Have I Found the Fastest Air Cannon Valve?? 

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First thing I thought of was destin at smarter every day and his cannon but your in luck cause he shoot baseballs xD

I know the answer. The ball is subsonic because your airflow is subsonic. You need a de Laval (convergent-divergent) nozzle at the outlet of your tank to make the air jump from sonic to supersonic.

That was awesome Tyler! Definitely fun into that issue before too -- more money spent doesn't mean a better project! Looking forwards to the car door!

The main limitation with your design is the flow restriction of the tank and/or valve. Also I would strongly suggest using a triggered burst disk design. Hard to explain this in a yotube comment but I'll try. You have two burst disks in sequence, where the space between the disks is pressurized to some amount below the burst pressure of the disks. Then the tank can be filled to a much higher pressure than the burst disk pressure since the pressure differential (tank pressure minus pressure of the space between the disks) is still less than the pressure to burst the disks. Then you can fire the gun by simply venting the space between the disks, thereby exposing the tank disk to the full tank pressure, rupturing it and the other disk shortly after. All the benefits of a burst disk design plus reliability and controllability since you can fire at will without any complicated things like hot wires.

1) Stab some holes in the tennis ball, they expand quite a lot in vacuum. They are sometimes filled with gas. 2) Your valve/feeder diameter should be at least double the size of your barrel. 3) Your Tank volume is waaaaaaaaay to small. 4) Want to use a unreasonable and unsafe amount of pressure for cheap? Try steam. Basically put some water in the tank and light it up in fire.

The weak link of your design is too small air tank. You have high pressure in your air tank, but not enough Air volume. By the time the ball reach the end of the barrel the pressure drop significantly because it has to fill the whole pipe with air. Double the size of the air tank and you will see significant increase in speed.

Years back I was working on an avalanche control invention using compressed air and a combustible mixture to try to imitate the explosive shockwave produced by small explosive charges. I built the device around what's called a 'regulator' cannon. This is a configuration where the projectile barrel is nested inside of the pressure vessel with a void space at the back. Inside that void space is a piston with a neoprene disc on the front of it. When compressed air is put in the back of the device the Piston is pushed forward pressing the neoprene disc against the back of the barrel. Compressed air squeezes around the edges of the neoprene disc filling the pressure vessel. When you let air out the back of the device, the vacuum pulls the piston away from the barrel creating a very large aperture. Nonetheless, with only compressed air you cannot exceed the speed of sound at the muzzle. Compressed gas can only expand at a maximum of the speed of sound in that gas at whatever given temperature and pressure. As the gas expands it becomes cooler and the speed of sound becomes slower. I overcame this by injecting oxyacetylene into the pressure vessel. Igniting that also pushed back the piston, achieving supersonic muzzle velocities.

Fun facts about this cannon: The fuzzy tennis ball polished the inside of the new barrel after a couple fires. This tennis ball has the kinetic energy of a 7.62x39mm AK-47 bullet.

Definitely need to go down and see Smarter every day's air cannon

The speed of sound is the speed at which a pressure wave will travel through air. When you open the valve to the tank, the outflowing air is limited to the speed of sound. You cant accelerate an object past the speed of sound with a propellant that wont expand faster than the speed of sound. The solution is a de laval nozzle between the ball and the air tank to accelerate the flow past supersonic. It's a nozzle typically used in rockets and high performance jet engines, with geometry that makes the flow accelerate past supersonic. That way the air is supersonic, and can carry the tennis ball past the speed of sound.

You’ll be limited by the speed of sound for pretty much any air cannon, the trick is to increase the speed of sound. Using heat works well for this, a heating element inside the pressure chamber will allow you to still operate within the pressure limits of your design but increase the speed of the flow. Changing from nitrogen to helium or another light gas would work well. You could also switch back to your burst disk design, and use a high pressure propane-oxygen mixture in the air tank, which would be ignited by a spark at the back of the tank. The increased pressure and heat will burst the disk and result in much higher exit velocities

Your air cannon is much cooler than ours. Ps you deserve more subs

If you want the valve to open faster, add a slot to the connection point between the air cylinder and the valve handle. That why the air cylinder has accelerated before it cracks open the valve. You can see the air cylinder jump, then slow down, then accelerate again. This is because of the same issue the cannon has, the air isn't flowing into the cylinder fast enough to build pressure to overcome the friction of the valve. If you let the ram accelerate before it opens the valve, then you're using the rams momentum to open it, not air pressure.

Awesome video Tyler! I wonder if that resin filled ball could achieve a higher speed because it would have less opportunity to expand from the high pressure as its trying to get itself out of the barrel! Can’t wait to see the harpoon! Don’t die!!

This was really interesting dude! Excellent work 🙌🏻 i always love your uploads

Gosh Tyler, no wonder you take some time between videos, you're always busy being a great inventor and a mechanic, and a super smart guy! Excellent video! I love it when you get excited about what you've achieved/accomplished!

If you think friction is slowing you down, you should try lubricating the barrel and projectile. You'll have to use lard to keep the Mythbusters references going.

The storytelling and and pacing of this video is insanely good. Watched and enjoyed every minute man. Those slow motion shots through the plywood were crazy!!

It's very refreshing to see a young man with so much talent, inquisitiveness and drive. Keep up the great work.

Your barrel needs to be longer, and you need a vacuum reservoir at the end of the barrel. When the valve is initially opened, air molecules will make it past the tennis ball, and cause drag as the tennis ball later accelerates past them. A vacuum reservoir is basically a much larger diameter portion of barrel located at the end, so that the rapidly expanding gases do not cause the interior pressure in front of the ball to increase sufficiently to cause drag. Ideally the volume of the vacuum reservoir would be as large as is feasible.

SmarterEveryDay wants to know your location

Awesome stuff! I need to go watch the previous vids in this series…

I did this when i was a kid, the burst disc is ideal, but if you are crafty enough you can also make and use a piston valve, thats actuated by the pressure in the vessel, and therefore incredibly fast. dont forget to build in something to slow the piston down safely. The key really is to have a large reservoir behind the valve or burst disc that necks down the diameter of the barrel. also understand that gas can only expand so quickly.

I don't know if you have made any further developments in this area, but what you need is a pilot-actuated diaphragm valve, or pilot operated piston valve. The pressure of the air itself holds the valve shut. The piston sits on the end of the cannon barrel. Both the bottom - the part of the piston against the barrel - and the top of the piston are subject to firing pressure, but air cannot leak around the piston. It's inside its own barrel with a good seal. Air CAN leak THROUGH the piston via a small passage, from the lower to upper chambers, but not to the barrel. An aperture is above the air space at the top of the piston. It's closed with a tappet valve or similar. Dislodge the tappet valve and the pressure in the top chamber dumps. Pressure on the bottom of the piston is now much higher, and blows the piston completely off the barrel. This opens a huge area very quickly for maximum gas flow. As soon as the tappet valve is released, pressure begins to build on top of the piston again, forcing it closed as air pressure from reservoir drops. Piston automatically resets as piston area on top is larger than piston area below, minus the area of the barrel cross section which is open to atmosphere. NOTE: this is how toilet flushometers work.

Oh man, you'd really get along with SmarterEveryDay, I feel like you got a while before you can beat his max speed but you're doing great! Hopefully you guys can collab in the future!

I think you had the right idea with the burst disk originally. You need something that's going to actuate within a fraction of a second. A pyrokinetic change, burst disk, or a very fast acting valve. You're also severely limited by the bore diameter of your pressure vessel. If you can overcome those two obstacles, you'll get significantly more acceleration.

I love the style of these videos! It really shows the process of your learning, and your struggles along the way!

I remember year ago Jörg Sprave building a supersonic air cannon and getting huge improvements by supercharging the ball valve by opening it with tensioned rubber.

The thing that always kind of has me scratching my head with these builds, is that they always seem to go down the 'potato cannon' route, when what they should probably be looking at for inspiration is paintball guns. Paintball gun valves (be it poppit valves or spool valves) are much quicker to release air pressure by design. Of course it would be much more complex to upscale a paintball gun than it would be to make a ball valve cannon, but a poppit valve would open much, much faster.

Love your vids keep up the good work

two potential modifications: 1.) add a de Laval to make your airflow supersonic 2.) make use of a striker and bolt valve like those found on older or cheaper paintball markers

I might humbly suggest pulling a strong vacuum in the barrel, and making a sled for the tennis ball to ride down the barrel in, to try and address the squishy friction issue. Though, having a vacuum in the barrel might cause the ball to expand in the tube/sled. Edit: I guess I missed him pulling the vacuum in the video, my bad

This is awesome! What is your barrel to tank volume ratio?

I've played with vacuum cannons and pressure cannons. in both cases to make them easily go supersonic I use a PVC and rubber tube wadding to seal on the cannons barrel. This transfers all the available power into the projectile.

I'd mention that there is a lot of specialty rental companies that you can pay much less to rent slow mo cameras based on your location. The camera for a slow motion setup will need a lot of light (multiple bright lights with stands and batteries depending on the location), usually a couple of speciality highspeed high capactiy hard drives (normal ones don't work, check it out) and protective shielding based on what you do (which you may already have covered) so I would suggest factoring those into your cost as well. Also thank you so much for the content and I'm always excited to see more!

Others have mentioned it but you need a convergent divergent nozzle out of the tank. Also if you think the ball squishes and rubs too much you can fit it in a sabot. Plus a giant valve.

You were on the right track with the burst disk. What you're essentially trying to create is a shock tube. What you need are two burst disks with different strengths. Consider this scenario; I have a tank I want to pressurize to 100 psi and then release as fast as possible. Attached to that tank I have a burst disk that will rupture at nominally 75 psi. Now the key is I need to prevent this disk from seeing a pressure differential greater than 75 psi until I want it to. So in front of this disk I’ll put another disk which will burst at nominally 50 psi and pressurize the space between them to let’s say 40 psi. Now when I pressurize my main tank to 100 psi, the first disk only sees 60 psi of differential pressure and the second only sees 40 psi, below the burst threshold for both. To trigger the system to burst I’ll begin equalizing the pressures in the space between the disks and the tank. Once the pressure between the disks is over 50 psi, the second disk should burst. Now the differential pressure acting on the first disk is 100 psi and it will burst immediately. For shock tubes, this is how you can get extremely precise pressure differentials. However you need to be VERY careful with a system like this as it is essentially fail deadly if you lose pressure in the space between the disks.

If you fix the barrel friction, valving, nozzle issues. You also have headroom in what pressurized gas you use, Helium, and especially Hydrogen have much higher speed of sound.

it really seams like you would benefit from extending the barrel length to three or 4 times longer with a vacuum pulled that would give you longer vacuum to accelerate in and should up the speed and would be a relatively cheap thing to test while only having to modify one variable

There are decades of hobbyist projects regarding pneumatic launchers online in forums, they solved the fastest valve question long ago, you need a piston valve with high flow geometry and its effective cross-sectional flow area has to be larger than that of the barrel. You achieve higher EFFECTIVE flow area by contouring the path of the flow so that it stays as laminar as possible OR you over-size the valve OR you build your launcher with multiple smaller valves that open simultaneously. If you are worried about tennis ball deformation, you may need to make it a sub caliber design and enclose the ball in a sabot, this will also make reaching super-sonic speeds easier.

I think your conclusion at the end about the ball compressing is correct. You could combat this by using the lower pressure but having a long distance of acceleration, ie. longer barrel (just watch your volumes to maintain pressure)

As you know, the problem is the speed of air release. This problem is solved industrially by valves that use an air pressure differential to suck a blockage out of the path. Basically, the barrel would be blocked by a plate that is free to move linearly. Move it back, and it unblocks the full barrel. There is a large tube around the back of the barrel that holds the air. but there is a small tube behind the plate just far enough that if the plate moved back to it, the open area between plate and barrel would be equal to the area of the barrel opening. This tube has a pressure release to the outside world. When you hit the pressure release, the pressure in the small tube drops to atmospheric pressure. The tube is sucked to the barrel by the barrel vacuum, but it also is exposed to the very high pressure of the tube holding the air, which more than counterbalances the vacuum. As soon as the pressure behind the tube drops below the pressure of the tank, minus the area under vacuum, the plate snaps open instantaneously leaving the barrel unobstructed. It takes a redesign of the gun though. You can't take the air right out of the tank--you need the reservoir around the barrel. This makes it critical to have a very solid design as you have a bursting hazard that is much less with your current scheme.

I worked with a company that build air cannons to shoot ice balls at aircraft landing gear for safety testing. We had to breach the speed of sound as the theoretical max speed of the impact was the max speed of hail plus the max speed of the plain. We’re talking about tennis ball seize monolithic iceballs. Now, I understand ice and tennis balls behave differently in terms of rigidity and compression. But I wanted to share some insights with you, you might be able to use. 1. Burst disks are definitely the way to go. If you find them unreliable you might have the wrong kind. We could never achieve the same speeds with valves as with pressure disks. We’re talking about a complete different magnitude of opening speeds. Basically the pressure disk opens with the speed of sound in that material. 2. Validate your speed measurement. It took us months and three setups to get it right. Especially with a tennis ball that compresses easily the speed will drop rapidly. The shorter amount of distance you can get an accurate reading of, the better. 3. U need a valve for the gas to move faster. 4. The most expensive solution, but a worthwhile one, I promise you. Use a gas lighter than nitrogen. Unfortunately you only have two real options. The very expensive helium and the very dangerous (and very leaky) hydrogen.

I’m blown away by your production quality and build quality! So glad I stumbled across your channel! 100% subscribing.

Airgun mad scientist here. I would recommend finding someone with some lathe skills (and a big enough lathe) to make you a scaled up version of a knock-open valve found on modern pre-charged pneumatic airguns. Obviously you'll need a big ass spring, a sear mechanism, and a cocking lever that's probably 3ft long. The idea here is that you have A LOT of gas not being put to good use. You reach max flow of the valve but way too late in the shot cycle. One thing a well engineered knock-open valve will do is open to max flow extremely rapidly (within milliseconds). The valve will also close itself with the ball about halfway down the barrel. What this creates, in turn, is a pressure gradient and, therefore, an acceleration of the expanding gases. As those gases accelerate, the ball does as well. You have way more than enough gas mass to transfer momentum into the ball, you just need that gas to go about 300fps faster to get the system (air and ball) moving at supersonic speeds. You could also just use a longer barrel, too.

You should try using an electric solonoid valve, Theyre perfect for small air rifles as they activate very fast and you can wire it to a switch. im sure larger industrial ones can be bought online for very cheap

You need a speed buffer for the valve. There are is a 12v Impact driver tool that basically starts spinning internally but only engages the outside shaft when the internal part reaches a certain rpm. It basically buffers all that rotational energy and releases to the inertial tip that acts like a hammering effect on bolts you are trying to lose or tight. If you use something like that for your valve it will open way faster. Also you don't need that much gas. As you can see, the ball is way out and the gas is not even a quarter empty.

Another option for your ball valve is a straight up hydraulic ball valve, They can still be used with compressed gases but are often rated up to 6000 PSI. Awesome video man

Agree, get larger tank. Some of the tank volume is filling the vacuum space of the barrel. Also, looks like the regular tennis ball may have ripped apart before hitting the steel.

Burst disc cannons are *_awesome,_* a couple decades ago when I was in my mid teens my main hobby was potato guns (back then I learned everything from an internet forum called SpudTech, currently known as SpudFiles), I have built literally hundreds of potato guns of all shapes and sizes in all three types, combustion, pnuematic, and hybrid, and the burst disc valve design was consistently found by all members of SpudTech to offer peak performance for both pnuematic and hybrid cannon designs (combustions not so much, they limit performance). It also makes reloading a _much_ more complicated task, the barrel has to be removed and the burst disc swapped every time so it wasn't popular with the everyday potato gunner, but some of us die-hards liked them. The Hybrid potato cannon is something you should also look into, you're 90% of the way there essentially. Way back when, two of our more prominent members (one of them a weapons developer for the DOD lol) were working on a burst disc pnuematic project together and got the brilliant idea to inject a stoichiometric mixture of fuel (propane) and air into a burst disc pnuematic cannon and slap in an electric igniter with the ignition pressure bursting the disc, it changed the potatogun game after they posted pictures of a refrigerator with a 3" hole through both sides (they shot it with a 3" diameter plug of concrete about 4 inches long at 800 FPS😂). The chamber of the gun has to be made very strong too, they need to be made of metal if shooting mixtures higher than 3-4 bars, Sch80 PVC will work below that (for a 2" diameter combustion chamber) but barely, steel is much preferred. A four bar fuel/air mixture will generate between 400-450 PSI at thousands of degrees F° upon ignition, and the gas can potentially undergo deflagration-to-detonation transitions if the chamber isn't designed properly which can put enormous shock stress on weaker materials. I could go on and on about this stuff but I'll end it here lol.

A longer barrel might help to give your projectile a longer time to accelerate. If you want to squeeze out every last bit of the stored energy in your tanks you could try heating them to keep gases from potentially liquefying for a split second as the pressure drops.

The amount of work you put in a video is tremendous. I am really excited to see the next one. I wouldn’t want to be a car door in your neighbourhood right now 🤣

The fastest valve for an air-cannon is to use the projectile's sabot as the diaphragm of the valve, so a sliding system that as it moves forward expands in diameter that can hold the rear of the sabot against the inlet to the "valve". This is somewhat how the cartridge crimp around a .22lr bullet works to ensure that the initial power from the rim primer doesn't simply blow the bullet into the barrel before the heat and pressure of it ignites all the powder. By using a cylindrical shuttle to control the release you can ensure even release all around by using only 3 trip-latches penetrating the barrel's pressure volume, when those are thrown the pressure immediately activates the release which unbinds the sabot AT full bore diameter. Puzzling it out? Air Chuck. You CAN operate a burst-disk system by putting pressure into the front of the barrel, when that pressure is relieved the disk will burst.

Love videos doing experiments like this! You're doing great Tyler!

Maybe a rigid low-friction sabot would help?

Love the video! An I love your enthusiasm keep it up 👊🏽

I think Mytbusters tackled this exact problem. They used a waaayy longer barrel to give the projectile more time to travel through low (zero) air pressure as to pick up more speed before leaving the barrel. Greetings from the Netherlands, Mark

love the subject , big fan, keep up the grind

See also: "Das Cannonon" which details the engineering behind the world's biggest gun attempt by the Germans during WW2. It utilized multiple combustion customers which would ignite as the projectile passed along the barrel.

You did a nice job on your air cannons and demonstrating them in this video 👍👍 I've got a bit of the air cannon bug 🤣😂 after attending a pumpkin lunch compaction a few years back. I've been working on putting the final touches on an air cannon, I built 10 years ago. It shoots tennis balls, 16.9 oz. Aquafina water bottles and commerical glue plugs. It would be great to see the speed difference in fitted water bottles in your cannons🤔

For this to work, you’re gonna need your gas flow to be faster than the speed of sound. You won’t be able to do that with normal air unless you make it hotter or use a gas with a faster speed of sound. Idk much about super sonic flows so maybe something can work that way.

your best bet would be an electromagnetic valve, there were training aircraft BB machineguns in about the 20s that used compressed air to fire steel BBs from a hopper, basically you need to make a solenoid that can move a needle valve style assembly working against the air pressure, this would remove the need for springs and even allow you to minimise how long the valve stays open since soon as the power is cut the pressure will shut the valve, only catch is how are you gonna power the electromagnet.....probably gonna have to have an insulated element that will allow you to have 2 isolated contacts for energising the electromagnet, or using a non-ferrous outer shell on that segment the valve is within.

I recently purchased a custom 22LR barrel. One of the primary features is that it has been hand lapped and hand polished. If you haven't tried this, it would be done exactly the same way for your purposes. In case you haven't tried this. A smoother bore always equates to faster speeds, all else being the same.

I don't know if anyone has brought this up in the previous comments (932 of them...) but I've found that the fastest acting valve is a Dust Collector Valve (or Pulse Valve). I use these for various special effects and whatnot - SMC - JSXFF-14N-5DSB PULSE VALVE. They're 1 1/2" but I believe you can get them in 2" through SMC and even bigger at other companies. Just a thought.

Great fun ! , i used to make QEV for my air gun couple years ago , its surely faster way to open

Greater seal of ball within tube needed....as you partially demonstrated . A cup of water or higher viscosity will help the seal. Sealing efficiency more important than drag. A wet leather cup seal is a great choice for a pusher design behind the tennis ball or other.

Great video. Try lubricating the inside of the barrel to lessen the friction which may be causing the speed to plateau .

Very cool, have you considered using a sabo style carrier to eliminate drag in barrel then splits off once it exists? Whoops guess that's already been mentioned, thanks for the great content!

You should follow the ball with a foam sabot. Cupped on the ball side to hold the shape and evenly distribute the force, flat on the back for maximum push down the tube like a piston. When it exits the tube the cup shape will force them foam to pull outward clearing away (cut in quarters btw).

after looking at the comments and destin's baseball cannon it seems two most important factors are size / dia of tank output and valve opening speed. You might think of some interesting new designs for it by watching the smart every day video, hella engineering involved though, this aint a simple problem like it seems

Your main problem in getting past the speed of sound, is the speed of sound it self. Gases only expand at certain speeds, which are not only determent by pressure, but also the gases specific speed of sound. To accellerate something, you hit it, with something faster. As your gas exits through a valve, that imposes lots of turbulance and restricts the flow, you lose a lot of velocity. Destin from SmarterEveryDay has created a cannon, I think you might be aiming for. He Build it as a baseball cannon. He uses a very clever custom build valve and helium, because its specific speed of sound is about four times that of nitrogen. Hope that helps.

Use a shell... 3D Print a split shell that prevents the ball from deforming inside the barrel. Something that catches wind and falls away at the split as the projectile leaves the barrel. This should remove the side pressure and put all the force into forward motion. Or at least a good bit more of it.

You might be interested in checking out a device called a Big Blaster made by Martin Engineering Co. This company also makes industrial vibration equipment. Their blaster used a differential pressure poppet valve with an air tank. The valve was extremly fast. The blaster was designed to break up material bridging in bin hoppers. I also heard where it was used to blast mine walls instead of explosives to relieve loose material and prevent cave ins. A guy told me they used concrete filled Dixie cups for the projectiles. I was at a demonstration where the salesman shot a baseball and I thought it was going to go into orbit!

Awesome channel man. Looking forward for what your truck has in-store.

you can use a pressure multiplier to increse the output pressure from your air compressor.

Not to jump into the science too quickly, i have several upgrades you might think about. Valving, this can be achieved with a tire machine component. The dump valve that empties the bead blaster portion of the tire machine is a component specially designed to empty a 6 inch diameter tank 5ft long in 1/ 10th of a second. Its useful when initially airing a tire that has been barrel stacked putting the beads close together. It blasts a huge amount of air through several nozzles to direct and capture the air inside the tire itself slamming the beads against the rim sealing itself off. This sets the tire on the rim so you can inflate it to operating pressure. Its easier to watch bead blasting tire videos than to typt it out. A small hose actuates the dump valve and if you have two resevoire and two dump valves plumbed into the same cannon im sure you could get sound barrier action. Also longer barrel

This is some serious quality content. New sub right here!

Light switches work by having the contacts spring-loaded, so that even if you throw the switch lever slowly, the actual switching happens very fast, to avoid arcing. You could have a similar spring system so that your valve opens instantly. That way you're not letting air through while you're waiting for the actuating force to build up.

I also think that with a longer barrel it would give more time for the ball to accelerate in the vacuum and be pushed faster by the air, especially if the valve doesn’t even open in time

great vid! what about using some sort of plastic sabot for the tennis ball? might help mitigate the deformation.

**CHALLENGE** Make this in to a more portable version, that can break down and be packed up. Applications in particular would be using as a bait cannon for surf fishing, and also firing a tethered line to hoist up radio operators antenna coax. Operating parameters should be similar to first three iterations, and above all must operate at 2000 psi.

Oh, this is just delightful, but a) You absolutely are an engineer (possibly not in the professional sense, but come over to the UK, you don't need to be a professional engineer to call yourself one). b) The intro to that jingle made me think you were rickrolling us :D c) try lubing the tennis ball. Use lard, the favoured engineering lubricant of Mythbuster's Jamie Hyneman :D

If you can incorporate some adjustable regulators you can fine tune it. You must also take into consideration the weight of projectile, ballistic coefficient and length of barrel

Awesome video! What about changing the size of the barrel at the end and middle to reduce friction, maybe you have thought of this.

Great stuff Tyler, love your experiments. Check out high power-big caliber precharged pneumatic (pcp) airguns. They rarely are able to go supersonic even at 300 bar! Consider getting inspiration from different valve design with a linear sliding valve and using a sabot, a technique used in firearms and in the big H.A.R.P. Supergun 😉

Video was great! Love your work on air cannons. The 305 is a V8. It has less HP than the average V6 now. Nice truck man! The LS is gonna be a welcome improvement.

Edit: ALMOST EVERYTHING I SAY IN THE FOLLOWING COMMENT IS INCORRECT that being said: You should try using compressed hydrogen (1270m/s) or helium (1007m/s) while theoretically you might breaks the sound barrier with the assistance of the vacuum in the chamber, you will never be able to breaks the sound barrier with compressed air alone (~343m/s) as the expansion rate of a gas is equal to the speed of sound in said gas. Hydrogen would be easier to source and cheaper as you could generate it you self if needed though helium has the added Benefit of not being flammable and being easier to store though you most likely won’t be able to take full advantage or the 1007m/s as most helium is sold mixed with a percentage of air a helium is in short supply you’d probably need to get it from a medical supplier if you wanted pure stuff though at that point it’d probably be helium or the high speed cam 😂. You videos are great keep up the great work. If you want to learn more about the expansion rate and the loss you will always have/ what speed is acceptable to hit, then Cody’s Lab has a great video where he fill a BB gun with helium and I want to say he hits 1400f/s or m/h though it’s been a while so I can’t quite remember

You may it helpful to dose the inside of the firing tube and the tennis ball fur with spray-on dry silicone lube. I think 3M make and sell it over where you are. You may you may need to lose the fur off the tennis ball and you may be at a wall with a spherical projectile. You may get a littler more velocity with a hollow cylindrical stored energy projectile. Think PVC tube with cap with built-up cone on the front, a reducer on the back with a tail tube and a doughnut soft sabot around the tube - pool noodle maybe. That may yield a little more sustained velocity as the barrel pressure drops.

If the sides of the tennis ball are expanded into the barrel walls as the tennis ball is squished by the air from the rear, it sounds like the best option might be to making a barrel that widens as the ball travels. But you would probably need a high speed camera and a polycarbonate tube to see what’s really going on in there. Alternatively, you could add wadding to the back of the ball like they do with cannons. This would not only seal the air for a bit longer to allow it to build up greater pressure behind the ball. But could also be designed to spread out the force across the rounded back of the ball so that it doesn’t flatten out as much.

You might try multiple synchronized high pressure dump valves into a high pressure manifold leading into the barrel to increase the flow. But please upgrade the wall thickness of the barrel before doing so. I recall seeing artillery cannons that had additional charges along the length of the barrel to increase the range (and muzzle velocity) which method may also be applicable.

A differential pressure diaphragm valve is made to dump air pressure instantly they are used in industrial blast freezers to clean frost out of the refrigeration coils

You can possibly get higher speeds by using a longer barrel. That will give you a longer acceleration time, however you can't break the sound barrier with an air cannon because the sound barrier is literally fastest speed that gasses are able to move. That said you CAN get above the sound barrier using a gas which has a higher sound velocity. (like helium) Bullets are technically gas powered and get above super sonic, but that gas is super heated and therefore has more kinetic energy within it.

I spent a lot of high school optimizing pneumatic cannons, and there is a huge diminishing return with both pressure and volume of air. You need to calculate the average pressure you want your projectile to be subject to based on your engineering requirements (cross sectional area of the barrel, mass of the projectile, intended distance). I had a cannon shooting a fin stabilized military glow stick around 1/2 a mile, or (since the statute of limitations has expired by around 20 years at this point) a fin stabilized... destructive device around 1/3 a mile. If your projectile needs an average 200PSI over, say, 10 feet to reach your velocity target, you need to size your tank to drop no lower than X if it fills the full volume of the barrel. You always end up with a tank and a pressure sized well below what your instincts would tell you. This bode well for me, because charging the pressure chamber was often done with a foot or floor bicycle pump, especially with platforms that fired potato sized projectiles.

Yeah, I was thinking, the way that the tennis ball seals inside the cylinder would also effect the ultimate pressure pushing the ball. Doesnt matter if you start with 200 or 2000, if you can't seal that extra 1800 in. Also, the fact the tennis balls are so light. Destin's team got a Baseball up to 1500MPH I believe. That has both weight, and a smooth surface to seal it

3:40 I'm sure someone has already commented. Impulse = force x time. So you not only need pressure, you need flow to create the impulse.

I think if the problem is the tennis ball expanding because it's being squished there is possibly a relatively easy solution. If you made the barrel dynamically shaped. so that the very beginning of where the tennis ball sits in the barrel it's the same diameter as it currently is, however rather quickly the barrel expands outward in a conical shape to allow for the increase size of the tennis ball. it would take some calculation and most likely experimentation to figure out how quickly it will need to reduce back into its original diameter after the tennis ball regains its original shape.

You need a much longer barrel. Maybe 50’. Coat the tennis ball with graphite... plus you could use two or more tanks on a wye and going up in pipe size and/or shorten distance from tank to valve...also you could go to 4 tanks, with 4 air powered identical valves so 1/4 way open of each valve equal full open on one valve making it 4 times faster than a single valve...I think high grade welding would be better than threaded fittings...also consider going with golf balls or baseballs... I also think you need a bigger tank or multiple tanks...

Possible ideas to try for increased speed: Venturi restrictor at the beginning of the pipe downstream of the valve - exchange pressure for velocity Helium instead of nitrogen - higher speed of sound, the particles travel faster and will fill a vacuum tube faster than nitrogen Great solo project, impressive Vs the money no object SED supersonic baseball cannon

Awesome videos man! Love it!