Conductive Target for Bullet Timing

Two things come to mind.\Shooting Chrony F1 Master Chronograph Should be obvious.

Or, Kynar ® /PVDF Film PVDF Film - PVDF FILM- Kynar - Order Online

This piezoelectric film could be wired to sense the impact of the bullet. I've played with this before. Made some simple mics and a sensor or two. Just connect a lead to each side and hook it to whatever you want to trigger.

Thanks for fast reply. I will suggest a bullet timer (it's new to me may well be new to the customer). It is possible that the true purpose isn't timing though, so on to the piezo film. In your experience of wiring it up, and you had 10 or 15 tests to do, over a few days, reliability is important, was the film easy to wire up, or would croc clips on paper be easier? Cnc jim

Clips are the way to go. There is conductive coating on both sides separated by a pvdf film. Just tape one side of each clip so you don't short across on the clips.

You might even find that you can use the film without destroying it. The shock wave of the bullet penetrating the paper should give you a healthy spike.

This stuff works as a vibration sensor, too, so direct hits to the film probably won't be necessary.

I think the chronometer can do a good job too, but if you hit it directly, it's toast.

Post pictures, please.

BTW, I have not shot competitively in years, so some one here may know a much better way.

Fantastic. Its a great idea, and I will probably talk myself out of some work, but that sounds like a good way to go. I'll get some more info tomorrow. Thanks for the input Cnc jim

Good luck. Shoot safely.

Remember, here in Arizona at least, gun control means hitting your intended target.

Something like this might work too.↓

images are CC BY-NC-SA 3.0

$2.95

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Piezo Vibration Sensor - Small Vertical
SEN-09199

Description: The Minisense 100 from Measurement Specialties is a low-cost cantilever-type vibration sensor loaded by a mass to offer high sensitivity at low frequencies. Useful for detecting vibration and 'tap' inputs from a user. A small AC and large voltage (up to +/-90V) is created when the film moves back an forth. A simple resistor should get the voltage down to ADC levels. Can also be used for impact sensing or a flexible switch.

Comes with solder pins that allows for vertical mounting.

Features:

• Flexible PVDF Piezo Polymer Film
• 
  

Thanks guys. I,m not firing the bullets myself, so don't worry about that. It's all under lab conditions, so there may be a load of instrumentation geared around the 150mm square product I mentioned and therefore it would be easier to keep going with that, or there may be a requirement i am not being told about because it is all a bit secret. I just wanted to check I wasn't trying to reproduce something that was off-the-shelf. I will make all your suggestions as if I had all this massive knowledge:) Thanks again. I knew there would be more to it than yes or no. Cnc jim

I second Lyn's choice. Just buy a Chrony, it is what all the pros use.

I don't know what your budget is ,but Midway USA sells them as well as most other shooting sporting outlets. The one linked is the one I used.

They work via optics and do so quite well. I used to place mine about 3 to 6 feet from the muzzle of the rifle and used it to check my hand loaded rounds for the National Match.

Playing with the piezo film might be fun, but the chrono would give the added benefit of checking bullet velocities too. (not at the same time though)

Never went to Camp Perry, wasn't good enough, and couldn't justify the costs.

Well, good enough is a bit subjective. I went a number of times against 800 other competitors. While I always did very well at local events, the Nationals are something else.

Nevertheless, the experience is worth it regardless of your skill.

When I wanted to measure the arrival of shotgun pellets at a target, I glued a piezoelectric crystal to a 1/2 inch thick steel plate and attached the 2 leads to an oscilloscope. Every time a pellet hit the target, it generated a voltage pulse so I could measure the arrival time between the first and last pellet.

Old technology - dates way back - similar to system used by Ohler chronos. Most shooters now use light screens.

http://www.automationdirect.com/static/specs/pehiresbx.pdf

It's easy to reject a technology for being old. OP didn't ask for a new technology. The piezoelectric sensor is an inexpensive, reliable, reusable system that rarely fails. Yes, it has some peculiarities such as the target rings after being hit. If that's a problem, you need some damping. Damping will not prevent all the ringing, but you are generally interested in the first pulse only. Light screens also have some fundamental problems. To discount a technology exclusively on the basis of its age, violates fundamental engineering principles.

Interestingly, the customer has experience of recording the info via some of the methods suggested, but it appears they specifically want the method they have asked me to copy. It looks like the 'foils' they have now were made especially for them years ago.I have yet to see one, but hopefully this evening.

Although I didn't ask for an alternative, i appreciate them all. 50% of my customers come in asking for something that isn't what they really need, they just don't know the alternatives. If I suggest one, and they don't go for it, no problem.

cnc jim

Read the OP's question again - he asked if anyone had heard of such a thing which is what I answered. When I said it was old technology I didn't say it wouldn't work. Steam engines will still propel vehicles but not as efficiently which is why they are not used much anymore. Light screens replaced the contact screens because they freed you of the cost and time required to change the screens when shooting. Since the OP (as usual) didn't give all the parameters applicable to his question he will get a lot of info that is not specific to his needs.

Hi Graycav. Are you saying you have seen these before? I gave all the info I had at the time, but I am being kept in the dark to some extent.

Apparently this method is more accurate than any other. I don't care if it is or not, the customer has asked for this specifically.

I have one in my hand. Thin transluscent browny orange celophane like backing, gloss reverse, kind of satin on the face, thin copper strips, not like printed, but actual copper foil, not like copper leaf or schlag either. I'll try and post a photo

cnc jim

That looks like a strain gage to me.

Copper plated circuit on polyimide film. Common critter.

Another option I'll throw in (just because we make them) is a high speed camera. Whether you want to see how the projectile leaves the gun or arrives at the target it will record it & can give more information than just speed.

The best photos of bullets and fast moving objects I have ever seen were taken by Harold "Doc" Edgerton. A book titled "Stopping Time" 'has a remarkable group of them. He even photographed the atomic bomb and caught it in a sequence from the very first instant. A friend, Steve Grohe, who was a well know photographer also, worked with him and is still around to tell the tale. His research on high powered strobes and photography are probably declassified by now since he worked in the 1940's.

Doc Edgerton is also one of my heroes. See his Electronic Flash, Strobe published by MIT Press. However, ballistic photography has progressed immensely. See: http://www.youtube.com/watch?v=QfDoQwIAaXg

The first thing that came to mind for me was aluminum foil glued to both sides of a piece of paper and wiring a capacitance meter to each piece of foil. Just thinkin.