Multicopter Warehouse was recently presented with a challange to come up with a way to drop 150 golf balls for a contest to open up the 33rd Annual Rotary Golf Tournament in Littleton Colorado. "Well of course we can" we said! Next we had to figure out how to actually accomplish it. Some of the design challanges we had to face included:
Given the weight of the golf balls, the only machine in our inventory that can handle this is the DJI Matrice 600. The problem is that with almost 16 pounds of golf balls, plus the weight of the drop mechanism, we are going to be slightly over the weight limit for the aircraft, especially considering we are flying it at over 5,300' above sea level. Since we only needed a few minutes of flight time, this wasn't going to be an issue on the Matrice 600.
The size of the golf balls is roughly a cube would fit nicely between the landing gear of the Matrice 600, so again, this made it much easier to figure out how to pull this off.
For the drop mechanism itself, we looked at designs like shipping peanut dispensers, bag designs that would release one side of the bag, and different box type designs. We finally settled on a box design with a slanted bottom and a door that was hinged on the bottom. Some quick tests proved that this would be a reliable mechanism that would drop all of the balls every time.
Knowing that we needed to keep the box as lightweight as possible, we quickly ruled out aluminum, wood, and acrylic as major design components. To save as much weight as possible a frame of aluminum was the covered with super light corrugated plastic sheets. The servo attachment plate and release mechanism were designed in-house and 3D printed on our Lulzbot Taz 5 printers. To trigger the servo, we used the landing gear switch. While this meant the landing gear wouldn't retract, it also meant that we didn't need to add a channel expansion board or a seperate radio system.
Bench tests proved the system worked perfectly every time, but bench tests never tell the whole story. the big question was how was the Matrice 600 going to handle an 18lb payload at over a mile above sea level. Once everything was finalized on the bench, it was out to the parking lot for a test flight. The Matrice 600 took off beautifully with zero adverse effects from the weight. Just as the Matrice 600 hit about 6' off the ground, the dynamic landing gear setting (which we obviously had forgotten to disable) kicked in and before we had flown over to the grass area, the system released all 150 golf balls onto the parking lot, sending them flying in all directions and taking us a while to round them all up. We reloaded the system, disabled the dynamic landing gear, and took off for another test. This time everything worked flawlessly and we were confident enough to go give the golf course a demo the evening before the event.
Why drop 150 golf balls from a drone? At many golf tournaments and events, attendees often have the ability to purchase one or more balls. The balls have been dropped by helicopter (very expensive) and sometimes from a tractor (messy, inaccurate, and potentially damaging to the golf course). The winner(s) are the ones whose ball comes closest to the hole or actually fall into the hole. By using a drone, the drop area was minimized, it was extremely affordable, and had zero impact on the golf course itself. And let's be real, dropping 150 golf balls from a drone is just cool as hell!