I have been around for two years now, and this is the first thread I start outside the WC. You will see some more in the next time, probably one about optimising yield towards nitric acid (instead of optimising for the stuff to-be-nitrated, while using access acids). Another will be about speeding up synths, while still having optimal safety and neutralisation. But let me start with my favourite: Electronic VoD Measurement!

As mentioned, I built a VoD-Meter with a processor that uses two ionisation probes in the column of explosive. Having only two wires cut by the detonation front needs too long columns, because the hot gasses behind the front stay conductive. Instead, I put two pairs of twisted, insulated wires into the charge at a given distance, which are successively shorted by the plasma of the det front. The micro counts the time between (at 20 MHz) and displays the result on some 7-segment LEDs.
Here are the first 10 results as a starting point, I will go on testing and would appreciate feedback. If possible, I will test compositions other forumites suggest, but don't ask for HNIW or ONC, and please do not send me your samples by post either...

To avoid low order detonation, and to always have the same conditions, I use steel pipes of 10, 14 or 20 mm ID, with 1mm walls, unless noted. Sensor distance is always 200mm, unless noted. The cap is always the same too, a compound cap with 2g MHN compressed to 1.7g/ccm at 10000PSI, with 0.5g at 1.4g/ccm pressed on top, followed by 0.5g hand pressed AP. They are made from 9mm ID brass capsules, deep-drawn with integral bottom, 0.3mm walls and 40mm long, top seal is epoxy. Most are electric, sometimes I use fuse though. The VoD-Meter has only 1m sensor cable, but is placed behind a concrete wall and survived well until now.
Given are the composition, the pipe ID, density and filling pressure, counter reading in microseconds (rounded), plus the calculated VoD in meter per second (rounded to 3 digits).


Test 1

AN dynamite with 40% NG, 50% AN and 10% wheat flour.
D = 1.45 g/ccm pressed at 200 PSI (exuded NG above that pressure).
Counter reading 36µs, VoD = 5550 m/s.
(NOTE: Aluminium pipe 8mm ID, 1mm walls)

Test 2

Pure fine HDN, dried at 50C for a day.
D = 1.4 g/ccm pressed at 1000 PSI, 10mm ID pipe.
Counter reading 52µs, VoD = 3850 m/s.
In contrast to most people's opinion, it propagated well even at 10mm dia.

Test 3

HDN dynamite with 40% HDN, 60%.
D = 1.45 g/ccm pressed at 500 PSI, 14mm ID pipe.
Counter reading --µs, VoD = ---- m/s.
(NOTE: Fragment must have cut second wire, or I mixed up the sensor cables :p )

Test 4

50% MHN + 50% RDX, intimately mixed fine crystals.
D = 1.25 g/ccm pressed at 500 PSI, 6.3mm ID pipe.
Counter reading 7µs, VoD = 6250 m/s.
(NOTE: 1/4" cardboard pipe, 45mm probe distance)
This test was done to see if the wires are sheared against the hole in the pipe wall, or shorted by the plasma. It works in cardboard, therefore it is No 2.

Test 5

HDN gelatine dynamite with 45% NG, 5% NC, 40% AN, 6% HDN, 4% flour.
D = 1.62 g/ccm pressed at 500 PSI, 10mm ID pipe.
Counter reading 31µs, VoD = 6450 m/s.
At least equal to 65% straight dynamite! Replacing wood pulp with HDN must have helped.

Test 6

HDN/NS gelatine dynamite with 17.5% NG, 17.5% NS, 45% AN, 15% HDN, 5% flour.
D = 1.63 g/ccm pressed at 500 PSI, 20mm ID pipe.
Counter reading 29µs, VoD = 6940 m/s.
Really high for so little NG! Cheap SC explosive (was tried, gave 50+ mm penetration in steel with a 1" cone)

Test 7

NS dynamite with 65% AN and 35% NS (from SA/AN/starch 13:5:2 in 2h @ 45C).
D = 1.15 g/ccm pressed at 1000 PSI, 10mm ID pipe.
Counter reading 46µs, VoD = 4350 m/s.

Test 8-10

APAN with 12% AP, D = 1.03 g/ccm, pressed @ 500 PSI.
10mm ID pipe: Counter reading 56µs, VoD = 3570 m/s.
14mm ID pipe: Counter reading 54µs, VoD = 3700 m/s.
20mm ID pipe: Counter reading 53µs, VoD = 3770 m/s.
This shows that for APAN, diameter has less influence than for other AN explosives, and max. velocity is reached sooner (ANFO = 6+ inches, donarite = 2+ inches).

To be continued ... :)

Excellent work Boomer! You are a real genius. :cool:

Umm, it would be cool if you could test ANNM in different percentages NM. Perhaps a 60/40 ANNM and a 75/25er one. My favourite ANNMAl is 65/25/10 it could be also a good Idea to test it wich influence Aluminium does REALLY make!

Ohh, APAN 80% AN and 20% AP or APANAl 75% AN 12,5% AP and 12,5% Al were also some really intresting candidates! I think I must not say whats about DPPP, huh? In some videos does it really looke like 8000m/s+ and some Vids look familiar to AP.

I dont know if you're intrested to measure the VoD of some pure HE's like NG or PETN or HMTD....

How the fuck could you built up such a device for your own??? That's a great honor to have a Member with such a potential here :) Could you please draw a picture how your apparatus works! I think it would be cool to have some more members with such a gadget, because I know what you're doing after work now ;)

Keep on Testing! Myrol

Did you use a Data Logger? Well that's what I would use for this kind of thing anyways. Good work! :)

Perhaps Boomer? You could now test the controversial "DPPP" to give us a ballpark figure of it's power.Hmmm??? ;)

[Edit] where did you find the plans to make such a useful piece of equipment? Or did you design the entire concept yourself. Either way it shows that you are a very smart person and you are most deserving of some praise for your work.

Might I be so bold as to ask you for what the cost would be to build one of these and if you could maybe draw up some detailed schematics to share with us? Please?

Thank you for the praise! But to be honest, the circuit is super simple. Apart from the standard configuration (battery-regulator-processor-xtal-LEDs) there are only two resistors and two capacitors (!) to convert a thermostat to the counter.

BTW I think VoD-Meter is too long, lets call it detometer.

I just made a CAD drawing and calculated the price using our purchase databank. Leaving off unnecessary stuff from the modified thermostat, the result is

2,66 Euro per piece without housing :)

OK, with a dip switch to select charge length, plus screw terminals for battery, sensors and a start button, it is 3,88 Euro. That is because we buy resistors in 50000 batches per value (=5 for a cent), and the procesor is 1 Euro if you buy 20000. At radio Shack it will be more like 15 Dollars for the parts.

Considering we can build them for what most of you pay for the parts, I think about selling. They can also measure bullet speed with alu foil as probes btw.

I know advertising is forbidden, so I will better contact a mod. Plus, I will of course post schematics and layout for those able to make them at home. I could also sell kits, or pre-programmed PICs. But as I said, that is up to the mods to sign off.
I will post a pic of the new model as soon as it is finished. The current one is a converted thermostat from our company, of which we sold 80000 all over Europe, so it might be recognised if I post a pic.

Now about your comments:

I will not measure pure compounds as those values are known. And I will not mess with big amounts of HMTD either. ANNM would be interesting if I get NM. Aluminized mixes are known to be slower, so VoD is less interesting. Measuring blast power would be called for, but that's another instrument.
DPPP is definitely on my list, but I will wait until more people have reproduced those synths before wasting some weekends with failures.

If you sell it at cost, plus reasonable shipping, then it's fine to sell, as it's a community service. :)

Being able to definatively measure an accurate VOD would be of great help to a great many people and their projects.

really, really good work!

posting schematics and layout would be nice!
soldering the invidual parts shouldn't be a problem for most people visiting this forum i think.

If you can use it as a shoot-thru chronograph, I will take two! Hell, make a run of 500 and sell them on eBay, that's what I would do!

I will not measure pure compounds as those values are known. And I will not mess with big amounts of HMTD either. ANNM would be interesting if I get NM. Aluminized mixes are known to be slower, so VoD is less interesting. Measuring blast power would be called for, but that's another instrument.

Vey, very nice work!
Is'n it a good idea to use NG as standard? I believe it is very good method you use, but a standard would 'prove' your instrument and give something to compare with. NG would be ideal because it has not something like a 'cristal density'.

I really like you instrument, it not that, but I would like to see an comparising with a know explosive with a known VoD.

I dont think so, NG is especially prone to low-order detonation. If you read Escales et altera, there are several figures of VoDs between 1500 and 3000 m/s even in metal pipes.

UPDATE:

I re-worked schematic + layout. The two-digit display showing processor cycles in HEX is not for everybody, you need a pocket calculator to get the VoD. I was not content with the 800ns resolution either. So here is what I changed:

1. Used the interrupt to get 4x accuracy (200ns at 20 MHz crystal)
2. Added a third 7-segment LED
3. Added a DIP switch to set charge length between 5cm and 1m
4. Added a switch to go from 0-9.99 km/s to 0-999m/s for bullets
5. Added a memory-recall button for the last 128 results
6. Scaled it down to full surface mount (50x45mm total size now)
7. Used screw terminals for everything, so you can choose a housing and probe connector

Our camera is screwed, so pics will have to wait, sorry guys.

Do you have any comments on what I might have overlooked? E.g. are there many people needing over 999 m/s for bullets? As I hate to re-do it again, would a dot from the first LED be ok for "add 1km" ?

BTW the parts price (without board) is up to 6 $ (at 20000 pcs) or 30 $ for radio shack prices. With everything SMT, I would recommend we do the soldering in the company via robot, as I needed 5 hours for the first unit.

Board price is 20$ if they make 5. Goes down to 3$ for 100. Self-etching is out of the question, it is double sided and you have to solder under the parts to connect tracks between the two sides... :o So give me an estimate number how many I can order !

are there many people needing over 999 m/s for bullets?

So give me an estimate number how many I can order !

I have only a couple of hand load possibilities that exceed 999 m/s. Varmint shooters might be more interested in measuring higher velocities.

Put me down for one...

Get a small clamp system, and make it so it can be clamped to the end of the barrel. Just use a bit of 90 degree angle, so it auto-aligns on the barrel. Ideal for air rifles. There is a guy in the UK who makes one, he can't keep up with demand. My gun club could use five, easy.

Do have the kind of over-speed measure, too. 7.62 goes to 850-ish m/s, and that's as far as I go at the moment. Getting something radical that goes over 1kmps would be really neat, and my current chrono goes to 6! However a dot for "add 1000" would be great.

This IS going to be capable of measuring explosive VoD's, correct?

With the HNIW thread having possibilities, it may soon be possible to make a 10k/m explosive, so would this be capable of measuring to that range?

If not, it's still useable, if it could be used to measure an EFP projectile, as these have about 3k/m velocity, but the device would have to be capable of a wide window for the projectile to pass through, as it's not a rifle, so accuracy in aiming would be problematic if you only had a few inches in which to aim. ;)

Correction: Turns out my chronograph goes to 7000fps or 2133.6 m/s

What would be the lower bound? My chrono goes down to 56fps, so you can measure airguns and bows?

Short update (little time):

worked further on the software, it can now be switched between xxx m/s and x.yy km/s for the display. Probe distance can be set with a DIP switch to be 5, 10, 20, 50 or 100 cm.
Memory recall function will be done next week.

NBK: That's what is was made for in the first place, 1.00 km/s to 9.99 are standard for HEs, 000 to 999 m/s for bullets. The bigger problem is sensing in the bullet mode: you have to shoot through two sheets of double-sided aluminized paper, with the bullet shorting the two sides of each sheet. An opto-device clamped to the barrel COULD be connected, but would increase price + complexity too much for a standard.

It occured to me that there is another use to which this device can be put to beside just measuring VoD.

By putting the two trigger sensors inside of the explosive charge of a device, such as a shaped charge, in particular spatial relation to each other (depending on what you wanted to determine), that you could (for instance) tell what the shockwave symetry was like, whether sperical or planular, whether a waveformer was actually working, and other things.

For instance, with EFPs, if the shockwave is too spherical, the center of the platter is deformed too far in advance of the edges, causing the liner to rupture.

If you were monitoring the wavefront and determined that the center was 20microseconds in advance of the edge, and the platter was rupturing, you could adjust things to bring the variance down.

A variance of near zero between the center and the edge means that the wavefront is flat, which is ideal for most EFPs. :)

Also related, but somewhat OT, is a microsecond delay circuit.

The really 'neat' things that you can do with more modern munitons, such as multiple initiation points for waveform modulation, require triggering the detonators with an error of a millisecond or less.

As EFP's that are intended for selectable attack have a central detonator, with annular detonators, the delay between the firing, and the sequence of, the detonators determines if the liner becomes a long-rod penetrator, a forward fold, or fragments.

Shooting through paper isn't an issue. In fact, for indoor use it would be better, since low light wouldn't be the PITA that it currently is with an airgun pellet. Messing about with the mains powered add-on light array is just such a waste of time and effort.

Each of your ideas triggered some changes, mostly to the software. The m/s <-> km/s slide switch is now used to switch from time to speed, the display toggles from xxx to x.yy to xx.y automatically depending on what it has to show:

Time-mode: 00.0 to 99.8 µs in steps of 0.2µs / 100 to 999 µs in steps of 1µs

Velo-mode: 000-999 m/s in steps of 1 m/s / 1.00 tp 9.99 km/s in steps of 0.01 km/s.

Still got trouble with the memory, maybe it is the 20 MHz Xtal (I emulated at 4 MHz). It sometimes forgets a digit!
Apart from these issues, there has been little progress, partly due to me ill for a week, plus unable to post for another.

At least my prototype lost virginity last week: I used it for the first time (instead of the modded thermostat) to measure a VoD: AN/HDN/NS 70/15/15 in a 20mm steel pipe went at 4580 +/- 20 m/s (+/- 0.45%)!

Each of your ideas triggered some changes, mostly to the software. The m/s <-> km/s slide switch is now used to switch from time to speed, the display toggles from xxx to x.yy to xx.y automatically depending on what it has to show:

Time-mode: 00.0 to 99.8 µs in steps of 0.2µs / 100 to 999 µs in steps of 1µs

Velo-mode: 000-999 m/s in steps of 1 m/s / 1.00 tp 9.99 km/s in steps of 0.01 km/s.

Still got trouble with the memory, maybe it is the 20 MHz Xtal (I emulated at 4 MHz). It sometimes forgets a digit!
Apart from these issues, there has been little progress, partly due to me ill for a week, plus unable to post for another.

At least my prototype lost virginity last week: I used it for the first time (instead of the modded thermostat) to measure a VoD: AN/HDN/NS 70/15/15 in a 20mm steel pipe went at 4580 +/- 20 m/s (+/- 0.45%)!

Each of your ideas triggered some changes, mostly to the software. The m/s <-> km/s slide switch is now used to switch from time to speed, the display toggles from xxx to x.yy to xx.y automatically depending on what it has to show:

Time-mode: 00.0 to 99.8 µs in steps of 0.2µs / 100 to 999 µs in steps of 1µs

Velo-mode: 000-999 m/s in steps of 1 m/s / 1.00 tp 9.99 km/s in steps of 0.01 km/s.

Still got trouble with the memory, maybe it is the 20 MHz Xtal (I emulated at 4 MHz). It sometimes forgets a digit!
Apart from these issues, there has been little progress, partly due to me ill for a week, plus unable to post for another.

At least my prototype lost virginity last week: I used it for the first time (instead of the modded thermostat) to measure a VoD: AN/HDN/NS 70/15/15 in a 20mm steel pipe went at 4580 +/- 20 m/s (+/- 0.45%)!

What sort of processor do you use? AVR?

Have you done multiple tests with the same batch and size of the bomb, to see the variation of you measurement?

What sort of processor do you use? AVR?

Have you done multiple tests with the same batch and size of the bomb, to see the variation of you measurement?

What sort of processor do you use? AVR?

Have you done multiple tests with the same batch and size of the bomb, to see the variation of you measurement?