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Jerkybot

Randy Scott Slavin, he of the NYC Drone Film Festival and the Liberty Cup, is kind of a big deal in drones. He's one of the drone world's most prominent proponents in the media, an advocate for racing with the FAA, and an accomplished aerial videographer. And unlike me, a hermit who spends his days inside Solidworks, he gets out into the world where he's invited to speak on panels and meet other leaders in their respective fields. It was at one of these talks that he met Paul Hoffman, the CEO of the Liberty Science Center, whose childlike enthusiasm for drones and technology has gotten us access to the most amazing venue for drone races.

Randy met James Percelay at another symposium. James is the co-founder of Thinkmodo, the agency that created just about EVERY insane viral video you ever saw – the telekinetic girl in the coffee shop, the possessed baby in the runaway stroller, talking produce in the supermarket, you name it. What's more many of these videos involved RC gadgets like the human torch and flying people, so he's kind of a kindred spirit. James approached Randy with the idea of a flying snack tray for Chef's Cuts jerky, and Randy looped me in. The two of us went to Thinkmodo's office to talk specs.

It was pretty fun to visit Thinkmodo's office and check out the props from their past videos. Michael Krivicka, Thinkmodo's other co-founder and a drone lover himself, laid out what they were looking for: a cutting board sized drone with ample space for jerky and plenty of protection as fingers reached for jerky. This drone, the Jerkybot, would follow David Ortiz wherever he went, providing jerky on demand no matter what he was up to.

This, at first, didn't seem that daunting, but it got more complicated the more I thought about it. As I saw it there would only be room for 4" props in a carbon fiber box that doubled as the frame itself, with slats in the top for finger protection. With limited air intake, extra weight, and a jerky payload, I guessed that such a build would require something like 80% throttle to hover, which leaves little headroom for maneuvering and control. Not only that, I didn't relish the thought of flying a drone next to David Ortiz with the motors screaming near full throttle.

Luckily for me, I'd just made the Liberty Ducted Quad, so I knew that 4" props in ducts can easily handle that weight at well below 50% throttle. Randy and I left the meeting and headed right back to my place to test the LDQ, to see how much we could limit its intake. We taped more and more gaffer's tape in strips across the top to see how much air we could block before it lost too much lift. The tape slats vibrated and screeched but the LDQ performed remarkably well up to a point, and then suddenly just said no. It was really weird to see a quad at full throttle, unable to get more than an inch off the ground.

You can tell I wanted this job 'cause I wore a collared shirt to the meeting.

Design

Time was severely limited – we needed five builds for safety, with no time for iterations. I would design the frame with 3 versions of the top plate, with 7, 9, and 11 slats covering the intakes. Once we got them built we'd then choose the top that offered the best combination of performance and safety. 

The design itself was fairly straightforward. I adapted the LDQ's ducts, and changed the mounting points to accommodate the different motor layout. The LDQ has a square motor layout, but the Jerkybot needed the motors spread out side to side to make space for jerky in the middle. The battery has to be hidden, so I made sure there was enough space for a 1300 between the ducts inside as well. The frame was just a bunch of rectangles, so it wasn't THAT hard to draw up. What I hadn't totally figured out was how the sides would be attached, and how the battery was to stay put inside the frame. But time was short so I ordered the carbon and left those problems for later.

There's a big ol' hole in the bottom to shove a 1300 inside.

There's a big ol' hole in the bottom to shove a 1300 inside.

With the top off. Each duct slips over 4 standoffs to keep it in place.

With the top off. Each duct slips over 4 standoffs to keep it in place.

Build

The parts came in and I built the first one. I used Rotorgeeks 2205 2700's with Aikon 30's, a D4rii and a DTFC and...nothing else! OMG LOS quads are so easy to build! The DTFC's are great time savers, no need to stack an fc on a pdb and connect them, just double stick tape them to the frame. It might have a suspect gyro for FPV but it more than does the job for LOS. I screwed on the top with 11 slats, the one with the least airflow, and it flew great, way better than expected. Since it offered the best finger protection it was the obvious choice. We flew it for Thinkmodo then broke it down and sent the carbon off to paint along with parts for the other four frames. I was pretty excited that James hired Nub (of Orange County Chopper fame) to do the paint.

Now, I've designed plenty of frames, but I've never designed one that's supposed to look like something else, in this case a butcher block cutting board. And with the tight time frame I hadn't fully thought through how we were going to secure the top without any screws at all. I ended up using 3d printed pieces that slip over a standoff in each corner. The side pieces would be glued to them, and the top would be glued to the sides. The top and sides would remain an assembly that screwed to the bottom via the standoffs embedded in the corner pieces, which would allow the frame to be opened up for maintenance. I really had no idea how well this would work, but with Nub spackling over the screw holes on the top there was no other option.

Once the spectacularly painted parts came back Randy and I hunkered down to build all five drones in a day. The drone building was familiar, but the gluing was not. After some experimentation we ended up using epoxy for the sides and corners, and CA for the tops and sides. All the scuffing, gluing, and clamping took an entire day. The results felt pretty solid but I had no idea if it would survive a crash or a hard landing, and I wasn't about to bash one before the shoot day. 

Look at this thing!!! Nub painted the TPU ducts as well. Many people had a hard time believing this was carbon fiber.

Look at this thing!!! Nub painted the TPU ducts as well. Many people had a hard time believing this was carbon fiber.

I had planned on designing a 3d printed cover for the battery bay, but the battery wedged itself inside nice and snug, so there was no need for another part.

The Shoot

We went to Thinkmodo a week before the shoot to practice all the moves in the video. Randy has a lot of experience flying on live TV so I gladly deferred to him for piloting. I've had jelly fingers on race day so I was happy to not deal with the pressure of flying on camera in close proximity to a millionaire athlete. Randy expertly piloted the Jerkybot through all the scenarios in the script, and Michael cut a reference video that looked just like the story board, so we were feeling pretty good.

We drove up to Boston the day before the shoot, and Randy and I headed out to do some flying as soon as we checked into our hotel. One turn out of the parking lot and we found ourselves in front of Boston Dynamics, so I had to pay tribute.

The shoot itself was both fun and super stressful. We only had David for a limited time, but Michael ran a tight ship and we busted through the shot list. The most interesting thing, for me, was seeing how much more David brought to the shoot, giving every motion a little extra charisma and flair. He really made the reference video we shot at the Thinkmodo office look very lame by comparison. 

He was super mellow to work with as well. At one point a red pepper flake from the jerky got blasted into his eye and he barely reacted, he just calmly removed it. At another point the drone got blown into his crotch as he sat poolside, and he just stayed still while Randy flew it out of there. If you've ever flown an enclosed drone you know that it's almost impossible to control when a corner gets wedged against something and the flight controller isn't getting the response it's expecting. This often leads to one of those feedback loops that sends the motors to 100% throttle in a split second. It was really frightening watching Randy work that drone out of David's crotch, just inches above the water. Fortunately everyone reacted like a pro and disaster was averted.

We wanted to know how much water we'd spray on David so Randy did a little hovering over the pool.

The drone performed really well. We flew it in angle mode to keep things tame, and Randy was able to execute all the moves but one. That shot was David working out in the gym with the Jerkybot hovering next to him. Space was tight and it had to be about a foot from a wall, which sent air swirling around and made it drift around like crazy. It was really interesting to see how badly it flew in turbulent air, just like a racing drone getting propwash shakes in a hard hairpin.

The last shot of the day was a gag where David would climb into a car and the Jerkybot would dutifully follow him, only to crash into the car and fall to the ground. We fully expected it to shatter to pieces but amazingly it held together as it smacked the driveway. 

The Shoot, Part 2

Michael had a cut within days, and surprisingly, test audiences weren't buying it – they thought it was CG! The solution was to add behind the scenes footage of us designing and building, so Michael came by for a half day of shooting. Like most photographers I despise being front of the camera but I sucked it up and stuttered through the lines. Here's the final product:

And here's the behind the scenes video, with the car crash shot.

The video did really well, with millions of views in its original form as well as recut in many Facebook videos. I had a great time working with new talented people outside of our little drone racing world – I've never had so many 'brushes with greatness' in one project. And the Jerkybot is still going. I went to the Chef's Cut offices to demo it for the staff, and even flew it up to their neighbors on a fire escape and fed them some jerky. We also took it to Live with Kelly and delivered jerky to Kelly Ripa and Zach Quinto. Check out Randy's one-take mastery: