======= Pneumatic T-Shirt Cannon ======= This project is a continuation on my independent study of pneumatics and motion control. Pneumatic sequencing and implementation has been studied and experimented with Legos. This project is my first time working with a physical pneumatic system, and is meant to serve as an introduction to constructing the physical systems. ---- ===== Design Concept: ===== The goal of this project is to build a self-contained pneumatic t-shirt cannon using PVC pipe, brass fittings, a polyurethane hose,and a sprinkler valve. For the cannon to be self-contained, it needs to be able to fire multiple shots from one charge. To do this, I will implement two separate PVC compressed air tanks in the design. A 3-inch diameter air tank will be used to store air for the next shot. One end of this tank will be connected to the sprinkler valve, while the other end will have a polyurethane hose leading to a larger 4-inch diameter PVC air tank. This larger air tank is meant to be worn as a backpack and it has two valves at the top: one to allow compressed air in, and one to feed air to the smaller tank. Both air tanks will be tapped with a 200 PSI pressure gauge to monitor the pressure levels. The solenoid in the sprinkler valve will be controlled using two different switches and three 9 volt batteries. One toggle switch will be used as a safety, while a momentary contact switch will be used as a firing mechanism. The toggle switch needs to be in the on position for the cannon to work. If the toggle switch is in the off position, nothing will happen when the momentary contact switch is pressed. ---- =====Parts List and Sources:===== [[http://www.pvcfittingsonline.com/ | PVC Fittings Online]]\\ [[http://www.homedepot.com/ | Home Depot]]\\ [[http://www.amazon.com/ | Amazon]]\\ ^ Part Description ^ Vendor ^ Qty ^ Price| | 4” Schedule 40 PVC Pipe - 5 feet | PVC Fittings Online | 1 | $16.70 | | 4” Schedule 40 PVC Cap Socket | PVC Fittings Online | 2 | $3.99 | | 3” Schedule 40 PVC Pipe - 5 feet | PVC Fittings Online | 1 | $12.41 | | 3” Schedule 40 PVC Cap Socket | PVC Fittings Online | 1 | $1.75 | | 3” Schedule 40 PVC Coupling | PVC Fittings Online | 1 | $2.02 | | 3” x 1” Schedule 40 PVC Reducer Coupling | PVC Fittings Online | 2 | $8.49 | | 1” Schedule 40 PVC Pipe – 5 feet | PVC Fittings Online | 1 | $3.91 | | 1” Schedule 40 PVC Male Adapter Mipt x Socket | PVC Fittings Online | 2 | $0.31 | | 1” FPT Auto Inline NFC Valve | Home Depot | 1 | $14.97 | | 0.25” x 25’ Polyurethane Air Hose | Home Depot | 1 | $15.98 | | 0.25” x 0.25” Lead-Free Brass Barb | Home Depot | 2 | $3.36 | | 0.25” Lead-Free Brass Hex Nipple | Home Depot | 2 | $2.72 | | 0.25” x 0.25” Lead-Free Brass 90-Degree FPT x FPT Elbow | Home Depot | 1 | $4.93 | | 0.25” Brass Packing Gland FPT x FPT Full Port Ball Valve | Home Depot | 1 | $4.46 | | 200 PSI Pressure Gauge with 0.25” Lower Connection | Home Depot | 2 | $4.99 | | 4 oz. PVC/CPVC Cement and Primer | Home Depot | 1 | $7.20 | | Contact Push-Button Switch | Home Depot | 1 | $4.98 | | Toggle Switch | Home Depot | 1 | $3.95 | | Teflon Tape | Home Depot | 1 | $1.47 | | JB Weld Epoxy | Home Depot | 1 | $5.67 | | MAX Alkaline 9-Volt Battery (6-Pack) | Home Depot | 3 | $12.98 | | Milton Industries S-684-4 0.25” NPT Tank Valve | Amazon | 1 | $8.33 | | Uxcell 10pcs Black Hard Plastic 9V Battery Clip | Amazon | 3 | $4.57 | ---- =====Construction:===== **Applying PVC Cement**\\ Every piece of PVC that is connected to another, is done so using PVC Primer and Cement. When doing this, it is important to remember that the PVC already has a smooth finish on it. Using a coarse piece of sand paper (60 grade was used in this experiment) you should briefly sand any surface that needs primer applied to it. Sanding it will create small scrapes which will give the cement more surface area to grab onto. Two coats of primer should be applied both to the outside of the pipe, and the inside of the fitting. Cement should be primarily applied to the outside of the pipe, however a small amount inside the fitting is good too. \\ \\ **Attaching the Brass Fittings:**\\ Anytime brass parts are fitted together, it is necessary to use teflon tape to seal any potential air leaks in the thread. Teflon tape is most effectively applied in a clockwise fashion around the thread, with about 3-4 layers for a strong seal. When attaching the brass fitting and pressure gauges to the PVC pipes,I used a 1/2 inch drill bit to drill a hole small enough for the threading to fit securely in. When drilling these holes, it is often necessary to start with multiple pilot holes for ease of drilling. The threading and PVC connection is reinforced using epoxy. \\ \\ **Step 1: Large Air Tank**\\ The large air tank will be used to store air so that a compressor does not need to be used for each individual shot. To build the large air tank, you will first need to cut a piece of 4 inch diameter PVC pipe, to a length of about 2 feet. Drill a hole about 4 inches from the top of the pipe for one of the two pressure gauges. Apply a small amount of epoxy to the thread of the PSI gauge, and screw it tightly into the hole, and then apply more epoxy on the threading inside the PVC pipe. Next, take one of the 4 inch PVC caps, and drill two holes into the top of it, about 2 inches apart. From the outside of the cap, insert and seal the threading of one of the brass hex nipples, and the threading of the NPT tank valve each into one of the holes. To complete the large air tank, cement a closed 4 inch PVC cap to the bottom of the tank, and the PVC cap with the brass fittings to the top of the tank. The large air tank is pictured below.\\ {{:img_2110.jpg?nolink&400|}} {{:img_2111.jpg?nolink&400|}} \\ \\ **Step 2: Small Air Tank**\\ For the smalle air tank, cut a 3 inch diameter piece of PVC pipe to a length of 1 foot. Drill a hole in the side of the PVC pipe for the PSI gauge. The elbow piece is not necessary, however I included it to make the gauge easier to read. Seal the connection with epoxy. Drill a hole in one of the 3 inch PVC caps to insert the threading end of one of the brass barbs and seal it with epoxy. Use PVC cement to cement the cap to one end of the pipe, and a 3-to-1 inch PVC reducer to the other end. Cut a 6 inch long piece of 1 inch diameter PVC pipe to cement into the reducer, and then cement one of the male adapter Mipt x Socket couplers.\\ {{::img_2108.jpg?nolink&400|}} \\ \\ **Step 3: Barrel**\\ The construction of the barrel does not require any drilling or brass components. Cut a 1 foot long piece of 3 inch diameter PVC pipe. Cement a 3 inch coupler to one end, and a 3-to-1 reducer to the other. Cut a 6 inch piece of 1 inch diamete PVC and cement it into the reducer, with an Mipt x SOcket coupler cemented on the other end.\\ {{:img_2107.jpg?nolink&400|}} \\ \\ **Step 4: The Electronic Connection**\\ All of the components need to be soldered in series to power the solenoid in the sprinkler. First solder the three 9V clips in series by soldering the black to the red wires. At the end of that chain, solder one wire from the toggle switch. Solder the other wire from the toggle switch to one of the solder points on the contact button. Finally solder the remaining end of the 9V clips and the other solder point on the contact button to the two wires coming form the solenoid. Right now it is easiest to tape the batters and switches to the build, but in the future I plan on designing an attachment to make in a 3D printer to organize the electronics better. I will update this document with that file when it is completed.\\ {{::img_2112.jpg?nolink&400|}} \\ \\ **Step 5: Total Assembly**\\ Connect the barrel and the small air tank using the sprinkler valve. Teflon tape should be used on the PVC threading to prevent any air leaks. Finally, connect the two air tanks together using the polyurethane hose.\\ {{::img_2109.jpg?nolink&400|}} ---- =====Testing===== On the planned day of testing, the wind was too strong to accurately test it outside. Instead, the cannon was tested inside the lab. The cannon was angled at 22.5 degrees to prevent it from hitting the ceiling. The compressor available only allowed testing to reach a maximum of 105 PSI. Three trials were conducted for each 50, 75, and 100 PSI. The results are included below, as well as pictures of the testing set-up and a video of the cannon firing at the maximum 105 PSI.\\ {{::img_2128.jpg?nolink&400|}} {{::img_2129.jpg?nolink&400|}} {{ :screen_shot_2016-04-16_at_5.12.40_pm.png?nolink&300 |}}\\ ---- =====Final Words===== The cannon functions properly, however I have not yet gotten to test it at pressures higher than 105 PSI due to needing a stronger compressor. In future iterations of the cannon, the design can be improved upon by using schedule 80 PVC instead of Schedule 40. Schedule 80 PVC pipe can withstand a greater internal pressure. With a larger internal pressure, the air tanks size can be decreased to still hold the same amount of air. Although the project has been assembled and tested, I plan to update the project at a later date by attaching the aforementioned 3-D Printed piece.