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Consistent velocity: Combustion or Pneumatic?

A place to ask general spud cannon related questions.
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Unread postAuthor: Ragnarok » Wed Apr 29, 2009 9:04 pm

King_TaTer wrote:May I ask what game and which show?

It's the next version of the Greg Hastings paintball game, unless I'm mistaken.

The show... Well, aside from the fact the Mythbusters own one, I know there are other shows, but although I think I've read which somewhere, I can't immediately remember the answer.
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Does that thing kinda look like a big cat to you?
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Unread postAuthor: Solar » Wed Apr 29, 2009 11:04 pm

Either the Stargate series or Smallville(if that is still on) The guys who run the weapons procurement for those shows are getting one. They tried out the prototype last year and we have just to meet up again. They are only about 3 hours north of here. Yes, it is the new Greg Hastings game. It is nearly done from what I hear. Greg is touring with one of the launchers at a number of scenario events and I hear it is working flawlessly.
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Unread postAuthor: jimmy101 » Thu Apr 30, 2009 11:51 am

Technician1002 wrote: :D Yes. On the t shirt cannon when scaling pressure/ speed and distance, we have lots of in barrel acceleration data. The variability is very little. :D The shots became about as predictable as shooting the same rock over and over from a slingshot.

T shirt flight dynamics were all over the map, but Oranges become very predictable and repeatable. :D

Hey Technician1002, have you posted a description of your detection coil setup somewhere? Looks like it is working pretty well.

Ever tried using a laptop sound card instead of the storage scope? The scope's screen resolution is probably pretty poor compared to what the scope is actually logging. A sound card should be able to log the data about as well as the scope (at least for this type of fiarly low frequency data) and it is easy enough to extract more accurate readings once the data is on a PC.
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Unread postAuthor: Technician1002 » Thu Apr 30, 2009 12:51 pm

jimmy101 wrote:
Technician1002 wrote: :D Yes. On the t shirt cannon when scaling pressure/ speed and distance, we have lots of in barrel acceleration data. The variability is very little. :D The shots became about as predictable as shooting the same rock over and over from a slingshot.

T shirt flight dynamics were all over the map, but Oranges become very predictable and repeatable. :D

Hey Technician1002, have you posted a description of your detection coil setup somewhere? Looks like it is working pretty well.

Ever tried using a laptop sound card instead of the storage scope? The scope's screen resolution is probably pretty poor compared to what the scope is actually logging. A sound card should be able to log the data about as well as the scope (at least for this type of fiarly low frequency data) and it is easy enough to extract more accurate readings once the data is on a PC.


Yes on both.

The write up on using the coils is documented on the official contest wiki.
From the home page, click on the barrel trim link in the menu on the left.
http://inteltrailblazerschallenge.wikispaces.com/

And yes again, I have used a sound card. It is documented on the same page.

Unfortunately my laptop screen is dead so it's easier to take the scope, shoot hard copy (uneditable results) and file them to pressure, projectile, and barrel groups. With the cursors on the scope, instant results were possible to view of all the coil crossings without math errors. Scope was used for convenience instead of precision.

If you do use a laptop, using Audacity gives very good results. If you can locate one of the inexpensive Behhringer USB interfaces ($40) they permit full 16 bit 44.1 KHZ stereo sample rate recording. (CD quality)

Other pages cover the construction and final game.
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Unread postAuthor: jimmy101 » Thu Apr 30, 2009 2:56 pm

Technician1002 wrote:And yes again, I have used a sound card. It is documented on the same page.

Unfortunately my laptop screen is dead so it's easier to take the scope, shoot hard copy (uneditable results) and file them to pressure, projectile, and barrel groups. With the cursors on the scope, instant results were possible to view of all the coil crossings without math errors. Scope was used for convenience instead of precision.

If you do use a laptop, using Audacity gives very good results. If you can locate one of the inexpensive Behhringer USB interfaces ($40) they permit full 16 bit 44.1 KHZ stereo sample rate recording. (CD quality)

Other pages cover the construction and final game.

Cool. Similar to my setup using phototransistors. Single channel if you let the laptop power the detector via the MIC input, dual channel if you supply external power and use the PCs line input.

http://www.inpharmix.com/jps/Jims_chrono.html basic shooting chrony for $5 (assuming you have a PC).
http://www.inpharmix.com/jps/Piezo_Spud.html Crude attempt at measuring combustion dynamics using a piezo transducer
http://www.inpharmix.com/jps/Tech_Gun.html Multiple photodetectors in a barrel, similar to your coil detectors.
http://www.inpharmix.com/jps/Closed_Cha ... udies.html closed chamber burn times as a funtion of number of sparks, fan etc.
http://www.inpharmix.com/jps/Chamber_Temperature.html Temperature versus time profile in a closed combustion chamber
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