Difference between revisions of "Chamber to barrel ratio"
(categorized) |
m (spelling and clarifaciotion) |
||
| Line 1: | Line 1: | ||
The '''chamber to barrel ratio''', or '''C:B ratio''', is the volume ratio between the chamber and barrel. The ratio determines how much of the available energy is transferred to the projectile, and a good C:B ratio is a major factor in [[combustion cannon]] performance. The goal of an optimal ratio is to have the barrel end at the exact point where the projectile stops accelerating. | The '''chamber to barrel ratio''', or '''C:B ratio''', is the volume ratio between the chamber and barrel. The ratio determines how much of the available energy is transferred to the projectile, and a good C:B ratio is a major factor in [[combustion cannon]] performance. The goal of an optimal ratio is to have the barrel end at the exact point where the projectile stops accelerating. | ||
| − | Higher ratio cannons are louder, since more energy is wasted as noise when the projectile exits the barrel. Too low a ratio will hurt performance, since a vacuum is formed behind the projectile when the | + | Higher ratio cannons are louder, since more energy is wasted as noise when the projectile exits the barrel. Too low a ratio will hurt performance, since a vacuum is formed behind the projectile when the combustion product cool. In extreme cases, it may even be sucked back into the chamber. [http://www.burntlatke.com/15cb-testday.html] |
| − | [http://www.burntlatke.com/launch.html Experiments] have shown that a C:B ratio of about 0.6-0.8:1 is the most efficient for a given chamber. The ratio will vary somewhat depending on the | + | [http://www.burntlatke.com/launch.html Experiments] have shown that a C:B ratio of about 0.6-0.8:1 is the most efficient for a given chamber using potatoes as projectiles. The ratio will vary somewhat depending on the weight, friction and blowby of a certain projectile, but it's in that area for most common projectiles. |
| − | This does not | + | This does not necessarily mean that the most efficient ratio is the best to use in a gun, if maximum power is the goal. If the chamber is designed around a certain barrel, a bigger than optimal chamber will give more power since more energy is available. When designing a barrel for a certain chamber though, one near the optimal ratio will make the most of the energy available in the chamber. |
In short, C:B ratios are good for determining what barrel is most powerful for a certain chamber, but not what chamber is most powerful for a certain barrel. A near optimal C:B ratio is always good however, if the goal is reduced noise and/or fuel efficiency. | In short, C:B ratios are good for determining what barrel is most powerful for a certain chamber, but not what chamber is most powerful for a certain barrel. A near optimal C:B ratio is always good however, if the goal is reduced noise and/or fuel efficiency. | ||
| Line 11: | Line 11: | ||
[[Burst disk]]s can be used to increase the performance of high ratio cannons, since they let higher pressure build up before the projectile starts to move. They will not increase the performance in near optimal cannons. [http://www.advancedspuds.com/burstdisk.htm Source] | [[Burst disk]]s can be used to increase the performance of high ratio cannons, since they let higher pressure build up before the projectile starts to move. They will not increase the performance in near optimal cannons. [http://www.advancedspuds.com/burstdisk.htm Source] | ||
| − | The C:B ratio of [[pneumatic cannon]]s is much less fixed, since factors like air pressure and valve performance play a greater part in determining overall performance. It is | + | The C:B ratio of [[pneumatic cannon]]s is much less fixed, since factors like air pressure and valve performance play a greater part in determining overall performance. It is advisable to use [[GGDT]] to determine the best design for pneumatic cannons. |
[[category:Concepts]] | [[category:Concepts]] | ||
Revision as of 05:26, 3 June 2007
The chamber to barrel ratio, or C:B ratio, is the volume ratio between the chamber and barrel. The ratio determines how much of the available energy is transferred to the projectile, and a good C:B ratio is a major factor in combustion cannon performance. The goal of an optimal ratio is to have the barrel end at the exact point where the projectile stops accelerating.
Higher ratio cannons are louder, since more energy is wasted as noise when the projectile exits the barrel. Too low a ratio will hurt performance, since a vacuum is formed behind the projectile when the combustion product cool. In extreme cases, it may even be sucked back into the chamber. [1]
Experiments have shown that a C:B ratio of about 0.6-0.8:1 is the most efficient for a given chamber using potatoes as projectiles. The ratio will vary somewhat depending on the weight, friction and blowby of a certain projectile, but it's in that area for most common projectiles.
This does not necessarily mean that the most efficient ratio is the best to use in a gun, if maximum power is the goal. If the chamber is designed around a certain barrel, a bigger than optimal chamber will give more power since more energy is available. When designing a barrel for a certain chamber though, one near the optimal ratio will make the most of the energy available in the chamber.
In short, C:B ratios are good for determining what barrel is most powerful for a certain chamber, but not what chamber is most powerful for a certain barrel. A near optimal C:B ratio is always good however, if the goal is reduced noise and/or fuel efficiency.
Burst disks can be used to increase the performance of high ratio cannons, since they let higher pressure build up before the projectile starts to move. They will not increase the performance in near optimal cannons. Source
The C:B ratio of pneumatic cannons is much less fixed, since factors like air pressure and valve performance play a greater part in determining overall performance. It is advisable to use GGDT to determine the best design for pneumatic cannons.
