Pneumatic Candy Canon Delivers COVID-Safe Halloween
Halloween is big deal in our household. Now is the time when I start thinking about how we might revise or update the presentation. With the onset of COVID, in 2020, we decided to skip the year. Prior to the availability of vaccines there was no way to ensure a safe experience with what has historically been a large crowd.
In 2021, given the availability of vaccines, we opted to resume engagement with trick-or-treaters. However, we did so taking precautions to keep our boo-crew at a safe distance from the kiddos. The core of this strategy was not allowing trick-or-treaters into the yard.
Instead, we enhanced the decor along our fence line, and delivered candy to the front gate using a pneumatic candy canon. While not yet perfect, this worked quite well. This post details some of the design considerations, experiments, and lessons learned in creating the candy canon.
Others in the neighborhood were experimenting with using PVC pipe to create a candy chute from a second story window to their fence line. This was nice and simple, since gravity did all the work for you. However, ours is a single story home. Further, we didn’t relish the idea of Boo Crew on the sloped roof.
I thought it possible to use air pressure to push the candy along the tube, not unlike the system we find at drive-up banks or pharmacies. I could use our existing Shop-Vac in reverse to generate the air flow, connecting it to a length of PVC pipe.
Experiment #1
The first experiment had the Shop-Vac in the front yard. If first of two 10-foot lengths of 2-inch PVC was secured to the gate at waist height. The length was held up by a couple of wood-working rollers borrowed from my table saw. The breach end of the pipe had a T-joint. The hose from the Shop-Vac forced air through the straight section. Candy could be dropped into the upward-facing T.
This arrangement worked reasonably well for a first try. Candy pushed into the T shot down the tube. In fact, with nothing at the muzzle end, the candy was lobbed across the sidewalk into the street.
To address this, I added a 45-degree fitting at the muzzle, directing the candy toward the ground. We then rigged a plastic cauldron under the muzzle, to catch the candy before it hit the ground. The result was candy landing in the cauldron with a most gratifying thunk, thunk, thunk!
We experimented with various different types of candy. Also, shooting several pieces of candy at a time, as we typically give to each kiddo.
Some candy in small boxes (Milk Duds) occasionally jammed in the tube, requiring a significant effort to clear. We fussed and tweaked to keep the barrel of the canon straight and gently inclined toward the gate.
Also, the Shop-Vac was very noisy. Far too noisy to have nearby.
Experiment #2
Our second round of experiments, the following week, built upon the first, but we changed to using a single length of 3” PVC pipe. In theory, the larger pipe would prevent the Milk Duds from jamming in the barrel.
The theory was sound, but flawed in another manner. We no longer had any candy jams, but the Shop-Vac was not able to deliver sufficient volume of air to reliably drive the candy down the much larger barrel.
The cross-sectional area of the tube was now large compared to the candy. There was much reduced back pressure. A dramatically larger volume of air was necessary to push it along.
Using the 3-inch pipe the breach end had to be elevated to an entirely impractical height to improve reliability of delivery.
October 31, 2020 – Production
The evening of Halloween we reverted to using a single length of 2” pipe, wrapping it in wide, black tape so it was not stark white. We used a taller, heavier and height adjustable speaker stand to hold the breach end at shoulder height, co-opting gravity to aid in moving the candy down the barrel.
The Shop-Vac was relocated to the back of the property to keep its noise from being a nuisance. Several lengths of PVC pipe and a long, flexible hose carried the air flow to the breach of the canon. It was about 70 feet away from the working end of the candy canon.
This third arrangement was an improvement over both prior experiments. Elevating the breach helped reduce the potential for jamming. Relocating the Shop-Vac made conversation much more pleasant.
It is worth noting that the flexible dust hose impacted the force of air in the barrel. When candy was loaded into the breach, the hose would react by stretching a little, absorbing some of the force of the air. This could be offset by placing a palm over the opening where the candy was loaded. That created a pressure increase to get the candy moving.
While we retained the plastic cauldron to keep candy from shooting out onto the ground, many kids simply held their bag under the muzzle and waited for the thump, thump, thump of the goodies arriving.
It’s said that, “if you built it, they will come.” And the kids did come. Our traffic of trick-or-treaters was only slightly reduced from a typical year.
The candy canon delivered upon its promise. We were able to distribute our usual (excessive) quality of candy to trick-or-treaters while maintaining safe distancing for our crew. None of our team contracted COVID as a result of Halloween 2021.
Thanks to Paul Hewes (pictured) for the assistance both in experiments and as one of two Boo-Crew gunnery officers.