Post your photos here. All teams are welcome to post photos here.

Initial testing of a valve for fast operation. Moisture in the launch tube provides a mist showing the no flow to full flow time is very short. Notice the initial blast before the mist is removing the label from the bottle. The photo sequence was captured by a high speed camera we were graciously loaned for the weekend of testing. The first set of photos was taken at 1,000 frames per second. By counting frames you can time the launch from the first sign of motion until the tank quits spewing spray. To get this result requires a fast full flow valve. Photo by Arlington Team

Valve test for flow and duration

Here is another test photo sequence. We got a little crazy with the pressure and hit that water bottle with an apple. Gotta love high speed cameras. Test pressure is classified ;-) Photo by Arlington Team. Composite photo from video by Technician

Composite edit by Technician

We were testing a pressure vessel and valve. Neither broke. The tank and valve that is. The water bottle and apple both broke.
This is a clocked launch from the 4 inch foam ball tube prior to finding the pressure for maximum efficiency. The speed increases early and then drops off. Cutting the tube at the maximum speed point for our operating pressure improves the launch speed considerably. Note the spacing of the last 2 pulses. It's almost twice the distance of the two closest pulses which shows we lost almost half our peak speed at the muzzle. The time measurements were done with an O-Scope and a set of pick-ups along the length of the launch tube. The higher the peaks and shorter the space between the peaks the higher the speed. Note the very high acceleration at the beginning of the launch. This is why short launch tubes work fairly well with a valve that opens quickly and poorly on slow valves.
Knowing the distance between the pick-ups and the time to pass between them gives the speed using the speed = distance/time. We launched a foam ball over 450 feet/sec from a 4 inch tube. The problem with shooting chronographs is that they give speed only after the projectile left the launch tube.
More details on this procedure are posted in the barrel length trim page. This particular graph is of the 4 inch tube under low pressure condition where the volume of expansion of the tank release is less than the volume of the launch tube. What is of note is the valve provided enough kinetic energy to the ball to launch it in spite of the fact the tube was below atmospheric pressure for over half the trip and slowing the ball. With higher pressure, the expansion of the air was enough to continue accelerating the ball all the way to the muzzle. Acceleration is in the first 2 feet and it was slowing down the remaining 3 feet. This shot was at 20 PSI.

Launch speed graph by Technician..

Launch Speed Graph by Technician

We took the time to clock a few launched t shirts and examine the flight properties. Video is too large to upload. Photo by Arlington Team


Ripcity ad
Intel is posting the following ad that will go into Ripcity Magazine, the Portland Trail Blazers publication, Nov 19 - December 16. I just received permission to post it here for you. Posted by Technician.

Ripcity ad

Action shots posted by the Arlington team.

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Field test at the last home football game. With a little help from TORCH of the Tri-Cities FEVER arena football team. see build page at

This is an oops.

Knocked over one sawhorse, folded the legs in under the other one backing it, and put a hole in the carpet with a t shirt.
Test pressure was within the contest rules. Be safe.
Photo by Technician

Here is a modified tire valve to fit in a 1/4 inch brass pipe cap. The ability to remove a tire valve fill and switch to an air tool quick coupler appealed to me.
Valve photos by Technician.


Fill Valve installed

An alternative to using PVC for

the air tank is to use metal.

My prototype is using a free disposable Freon tank from an auto service shop. For safety and to prevent leaks and the thin metal from tearing, the hole for the new larger pipe was cut smaller than the pipe and beveled in with a ball peen hammer. This provides a large surface for the brazing job and protects the edge from starting a metal tear. We retained the original safety rupture disk. The hand beveling gave us a feel for the strength of the metal and confidence it won't tear out. The large joint area is for the mechanical load the joint must hold. It no longer just holds a service persons charging hose, but now supports a launch tube. The metal is malleable and shows no sign of cracking or splitting in the beveled area.

The tank used to contain Freon refrigerant R134a. The temperature pressure chart for this refrigerant is simple to find with a Google search. It's temperature chart indicates the tank was designed to store Freon at the pressures we will use for the launcher. The tank should retain it's strength except in areas we modified it, so it will need proper pressure testing. We will not be using this tank above it's original design limits. We are assuming it is designed to store Freon in the normal summer conditions of an AC service tech in summer sunlight, on pavement servicing cars, etc. I believe the tank was designed to safely store compressed gas at over 100 PSI. Metal tank photos posted by Technician.

Original tank

Beveled top and rupture disk

After brazing the tank is ready for leak tests, pressure tests, and paint.
Brazed outlet and fill pipe

Another alternative to PVC is to use ABS. This apple cannon is air powered and been in use every year for the last 6 years at a church camp. It was built to test ABS cellular core pipe for air pressure as spudders were using it for combustion spud launchers. I did everything wrong except the glue to test the pipe. I used DWV cellular core which is not rated for pressure and put the fill valve in the side to create a weak spot. The pressure test failed to cause a failure when tested to 85 PSI. We have been using it every year to launch fallen apples cross the field using pressure from 30-65 PSI. An apple that doesn't come apart from a rotten core will travel a little over 500 feet with this cannon.
I would not hesitate to use ABS for the t shirt launch tube. 4 inch ABS DWV pipe has stood up to years of moderate pressure testing.
ABS apple launcher by Technician.
ABS test cannon is now used to launch apples

My bucket for clocking launches took a beating. The initial crack was from testing with a foam ball at higher pressures. The ball launch has been discontinued after the launch tube was optimized in length for maximum launch speed. We managed to exceed 400 FPS with this foam ball.
Broken Bucket by Technician.

bucket sand and ball

While clocking a few t shirts in my backyard, the bucket I was catching them in gave up. High impact plastic buckets are impact resistant to a point. Tossing a few t shirts in the bucket was too much for this laundry basket.

Broken by laundry

Recorded test pressure that did this to the bucket. Ouch. I need a steel bucket for full pressure testing.
Tank pressure photo by Technician.
Test Pressure and paint masking