made the knobs from three segments of 1/4″ wood plus a very thin wood layer for the eye.

The knob is made up of 4 parts. You can kind of see the funky strait knurl.

I glued the knobs up on a brass rod held in the lathe’s chuck, so you can make sure the rod would be plumb. Otherwise the stack of laser cut parts is bound to wobble as it turns. However you could just as easily do this with a piece of brass rod stuck into a hold that was drilled plumb. There’s no real need for a lath with this project. It was there, and that made it easy.

You can see a little to much glue sticking out of one of the glue joints. It’s nice to wipe it down with a damp sponge to reduce the amount of glue visible.

Here’s an early test cut of the corner joint. The laser cuts in a slight V shape, but you can compensate for that a bit by shaping the fingers into actual dove tails. (Thanks Heath for the idea!) However you can only do that in one direction if you try to compensate in two directions you get a tight joint that needs a teleporter to be able to assemble it (since there are then wide fingers on the outside of each joint) I guess you could do it the other way around, and have 2 axis fixes for both joints with reverse dove tails, but then I would have had to flip the wood over after etching but before cutting, which would have been an alignment hassle. The joints where plenty tight as it was. This test is using Cedar, but I ended up using Alder which has a less pronounced V shape to the laser cut. (And which I could get locally at Home Depot)

Here’s a final corner with a detailed look at the ball exit. The bottom part of the box extends to create the ball return area. That makes it much stronger since there’s 1/4″ plywood supporting the return area instead of something just glued onto the side.

After the design was done I had to crank up for mass production. Here are the sides/lid sides for three boxes (well minus the lid sides for one.) A set of 2 sides takes about 15 mins to etch/cut out on the 60Watt laser.

Here’s the design of the box floor. It has 3 wedges which will hold the tilted floor that makes the ball go to the exit. You can also see the 4 screw holes since the floor needs to be removable for possible maintenance.

I sanded the bottom corner of the tile floor so that it can smoothly go down to almost nothing at the exit port.

I do however have to provide a special corner piece to keep balls from getting stuck behind the post that the screws screw into. In theory the ball could still fall onto the upper corner of this piece and get stuck, so if you really cared you could sand the top to be slightly curved, but the chance of that happening are small enough that I just don’t care to do the extra hand work to handle that case.

Here you can see three of those corner pieces getting glued down. The middle tilted floor was the very first floor, using different wood. On some of them I also sanded a slight dip in the top of the plywood at the exit, but that turned out not to be necessary and it doesn’t look that great.

Here you can see the tilted floor in place. You’ll notice that the blocks glued into each corner (so the base can screw into those blocks) have tops that are cut at an angle to make it so the ball can’t get stuck on top of one of the corner blocks. You’ll notice that in this fit up I don’t have the special corner piece glued in yet.

I decided to wind my own springs for this project. Mostly because I couldn’t find the right quantity of the right size/tension of spring locally. This wasn’t that hard to do, but was a bit of a time sink. Here you can see me using a Jorgenson clamp to tension the wire as I hand crank the lathe to wind the wire into this brass rod. That is the easy part. The annoying part is then cutting/forming the ends on the wires.

Here you can see two of the better resultant springs. I used a dull Exacto blade to spread the coils enough to get in and bend the loops the rest of the way out with pliers. After the first three were built I had some time after Christmas and found some suitable springs at Tool Land, so I only had to build the first 6 springs, not all 12.

I used brass tubing pressed into the wood to form bushing for all the brass rod joints, this makes for super smooth action and long life.

Here you can see me cutting a bunch of the bushings. I used this super cheep Harbor Freight micro chop saw, and hot glued a stop to the saw at the right distance. That makes it super easy to cut 20 zillion of these things. Note how the stop is angled and only touches the edge of the tube, so it doesn’t cause binding when the tubing cuts through. After you’re done with the stop you can just pry it off of the saw. Some day I’ll make a fancy tubing holding/adjustable stop system, but this works well as long as you don’t have to do too many different sizes, and it could just be used in the saw as-is. I didn’t have to dive into an extra project rat hole.

Here you can see one of the bushings in place around the rod.

I also made a number of pivot pins using a round wooden washer and a bit of tubing. You can see one here (blurry) ready to go into the hole.

Here you can see a frame getting glued to the maze floor. I laser etch the locations of all the wall segments, and put numbers in them so I know which pieces go where. There’s also an arrow, and hazard numbers for the game itself. Notice how I used scraps of wood that were cut from the jaggy edge areas as clamping sections so the clamps wouldn’t damage the pointy parts of the wood. The first one of these I did I didn’t do that, but used padded spring clamps, but there was some slight damage done, so I switched to this system. There are about 45 pieces that get glued down to make the maze.

Here is the maze partially populated. I didn’t bother to number unique segments since there aren’t a lot of them and it’s easy to keep them strait. In the upper right you can see the piece of wood that the parts are coming from. The parts are numbered in columns from top to bottom 13 to a column.

Here’s a closer view including the now fully empty parts sheet.

The walls of the maze have this herring bone texture on them, including miters at the various intersections. The circular arc wall segments have a slightly bigger pattern because it was a pain to get them distributed along the circles in Illustrator. I think I could do a better job now knowing more about pattern brushes, but I was just using the Offset Effect, and getting that with perfect spacing was a pain.

Some of the miter work on the maze walls. Lots of tiny herring bones.

Here are some more parts glue drying getting ready for assembly.

Here you can see how easy it is to make a mess of wooden washers (left) and wedges for the tilt floor (right). This is enough for all 6 labyrinths.

I was originally going to drill/bend brass wire loops to attach the drive train to the pivoting frames, but that was going to take FOR EVER to do, so I opted to just my staple gun. This was terrifying because I was stapling into fully finished things on Christmas Eve. So being off and having a staple come splintering out would be VERY bad. So I practiced on some scrap first. I used this brad to keep the staples from fully seating so you could then tie strings/ attach tensioning springs to the staples.

Here you can see one of the springs attached.

And the way that the spring tensions the string as it wraps around the rod.

A closeup of the two rods in place with the strings on and tensioned.

That’s the full view of both rods in place and strung up.

The knobs for the first size mazes are sprouting like strange flowers from a pink bucket. (glue drying stand.)

My brass control rods are 5/32″. Thankfully they make 5/32 locking collars for some sort of hobby use, so I was able to buy them for cheap. Here are enough locking collars for two mazes.

A closeup of one of the collars before I put the set screw in.

This is a closeup of one of the knobs with it’s spacer washer and locking collar in place.

The bottom of the box screws into place just inside the corner feet that that box has.

Both frames and the knobs in place for the first time. Time to play test! The first play testing happened at 9pm Christmas Eve, so it was good that it worked because there wasn’t time to make any major changes. I did end up re-tensioning things to deal with some stretch in the strings/knots.

Then it was time to sew up some black velvet bags for the ball bearings to go in.

There the bag is turned right side out.

The three balls on the velvet bag.

The maze opened up so you can see the maze surface.

I made a video of the laser cutting, and the kiddo’s playing with it on Christmas Day.

The final finished box. I managed to make 3 by 2:30 am Christmas Eve.

Building a Mechanical Cryptograph

January 8, 2010 by Kurt

This year I’m building an encryption device for my Retrotechnology Society. If you recall last year 6 of my friends/relatives were “antecedently” inducted into a secret society. The only down side being that the society was so secret that I never heard back from anyone. This year I’m going to change all that by providing them with this encryption device, so they can communicate with me (and one another) in cipher. Functionally it’s based on the 1850’s Wheatstone Cryptograph, design wise I’m working on spicing it up a bit.

These images are of the very first prototype. It’s totally rough. I want the basic shape to be the Retrotechology Logo of the 11 toothed gear with an eye in the middle. I’m trying to design the eye so that it “looks around” as you encode/decode messages. You turn the thumbwheel at the upper right, and that drives two gears which turn two rings of letters which are visible though two openings in the face of the device. The eye design is really rough, and various spacings will be adjusted, but this is mostly just a proof of concept to make sure things are actually going to be functional.

These were laser cut out of clear 1/8″ acrylic. Later versions will have to have clearance areas etched into various parts, etc. (to prevent binding) and I’ll have double brass sleeves acting as the bearings. (right now it’s all just jammed in 1/8″ brass rod to hold it together enough to make sure things were working out.) I like how it’s coming out, but I think the aesthetic of the eye design really has to be worked out some more. Still I think it’ll be fun. The final color scheme is going to be black, with white disks inside. I haven’t deiced yet what to do with the back. I could add some cutouts that would expose the gearing a bit. Kind of a skeleton Cryptograph, but that might make it less functional. “keep your fingers and crud out of those holes!” so I haven’t decided. Maybe just a redux of the eye.

I wrote the code to generate the gear profiles in python, and then imported that into illustrator and did all the rest of the work there.

Ok, so then it was time to cut out real versions in the right colored plastics, etc. I used black for the outer casing and “Ivory” for things like the friction wheel, and the lettered discs. In the design the black front/back called for gold and white lines. I thought this was going to be a real pain to do, but I came up with a trick. I used a little rubber squeegee (cut from a Speedball rubber pad) and was able to squeegee gold paint down into all the lines and curves in a jiffy.

This squeegee system reduced the amount of paint used, and really speeds up the whole process. The fills are more uniform too. I don’t want the fills to be perfect because the device is supposed to look sort of old, but the amount of time I was saving painting all that stuff made using the squeegee super important.

Once the splops were on, it was just a couple of strokes to fill every line.

I did have to manually clean out the center hole. It doesn’t matter if there’s a bit of extra gold paint in there since it’s going to have a brass tube pressed in, but we can’t have a thick blob.

If you look closely you’ll also see that I have scraped the outer ring free of most of the gold paint using a paper towel and my fingernail. Then I painted white over the top.

These are the faux Ivory thumb wheels with their special strate knurl, and inlayed arrows. (Done with the same painting technique)

I would have rather had the gears be “ivory” but since they’re not actually visible, I was able to cut them nested inside the other black components, and save a lot of material. I’ve toyed with the idea of making a fancier gear and a “skeleton” version of the Cryptograph, but decided to punt. The dark rings and little “tabs” you see in this are places where I’ve etched extra clearances on the gear/outer wall of the device so that friction wheels can run more smoothly without their knurl making their action feel “notchy.”

I also did some initial tests of burning a deep deep hole in a book. I’ve had people tell me it’s impossible to laser cut books, but you can. You simply have to clamp the pages together so they aren’t as prone to catching fire. I laser cut a clamping jig, and the first cut went well. (Probably 1/4″ easy) but subsequent cuts are bad because the loose paper and forced air cause a lot of burning. (I remove the inner paper, but the walls aren’t as well clamped as they were before and there’s a lot of smoke and mayhem. So I think I’m going to have to change the way I index the rig and flip pages/reclamp after each cut until I get to the needed 5/8″ inch depth. Still here you can see a piece inside a book with only minimal effort. I don’t think I’m going to glue or do anything extra. Just cut the hole so the device can be tucked into the book for safe keeping.

I did this test on a volume of a Funk and Wagnalls New Encyclopedia. (Millions were given away free in super markets back in the day, and it’s hard cover with gold outer trim, so it seemed like a good call.) I really need to find some uniform nice looking old hardbound books that no one wants/cares for. Not sure how I’m going to do that, this thing was $4 at Goodwill. I have no idea why anyone but me would buy such a thing, and that’s a kind of steep price! If I could have snagged 10 volumes of this F&W I might do that, but I’ll have to keep looking.

So this morning I started assembling a final unit. Here’s the parts mostly laid out. They gray part of the eye is supposed to look a bit rough like that. I want the device to seem a bit old, not super crazy snappy new.

Here’s the body assembled with its 11 pins in place. (11 pins! I have to cut and deburr all those by hand, 1/8″ is a bit small to automate on the lathe. (Kill me.) You can also see the super fancy inner pin that drives the middle disc via a square drive shaft that passes though the center of the other gear.

Here’s a closeup of the friction wheel on it’s shaft. You can see it’s inner brass sleeve.

Here you can see the most complicated brass part for the project. Most of the 18 brass pieces are just bits of rod or tube, but the central drive shaft is made up of a brass rod, and square brass tube, and then a custom machined brass tube (the needed to be machined so that it nested to the outside of the square tube and then nested properly inside the 1/4″ brass tube sleeve that is in the center of the upper gear. This shaft lets the bottom gear smoothly drive the lettered disk that is on top of the upper gear.

I was originally going to solder the bits together, but they pressed together so nicely all I really had to do was add a dab of JB Weld to eventually fix the central rod to the inside of the square shaft. This let me adjust things up/down slightly on assembly. Which was nice.

Another device nearing completion.

Here you can see four of the devices, three done, and one just needing to have the bottom paper pealed off. You can also see last years wax seal, and some sealing wax because I’m about to put the devices in their books and package them up for shipment.

The process of cutting the books was a real messy pain. In order to be able to cut a lot of pages at once I had to make this book press which clamps 80 some pages at a time, and lets me do alignment of the cut. You can see the little ‘L’ shaped page alignment guides for positioning the corners of the page.

The problem with cutting so much paper is that you have to go slow, and the compressed air blowing in the machine makes the paper char a lot more then it would for cutting just a few sheets. So there’s a lot of char and mess, and although you only spend maybe 3 mins in the laser doing each cut the time it takes to do a cycle (take out the old paper, clamp up the new paper, and tape things up so various pages don’t fly around while the laser is cutting, etc. eats up a lot of time, and you have to watch the cut like a hawk to make sure it doesn’t go to open flame, or something comes untaped and is flapping around, etc. Nothing I’ve ever done on the laser before was “messy” in this way.

In the end I did manage to cut 6 books before Christmas.

I was lucky to get this 1909 lavishly illustrated 12 volume set of “Adventures in Bookland” which was great because they were all the same size, which simplified alignment. I got all of them (plus some more books) for $5 at the Friends of the Library book sale. So it was a great deal, but I paid a heavy price in terms of guilt. It was horribly Fahrenheit 451 and I felt awful cutting though all the stories I knew like Robinson Caruso, etc. I’ve kept all of the cut out illustrations for possible future use, but my hands have run black with the blood of many an old book and that made me feel bad.

Here is an image of the device in a book. I love the way it looks like the device has burned its way into the book.

Here’s a close up of it in the book. The “top” page here is quite burnt because it was exposed to the most compressed air laser action. Intermediate pages were much less burned looking, but every sixty pages or so theres are a few really burnt ones because that was the next layer I cut. Alignment between the layers isn’t perfect, but it’s decent. You can see I added a faux window reflection that holds still as the eye looks around. I’m really proud of the way this turned out. Now to see if I get an encrypted messages!

Building a Custom Waffle Iron

March 23, 2003 by Kurt

Sometimes a project gets started with something as innocent as having a few waffles.

I was at my uncle’s house having breakfast, and I noticed that he was using a quaint electric waffle iron. It looked like it dated from maybe the 30’s or 40’s, and it was pretty cute. The thing that really caught my interest was that the waffle “iron” had aluminum grids on it. I realized that I could probably buy an electric waffle iron, make some new grids for it, and turn it into a personalized waffle making machine. That thought put quite a sequence of events into motion.

The first order of business was to select the right candidate for conversion. I went to a number of thrift stores, but most of their waffle irons didn’t have much character. However, I did discover a few things about electric waffle irons. There seemed to be a wide variety of ways the grids were mounted and heated. Some grids were clipped in and could be popped out for cleaning; others had the heating element and grid as a single integrated unit. Clearly I needed to steer clear of those.

So it was off to eBay for me. What did I find? 154 waffle irons, almost all of them different. Luckily I could ignore the cast iron ones which were designed for use with a coal stove, and that cut the list down to something like 50 electric irons. After much indecision, I eventually bid on an iron which I thought looked nice and seemed to be in excellent shape. I couldn’t tell from the pictures if the thing was going to be easy to retrofit with custom grids, but it seemed worth the risk. No one seems to take pictures of the inner workings of the waffle irons they’re selling on eBay. Not surprising I guess.

I won the auction, and a few days later the iron was at my house undergoing a thorough cleaning and disassembly. I was lucky that the iron had heating elements which simply screwed onto the grids. Removing these elements was a bit ticklish because I could tell that the fragile heating element would be very easy to break, and there’d be no real hope of re-attaching it if it did. So I removed the heating elements from their nest of hook-up wires, which felt a bit like defusing a sticky 50-year-old time bomb.

After the heating elements were out, it was nice to give the rest of the iron a very thorough cleaning. WD-40 did a good job of cutting through the ancient baked-on oil and flour mixture that filled every nook and cranny. I wouldn’t recommend using it on any section that you can’t later de-grease, or on parts which are going to be coming in contact with food, but for cleaning parts like the hinges, it really did the trick. I was thinking about giving my Mom a little fire extinguisher as one of the auxiliary gifts. 95% as a joke.

The plan was to cast new replacement grids out of aluminum so I needed to come up with a pattern. The original grids had been die cast and had various knobs and bumps that were drilled and tapped to take mounting screws. I realized it would probably be a lot easier to use the back half of one of the actual grids as the pattern for the back of my new grids. I used auto body filler to fill all the waffle grid holes and remove some of the extraneous details which would make it harder to cast in a sand mold.

What about the actual grid design?

I thought it would be best to make a board-mounted pattern and design it so the deepest parts of the mold were less then halfway through the board. As long as I kept the outline of the design symmetric I could use the same pattern to cast both the top and bottom grids.

The plan was to give the waffle iron to my mom for Christmas. She and her husband Stan have been building a victorian home in Historic Rugby, Tennessee. Since Stan likes Calla Lilies, they named the house “The Calla Lilly Cottage”. I thought the house would be a nice theme for the grid design, so I decided to make the Calla Lilly Cottage Waffle Iron.

I drew sketch after sketch trying to make a design that embodied Calla Lilly Cottage but was simple enough to act as a practical waffle iron. The design had to have a balance of high and low regions so that the waffles wouldn’t be too fat and doughy or thin and crispy.

Eventually I settled on a design that produced a simple house silhouette-shaped waffle with a calla lilly embossed on it.

Carving begins

I decided to lay out the design on thin poplar, cut out the rough high and low areas, carve in the details, and then glue and fillet the whole thing back together. This was by far the most time consuming part of the construction. I put more then the usual amount of draft on the pattern because not only would the waffle pattern have to come out of the sand, but waffles would have to come out of the iron, so I based my draft on the amount of draft on your average waffle griddle squares.

Casting begins, but time is running out

Finally the pattern was finished. The iron was cleaned up and ready to go, and the stage was set to cast the new grids and get a move on. I made a board-mounted pattern with alignment pins so I could use the original waffle iron grids in conjunction with the calla lilly pattern. This required making a flask with some very long alignment pins so the flask could maintain its alignment both with the board in place and after it was removed. So I made a new flask with long dowels, but that was the cause of the first big failure of the project.

The Christmas holiday was fast approaching, and I still had a long way to go with the project. The special flask made it so I could only cast one iron at a time, and that meant pretty much one casting per night. It was down to the last week, and I really needed to get two good castings right out of the gate in order to be able to have enough time to finish the project.

Then disaster struck. I rammed up the mold as usual, separated the flask, and removed the pattern. So far so good. The cope (the top part of the flask) was pretty darn heavy. The grids are perhaps 7″ across, and that meant the cope was maybe a foot on a side. With it rammed full of sand it weighed as much as two cinderblocks. As I was heaving it back into place and aligning the unfamiliar alignment pins, I (unbeknownst to me) brushed the face of the sand with one of the alignment pegs. This cut a channel from the mold cavity to the outside world. And I didn’t know.

Fountain of molten aluminum!

So I fired up the furnace, and melted a large charge of aluminum. I used cut up pressure cookers and other things that I felt were probably semi-food-safe flavors of aluminum. I got everything up to temp, skimmed the dross off as usual, and then went to pour. As I poured, a stream of aluminum shot out the far side of the mold and began to pool on the ground.

I stopped pouring into the mold. I poured the remaining aluminum into the muffin tin ingot molds, but I could tell that the casting was shot for sure.

The interesting thing about the resulting casting was that you could see the exact path the the rouge dowel took as it cut that channel. The aluminum frozen into the channel had the exact shape of the dowel’s path.

The other interesting outcome was that the form created by the spilled aluminum was rather beautiful.

The aluminum was on concrete, but the puddle actually spanned a gap in the concrete that was filled with a piece of wood. The wooden strip burned and produced a nice colored line across the form. I’m thinking about making that into a lamp.

As far as casting screw ups go, no one was hurt and I got two interesting pieces out of it, but it didn’t exactly help my time table. The next two nights of casting went without a hitch, but I still had the task of cleaning up and machining the castings.

I had designed the main casting with a sprue that was centered and perpendicular to the face of the iron. I did this by taking advantage of a long mounting screw that was centered on the original waffle iron grid. This gave me a handy shank to mount in the lathe so I could clean up the casting and make it fit exactly into the waffle iron body. Now you know why I selected a round iron rather then a rectangular one. This turned out to be a god send in terms of getting the whole thing to fit. The cast plates had warped a little as they cooled, so it was nice to have some extra meat on the casting that I could face off on the lathe so they would fit together nicely. (There should be a little space between the plates so that steam can escape from the waffles.) If I had it to do again, I’d probably leave a good 1/8″ of extra material on there and just face off the whole thing.

In the end I took one extra day of vacation and worked from 9am to about 2am. Fitting, machining, sanding, filing, drilling, tapping, wiring. *phew* Finally the iron was finished. A few hours later I was off to the airport with my waffle iron in a carry-on bag. There was no way I was going to check that baby! I was hoping to get to see an X-ray of the iron at the security gate, but no such luck.

Where there’s Smoke there’s Wire!

Of course, I hadn’t had much time to run a test of the iron. I had checked for shorts and continuity across the coils, but that was about it. On Christmas Day the iron was put to the test and FAILED. The iron would not heat up. I quickly discovered that the cord that had come with the iron was a dud. All that testing of the iron’s wiring, and I never checked the cord. Crazy. So we were off to Drogan’s for a new cord.

Was that the happy ending? No. As the iron came up to temp, we noticed some smoke! I had given my mom a kitchen fire extinguisher as a warm-up gift for the iron, but I hadn’t actually thought we might need it! Actually it wasn’t that big a deal; it was just a thin plume of smoke rising from the top grid. The ancient wiring was slowly smoking because it was still somewhat soaked in oil and pancake batter.

Argh! This fix required another trip to Drogan’s for a few lengths of high temp appliance wire and some crimp connectors. I spent an evening doing the ticklish bomb defusing dance trying not to break the heating elements while attaching replacement wires. The iron was reassembled with fresh new wiring, and finally it was taken on its first fully successful waffle run.

It works!

We set about making a whole pile of waffles. The waffles came out easily and were lovely. For added fun, the pattern in the waffles fills with butter and syrup. Mom, Stan, Cheryl, my sister Inge, and our friend Heather all tried a few waffles. Finally the Calla Lilly Cottage Waffle Iron was fully operational.

It’s funny casting a waffle iron grid because the iron grid, in turn, is used to cast the food batter. Now mom can have fun casting waffles in the kitchen. I had originally thought it would be fun to make more custom irons, but I think I’ll put that off for a good long while. It is rather a crazy amount of work, but can be pretty rewarding.

I was thinking it would be somewhat easier to make two matching “mirror image” grids by sandwiching two thin boards together, cutting them at the same time with a scroll saw, and mounting them on two different boards. If the pattern were a simple two-level design without any carved bass relief, it wouldn’t be to hard to knock a pair out, glue them up on two boards, and then fillet them with filleting wax. That would be a lot faster then my approach. Maybe in a few years I’ll have forgotten enough about how much work it was that I’ll be willing to embark on another one.

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Category Archives: Christmas Project