The Official High-Speed Camera Thread

[Technician1002]

The short vid is about 600 meg in size.. The still frames are located here.
https://inteltrailblazerschallenge.wiki ... com/Photos
Photos are 1 ms apart. Note the frame where the label is peeling off the bottle. Look at the next shot with the mist. That's only 1ms later.

The second frame of that sequence when viewed full size in the original video shows a pressure wave a few inches out from the muzzle. It is hard to see in the compressed stills for the website.

Note the lump in the stream in the 6th 7th and 8th frames. Go back and look at the distance in the ruller behind it. That lump is a broken apple. It is traveling slightly less than 1 foot per ms.

[Labtecpower]

http://www.spudfiles.com/forums/viewtop ... tml#318259

This is the damage I did to a water bottle with a potato slug at 80 psi. I still haven't found the top part of the bottle.

Very nice pictures of that shot!

[Ragnarok]

Something to prove I'm not dead...

Trying rope throwing with a Monkey's Fist (a large knot used to add weight to a line) I tied recently.

[youtube][/youtube]

I threw it too hard in this test (the line springs back), but it's really intended for throwing twice this distance or more, so it's hardly surprising that it was overkill here.

[LeMaudit]

Just having fun with new toys... Casio FC100 and a remote minicopter

[youtube][/youtube]

All I need a MiniBoy launcher to destroy it in flight now!

[jackssmirkingrevenge]

Glad too see the influence is working both ways

And you don't need a Miniboy, you need a 1mm gatling

[al-xg]

850psi, a basic spring loaded ball valve, and a tub of water...
[youtube][/youtube]
This was just a quick test, i'll try and do some more useful experiments soon.

The double recoil was fun, although din't really know what was going on at the time. That tub has a few tens of litres of water in it and it just leaps up

[Technician1002]

Very nice. That has answered the old question of; how fast is a spring loaded ball valve?

[MrCrowley]

That's interesting, I have a feeling the estimated opening time for a spring loaded ball valve was in the vicinity of 20ms. Whenever someone asks how to model one in GGDT, I think 20 to 30ms was the common response given.

[saefroch]

I agree with Crowley here, it seems the generalized value was quite close to what we normally predict.

Care try to evaluate how fast you can pull one open manually via high-speed filming?

[MrCrowley]

I agree with Crowley here

Did I put forward some form of argument I'm not aware of?
To clarify, it's interesting that al-xg's results were quite similar to predicted results. Obviously opening time will differ depending on the ball valve and spring used (not to mention spring placement).

[evilvet]

Caveat: None of this is new, this stuff is all over the Intergoogle and all I have done is pull together a few disparate threads and tie it into a pneumatic related post. It may be a high speed camera now but with some work it can also be a chronograph, all for a total spend of about $45.

Right at the start of this thread Insomniac said "More and more members of spudfiles are getting access to high-speed cameras".

I don't but I do have a way that might be of interest to others.
If you can't get a high speed shutter, get a low speed shutter and control the light source instead.

1. Arduino Uno board
2. $2 laser pointer
3. Light dependent resistor
4. Lots of Google
5. Two bottle of a rather good 2008 Shiraz

Mini howto:
Set the camera to 5 second exposure in a darkened room.
"Modify" the flash gun to disable the hot shoe and take it's power from a Nokia phone charger.
Wire the flash gun via a solid state relay to protect the micro controller.
Point the laser diode at the LDR and read the output value.
Fire the camera shutter by remote control to avoid shake.
Fire the solenoid to launch our projectile.
When the LDR drops below a threshold the beam must have been broken.
If so close the contacts on the SSR and fire the flash gun.

I played with the Arduino code and can vary the delay between the beam being broken and the flash firing.

Photos below, my first attempt at firing 10mm plastic BB's from 300mm of brass tube at 1 bar. I need to work on tuning the LDR to cope with sub millisecond variations so I can move to 8-10 bar with corresponding muzzle velocities.

[jackssmirkingrevenge]

Seriously.



Any idea at what fps they were screaming along at? Fairly low I imagine, given the dented as opposed to perforated can...

Also,

Two bottles of a rather good 2008 Shiraz

Mental lubricant

[Technician1002]

With a small change, you can trigger multiple flash units in sequence to capture the distance traveled between flashes for a visual chronograph. I'm working on a version in my spare time using flash units from disposable cameras.

The LDR tends to be a relatively high capacitance item so the response is somewhat slow. If you use the high speed photo diode with low junction capatance, you can get very tight times. Salvage one of those gems from a broken CD player. They are very high speed in relation to a LDR.

A note on the relative speeds is in this forum;
http://www.dutchforce.com/~eforum/index ... opic=22315

[evilvet]

Seriously.



Any idea at what fps they were screaming along at? Fairly low I imagine, given the dented as opposed to perforated can...

At full blast (10 bar)they perforate the can and do a fairly good job of adulterating the backstop. Trouble is they transit way to fast to trip the LDR. I think I can see them in motion so maybe 30-40 metres per second the low pressure I am testing with.
Also,

Two bottles of a rather good 2008 Shiraz

Mental lubricant [/quote]

Followed by some 12yo Glenlivet while posting 8)

[evilvet]

If you use the high speed photo diode with low junction capatance, you can get very tight times.

Maybe one of these ??
http://www.jaycar.com.au/productView.asp?ID=ZD1947