Mr. Bruce, I really admire your work. I wish I could be your trainee for a summer and teach my students the way you do. I would've loved to have a physics teacher like you!!! Keep it up!!
Great video as usual, Some guys suggested using a one way valve in the combustion chamber and I think it may work. I also suggest drilling a small hole somewhere between second and third can so when the pressure decreases the ball will be already passed the hole and the air get sucked from it to stabilize the pressure inside, and I'm not sure whether this going to work or not
That's a neat effect to hear a bang and then have the ball reverse direction before it gets out the barrel. I wonder if the ridge or ball stop on the first can is creating a lot of drag on the air flow when it fires aiding the vacuum effect? Maybe a completely smooth bore without the swirl or turbulence inducing ridge would increase the chance of an escape velocity.
Great video as always !! Maybe in the future you could built and test a vacuum cannon. The type with a burst disk at one end of a vacuum chamber and then a barrel at the other end. I think NightHawkinLight did a video. Or maybe you did a video already and I don't know.
The wheels came from a student, I think they might have been old roller skate wheels. If I were building this project again, I think I would use some that are larger than the ones that I used
Please make more series of this and put valve in combustion chamber to prevent vacuum when the pressure decrease. I think it would has significant difference.
Phillip Toone not only condensation. A rapid decrease in temperature is quite enough. But you are definitely right. Have you ever seen so called "flame licker" engines? Quite interesting use of this phenomenon
You could secure the cannon to that brick and test the aluminium ball with the 3 cans to check if the vacuum is mainly caused by rapid temperature decrease or the expansion of volume, or even the explosion transferring all its energy to the cannon holder.
There's a video entitled Propane Powered Nerf Blaster where he experiences the same effect of the projectile reversing direction in the barrel around the 10:30 mark.
Yeah there's an ideal barrel length, which would be the point at which the expanding gases are done expanding. Too short and the pressurized gases can escape out to the side before they have imparted all their energy into the projectile. Too long and you get the decreased pressure you were seeing. Plus even if you had a release valve, you have friction on the side of the barrel. There's also -- depending on the quality of the seal between projectile and barrel -- the matter of gases escaping past the projectile and getting in its way. IIRC they showed that happening on an early Mythbusters when they were using compressed gas to launch frozen chickens at airplane windows. (LOL) It would be interesting to see a clear version of this with some sort of visible floaty particles so you could really see what's happening as it happens.
I was surprised how short the ideal barrel length was for this, I guess it is due to such a small combustion chamber. I do like the idea of a clear tube and I remember the myth busters episode with their firing the turkeys, the way to get the good seal in a cannon is using something called a sabot, I have a small air cannon that I do the same thing with. As for adding the valves, I'm not seeing the advantage of putting one on it, seems the ideal choice is finding the right length of barrel. If I add a valve, it would simply balance the pressure inside and outside, so there would be no more acceleration, then no need for any longer barrel. If I want it to go faster, I either need a hotter fuel or a bigger combustion chamber
Another test with the bi-directional cannon would be having one of the balls further away from the center of the combustion. That is, one ball as it was right up against the combustion chamber, but put the other ball 1 or more can lengths further down the opposite barrel.
Please try a smaller hole for the expansion chamber. Instead of a ridge or the wires to stop the ball. Make a hole opposite the lighting hole about 3/4 inch I don't think the ball will go backwards this way?
What if there was a one-way air valve on the side of the combustion chamber, to give surrounding air an alternative path to enter instead of pushing on the tennis ball?
Once it gets to atmospheric pressure, letting more air in won't propel the ball any faster. Unless you can make more combustion happen, so that you have more moles of exhaust gasses than you started with moles of air, then you are pretty much set with what you've got. This is why the 2-can/3-can cannon produced nearly identical speeds on both sides, and the 3-can side that became vented once the ball on the 2-can side departed, didn't get any extra propulsion.
I thought about it some more, you could add a check valve to make the longer barrel work, but then there is no point in having a longer barrel. Once the pressure equalizes in the chamber, the ball would lose momentum to the friction of the barrel. The goal is to find the ideal barrel length. I'd like to see a line graph correlating barrel length to ball speed.
you are right about adding the check valve, once the pressure is equal or less than atmospheric pressure there is no reason to have the barrel any longer. I've kicked around the idea of using shorter cans, that way I could get closer to the ideal barrel length but it will have to wait as I have several other ideas I want to get to and a limited amount of time.
I tried making this for my physics class and can not get it to shoot the tennis ball out. Not sure what I am doing wrong. The only thing I think might be different is the hole in the top of the bottom of the can is bigger than yours. Any suggestions?
hard to tell with much information, I'd say the most common mistake is not allowing the fuel to sit long enough to evaporate, add the drops and let it sit a few minutes before lighting
To reduce the vacuum causing the balls to get pushed back in, could you make a one way valve that would allow air an access to the chamber when the pressure is low, but hold a seal while the pressure is high? Could fashion a cheap check valve from pvc and a rubber ball, or maybe just a set of holes covered by a metal sheet in the inside of the combustion chamber possibly?
Hardware stores sell air admittance valves for retrofitting unvented plumbing drains. Perhaps that's the kind of valve you could use for letting the air in and stopping the suck-back effect.
Honestly, this is such an inspiring UA-cam channel. It's just awesome to see someone do this much stuff.
I enjoy it
I wish I had you as my physics teacher
Mr. Bruce, I really admire your work. I wish I could be your trainee for a summer and teach my students the way you do. I would've loved to have a physics teacher like you!!! Keep it up!!
At first this seems like a simple experiment, but it end up raising some interesting (and also hard to answer!) questions! Great video
Always a pleasure seeing another video. Keep up the amazing work!
Man, if only you were a teacher of mine when I was at school!! Brilliant!!
Very very very special!! My congratulations 😍😃
Some...of the coolest stuff I have seen
This is a great channel
Such a clever into with the glass. I love it!
Awesome video Bruce
Imagine going for a break during class and seeing you physics professor just playing around with cool stuff down the hallway
Great video as usual,
Some guys suggested using a one way valve in the combustion chamber and I think it may work.
I also suggest drilling a small hole somewhere between second and third can so when the pressure decreases the ball will be already passed the hole and the air get sucked from it to stabilize the pressure inside, and I'm not sure whether this going to work or not
The comically long cart rolling sound at 3:07 had me laughing
Awesome channel 😀
That's a neat effect to hear a bang and then have the ball reverse direction before it gets out the barrel. I wonder if the ridge or ball stop on the first can is creating a lot of drag on the air flow when it fires aiding the vacuum effect? Maybe a completely smooth bore without the swirl or turbulence inducing ridge would increase the chance of an escape velocity.
Great video as always !! Maybe in the future you could built and test a vacuum cannon. The type with a burst disk at one end of a vacuum chamber and then a barrel at the other end. I think NightHawkinLight did a video. Or maybe you did a video already and I don't know.
Fascinating!
Hi, great video! May i know where can i get those metal wheels from?
The wheels came from a student, I think they might have been old roller skate wheels. If I were building this project again, I think I would use some that are larger than the ones that I used
You should make a rig so you can light it safely from a distance if you plan to do more craziness. Props to you!!
Please make more series of this and put valve in combustion chamber to prevent vacuum when the pressure decrease. I think it would has significant difference.
Condensation of the combustion gases are creating a vacuum that sucks the projectile back into the barrel if it is too long.
Phillip Toone not only condensation. A rapid decrease in temperature is quite enough. But you are definitely right.
Have you ever seen so called "flame licker" engines? Quite interesting use of this phenomenon
That's what it looks like to me, too
and add the contraction from cooling. Much of the original expansion is from heating.
Dang Bruce Yeany is one kick-ass dude.
I love this New introducing
It is glass from a couple of broken bottles on top of the writing, the oil and th glass have the same index of refraction
Bruce Yeany i like this
You could secure the cannon to that brick and test the aluminium ball with the 3 cans to check if the vacuum is mainly caused by rapid temperature decrease or the expansion of volume, or even the explosion transferring all its energy to the cannon holder.
There's a video entitled Propane Powered Nerf Blaster where he experiences the same effect of the projectile reversing direction in the barrel around the 10:30 mark.
It's warmer out now! When does that next video come out :D
Excelentes videos
Have you tried poking holes in the further ends of the longer barrels? It seems like that could make them work better.
Possibly having a open end on both sides could help with the longer barrels
Fine Vid/Tutorial
Yeah there's an ideal barrel length, which would be the point at which the expanding gases are done expanding. Too short and the pressurized gases can escape out to the side before they have imparted all their energy into the projectile. Too long and you get the decreased pressure you were seeing. Plus even if you had a release valve, you have friction on the side of the barrel. There's also -- depending on the quality of the seal between projectile and barrel -- the matter of gases escaping past the projectile and getting in its way. IIRC they showed that happening on an early Mythbusters when they were using compressed gas to launch frozen chickens at airplane windows. (LOL)
It would be interesting to see a clear version of this with some sort of visible floaty particles so you could really see what's happening as it happens.
I was surprised how short the ideal barrel length was for this, I guess it is due to such a small combustion chamber. I do like the idea of a clear tube and I remember the myth busters episode with their firing the turkeys, the way to get the good seal in a cannon is using something called a sabot, I have a small air cannon that I do the same thing with. As for adding the valves, I'm not seeing the advantage of putting one on it, seems the ideal choice is finding the right length of barrel. If I add a valve, it would simply balance the pressure inside and outside, so there would be no more acceleration, then no need for any longer barrel. If I want it to go faster, I either need a hotter fuel or a bigger combustion chamber
Another test with the bi-directional cannon would be having one of the balls further away from the center of the combustion. That is, one ball as it was right up against the combustion chamber, but put the other ball 1 or more can lengths further down the opposite barrel.
The cannon is so cool
Please try a smaller hole for the expansion chamber.
Instead of a ridge or the wires to stop the ball.
Make a hole opposite the lighting hole about 3/4 inch
I don't think the ball will go backwards this way?
What if there was a one-way air valve on the side of the combustion chamber, to give surrounding air an alternative path to enter instead of pushing on the tennis ball?
Please add a one way valve in the combustion chamber. Outside air then should represure the chamber if the presure gets to low.
Once it gets to atmospheric pressure, letting more air in won't propel the ball any faster. Unless you can make more combustion happen, so that you have more moles of exhaust gasses than you started with moles of air, then you are pretty much set with what you've got.
This is why the 2-can/3-can cannon produced nearly identical speeds on both sides, and the 3-can side that became vented once the ball on the 2-can side departed, didn't get any extra propulsion.
I wonder what would happen if you added a check valve to the combustion chamber to eliminate the negative pressure.
I thought about it some more, you could add a check valve to make the longer barrel work, but then there is no point in having a longer barrel. Once the pressure equalizes in the chamber, the ball would lose momentum to the friction of the barrel. The goal is to find the ideal barrel length.
I'd like to see a line graph correlating barrel length to ball speed.
you are right about adding the check valve, once the pressure is equal or less than atmospheric pressure there is no reason to have the barrel any longer. I've kicked around the idea of using shorter cans, that way I could get closer to the ideal barrel length but it will have to wait as I have several other ideas I want to get to and a limited amount of time.
You should make the cannons with a curve
I tried making this for my physics class and can not get it to shoot the tennis ball out. Not sure what I am doing wrong. The only thing I think might be different is the hole in the top of the bottom of the can is bigger than yours. Any suggestions?
William, can you email me pictures and describe how you are setting it up and I will try to help. Bgoknee@comcast.net
@yeanyscience I will send pictures tomorrow
Cool
I wish ur my science teacher
This guy is the new Bill Nye. It is declared.
why doesn't my cannon work, ball won't shoot out, please help
hard to tell with much information, I'd say the most common mistake is not allowing the fuel to sit long enough to evaporate, add the drops and let it sit a few minutes before lighting
@@YeanyScience oh I forgot to put fuel, where would I place it
Not to self plug, but you should make the simple pulse jet I designed for your class. It was designed for safety, display, and ease of parts finding.
To reduce the vacuum causing the balls to get pushed back in, could you make a one way valve that would allow air an access to the chamber when the pressure is low, but hold a seal while the pressure is high? Could fashion a cheap check valve from pvc and a rubber ball, or maybe just a set of holes covered by a metal sheet in the inside of the combustion chamber possibly?
Hardware stores sell air admittance valves for retrofitting unvented plumbing drains. Perhaps that's the kind of valve you could use for letting the air in and stopping the suck-back effect.
I heard Trump wants teachers to have guns... well, you could just make your own guns, huh?
GREAT MILLS, TOO SOON!
If your reading this it's william
Hi Mr Yeany ,can we do this in class?
when it's warmer, there are some ideas we can try outside during double period
Ok
surprised the school would allow this.
Dude hi
use carbide much better
i think your barrel is too long. check out smarter everydays see through potato cannon
Anyone else knows the intro tune from Shower with your dad simulator 2015...? No? okay...
like the ol egg in the bottle tric