Engineer vs Cat, part 2

My original idea for the initial set of posts on this blog was to talk about my experience growing strawberries hydroponically in my New York apartment. Cue my cat, who despite her innocent appearance and occasional cuddles, can be described with the following Venn diagram:



I call Dixie a turd because she poops where she's not supposed to. Like my bed. Is it a me problem or a cat problem? Probably both…

So, instead of a nicely documented journey about growing food in my apartment, welcome to part 2 of the saga where I try to keep my cat and my plants from killing each other (see here for part 1).

Experimenting with strawberries

In addition to my tomato plant shelf, I have a wire rack in my entrance hallway where I grow plants like bok choy, lettuce, and other edibles; the bottom of the shelf has a mini fridge for expanded freezer space in the apartment. There's a modified shower curtain strung onto a rope, which is zip-tied to the top of the shelf. This is intended to both keep the cat out and dim the brightness of the grow lights.

Last summer, I bought a strawberry plant from a farmer's market and tried growing it in this hydroponic system. I was able to propagate the mother plant a couple times and harvested a couple handful of tiny berries before the plants died out in December.



This year, I decided to grow strawberries again, but with the goal of larger berries and enough plants to fill an entire shelf. I knew from prior research that growing strawberries from seeds is notoriously hard, so I found some strawberry bare root plants on Amazon. Bare root plants are just the crowns of strawberry plants and their roots, without any leaves or dirt. Once you put the bare roots in some water, new leaves will start to grow from the crown, eventually growing into a full strawberry plant. They're much cheaper than buying potted plants (I got 24 for ~$1 per plant), and I don't have to deal with dirt I don't need.

The bare root plants sprouted new leaves pretty quickly and were doing great – every plant I received was thriving, so I was well on my way to my vision of a shelf full of strawberries.



While the strawberries were growing, I started planning out this blog to post about the strawberries. I even bought a security camera from Wyze to make a timelapse of the strawberries... and then Dixie started puking again:



Caught red-pawed

Turns out Dixie was not nibbling at my dead bell pepper plant, since she only likes eating living plants. Since the only living plants at this time were my strawberries, I was reasonably certain she was getting past the shower curtain. To confirm this, I turned on the motion detection feature of my security camera. Not a day later, I get a "Motion detected" notification on my phone while I'm working from home one day:

I stomp out of my room and she jumps off the shelf, startled. Dixie doesn't understand why I'm upset so she walks away with an offended-sounding huff (and then later pukes for good measure). My poor tortured strawberry plants and I were not happy:



To try and deter the cat, I took some small clothespins I had on hand to clip the front edges of the curtain together and the bottom edge of the curtain to the bottom shelf. The next morning, I am woken up by this notification on my phone:



Dixie has evidently learned she can hop onto the small ledge created by the mini fridge below the plants and use that to gain access to the plants. Although I'm not sure why that took her a year to learn, clearly stronger measures needed to be taken. Cat: 3, Human: 2

Attempt 1: Velcro

First, I moved the strawberry plants to the top shelf and sacrificed my lettuce plants to the cat on the bottom shelf. I ordered a Velcro roll that had a sticky back from Amazon, adhered one side to the bottoms of the shelves, and stuck the other to the curtain itself so that the bottom of the curtain no longer had a gap. I didn't add velcro to the left side of the shelf because all the power strips for the hydroponics were secured to that side, and I didn't feel like moving them.



Dixie started investigating the velcro as I was adding it. She seemed suspicious.

After several weeks without incident, one morning Dixie comes into my room and pukes what are very clearly leaves onto the floor. I go to look at my lettuce, and see that the larger plants have pieces missing while the new baby ones have little vampire bites in them:



I know it's gross, but I felt vindicated to have visual proof this causes her to puke.

The velcro was still attached to the shelf, so I assume she got in through the left side of the shelf somehow. A few weeks later, I was in my room when I heard the sound of velcro ripping and ran out just in time to see her hopping off the shelf. I check the security camera footage afterward and see that she's figured out how to brute force her way through the gaps in the curtain:



So much for that idea.

Fortunately (or unfortunately), around the middle of April my plants were overcome by spider mites, so I had to compost all the plants and start over anyway. I cleared out the shelf and took down the curtain, since there was nothing to protect anymore. Cat: 4, Human: 2

Attempt 2: Engineer the s*it out of this shelf

My coworker and I have a saying we use for engineering solutions. Sometimes, we'll take a problem and "nuke it from orbit", which means the intention is to not just solve the problem for the short term, but to solve the problem so thoroughly we don't have to think about it for the next 3+ years.

I'm going to take the problem of cat-proofing my hydroponics and nuke it from orbit.

Back to first principles

The Velcro idea didn't work because it was both ineffective and also pretty annoying to deal with on a day to day basis. The curtain was too long, so the ends kept getting caught in the mini fridge door. The velcro also wasn't all that sticky, so if I pulled carelessly, the velcro would peel off entirely. Taking a step back, I needed a solution with the following characteristics:

• Hard to open for the cat: First priority, keep the cat out!
• Easy to open/close for a human: This was something I did several times a day, so I wanted to optimize for ease of access.
• Doesn't obstruct the hallway: The shelf stands in a fairly narrow hallway, so whatever covering I designed shouldn't block the hallway when opened.
• No false positive motion detection: The shower curtain was see-through when light shone through it, which meant that the security camera would constantly pick up motion outside of the shelf (e.g. someone walking by). I needed something more opaque to prevent false positives from the camera.
• Aesthetically pleasing: The shower curtain + rope combo looked a little janky at the end of the day.
• Worked with my existing shelf: I've invested a lot of time and other equipment into the current hydroponic setup. Ideally anything I did would be built on top of the existing shelf so that I didn't need to start completely over.

I cycled through various ideas (doors, curtains on tracks so it could curve, curtains with buttons to snap shut, rollable shades, retractable shades, sliding doors, etc.), each of which would be difficult to build or didn't satisfy one of the above characteristics.

One day it finally occurred to me that the shelf was magnetic. An idea started to take shape– I could have curtains that opened side to side, build proper curtain rods at the top, and 3D print brackets to fasten the rods to the shelf. Strong enough magnets along the edges of the shelf could keep the curtains shut in a way that I could easily pull them apart, but be difficult for a cat to open.

This was enough of a design outline for me to get started. I'm a "figure it out as I go" type of tinkerer.

Gathering materials

First stop, Home Depot. For the curtain rods, I found two ¼" diameter dowels that were long enough to be cut down into 3 curtain rods, one for each exposed side of the shelf. I also got a grommet install kit with brass grommets large enough to slide onto the dowels (I watched enough DIY shower curtain tutorials on YouTube to convince myself they wouldn't be that hard to install). Finally, I got a variety of magnets to try out, since I hadn't figured out exactly how they should interact with the curtain.

Second stop, the Garment District. This Manhattan area has a high concentration of fabric stores, which generally cater to the apparel industry. If you're like me and subscribe to the "I'll know it when I see it" philosophy, then these stores can be a lot of fun.

My sister and I walked into the first store we saw on 39th street (AK Fabrics). The entire store was packed floor to ceiling with bolts of fabric of all different materials, textures, and colors. After wandering around aimlessly for a bit, a bolt of black fabric with elegant gold flower embroidery finally catches our eye.



Embarrassingly, I miscalculated how much I needed and bought 3 times the length necessary for my shelf (reminder to self: a yard is 36 inches, not 12 inches). Ah well.

Finally, finding a sewing machine. Turns out the same friend who helped me out with my tomato-protection project also happened to have a sewing machine that he could let me use.

Building out the curtains

I designed some brackets that had holes to fit the dowels in and could be attached to the top corners of the shelf. The brackets were composed of 2 pieces that would wrap around each corner post and could be screwed together (this took several iterations and failed 3D prints to get right). I then cut the wooden dowels to size so that each piece could fit along the length of the shelf, with just enough extra length to squeeze into brackets on either side.



For the curtain itself, I measured and cut 4 pieces – 2 for the shelf sides, and 2 for the front so that I could open and close the curtains along a central seam. After brainstorming how the magnets should work with my friend, he gave me some washers and magnets to sew into the curtain hems. If I spaced out washers, I could fasten magnets in the corresponding locations on the shelf edges so that the curtain would snap into place upon closing. For one of the front pieces, I sewed magnets instead of washers into the side hem so that the front 2 curtains would snap shut in the middle. The washers and magnets were all sewed into the bottom half of each piece, since I was optimizing for keeping Dixie out.

I re-learned how to use a sewing machine, broke one needle when it landed on a washer (sorry Landon), and decided that making clothes is definitely not for me. But I got the job done, and luckily the cloth is black and hides my mistakes if you don't look too closely.



Once I finished sewing the curtains, I needed to install the grommets. This involved cutting holes into the top of the curtains and then hammering in the washer that holds the grommet into place, so that the cloth is sandwiched in between (apologies to my downstairs neighbor).

As I started hanging up the curtains for real, I realized the washers on one of the front curtains did not line up with the magnets on the sibling curtain. This meant I had to rip out the stitches, slide the washers into the correct position, and re-sew them into place by hand.



While I was sewing, Dixie caught on to the fact that these curtains were bad news for her.

Final assembly

I threaded each curtain onto the wooden dowels, squeezed the dowels into their brackets, and then screwed the brackets shut around each corner of the shelf. I lined up circular magnets with the washers on the sides of the curtains, and stuck each magnet to the corner posts using double sided foam tape. For the middle of the front shelf where there was no corner post, I 3D printed a small block with a hole and screwed a ceramic magnet into the block to hold it into place. I also moved the power strips on the left side of the shelf to the back of the shelf so that the side curtain could be flush and leave no openings for the cat.



When trying to slide the curtains open, I found the grommets would get stuck because there wasn't enough room between the dowel and the edge of the shelf. I tweaked the bracket design so the dowel would be spaced further away from the shelf edge, reprinted all the outer brackets, and re-installed the curtains.

I also realized that having washers in just the bottom half of the curtain wasn't enough, since the top corners kind of flopped around with nothing to secure them. My friend gave me some more washers, and I hand sewed them to the top edges so that I could close them fully shut. Admittedly this was just for aesthetics at this point, as Dixie probably wasn't going to be doing acrobatics into the top openings of the curtains.

In the end, the curtains looked pretty good. The flowers created a nice sparkly effect when light shines through (totally unplanned), and it was easy to pull the curtains open yet have them snap shut upon closing. There's no visible gaps on the bottom for Dixie to try and get through, and the curtain is opaque enough that I don't get notified by the security camera every time my sister walks by to go to the bathroom.



As of publishing this post, Dixie hasn't figured out a way into the curtains. Fingers crossed it stays that way...