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Homemade pistol shrimp

Posted: Mon Jun 13, 2011 7:57 am
by inonickname
I want to make a mechanical piston shrimp claw... Why?
The snapping shrimp competes with much larger animals like the Sperm Whale and Beluga Whale for the title of 'loudest animal in the sea'. The animal snaps a specialized claw shut to create a cavitation bubble that generates acoustic pressures of up to 80 kPa at a distance of 4 cm from the claw. As it extends out from the claw, the bubble reaches speeds of 60 miles per hour (97 km/h) and releases a sound reaching 218 decibels.[8] The pressure is strong enough to kill small fish.[9] It corresponds to a zero to peak pressure level of 218 decibels relative to one micropascal (dB re 1 μPa), equivalent to a zero to peak source level of 190 dB re 1 μPa at the standard reference distance of 1 m. Au and Banks measured peak to peak source levels between 185 and 190 dB re 1 μPa at 1 m, depending on the size of the claw.[10] Similar values are reported by Ferguson and Cleary.[11] The duration of the click is less than 1 millisecond.
The snap can also produce sonoluminescence from the collapsing cavitation bubble. As it collapses, the cavitation bubble reaches temperatures of over 5,000 K (4,700 °C).[12] In comparison, the surface temperature of the sun is estimated to be around 5,800 K (5,500 °C). The light is of lower intensity than the light produced by typical sonoluminescence and is not visible to the naked eye. It is most likely a by-product of the shock wave with no biological significance. However, it was the first known instance of an animal producing light by this effect. It has subsequently been discovered that another group of crustaceans, the mantis shrimp, contains species whose club-like forelimbs can strike so quickly and with such force as to induce sonoluminescent cavitation bubbles upon impact.[13]
I'm just looking for any suggestions... Air rams, spring loaded levers, anything. The claw only reaches around 60mph which should be very achievable.

Image

Also going to have to grind a shape basically like that... Hopefully it will work!

Posted: Mon Jun 13, 2011 8:47 am
by jackssmirkingrevenge
To you want to replicate the shape or the effect?

Posted: Mon Jun 13, 2011 3:53 pm
by POLAND_SPUD
Air rams, spring loaded levers, anything.
you know what I am going to suggest and you know that the best option... so why do you ask?? :D

Posted: Mon Jun 13, 2011 6:29 pm
by Zeus
Look, give any animal 50g of ETN with a 24 hour fuze. It will whoop the shrimp and the whale.

To be serious, I'd use an air cylinder with the air input the same diameter as the piston. Feed that with a piston valve or burst disc with a porting equal to or greater than the diameter of the piston.

That should be rather fast.

Posted: Mon Jun 13, 2011 9:18 pm
by saefroch
inonickname wrote:The claw only reaches around 60mph
Where along the claw? :wink: It actually might be better to convert that value to rotations/second or radians/second, it'd be easier to think about.

Done being a smartass. I suggest against a spring, we've seen before that springs just don't oscillate quickly enough. I actually might go with Poland on this one, you don't need a really fast valve... or you shouldn't.

Posted: Tue Jun 14, 2011 12:24 am
by Lockednloaded
What about a torsion spring like those found in mouse traps? I have no idea how fast a mouse trap shuts, but it may be close enough to get the job done

Posted: Tue Jun 14, 2011 1:51 am
by jackssmirkingrevenge
Lockednloaded wrote:What about a torsion spring like those found in mouse traps? I have no idea how fast a mouse trap shuts, but it may be close enough to get the job done
Agreed - it's not really a matter of force but the shape of the claw.

Why not just buy one for less than $30 and use it to make a cast ;)