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Sonic boom>?

Post questions and info about hybrid (compressed gas with fuel) powered cannons here. This includes discussion about fuels, ratios, ignition systems, build types, safety, and anything else relevant.
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Sonic boom>?

Unread postAuthor: CannonBall » Thu Jul 26, 2007 3:24 pm

Well ive read alot about super sonic speeds and my hybrid is operationel.
My chamber has 33 cubic inch
Barrel is 2 meters long 22mm wide
C:B is 07.1
Fuel special gas 30% propane 70% butane
So far mixes tryd.
4x 5x 6x
When im shooting sometimes the gun makes more noice then usual is this a sonicboom?.
How do i know that i got supersonic speeds? i dont have a chrony

Cheers
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Unread postAuthor: SpudBlaster15 » Thu Jul 26, 2007 3:33 pm

What is the mass of your projectile?
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Unread postAuthor: paaiyan » Thu Jul 26, 2007 3:35 pm

Well, the only way I know of, is to have a friend stand about 100 yards downrange and shoot. If the thing hits him before he hears it, it'ss supersonic. I'm kidding! But really, without a chrony I think the only way would be to have someone stand downrange, but where you know you won't hit them. Set up a large target that you know you can hit. Have them stand fairly near it, but far enough away that they won't get hit. Make sure you can hit that target every time. If they hear the object hit the target before they hear the boom of the cannon, it's supersonic.

Well you could do math, but I hate math, and don't feel like doing it now.
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Last edited by paaiyan on Thu Jul 26, 2007 3:37 pm, edited 1 time in total.
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Unread postAuthor: CannonBall » Thu Jul 26, 2007 3:37 pm

projectiles that i shoot are about 20 to 50 grams.
is my C;B good for super sonic speeds?would a barrel extension be helpfull cause im not really statisfied yet. i shot threw a house door but i hoped for more damage.
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Unread postAuthor: robert23 » Thu Jul 26, 2007 3:51 pm

CannonBall wrote: i shot threw a house door but i hoped for more damage.


Like busting the back door down? :lol:
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Unread postAuthor: Jumpin Jehosaphat » Thu Jul 26, 2007 3:54 pm

paaiyan wrote:Well, the only way I know of, is to have a friend stand about 100 yards downrange and shoot. If the thing hits him before he hears it, it'ss supersonic. I'm kidding! But really, without a chrony I think the only way would be to have someone stand downrange, but where you know you won't hit them. Set up a large target that you know you can hit. Have them stand fairly near it, but far enough away that they won't get hit. Make sure you can hit that target every time. If they hear the object hit the target before they hear the boom of the cannon, it's supersonic.

Well you could do math, but I hate math, and don't feel like doing it now.

Never fire down range at a person, set up a video camera or something else.
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Unread postAuthor: CannonBall » Thu Jul 26, 2007 4:00 pm

for ammo i use bolts batteries leadballs marbles.
well i shot lead ball and a marble a 5 times mix.
the marble made much more sound than the lead ball ..
Would that be supersonic?
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Unread postAuthor: Modderxtrordanare » Thu Jul 26, 2007 4:01 pm

Or a microphone, so if you hear *thud* *boom* you'll know it was supersonic, whereas if you hear *boom* *thud* then it wasn't.
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Unread postAuthor: CannonBall » Thu Jul 26, 2007 4:07 pm

did u test this? .. or somebody else
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Unread postAuthor: boilingleadbath » Thu Jul 26, 2007 5:17 pm

Generally, supersonic objects make a 'crack' sound as they fly by, which sounds a bit like the click on a peizo igniter. (but louder)
(I recorded a rifle bullet once)

The problem with this is that our projectiles are only slightly supersonic and aren't very aerodynamic, so you would have to place the microphone close to the muzzle to record this - and then you'll have a hard time distinguishing the sonic boom from the report.

For instance, if we have a cannon which shoots marbles at mach 1.1, we find that it falls to mach 1 at about 11 meters... if I did my math right.

On the other hand, EVBEC is telling me that we would expect a velocity of ~1600 fps with a marble, so you probably are getting supersonic velocities.
(that's a 6x mix, 6g marble)
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Unread postAuthor: paaiyan » Thu Jul 26, 2007 5:27 pm

Jumpin Jehosaphat wrote:
paaiyan wrote:Well, the only way I know of, is to have a friend stand about 100 yards downrange and shoot. If the thing hits him before he hears it, it'ss supersonic. I'm kidding! But really, without a chrony I think the only way would be to have someone stand downrange, but where you know you won't hit them. Set up a large target that you know you can hit. Have them stand fairly near it, but far enough away that they won't get hit. Make sure you can hit that target every time. If they hear the object hit the target before they hear the boom of the cannon, it's supersonic.

Well you could do math, but I hate math, and don't feel like doing it now.

Never fire down range at a person, set up a video camera or something else.


Dude, seriously. I said "I'm kidding" when I said that. I was saying put someone near enough to hear the projectile hit the target. If they hear the target being struck before they hear the cannon fire, it's supersonic. Never did I seriously suggest shooting it at someone.

EDIT: 1600 fps is mach 1.41
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Unread postAuthor: jimmy101 » Thu Jul 26, 2007 8:04 pm

Boiling hit on the key element. It really doesn't matter what you do down range, with a non-aerodynamic, high drag projectile it'll go sub-sonic in a very short distance from the barrel.

You really need to be measuring the velocity within a few feet of the muzzle.

You could make your own chrono for $5 using photodetectors (assuming you can scrounge up an old PC or laptop from somewhere) like this.
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Unread postAuthor: Velocity » Thu Jul 26, 2007 9:05 pm

Considering the high mixes which you are using ($X to 6X), you might want to consider extending your barrel until you get around a 0.3:1 ratio for greater efficiency and more power as well.
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Unread postAuthor: CannonBall » Fri Jul 27, 2007 8:33 am

well i have 3 ways to do this...
Buy a new barrel same diameter only from 2 meter till 5
or buy one with that is more wider (28mm) 3 meter
or buy a longer and wider barrel what would u guys do?
Cause if i extend currect one to 5 meters it aint gone be handheld and thats what i want..
3meters is my max barrel length i want
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Unread postAuthor: SpudBlaster15 » Fri Jul 27, 2007 1:29 pm

If you extend the barrel from it's current length, you are unlikely to see a drastic increase in performance. Why are you not satisfied with the performance of your launcher?
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