ExtremeBallistic - not so bulletproof?

NateChrony

NateChrony

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Joined
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Location
Sydney, NSW, Australia
Anyone want to share this humble pie?
Plenty to go round....

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Also not immune to sawdust... However it did take a few hits @20m with 12fpe & they held up really well.
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Will adjust the design a bit to minimise this.... learning
 
Congrats to Nate for honesty!

Sometimes, cure is easier than prevention. It's interesting that no chrono manufacturer designs against this problem and offers spares for the most likely damage that may be caused.

It's for exactly this "shoot it" reason that my humble home made chrono has the LEDs and Sensors recessed 2mm into the holding tube. I found even that was not enough!
When shooting a PCP pistol, it's all too easy to treat the air tube as the muzzle.... so the muzzle itself goes up by about 30mm. Enough to make the pellet go through the cover above the usual chrono path, and pass straight through the sensor board! I've now done that twice. My main electronics is tucked well away down the side, and could be located several feet away from any possible damage, so that has never been shot....yet.

A stray shot being somewhat unavoidable, my fix is simple. There is an LED board and a sensor board top and bottom at each end, so 2x2 = 4 in total. Each board is a standard size with a small connector. Off come the covers, the like for like replacement is put in, and off we go again. My circuitry contains an AGC (Automatic Gain control), so if the replacement has somewhat different gain compared to the original, the circuitry just adjusts the gains automatically to find the correct operating point. I have nothing to twiddle.
No recalibration is necessary, as the dimensions are finally determined by the holes in the holding tube. I did eventually have to patch up the hole in the cover too...

There is no microprocessor to go wrong. The readout is actually a cheap (£2.50 originally ) plug in DVM, easily replaceable in seconds. Why make when you can buy cheaper?

My plug-in calibration/test board can easily check that all is well. Imagine the fun if Plod comes along, to have a system where I can immediately prove the accuracy of the chrono without even touching a gun.

For the purist, my final timing calibration link is a timer counter, in turn calibrated to an off air frequency standard. But all of that is not really necessary, because in all chronos, 99.9% of the time the biggest uncertainty factor is the placement and performance of the sensors.
 
I would like to say a massive thanks to Nate for taking the time to talk to me via email on the top one and I look forward to the replacement bits once you get a chance to settle in from your European tour.
Apparently point blank to the LED it doesn’t seem to like and for some reason I didn’t get a velocity reading! 😂
 
NateChrony said:
Np - its a hard balance, the LEDs can get dirty from filthy powder burners - so they need to be easily accessible for cleaning....
just hard to judge exactly where the line needs to be.
Fully exposed = super easy cleaning
Recessed = may need a screwdriver
Click to expand...
Yes, filth is a problem. My tube of sand as a backstop has the sand dampened, but even so fine dust comes back and lodges in the lower LED holes. Sooner or later, it screws up!
 
Firsttwodie said:
I would like to say a massive thanks to Nate for taking the time to talk to me via email on the top one and I look forward to the replacement bits once you get a chance to settle in from your European tour.
Apparently point blank to the LED it doesn’t seem to like and for some reason I didn’t get a velocity reading! 😂
Click to expand...
Point blank clearly has a muzzle blast. On a PCP you get a blast of very cold air. It's so cold that it can instantly freeze any moisture in the air, creating ice particles or fog that in turn get blown away- you can sometimes see a tiny cloud, but not always. If that happens, then the first sensor pair can miss.
It's this sort of thing that means measuring muzzle velocity close up can be extremely difficult- and very much so in some damp, warm, conditions. Just try and give it a couple of inches.
The single sensor solution (best for a chrono fixed to the muzzle) gives stronger signals and less problems, but my opinion is that a spread sensor is not as good..
 
Everyday is a school day even the big companies have their mishaps. Possible removable cover to allow cleaning of the recessed LEDs or hinge the top section for maintenance access. Just a thought 🤔
 
NateChrony said:
Will adjust the design a bit to minimise this.... learning
Click to expand...
Really appreciate your transparency on issues like this Nate. I think you're a little bit of a victim of your own success when it comes to the line between a commercial product, and an enthusiast making products for the community. I guess it must be nice that we hold you to a high standard, because at least then you know that we see you as something of an authority - even if that brings with it a certain level of scrutiny...! 😅

What's the autopsy findings on this? Shot down into the steel and the riccochet came up and took a bite out of the sensor? (excuse the MSPaint...!)
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I think you'll be quite hard-pressed to make it indestructable unless every inch of it is seated behind some kind of plate. From looking at the images of the NCEB - my biggest concerns for vulnerability are the exposed cables joining the upper and power half, as they're inside the bullet tunnel and seemingly exposed to the shooter:

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Having replaced a fair few of those connectors when I was flying drones, it can be annoying if you don't have the right tools to crimp those terminals.

Also having the USB cable at the rear like that - might represent an issue as it could sag down. A small hook like the one the antenna is mounted too on the other side might be a really easy solution to ensure it never hangs down into the line of fire. Would be really annoying to lose the cable in the middle of a shoot.
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But this is all probably just the result of accumulated trauma from my IT Desktop support days, where any lose cable was one user interaction away from a broken bit of kit...!

Thanks Nate!
 
Bazzatron said:
Really appreciate your transparency on issues like this Nate. I think you're a little bit of a victim of your own success when it comes to the line between a commercial product, and an enthusiast making products for the community. I guess it must be nice that we hold you to a high standard, because at least then you know that we see you as something of an authority - even if that brings with it a certain level of scrutiny...! 😅

What's the autopsy findings on this? Shot down into the steel and the riccochet came up and took a bite out of the sensor? (excuse the MSPaint...!)
View attachment 910825

I think you'll be quite hard-pressed to make it indestructable unless every inch of it is seated behind some kind of plate. From looking at the images of the NCEB - my biggest concerns for vulnerability are the exposed cables joining the upper and power half, as they're inside the bullet tunnel and seemingly exposed to the shooter:

View attachment 910828

Having replaced a fair few of those connectors when I was flying drones, it can be annoying if you don't have the right tools to crimp those terminals.

Also having the USB cable at the rear like that - might represent an issue as it could sag down. A small hook like the one the antenna is mounted too on the other side might be a really easy solution to ensure it never hangs down into the line of fire. Would be really annoying to lose the cable in the middle of a shoot.
View attachment 910844

But this is all probably just the result of accumulated trauma from my IT Desktop support days, where any lose cable was one user interaction away from a broken bit of kit...!

Thanks Nate!
Click to expand...
Yeah- those connectors are used on model boats and LiPo battery chargers. I still have not found a suitable crimp tool., though I have just received one that looks like it may work. Those JSB connectors come in a large variety, and frankly I've found them unreliable, tho that is in a scenario where they are removed and reinserted regularly. The British Molex connector was far better. The cheap Chinese chrono cunningly uses two of its pillars to connect to the bottom board. You can't argue too much with M4 brass.
 
NateChrony said:
yeah for sure - can provide new parts or designs to DIY
Click to expand...
Hello Nate could you xplain to us what this message means that its a parallel error.
Please see screenshot
 

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Bazzatron said:
What's the autopsy findings on this? Shot down into the steel and the riccochet came up and took a bite out of the sensor? (excuse the MSPaint...!)
View attachment 910825
Click to expand...

yeah pretty much this...

Bazzatron said:
I think you'll be quite hard-pressed to make it indestructable unless every inch of it is seated behind some kind of plate. From looking at the images of the NCEB - my biggest concerns for vulnerability are the exposed cables joining the upper and power half, as they're inside the bullet tunnel and seemingly exposed to the shooter:

View attachment 910828

Having replaced a fair few of those connectors when I was flying drones, it can be annoying if you don't have the right tools to crimp those terminals.
Click to expand...
Its tied in place & behind the plate - its also a very cheap & easy to replace cable, spares will be available from our retailers. Its an xh2.54 cable 10cm, pretty easy to get online from a few market places & not generic. I went with generic/easy to get - so it can be replaced locally & without coming to me.

Bazzatron said:
Also having the USB cable at the rear like that - might represent an issue as it could sag down. A small hook like the one the antenna is mounted too on the other side might be a really easy solution to ensure it never hangs down into the line of fire. Would be really annoying to lose the cable in the middle of a shoot.
View attachment 910844
Click to expand...
Where is the 90deg USB cable that is supplied? Thats why I supply that one specifically.
Notice those little holes on the side arms? they're for exactly that - zip tie it in place if you need to by using those holes in the arms ;)
 
tonyghost said:
Hello Nate could you xplain to us what this message means that its a parallel error.
Please see screenshot
Click to expand...
What does the help page say? 🤣
Help page calls it a perpendicular error lol...
That tells you that the sensors that detected the START of the pellet were not in line. (timing is off the back of the pellet).
As long as they're the sensors next to the right one - you're golden. i.e. 2 & 6 is perfect, 2&5 or 2&7 are fine.

This can be used to really dial in the accuracy (squeeze that last 0-2 fps) and if you're shot was not perfectly perpendicular.

Its a lot of extra data to really help you know that the reading is correct. It is a bit too worrying (calling it an error & Red) I think, but its valuable data so you know what is going on.
 
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