Half BBQ Grill, Half Drone | AI Design
A flying charcoal grill: a quadcopter that cooks four burgers while it hovers over a field.
The surprise: cooking electrically off the drone's battery would need about 2.5 kg of battery just for the heat, before it ever leaves the ground. So the fire stays charcoal and the batteries only fly.
Where we landed: a four-motor X-frame on 22-inch props, one-inch square aluminum tube arms, and a half-millimeter stainless firebox mounted on standoffs. The LiPo packs ride out on the arms, away from the heat plume, with a polished aluminum and ceramic fiber heat shield. Side intakes, an ash pan and a stainless spark mesh keep embers from dropping into the grass. Coals get lit in a chimney on the ground, and quarter-inch smash burgers cut the airborne time to two flights of about 2.5 minutes, with one landing to flip. That's about 200 Wh of battery (two 6S 5Ah packs in series, about 1.5 kg), roughly 10 kg all up, and about 1 kW in hover. Estimated cost is about $1,030 and about 50 hours of build time, plus a test flight with a 10 kg sandbag before anything gets lit.
Should I build it? Comment BUILD IT if you want to see the real thing. I'm not building it without comments.
The real builds: https://lardrocket.com
The AI in this video is Claude by Anthropic. Her voice (ElevenLabs) and the avatar (HeyGen) are AI-generated. The engineering conversation is real and unscripted.
Chapters
- 0:00 The Flying Grill Pitch
- 0:30 Battery vs. Charcoal Heat
- 2:20 Bicopter vs. Boring Quad
- 3:14 Flight Time and Weight
- 5:08 Keeping LiPos Away From Fire
- 6:35 Embers, Vents and Spark Mesh
- 7:33 The $1,500 Reality Check
- 8:58 Foil, Stainless and Aluminum Arms
- 10:24 Smash Burgers Save the Budget
Full Transcript
Brandon: Are you there?
Claude: Yep, I'm here. What are we building?
Brandon: Okay, here's the problem. My barbecue grill is always in the way. So I want a half drone, half barbecue grill that can fly.
Claude: (laughs) So the fix for a grill that's in the way is a grill that's in the way at twenty feet up. (sarcastic) Love it. What grill are we talking about, and how much does it weigh?
Brandon: Great question. I need to figure out a way to get the grill as light as possible. I'm thinking maybe it'll grill like four hamburgers, something kind of tiny.
Claude: Okay, four burgers is a tabletop grill, so maybe ten to fifteen pounds stock before you start cutting. The big fork in the road is fuel. Are you thinking charcoal, propane, or electric off the drone's battery?
Brandon: Ooh, I didn't think of electric. I was originally thinking charcoal. What are you thinking?
Claude: (exhales) Gut call, electric hurts. A burger grill wants around fifteen hundred watts for fifteen minutes, that's close to four hundred watt hours, and at maybe a hundred fifty watt hours per kilo for a real pack, you're hauling two and a half kilos of battery just to cook. That's before it flies. A one pound propane canister holds several kilowatt hours of heat at about a pound and a half full. Charcoal's light too, but the downwash turns it into a forge. So which matters more to you: does it actually cook WHILE flying, or just fly to the patio and land?
Brandon: It definitely needs to be cooking while flying at the same time. But let's cover the grill so that the wind from the… This is so funny. So the wind from the drone doesn't blast the charcoal because that'll be dusty.
Claude: (chuckles) Dusty is the polite version. Glowing embers in a rotor wash is more like a sparkler. Before we design a cover though, where's the grill sitting relative to the props? Dead center with the props out on long arms, or tucked right underneath them?
Brandon: I'm thinking, yeah, dead center is the grill, and then it has, I guess, two long arms, or maybe not long, but two arms with a drone on each side, and they have to self-balance. What do you think?
Claude: Careful with "two." Two rotors total is a bicopter, and that needs servos tilting the motors for pitch and yaw, which is twitchy even without a lit grill. Four motors on an X frame with the grill in the middle is the boring, solved version, off the shelf flight controller, done. Do you mean two props total, or two full drones bolted on either side?
Brandon: I was thinking two full drones bolted on either side, but I'm cool with the boring four motor option like you mentioned.
Claude: Good call, two separate flight controllers bolted together just fight each other. Next big number is flight time, because that sizes the battery and the battery sizes everything. Are we hovering for the whole cook, like fifteen minutes of burgers, or just a few minutes airborne?
Brandon: It would be great if we could make it the whole cook, but does this have to be electric, you think?
Claude: For the flying part, yeah, electric is the sane answer. A fixed pitch quad steers by changing motor speed many times a second, and a gas engine can't throttle that fast, so gas means variable pitch rotors or a hybrid generator, which is a whole other show. Fifteen minutes on batteries is very doable. Rough guess, grill plus frame plus batteries lands around fifteen kilos, big heavy lift props get maybe ten grams per watt, so call it two kilowatts in hover, around six hundred fifty watt hours with reserve. That's about four kilos of battery. The heat for the burgers still comes from charcoal or propane. What's your budget ceiling?
Brandon: Hang on, back up a second. So with 15 kilowatts, or sorry, 15 kilos, kilograms, how did you get that? It seems like we could make a homemade grill, custom made for this for like three kilos. What do you think?
Claude: Fair, I was guessing high on the grill. My fifteen was roughly five kilos of grill, about one and a half of charcoal and burgers, four of motors, props, speed controllers and frame, and four of battery. If you build a three kilo grill out of thin stainless, that's believable for a four burger firebox. Redo it: three grill, one and a half fuel and meat, four airframe, and the battery shrinks a bit because it's lifting less, call it three and a half. That's about twelve kilos all up. The catch is that battery and weight chase each other, every kilo you add needs more battery, which adds more kilo. One thing that won't shrink much: you'll need heat shielding between the firebox and the batteries. Where were you picturing the batteries sitting?
Brandon: I have put zero thought into the batteries versus heat problem. Surely we can isolate those easily, cheaply, right?
Claude: Mostly, yes, and cheaply, if you respect three rules. Lithium cells want to stay under about sixty C, and a charcoal bed is several hundred C, so first, never put the packs above the firebox, that hot plume rises straight into them. Second, put distance between them, out on the arms is great because the downwash cools them for free. Third, a polished aluminum radiation shield with an air gap, maybe a layer of ceramic fiber blanket, call it twenty bucks and a few hundred grams. And yes, I'll say it once: a lithium pack in thermal runaway over a lit grill is a real fire, not a bit. Are you okay with batteries out on the arms?
Brandon: Yeah, let's keep the batteries out on the arms. I like keeping them cool.
Claude: Good. Bonus, packs out on the arms also mean shorter power leads to the motors. Now back to the fire. Still set on charcoal, or would you take propane? Propane gives you a throttle and no flying embers, but charcoal is, well, real barbecue.
Brandon: I want to try charcoal if I can. That is real barbecue, as you said.
Claude: Then the cover needs to breathe. A sealed lid starves the coals, and charcoal wants bottom vents, which on a flying grill means embers and ash dropping out the bottom onto whatever's underneath. Were you picturing a kettle style lid with vents, or something more like an enclosed box?
Brandon: We definitely need vents. I was thinking anyone underneath the grill could be wearing like an old fireman suit. Like firefighters.
Claude: (deadpan) Sure, mandatory bunker gear for the barbecue guests. Or you could put an ash pan under the vents with side intakes and a stainless spark mesh, like a spark arrestor on a chainsaw muffler, so nothing glowing falls out. Where's it actually flying, over a patio, or over dry grass?
Brandon: Definitely away from a house, away from a patio, in a field, we'll say.
Claude: A field's good for the crash, bad for the embers. If that grass is dry, one spark through the mesh starts a brush fire, so mowed and green, with an extinguisher nearby. Okay, I asked earlier and you dodged it. What's the budget ceiling?
Brandon: I dodge all budget ceiling questions. Free is better. 100 bucks isn't bad. Let's just say $1,000. Can this be done for $1,000, you think?
Claude: Honest answer: not at a thousand, closer to fifteen hundred to two thousand. Here's why. Twelve kilos needs about two to one thrust for control margin, so roughly six kilos of thrust per motor, which means big heavy lift motors on twenty-two inch props. Budget versions are about eighty bucks each, so three twenty for motors, two hundred for speed controllers, a hundred for props. Flight controller with GPS and a radio, about two hundred. The killer is batteries: around seven hundred watt hours of LiPo is four to five hundred dollars, plus a charger that can handle it, call it one fifty. Frame and grill materials, maybe two hundred. That's about fifteen fifty. Time, I'd guess sixty hours: twenty building the grill and shielding, twenty on frame and wiring, twenty tuning and test flying with a dummy weight before you ever light it. If you'd accept five minutes of hover instead of fifteen, you could get near a thousand. Which way?
Brandon: Okay, so first off, I know we can knock down the price on the grill itself. The grill we can make out of like aluminum foil. Now it needs to be a stiff frame though.
Claude: Two problems with foil. Aluminum melts around six sixty C, and a charcoal bed with good airflow runs hotter than that, so the firebox burns through. And honestly, the grill was only maybe fifty bucks of the budget, the money's in motors and batteries. Thin stainless sheet, like half a millimeter, is light and survives. You're right about stiffness though, a floppy frame shakes the flight controller and wrecks the tuning. What were you picturing for the arms, carbon tube or aluminum?
Brandon: I was initially thinking broomsticks, but it sounds like you have a better idea.
Claude: (chuckles) Broomsticks would technically fly, briefly. Wood flexes, it's not consistent, and it gets heavy at the length you need. Twenty-two inch props put you around a meter and a half motor to motor diagonally, so I'd use one inch square aluminum tube from the hardware store, maybe thirty bucks, stiff and cheap. Carbon is lighter but triple the price. One catch, aluminum conducts heat beautifully, so mount the grill to the frame on standoffs, not bolted flat. Does aluminum tube work for you?
Brandon: Yeah, I think I can do aluminum tube.
Claude: Great. Then the big open question is still the one you skipped: full fifteen minute cook in the air at around fifteen hundred to two thousand dollars, or a five minute hop closer to a thousand?
Brandon: We need to figure out a way to burn these burgers faster. What do you think?
Claude: Good instinct, because the cook time is the spec driving the whole battery. Two tricks. First, light the coals in a chimney on the ground and only take off once they're ashed over, so preheat costs zero flight time. Second, smash burgers, about a quarter inch thick on a hot grate cook in roughly two minutes a side and still hit a hundred sixty F inside. That puts the airborne part around five minutes, which is your thousand dollar build. So who flips the burgers mid-flight?
Brandon: I was kind of figuring a crash would rotate the burgers as needed.
Claude: (laughs) Crash as a spatula. Bold. Cheaper option: land at halftime, flip, take back off, two flights of about two and a half minutes each, which is easy on the batteries too. Does landing count, or does it have to stay airborne the whole time?
Brandon: I think a single landing for flipping the meat is totally reasonable.
Claude: Then the numbers finally say something. Two flights of two and a half minutes, plus reserve so you never drain the packs below about twenty percent, means maybe two hundred watt hours. That's two six-cell, five amp hour LiPos in series, about a kilo and a half, around a hundred fifty bucks. All up weight drops to roughly ten kilos, hover around a kilowatt. Rough budget: motors two forty, speed controllers one sixty, props eighty, flight controller with GPS and radio two hundred, batteries one fifty, a charger eighty, aluminum tube forty, stainless grill sixty, heat shielding twenty. That's right around a thousand thirty. Time, I'd say fifty hours, and test fly it with a ten kilo sandbag first, because a tuning crash with lit charcoal is the expensive kind. Verdict: it works, and it's barely in budget.