[time-nuts] A real-world precision timing need....

[Bob Camp]

Hi

There are a number of commercial systems that look at group size based on
correlating the outputs of a number of ultrasonic sensors. The "shock wave"
off of the bullet gives a pretty good impulse into a piezo element. The
systems typically quote numbers in the "couple of centimeters" range for
accuracy over a 1 to 2 meter square. 

Bob

-----Original Message-----
From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
Behalf Of scmcgrath at gmail.com
Sent: Monday, November 01, 2010 8:07 AM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] A real-world precision timing need....

Initial suggestion would give muzzle velocity only - need coffee before
commenting

A piezo detector bonded to the plate would give time of impact.   I'm
interested in how you would compute group size 
Sent from my Verizon Wireless BlackBerry

-----Original Message-----
From: scmcgrath at gmail.com
Date: Mon, 1 Nov 2010 11:57:43 
To: Discussion of precise time and frequency measurement<time-nuts at febo.com>
Reply-To: scmcgrath at gmail.com
Subject: Re: [time-nuts] A real-world precision timing need....

Why not purchase one of the existing ballistic chronographs and upgrade the
time base?


Sent from my Verizon Wireless BlackBerry

-----Original Message-----
From: Bob Camp <lists at rtty.us>
Sender: time-nuts-bounces at febo.com
Date: Mon, 1 Nov 2010 07:49:06 
To: Discussion of precise time and frequency measurement<time-nuts at febo.com>
Reply-To: Discussion of precise time and frequency measurement
	<time-nuts at febo.com>
Subject: Re: [time-nuts] A real-world precision timing need....

Hi

The original request was to measure both velocity down range and time of
flight. They certainly are related, however the relation (especially around
the speed of sound) is difficult to estimate. If you are dealing with a
projectile that drops sub-sonic as it goes down range, velocity is indeed
worth checking. 

-------------

If you own the range (800 yard range in the back yard hmmm...): 

Head over to the local cable TV outfit's scrap yard. Pick up a spool of what
ever they are throwing away. Dig a trench and burry some out to each
observation point. Coax in the ground is going to be much more stable timing
wise than  anything else you can get for free. With it buried it will last a
bit longer than wire on the surface. 

Bob

On Nov 1, 2010, at 1:37 AM, Mark J. Blair wrote:

> 
> On Oct 31, 2010, at 7:21 PM, Bob Camp wrote:
>> The gotcha is that the gong can move / twist when hit.  The plate buried
in front of the electronics has to just sit there and take it. More energy
transfer to the anchored plate. 
>> 
>> I'm sure there are alloys that will get you under 1", the issue will be
making sure you have the right one...
> 
> Ah, good point. Also, it won't matter if the steel stops the bullet from
penetrating if the shock turns the enclosed electronics and optics into
powder.
> 
> As an aside, when I bought my high power rifle rated steel gong target
(which, sadly, I haven't taken for a test drive yet), I looked at pre-shot
samples from about four different vendors who had displays at the gun show,
and there was a noticeable difference in the steels that they used. The
vendor I chose had little more than faint dimples surrounded by lead
spatters where .308 rounds allegedly hit their target, while other vendors
had substantial craters.
> 
> Back to the topic at hand: If muzzle velocity and time of flight alone
would provide enough data (*), then one possibility would be a downrange
target with an attached transducer (piezo?) to register the bullet impact,
with a wire pair going back to the shooting bench. In this case, the
downrange sensor would be cheap to replace when it eventually fails, and all
of the expensive/delicate stuff would be back at the shooting bench.
> 
> (*) I haven't studied ballistic equations carefully enough yet to know
whether this would provide enough information to estimate fun details like
ballistic coefficient.
> 
> 
> 
> -- 
> Mark J. Blair, NF6X <nf6x at nf6x.net>
> Web page: http://www.nf6x.net/
> GnuPG public key available from my web page.
> 
> 
> 
> 
> 
> _______________________________________________
> time-nuts mailing list -- time-nuts at febo.com
> To unsubscribe, go to
https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
> and follow the instructions there.


_______________________________________________
time-nuts mailing list -- time-nuts at febo.com
To unsubscribe, go to
https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
_______________________________________________
time-nuts mailing list -- time-nuts at febo.com
To unsubscribe, go to
https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.