High speed shots

[Don Hoey]

Originally Posted by miketoll

With your engineering skills you could make something better to fire a projectile with repeatable performance? BTW are you eating lots of fruit salad?

Kind of photographic scrap heap challenge then Mike. Not sure Stevie would impressed with mini explosive charges as in bullets, no moving parts there.

I did try a large lump of grape but it was lead flavoured.

I guess I just need to get round to taking more frames. Only fired around a dozen in this exercise so far.

Don

[Don Hoey]

First attempt at cutting a card with a pellet. Not as dramatic as the well known bullet shots. Slight alignment adjustment needed as the pellet is slightly rear of centre.

Attatched composite shows the frame at the moment the flash triggered and a frame taken after the action.

Vivitar flash at 1/30,000 sec burst

Don

[miketoll]

Thats a really difficult task you have set yourself, the pellet must be behind the card and only just clipping it whilst moving away. I was thinking along the lines of a gas driven 'gun' like the more expensive air rifles or a mini crossbow which should both be more repeatable and if you used steel pellets for the gun you could eat the grapes.

[Lello]

Don, As you are missing the pellet in the shot , am I right in thinking you've either need to slow the pellet down or increase the speed of the flash? I take it the flash is at max speed (min power) if so then we need to try slow the pellet down! just thinking, what if you increase the thickness of the cardboard between the foil! would that help or have I missed the plot completely

[andy153]

Very good Don - I think the pellet has just moved behind the card as it pushed it out of the way - fixing the top of the card as well might help?

[Don Hoey]

I am attatching a snap of my rather limited play space to give you guys some idea. Barrel end to target is 1 metre so there are limitations to the power of canon that can be safely used.

I agree on your comments on a gas gun Mike, but getting one is not really an option just to get this pic. My air rifle although very accurate is just too powerful to use in this space.

After my last post I tried with flat head pellets but they just mashed their way through so they are a non-runner. I have had 3 clear cuts but the trigger tripped before pellet/card contact, and where I got a clean cut and correct trip then the two strips of foil for the trigger stuck together causing the flash to strobe so that was a dead shot.

Lello, I am still using the Vivitar at min power giving 1/30,000 flash duration. Part of the problem is that I just went for this without sorting the trigger timing thing which perhaps I should have done as I would have had 3 good ones to post. Second and trickier thing is even at this range with the pistol clamped to my mill it is not consistantly accurate. I have done the 3 shot dry run all perfect, then set up the flash and that has worked fine but I had poor or partial cuts of the playing card. Very frustrating . On the pellet shape front then pointed pellets would make perfect cuts but give even greater alignment probs to hit the card edge on.

Full marks to the guy that did those shots with a proper gun. I have not given up yet though.

Andy, you could be right about greater support for the card but I am not sure if the work involved in making that will pay off in terms of increased good card cuts.

Don

[miketoll]

I did not mean buy a gun Don but more the idea behind it. A tube for the projectile and a gas-tight chamber which you could pressurise with a bicycle pump through a non return valve (bicycle valve) and an accurate pressure gauge and a trigger or release mechanism. Or maybe one of those gas cylinders you can buy to make fizzy drinks to prime the cylinder. The thing is you could alter the pressure and so the velocity easily and over the short range you have that would not alter the trajectory significantly. Just happy thoughts to help keep you from getting bored!

[Joe]

Did anyone see BBC Television's "SpringWatch" on this last thursday?

Had an interesting few minutes talking and demonstrating the Sony box of tricks for capturing slo' mo' frame by frame footage of diving birds.
The demonstration was a water filled ballon, popped with a swiss army knife.
Worked really well, and in bright sunlight.....but he did say it takes 20 minutes to download a short burst of footage!! (and I should imagine the box of tricks costs silly money)

Great thread.
I'm sure there are many like me reading this through, watching to see what intrepid experiments are coming next

[miketoll]

Originally Posted by Joe

Did anyone see BBC Television's "SpringWatch" on this last thursday?

Had an interesting few minutes talking and demonstrating the Sony box of tricks for capturing slo' mo' frame by frame footage of diving birds.
The demonstration was a water filled ballon, popped with a swiss army knife.
Worked really well, and in bright sunlight.....but he did say it takes 20 minutes to download a short burst of footage!! (and I should imagine the box of tricks costs silly money)

Yes I saw it and it gives interesting results. Bet you are right on the silly money but there is still something special about a stills shot taken at precisely the right moment.

[Don Hoey]

Originally Posted by miketoll

.......but there is still something special about a stills shot taken at precisely the right moment.

Just failed here then Mike.

Today I had a read up on pellet gun ballistics and its way beyond the kit that I have to produce something more accurate than what I have for cutting a playing card. While on the subject of ballistics I found that the pellet from the pistol is travelling at around 380 ft per second, so it is in frame for 0.002 secs . No wonder I was struggling to get it in shot with my rudimentary trigger.

Well I had a play anyway and still never managed to get the pellet in shot. After a few partial cuts I decided to use flat head pellets to increase the possibilty of a full cut.

Attatched is a shot alas less the pellet but fractionally after the card was cut. I assume the shadow on the lower left is from a bit of the card as I used a flat head pellet for this shot. Exposure info : 1.6 secs @ f11, sufficient time to trip the shutter fire and fire the gun but not record ambient light. Flash duration, the critical thing 1/30,000 sec. Pellet travel time across the frame approx 0.00197 secs.

Also attached is a pic of a different view of my set up for the card shots. The trigger is the bit of card held by the red clips, and the red and black leads are connected to a standard pc lead linked to the Vivitar 283. To get alignment of the card, the kit on the bench is a vice on a compound table, mounted on a rotary table. The splatter on the background card is from the grape shots.

Don