For this year’s That Takes the Cake! show in Austin, TX – which had a theme of The Science of Cake – I decided to make a cookie version of Leonardo Da Vinci’s Aerial Screw, sometimes called Da Vinci’s helicopter. Da Vinci drew this concept but never built it, and even if he had it never would have actually flown. But it was a very interesting concept for his day and part of his artistic contributions to science, so I thought it would be a great way to pay homage to the concept of science and art coming together.
I found a museum model kit made out of wood and cloth that comes together to make a working model of the Aerial Screw, and decided I’d make a cookie version of that entire thing. I’d long wanted to see if it was possible to make gears in gingerbread, and in fact my next choice of a Da Vinci homage would have been his Self-Propelled Cart, but I decided that would be less aesthetically interesting since it was flatter and many of the elements were hidden under each other.
The subject of making edible gears poses many challenging problems. First of all, gears need to be strong enough to push against each other under whatever weight they’re bearing, and edible media is generally very fragile, especially in small pieces. Secondly, gears require precision that is difficult to achieve in media that spread as they bake or shrink as they dry. If a gear train is even slightly off somewhere along the line, the entire thing can seize, slip, or otherwise fail.
So by having this wooden, working model to base everything on, I figured as long as I checked at every step to ensure my cookie pieces were precisely aligned with the wooden ones, it would work. And it did…mostly. Because things dried about a millimeter off in one piece, there’s a slip in the mechanism so it only works in reverse; as in, the top turns the handle and the slip fixes itself that way, but the handle doesn’t turn the top because then the slip turns into a sticking point. That goes to show just how difficult edible-media gears are! So if you’re going to attempt something like this, make sure you have tons of time to make and possibly re-make pieces, because as I learned the hard way, messing with semi-dried pieces will go badly for you, some things will need sanding, adjustment, or remaking, and it’s all very fiddly on a very fine level. It’s an exciting thing to attempt, but it’s not for a rush job!
Because I’d used Julia Usher’s â€œconstruction gingerbreadâ€ recipe from her book “Cookie Swap” for my sewing machine 3D cookie construction the year before, I knew I could use that again for the â€œwoodâ€ parts, and I considered using pastillage for the sails. I knew I could make a drying rig that would dry pastillage nice and flat as the taut cloth would look on the model. But I decided no, this is a cookie entry, so I should make as many elements out of cookies as possible. I’d seen Julia Usher’s videos about using tuile dough, and I knew fortune cookie dough is basically the same thing, so I found a UK recipe for fortune cookie dough (because as mentioned in other posts, UK plain flour is softer than US all-purpose flour, so it’s important when spread and strength are key to ensure your recipe matches your local ingredients). I made some actual fortune cookies for a Christmas event so that gave me a feel for how that dough spread, how to shape it, and most importantly how it performed for weeks afterwards. I saved two of the fortune cookies and placed one in a dry part of the house and the other in a humid part of the house, and every week or so I’d go check them for mould and poke them. I wanted to know how that dough held up after a long time out and exposed. But it grew no mould and stayed surprisingly hard, even in humidity, so I knew it was up to a week of construction, a flight, and then the actual show.
After a careful accounting of how all of the wooden kit’s parts went together, what was needed for where, and how I’d be translating all of that to cookie, I then realized that not only would I have to take this in two halves to be assembled in the US, but that one of the halves as per the kit would be slightly too tall to fit under an airline seat, which is where I’d need to put it on the flight to ensure nobody else smashed or crushed it. So I did a bunch of math to calculate where I could shave off a bit of width and height to keep the proportions of the outer bits but still keep the inner gears exactly sized to the model kit, because again, you can’t just shrink or expand gears without messing up the timing and then they won’t work.
In particular, I knew the length of the poles holding the sails needed to come in a bit, and I was dubious about being able to make the sails in two pieces as per the kit. So I decided to get the sail frame built first, then take its exact measurements, and then tailor the sails as needed to fit.
I also decided that since the rules for this category just said, â€œAll types of cookies are allowed including 3-D designs. Any combination of techniques and/or media may be used,â€ that I didn’t have to cover everything with icing, so wherever possible I decided to keep the beautiful golden-brown hues of the gingerbread exposed. Da Vinci’s science art was frequently utilitarian in an age when many other things were heavily decorated, so I decided it was in keeping with Da Vinci’s spirit to concentrate on the beauty of the mechanism, not excessive decoration.
I initially used royal icing to affix pieces together, but soon found that the Renshaw premade royal icing I was using was just not setting up hard between the cookies as I needed (I have found this problem consistently and would never use this product again for anything, to be honest). So instead I looked around for a colour mix to make gingerbread-coloured gumpaste, but stumbled on some â€œTeddy Bear Brownâ€ Squire’s Kitchen modelling paste I had because it came in one month’s Cake Bag. When I took it out and compared it to the gingerbread, I realized it was already an excellent match and that meant I could buy more and not have to worry about colour matching. I ended up using about a pack and a half in the end, so that was a good choice!
In fact at the show after judging, Mike McCarey asked me how I’d made the “paste” because he thought I’d ground up gingerbread and turned it into a matching paste of some kind. I told him it’s just regular Squire’s Kitchen modelling paste and he was surprised! I guess that means the colour really did match well.
I also decided that while 100% edibility would be great, there was just no way any edible medium at this scale was going to be hard enough to turn as gears without breaking. So I decided on pastillage over round cocktail sticks (toothpicks) for the gear bits, and pastillage on bamboo barbecue skewers for the sail poles.
Ultimately, this piece used 47 cookies, plus Polo candies (hard, dry white mints with holes in the middle, similar to Lifesavers mints for anyone looking for a US version), about 300 grams of modelling paste, a small amount of royal icing, and a small amount of pastillage.
Here’s a list of where all the cookies went:
Museum Model Rotating Assembly
Baseboard – 1 cookie
2 Narrow Pillars – 2 cookies each, affixed together with royal icing with exposed edges covered in modeling paste – 4 cookies total
2 Wide Pillars – 2 cookies each, affixed together with royal icing holding a Polo mint candy embedded between, with exposed edges covered in modeling paste – 4 cookies total
Horizontal Gear Mechanism – 1 end cap cookie covered in modeling paste, 1 large gear cookie embedded with pastillage-covered toothpicks held in place with modeling paste and covered with the same on the back, 1 spacer cookie covered in paste, and a handle comprised of 2 cookies held together and covered in modeling paste – 5 cookies total
Vertical Gear Mechanism – 2 Polo candies covered in modeling paste, 2 cookies embedded with pastillage-covered toothpicks held in place with modeling paste and covered with the same on the top of one – 2 cookies total
Top Platform for the base – 1 cookie
Total: 17 cookies
Aerial Screw Components
Support Disc – 1 cookie
Mast Base – 3 cookies held together with royal icing and covered in modeling paste
Central Mast – 15 very small cookies, some interspersed with pieces of Polo candies to facilitate strong holes, held together and covered with modeling paste, with pastillage-covered skewers affixed into the holes with modeling paste
Mast to Arm Support Ring – 1 cookie, covered in modeling paste
3 Angled Arms – 2 cookies each, held together with royal icing and covered in modeling paste – 6 cookies total
Base Ring – 1 cookie, covered in modeling paste
Sails – 3 fortune cookies
Total: 30 cookies
GRAND TOTAL: 47 cookies
Below are many photos showing how it came together and how I kept comparing it to the model to maintain the gear precision as much as possible.
First I rolled the gingerbread out to the same thickness as the wooden pieces, and then rolled once more gently to make them slightly thinner so they’d hopefully bake to about the right thickness (I also did the “ironing” method on each cookie as they came of the oven, which is taking a metal fondant smoother over the hot cookies gently but firmly to squish out any unwanted puffs). I cut a circle to the same size as the gear (erring on the slightly smaller side when matching to my circle cutters, again because of anticipated expanding during baking) I put the wooden gear right on top of the dough and used my needle tool to poke the location of every hole, making several pokes so I could clearly see where the hole was.
But I quickly realized that the very act of cutting the holes was pushing the dough out of shape ever so slightly, so I put the round cutter back around the dough to act as a support as I did the cutting.
I did likewise with the smaller gear cookies, and then after baking placed them on the actual wooden model (with the wooden gears pushed down so their rods poked up to test the cookies on) to make sure everything lined up.
For the inner mast, at first I tried to make it in all one piece. It was a challenge from the start to make holes that went crosswise through the dough because each new hole through wrecked previous ones. And then, as I pretty much expected, it didn’t cook well so not only did the holes bake closed, but the whole stick was split inside and along part of the outside.
For all four side supports on the base, I made two cookies each that would be glued together back to back for maximum flat surface matching. To provide strength inside for a rotating shaft, I reinforced these supports with a Polo candy embedded in the middle. This meant I had to carve out space for the candy to be embedded in between but still allow the cookie surfaces to come together flush.
Filing straight edges is fairly easy, as long as you take care to go slowly and evenly and are protecting the cookie against any stress that could break it. Filing perfect curved edges is not so easy, so given that I was making this piece to replicate wooden counterparts, I used those wooden parts to help me get a perfect edge.
Turning my attention back to the central mast, I needed to have a very strong way of supporting the arms for the sails that could also have a shaft going down into the gear assembly. Since the Polo candies had worked so well for the side supports of the gear mechanism, I decided to make them work for me in the mast as well. It wasn’t going to be stable to use them on their sides to use their actual holes, though, and they were slightly too wide compared to the cookies I’d made to stack in the mast, so I decided to cut each Polo candy in half and then file the cut edge down so they’d make a supportive insert on either side of the gaps between cookies, thus giving a lot of hard strength to the mast while still being edible and really within the spirit of gingerbread, which often comes with candies stuck onto it anyway.
Once that mast was definitely together, dried, and as needed, I filed it as a whole with the grater to smooth the sides, and covered it with the modelling paste. Filing the candies and the cookies at the same time was a bit tricky because of the different hardness between them, but I went slowly and carefully. This is pretty much why I listen to so many podcasts while I make my sugar art! (If you need one to listen to, start here!)
Once all of these bits were covered and tested, it was time to actually commit to assembling them!
Finally it was time to make the sails.
I mounted the base/gear box unit on a thin cakeboard, glued a ribbon around it all, and then it was done pending final assembly in Austin. The photo and video at the top of this post show it sitting in place but not actually glued together. Here are some more photos from that shoot:
Of course, then I needed to actually transport the thing in a cab, on a bus, on a 10-hour plane ride, and then in Kyla’s car to her house and then the actual venue. I know from past experience that my cabin bag fits under the seat in front of me on the plane, so at first I considered trying to build some kind of container within that bag, because it would also give me rain protection and handles, but as I worked on the piece it became clear that while the halves would actually fit in my bag, I wouldn’t be able to get them both in the narrow opening of my bag. So I decided to build a box instead, partially using some instructions shared with me from ICES friends, but tailored to materials available in the UK.
I bought some A3 sheets of 5mm foam core, measured out a base board that would fit both pieces including all of their bits sticking off to the side, and a cardboard one as well to be glued on the bottom as additional support. I placed the actual pieces on before cutting to be extra sure there was ample room. Then I cut a piece sized to the baseboard less 5mm on all sides to accommodate side walls, and placed the gingerbread pieces on that one to trace out their bases. I cut out their bases from this second piece and glued it down onto the baseboard. This gave me a perfect custom-fit recess into which each piece could sit, reducing the chance of them sliding around inside the box, as well as perfect grooves to line up the side walls.
I then measured the height of the pieces on that baseboard inside those recesses. The maximum height was 21.5cm, and I knew the official clearance for the under-seat carryon was 25cm, so to be sure of clearance on both sides I measured side walls to a total height (including the base board) of 23 cm. I knew I was going to be using a plexiglass lid, which would be less than 1 cm, so it would still come in under 24 cm total. I also cut a middle wall that was 5mm shorter than the side walls because it was to sit on top of the inner board with the recessed holes, but for strength I did not cut a recess for that middle wall.
Then I grabbed the old plexiglass I had on hand from my 2016 entry, which had actually ended up damaged on one corner in my kitchen so it was no longer useful as a full piece. I cut a lid to fit the outer dimensions of the box, and rounded the corners because plexiglass corners can be sharp and I didn’t want anyone to be hurt, including myself, or for airport security to have an issue with it. I then did a second one since I had enough spare plexiglass and mounted that to the bottom (on the cardboard under the foam core) as extra protection against water and to make it easier to slide on the carpet under the seat.
After assembling the first two walls, I took the taller piece and tested it, just to be sure that it would indeed have sufficient height clearance for the lid.
I knew I’d be using rolled-over packing tape under the cardboard baseboard under the base/gear box cookie unit to affix it down into the box, but I couldn’t tape the upper unit because tape doesn’t stick to the cookie at all, and I also was wary of damage anyway. So as I built the box, I cut scraps of foam core to make corner-strengthening units inside (taking care that they’d be nowhere near any elements protruding out beyond the boundaries of the recessed holes), and as I glued them into place I also glued in lengths of cheap but strong curling ribbon.
Then as I put the pieces in, I pulled those ribbons flat and taut over the base of each half and glued it down into the opposite corner on diagonals.
This created a very strong way of tying the cookies down in the box without actually touching them very much; it would stop them from going anywhere if the box was tipped, but it wasn’t putting any constant pressure on the cookies at all. It was a fail-safe that wasn’t needed, but it was very comforting during some of the bouncier bits of the journey to know that it was there. Plus, last year Heathrow security turned my bag with my sewing machine entry on its side to go through the x-ray, so even though this year I had the box exposed and asked that it not be turned (after all, it was built to the height clearance so it shouldn’t need it), if someone had turned it the pieces would probably be okay. They didn’t tip it, but having the extra security built in eased my mind throughout the trip.
Once I had the pieces in and strapped down, I was ready to add the final wall in place. But I also realized I didn’t like how much the gear mechanism was rattling around. I knew it would probably be fine to rattle but figured more security would be better, and I still had foam core scraps left. So I measured and cut an additional piece to slide down just above the base’s top, not touching it, but with a hole fairly narrow for that mast pole so it could only move by a few millimeters instead of jiggling widely.
I realized that in my cold kitchen, the hot glue was going to start setting up as I tried to cover all of the edges needed for the front panel to go on, so I started by putting down a large bead of the glue for the bottom edge. Then I could put that edge on and it would stay warm enough while I quickly put some hot glue up the three walls and the two angled supports I had in place. I didn’t worry about perfect coverage, because I also knew I’d be taping all of the seams; I went for careful speed instead of perfection at this point.
I then taped in some spare airbags around so they weren’t touching the entry, but once again would give an added fail-safe in the event of any other point of failure. I also had purchased some bags of silica desiccant, and taped in some of those around where they wouldn’t be at risk of damaging anything.
Next I glued on the plexiglass lid, and then ran clear packing tape around all edges. Once it was all secure, I compared it to the height of my regular carryon bag which I know fits under the British Airways seats.
I made signs for the two long sides of the box explaining the fragility and contents so the various transport staff would understand what was going on with this weirdness, and I taped that on running the tape all the way around the box in two stripes, giving added security to the entire construction. Finally, I used a long big of wire-edged ribbon leftover from a previous cake board and wrapped that around the entire box, taping it down separately so that if airport security had an issue with the wire, I would be able to remove the handle without taking the rest of the box apart. Again, they didn’t have an issue with it, but it’s always best to plan to be very accommodating of airport security!
It all worked! Here it is under the seat in front (well actually the middle seat’s spot, because nobody was in the middle seat and the man on the aisle seat was happy for me to use that entire space):
And here it is cut open at Kyla’s house, all intact!
The severe humidity we had at the show impacted a lot of pieces, including mine. The cookies got so soft inside – almost sponge-like – that the mechanism never did work very well. It looked good on the first day and worked enough that the judges could see that, barring such horrible humidity, it would have worked better. The wet winds blowing as I took the piece into the hall made the cake lace blow and stretch slightly, so what had been taut was now slack, which really bugged me. But I didn’t want to risk taking anything apart to repair, so I marked it as DAMAGED IN TRANSIT on the entry form and that, along with the sheets of in-progress photos I put beside the entry, had to suffice to show the judges that it had been fine before the weather got to it.
And the judges did like it! It won a Gold as an overall grade, and placed Second in Masters: Cookies. It also won Second place in the overall show award for matching the theme of science.
And then at the very end, since I couldn’t bring the assembled piece home, we decided to SMASH IT. Tien Bui recorded me dropping it, but because of the humidity and how much moisture the cookies had absorbed, it didn’t shatter so much as fwopped as it landed. If you listen in the video, it makes a wet-thunk noise, and the only breakage was the sails popping off and going flying.
So that was it for my experimental gear-based moving cookie. It was a fun challenge to make, and now let’s never do that again wheeeeeee….