For the tech-savvy Hackaday audience I wanted to share a couple of technical details behind my latest "wearables" project that didn't make it into the youtube video.
My goal was to design a system to launch a 150 pound person at least 6 feet up in the air. The main technical challenge then is how to apply a LOT of force in a very short amount of time. I went with four 1.5 inch bore pistons that will max out at a total of 1416 pounds of force when supplied with 200 PSI. The air is stored in a spun aluminum air tank from the world of "air ride" vehicle suspension systems, which I attached to a fall-stop harness so it can be worn on the user's back. The tank has a schrader valve for easy filling, along with a pressure gauge for monitoring tank pressure and a pressure relief valve in case I fall asleep while filling the tank. Next comes the interesting part. In order to achieve maximum piston speed, you need to move air into the cylinder as quickly as possible, which means using large diameter tubing (I used 1/2 inch), high flow rate pneumatic valves (I used these 5/2 solenoid valves), and most importantly - NO REGULATOR. A regulator would absolutely wreck the performance of the system because of how much it limits your flow rate. The system will only move as fast as the slowest link, so I designed everything to be as high flow-rate as I could reasonably get with off the shelf parts.
During bench testing, I noticed one piston started to move earlier than the other. This would have thrown the user off balance, and I realized that the reason was that in my hurry to get testing I had made the tubing lengths different, and a longer tube meant that it took more time for the air to get into the cylinders. So, when attaching the final version to TikTok star Tyler Csatari, I made sure that all of the tubing circuits were exactly the same length from the air tank to the solenoids and then off to the pistons. That way the pistons all fired at exactly the same time, and Tyler was never thrown off balance due to unsynchronized pistons.
The system needed some way to be triggered, and I went with one of my favorite tricks - taking apart a broken cordless drill off eBay and using the very robust and ergonomic trigger switch built into the body of the drill. The idea is that the user starts to jump, and then just as their feet are about to leave the ground they press the trigger which fires the solenoids, so the pistons shoot down and launch the person much higher than they could normally jump. It turns out this was a bit of a mistake. Although it worked, it was very difficult to press the button at just the right time. A difference of 0.1 seconds meant the difference between a mild jump and a really high jump, so it was really inconsistent. For the next version of this device, I need to find a way to automate this to take human error out of the equation. Any suggestions, Hackaday smarties?