The background to the question stems from the Unconventional Shaped Charges thread on the main page. Reading about modern SCs lead me to the use of
Pentolite in many older SC weapon systems. Its properties made it rather ideal in terms of castability, VoD, handling, and brisance. PETN is of
limited accessibility to the experimenter due to the lack of available pentaerythritol, but ETN is simple enough to be made if one is careful and TNT
can be produced in small batches at fairly low cost. It is well known that ETN has rather similar characteristics to PETN for many purposes.
Could an equivalent material to Pentolite be made by combining TNT and ETN? Would it be a true eutectic combination?
Pentolite is produced by the gentle heating of pure TNT to 90C, followed by slow addition of equal parts by weight of PETN in small (5-10% total by
weight) batches and stirred gently. As each batch is added, the TNT cools and begins to solidify The TNT is then reheated to 90C and more PETN added
with stirring. The cycle is repeated until the combination is 50/50 PETN and TNT by weight.
This could make a very potent explosive for small shaped charges, but I don't have mastery of the two materials to tell at a glance if this is
workable. Would anyone care to chime in?Ral123 - 19-2-2013 at 21:44
I tried to add small amounts of DNT/TNT to my ETN. It doesn't mix. How do you plan separating isomers and lower nitration products from your TNT? And
it wont be storage stable. What's the point in the TNT then?Motherload - 19-2-2013 at 22:10
eBay. You can buy Pentaerythritol. $52 free shipping.
Having said that .... I always wanted pentolite but TNT was the limiting factor.
I would think ETN would work just fine to make entolite.
ETN might be a tad bit better as it has positive OB.
[Edited on 20-2-2013 by Motherload]Farnsworth - 19-2-2013 at 22:20
I tried to add small amounts of DNT/TNT to my ETN. It doesn't mix. How do you plan separating isomers and lower nitration products from your TNT? And
it wont be storage stable. What's the point in the TNT then?
Urbanski in Vol 4 gives the basis for purification of industrial TNT via the stellite process and washing. I don't recall it being anything
unreasonable for a laboratory setting. Further I don't think the existent isomers and remaining (.02% IIRC) impurities would be a factor if they
don't inhibit a combination with PETN (correct me if I'm wrong).
Full disclosure - I've made lab TNT only once.
[Edited on 20-2-2013 by Farnsworth]Ral123 - 20-2-2013 at 04:36
You are right, with the storage issues of ETN, the side products of TNT are's so much an issue. Why the military separates isomers? It's because one
or two of them aren't as stable or what? For that thing I'm a fan dinitrobenzene. Ultra insensitive and may be the most storage stable home made
explosive ever.
Entolite Production
Hennig Brand - 2-12-2014 at 05:19
I made a small amount of 50/50 Entolite this morning by the co-precipitation method, which is briefly described in "Military Explosives" for producing
Pentolite. Two separate solutions of approximately the same volume were made; 2.05g of ETN was dissolved in 10mL of acetone and 2.05g of TNT was also
dissolved in 10mL of acetone. Fine, low bulk density, TNT which had precipitated after the methanol recrystallization solvent had mostly cooled during
TNT purification was used. The two solutions were pipetted into about 150mL of vigorously stirred room temperature (was colder in my case) water at
the same rate in a slow stream of drips. The Entolite precipitated immediately. Pentolite is undoubtedly superior to Entolite in most ways, but
Entolite is still interesting and will most likely produce great base charges, although with less storage stability than Pentolite. According to the
usual sources, Pentolite's sensitivity is between that of PETN and TNT and this should also be the case with Entolite (sensitivity between ETN and
TNT).
Once it dries I am going to try a gram or two in a compound cap.
Ral123,
I believe some of the isomers and lower nitrate nitrotoluenes can form low melting point oils that can exude/separate from a TNT charge and can be
very hazardous, for a number of reasons, for some military applications.
[Edited on 2-12-2014 by Hennig Brand]PHILOU Zrealone - 2-12-2014 at 08:42
The military simply don't rely on unpredictable mixes of isomers...they prefer to have a pure enough compound in a way to get reliable
physico-chemical properties from batches to batches. This is most important for detonic properties and storage of military ammo's.
ETN/TNT mixes are very interesting and may prove to be more powerful than PETN/TNT mixes!
Because density of ETN is 1.72, it may display a slighly lower VOD than PETN (d=1.76); but on the other hand it displays a positive OB (one extra
oxygen atom per molecule) that will help burn the exces carbon rich TNT so the energy output will be higher for a given composition (probably the
perfect OB mix) and this might increase VOD and brisance of Entolite (Tetrolite) vs Pentolite.
O2NOCH2-CHONO2-CHONO2-CH2ONO2 --> 4 CO2 + 3 H2O + 2 N2 + 1/2 O2
CH3-C6H2(NO2)3 --> 3 CO2 + 4 C + 3/2 N2 + 5/2 H2
So the perfect OB mix needs 10.5 moles of ETN for 1 of TNT!
Sole problem ETN is about 10 times more shock sensitive than PETN and less stable towards heat because it is a viccinal nitric ester
(R-CHONO2-CHONO2-R with R= H or alkyl).
If there is a quest for higher densities, VOD and densities...
One would have to play:
-with MHN (mannitol hexanitrate) instead of ETN (denser, higher VOD and more extra oxygen)
-with TNB (trinitrobenzene) instead of TNT (denser, higher VOD and slighly better OB)
-with TNN (tetranitronaphtalene) instead of TNB (denser, higher VOD)
[Edited on 2-12-2014 by PHILOU Zrealone]Hennig Brand - 2-12-2014 at 10:18
I believe what you are saying about TNT purity is true, but I believe there are other reasons that may even be more important. I would have to dig for
references, but I know I have read in several places that TNT oils, from isomers and lower nitrated nitro-toluenes would leak into moving parts of
guns, etc, and pose very serious hazards. Exudation of these oils could also create voids in a shell which is a real hazard, particularly on setback.
There were other physical reasons as well why TNT with much of these impurities was incompatible with a lot of military equipment (guns, etc).
Interesting that Entolite/Tetrolite could be more powerful than Pentolite. I think a lot of the great properties of the 50/50 mix would be lost if the
mix was oxygen balanced however. A 50/50 mix will probably have a very desirable level of sensitivity to initiation. I didn't think that the
difference in shock sensitivity between ETN and PETN was really all that great. From what I have read, ETN is more sensitive but only tens of
percentage points more, if that. The big reason PETN is so much more preferred, from what I understand, is because of its greater storage stability;
it has a different structure altogether that ETN and NG and the other common nitric esters.
Here is a picture of the dry yield. It dries very quickly, which is great. The dry mass is 4.04g, which means that about 0.06g from what was started
with was lost, which is very little. A bit was lost during filtering and transfers and a tiny amount would have been dissolved in the water.
[Edited on 2-12-2014 by Hennig Brand]Dornier 335A - 2-12-2014 at 12:45
Do you think the precipitated entolite is as homogeneous as a cast mixture Henning Brand? To fully utilize the extra oxygen in ETN, the molecules
should be pretty much perfectly mixed.
PHILOU Zrealone, I ran some calculations on your proposed mixtures. It's interesting how similar performance ETN, PETN and MHN gave. PETN compensates
the negative OB with higher density to some extent, but MHN gives best results thanks to its better oxygen balance.
1.0g of Tetrolite Initiated; 7.6mm id Al, 0.30g LA (Unreinforced Configuration & ca. 6000psi Loading Pressure)
Hennig Brand - 2-12-2014 at 12:47
PHILOU, I think I prefer your name for this material (Tetrolite).
I am very impressed with this material. Just 1g of Tetrolite produces results which are very comparable to the best results I have obtained with 2g of
picric acid, as can be seen by viewing the witness plate shots below.
The hole on the right, in the witness plate shots, is from this test.
Dornier 335A,
I think how well they are incorporated would vary with technique. I may have a closer look under a microscope, but to the naked eye it looks just like
a single compound has been formed (solid light pink color through the material). This method was one of the standard military methods for producing
Pentolite, according to the text "Military Explosives", which says a lot in my opinion.
[Edited on 2-12-2014 by Hennig Brand]Bert - 2-12-2014 at 13:04
Not quite sure which hole is the one of most recent interest!
How about we take up a collection to buy this man a supply of nice, uniform (single use) witness plates? Least we could do in return for for the
interesting posts...
Also: Is it possible the repeated shocks by many tests to that steel disc could be work hardening it or otherwise changing the target's
characteristics meaningfully?Hennig Brand - 2-12-2014 at 14:17
I always try to put the last test hole about the middle of the picture, vertically, and to the far right. Also the most recent hole has no rust. I
think you are right about the explosive hardening. I wondered about that back when I was doing the DDNP tests, but was unsure of how significant it
really was and wanted to keep using the same piece for comparisons. Yeah, one way or another it is just about time for a new witness plate. I think I
have two or three more of those same ones (undamaged) if I can find them.
Edit:
BTW, I jumped the gun a little on proclaiming the Tetrolite dry. I weighed it this morning and in the last 14-16 hours the weight of what is left
dropped an amount that would translate into the entire sample losing another 0.10g. It was actually obvious during the processing that a fair amount
of small particles were lost, stuck to the reaction vessel, etc. They could have been recovered, but it would have been more bother. Losses are
usually greater when handling smaller amounts of materials.
Here is a picture of what is left of the Tetrolite (slightly less than 3g). It should be very close to the equilibrium moisture content now. Notice
how it has taken on a lighter color as well.
Here is a table of experimentally determined physical properties for ETN and PETN taken from the article, "Characterization and Analysis of
Tetranitrate Esters". Dh50 is the height at which there is a 50% probability of explosion. ETN is only slightly more sensitive to impact
than PETN, however, it really falls short of PETN in terms of heat release.
[Edited on 3-12-2014 by Hennig Brand]Dornier 335A - 3-12-2014 at 11:02
I'm curious to hear what you see under the microscope. I have coprecipitated mixtures before and the crystals formed were about 5 µm - not
particularly homogeneous that is. That was by pouring a hot concentrated solution of potassium chlorate and potassium ferricyanide into cold ethanol.
The particle size could probably be reduced further by spraying a mist of the solution into the ethanol and possibly using a more dilute solution, but
still. Hennig Brand - 3-12-2014 at 12:06
I will have a look under the microscope, but I am not convinced that it is imperative that mixing be that fine. I have attached a jpg image of a
snip-it on Pentolite production from "Military Explosives".
Also from "Military Explosives", "The minimum detonating charges of lead azide and mercury fulminate required for pentolite are intermediate between
those for PETN and TNT and are very close to that of tetryl."
[Edited on 3-12-2014 by Hennig Brand]Microtek - 4-12-2014 at 04:59
I have to point out that in the co-precipitation method you should mix the solutions of TNT and (P)ETN before you add them to water
to precipitate the solid explosive. This will give you an even more uniform distribution.Dornier 335A - 4-12-2014 at 07:09
According to Fedoroff, only 20% of the PETN dissolves in the molten TNT. I actually thought all of it dissolved. Anyway, it shouldn't matter too much
how well the two compounds are mixed as both are oxygen negative. Entolite will of course work well too even with rather large particles. But to get
the maximum performance (especially brisance), the extra oxygen in ETN should be utilised by the excess carbon in TNT as quickly as possible. Hennig Brand - 4-12-2014 at 09:38
Thanks Microtek, that would make the process easier as well. I now see that it actually does say in "Military Explosives" to mix the two solutions
before adding them to the vigorously stirred water. Microtek, do you know how much acetone and water should be used for the co-precipitation method? I
was unsure of how much to use. I was feeding the two solutions of about the same concentration in at approximately the same rate, but mixing them
beforehand would be much easier that is for sure. Interesting to note that in the more modern slurry method, of pentolite production, preformed
particles of PETN are used which are then coated with TNT. So the better particle size control of this more modern slurry method was deemed more
important than the more intimate mixing of the co-precipitation method. I assume that the co-precipitation method could easily achieve a more intimate
mixture of the two components though not as much uniformity of mixing and particle size.
Dornier 335A, I imagine that degree of mixing can be very important, but I imagine that it becomes less and less important as you get finer and finer.
It would depend on intended use as well how important it was. I am not exactly sure how to quantify it though. I took a microscope picture at 100X
magnification, but with a bottom light I had to flatten the sample out with the back of a spoon so the light could get through and make it visible.
The sample was on a piece of clear plastic also (I have glass slides somewhere). I think you can get an idea of how fine the crystals are by looking
at it, but it would be better if a scale was there.
According to "Military Explosives", 87% TNT & 13% PETN form a eutectic with a melting point of 76.7C. So 50/50 pentolite when cast has about 42.5%
PETN and about 57.5% of the eutectic mixture. So in this case about 15% of the PETN dissolves.
[Edited on 5-12-2014 by Hennig Brand]Bert - 4-12-2014 at 10:05
I would be interested in seeing the "Entolite" further characterized-
Melt point?
Impact tests, even if so crude as hammering a few milligrams on a steel surface?
Friction test, ditto.
And as a quick & dirty test- wrap perhaps 100mg of "entolite" tightly in several layers of Aluminum foil, place on a thin sheet metal witness
plate and place a disposable alcohol burner or small torch head below the plate in a fashion that will cause the sample to be slowly heated to
deflagration temperature. ETN reliably undergoes transition to detonation under these conditions, what would the co precipitated or melt cast mixture
do?Hennig Brand - 4-12-2014 at 11:09
Good idea Bert, I will see about doing a few tests in the next little while. Anyone else is welcome to test some as well of course.Bert - 4-12-2014 at 11:22
Mainly curious about safety, one had best assume it to be at least as touchy as straight ETN until data is collected-
Also: If people were going to consider this as a melt cast filler, it would be well to check how shock & friction sensitive the liquid mixture is
BEFORE choosing to expose yourself to risk of an accident... Can anyone propose a method to determine that. Impact testing of a melted sample- How
best to conduct such a test???Hennig Brand - 4-12-2014 at 11:38
That was the main reason I chose the co-precipitation method of forming the explosive. I am sure ETN can be melted safely, but I have heard or read a
lot of scary stories and wanted to avoid melting it if I could.
Ok, I just did the first crude test. A bit of the loose powder, in amount less than the size of a paper match head, was put in one fold of aluminum
foil, put on an anvil and struck hard with a ball peen hammer. The sample was hit several times, with fairly solid shots, which did not result in
explosion. To put it subjectively, the blows were maybe not what would be needed to set off picric acid, but they were not too far below either. I
would need to get or build a precise apparatus to get any kind of accurate quantification of impact sensitivity, but the sample appears to be
significantly less sensitive than ETN to hammer blows which is no surprise.
[Edited on 5-12-2014 by Hennig Brand]Hennig Brand - 6-12-2014 at 12:05
According to "Military Explosives", 87% TNT & 13% PETN form a eutectic with a melting point of 76.7C. So 50/50 pentolite when cast has about 42.5%
PETN and about 57.5% of the eutectic mixture. So in this case about 15% of the PETN dissolves.
I did a little reading on eutectics. Hopefully this explanation is more or less correct. I should have said the composition of what solidifies last,
and at the eutectic temperature, from the melt contains about 15% of the PETN. More than 15% of the PETN may dissolve and be part of the melt above
the eutectic temperature, but any PETN dissolved above that amount crystallizes out before the temperature drops to the eutectic temperature. Once the
temperature has dropped to the eutectic temperature the temperature and composition of the melt, and consequently the composition of the solid being
formed, does not change as the melt solidifies. Once the eutectic mixture has completely solidified the temperature will begin to drop again as the
solid cools.
Also, the physical properties table posted several posts up had DSC heat release values displayed. The DSC kinetics values found in the study and
displayed in the table were there mostly to make stability comparisons. They found PETN to be more thermally stable; for details the study can be
easily downloaded from this forum or elsewhere online. Here is a table which contains more of the performance related information, from the same
article. The values were determined using a computer software called Cheetah.
[Edited on 7-12-2014 by Hennig Brand]
thickness
Laboratory of Liptakov - 7-12-2014 at 02:22
This is the hole from one gram tetrolyte? It is labeled correctly? What is the thickness of steel? I do not see written anywhere. 3 mm or 1/8 inch?
Thank you, LL .....
Tetrolite Melting Point
Hennig Brand - 7-12-2014 at 05:07
Melting point of the eutectic portion of the 50/50 tetrolite was found to be about 45-46C, which is far below the melting point of ETN (~60-61C) or
TNT (~80-81C). At that temperature there was still a small amount of un-dissolved material, but it appeared to be less than 10% of the total sample
under test which is just a crude estimation based on site. After running the test several times it looks as though all solid becomes part of the melt
at only a couple degrees above the first main melt temperature (eutectic temperature). The melting point is far too low for this explosive to be of
military use. More sensitivity testing will need to be done, but it would likely be perfectly safe to cast for amateur charges. The low melting point
would normally not be a problem, and possibly an asset, in an amateur application (I think).
LL,
Thickness of witness plate is only about 2.6mm; I have been using the same plate for so long that I didn't think to give specifics again. Yes, that is
the correct hole. It is the only one without a layer of rust covering the exposed steel surfaces so it is easy to tell. The exposed steel accumulates
rust very quickly. The loading pressure could have been much higher for the tetrolite base charge which likely would have significantly improved
performance. All the other holes were made with picric acid base charges, except one shot made with an improperly primed TNT base charge which did not
perforate the plate.
[Edited on 7-12-2014 by Hennig Brand]markx - 8-12-2014 at 03:24
That witness plate has really been subject to an extensive amount of sustainable exploitation
Bet you can squeeze in at least one more test with that perforated plate though
Hennig Brand - 8-12-2014 at 04:50
Oh at least one more; someone with a great deal of experience and skill in the art of frugality could likely squeeze in several more shots.
Tetrolite Friction Sensitivity Testing
Hennig Brand - 8-12-2014 at 07:09
A crude friction test was performed on ETN, melt/cast ETN, co-precipitated Tetrolite and melt/cast Tetrolite. A set of bathroom scales was used to
measure downward force applied. A marble pestle, from a pestle and mortar set was used. A piece of carbon steel with surface rust was used, which was
extremely abrasive. Downward force was kept between 40-45lbs as the pestle was drug over the sample (ca. <5mg sample weight). The pestle was rubbed
across each sample six times or until ignition. The only sample that was initiated by this treatment was the melt/cast ETN, which produced a loud
snap.
Note:
I suppose the rust could be seen as a contaminant and could have altered the sensitivity of the sample it mixed with. It was of course a crude test
and if anything the rust would have likely increased sensitivity not decreased it.
[Edited on 8-12-2014 by Hennig Brand]Laboratory of Liptakov - 8-12-2014 at 09:58
[Edited on 8-12-2014 by Laboratory of Liptakov]
Holes
Laboratory of Liptakov - 8-12-2014 at 10:12
This is a pretty good method. Test friction. And the results are good. Sensitivity is low.
I also have results ........ Also, saving material....LL
Hennig Brand - 8-12-2014 at 10:33
Nice collection! I would have quite a pile too, at this point, if I went around and gathered everything up.
I was thinking of performing an impact sensitivity test on molten Tetrolite. I could easily heat a small anvil up with a propane torch to above the
melting point of Tetrolite. I have a small 11lb anvil that would likely work well.
TNT Acidity
It was brought into question a while ago whether or not the acidity of TNT would be a stability problem for mixtures of it and ETN. I still don't have
a definitive answer, but I understand better now what I am dealing with. ETN is much less storage stable than PETN and this instability gets worse in
the presence of acidity. Gladly, it turns out that TNT has extremely low acidity. Also, TNT and ETN are non hygroscopic and have very low solubility
in water. The attached jpg image below was made from the first few paragraphs of page 300 from Urbanski Volume 1.
[Edited on 8-12-2014 by Hennig Brand]PHILOU Zrealone - 10-12-2014 at 05:57
Acidity of TNT only express in strong alcaline media (NaOH for example)...the resulting compound is coloured red and this is a proof of an
aci-nitronic/nitronate form. The resulting form is also more sensitive to shock (impact sensitivity).
The rest of the aromatic ring has been left aside because it doesn't enter the reaction
CH3-C=C-NO2 <==--> CH2=C-C=N(O)-OH
CH2=C-C=N(O)-OH =NaOH=> CH2=C-C=N(O)-ONa + H2O
So there is no acidity concern to fear about TNT in admixture with ETN...as long as both ingredients are wel acid-free washed
and recristallized.
[Edited on 10-12-2014 by PHILOU Zrealone]Hennig Brand - 10-12-2014 at 13:25
Thanks for the great description.
There really are a lot of things that can be done with TNT that can't be done with picric acid. For instance, because it has virtually no acidic
properties, a relatively low melting point and great compatibility with most other explosives, among other desirable qualities, TNT can form many
useful mixtures with other explosives. Picric acid has its place too though; it is much easier to make and many other useful explosives can be made
from it. Picric acid seems a bit easier to use as a base charge as well. Both of these cousins have a lot going for them.
[Edited on 11-12-2014 by Hennig Brand]
Cast 50/50 Tetrolite Base Charge Explosive Testing in 7.6mm id Aluminum Casing
Hennig Brand - 19-12-2014 at 12:47
I found some more witness plates, so this is the last time I will show this over exploited old one.
A while ago now I tested some cast 50/50 Tetrolite. A stainless steel pot with ca. 60-70C water was used to melt the 50/50 tetrolite. The aluminum cap
casing was taped to the side of the pot so that it would also be above the melt point, which prevented premature solidification and also provided a
larger thermal mass allowing for slower cooling of the casting. The tetrolite was melted in a small polypropylene plastic container partially
submerged in the hot water.
Three cast 50/50 tetrolite explosive tests have been performed all with similar results. The first test involved 1g cast tetrolite with 0.2g of lead
azide pressed on top. The second test involved 1g of cast tetrolite and 0.3g of LA pressed on top. The third test involved 0.75g of cast tetrolite,
0.25g of granular tetrolite pressed on top and 0.3g of LA pressed on top of that. A little basic lead picric was used as flash igniter in all tests.
None of the tests showed the plate penetration that the pressed granular material displayed. The cast material did however make by far the biggest
dents in the witness plate that I have seen so far. I assume at this point that cast 50/50 tetrolite has a lower detonation velocity at the 7.6mm
charge diameter than does pressed tetrolite. I will need to test the cast tetrolite at a larger diameter to see if that shows an improvement (I
suspect it will).
Attached are a few pictures from one of the tests. The hole/dent and scab on the right, in the witness plate top and bottom views, are from this test.
Last time using this witness plate I promise.
[Edited on 20-12-2014 by Hennig Brand]
Tetrolite Impact Testing
Hennig Brand - 20-12-2014 at 07:00
I built an impact testing machine in the last few days. I spent a bit of time in the past watching a large electromagnet being used to move scrap
metal around at a scrap yard and noticed that when the electromagnet was de-energized the steel fell basically instantaneously and straight down. I
though it would make a great quick release mechanism for a fall hammer. The fall hammer quick release could be controlled from as far away as desired
by running a thin copper pair with a switch at the end. An electromagnet was made from an old 16V, 1A, "wall wart" type DC power supply transformer.
The core was cut off at one end with a hack saw and the 16V secondary winding was removed. The top of the hammer head was too small and rounded so a
steel plate was welded onto one end for the magnet to attached to. It was found that 5V DC, across the 120V primary winding, was more than enough to
hold up the 2.85kg hammer, but 9V DC was used instead which could hold the weight of at least several times the weight of the hammer. A wooden slide
was made, for height adjustment, which could be fixed in place by tightening a wing nut. A plumb line was made from a bit of nylon cord and a steel
nut was used as the plumb bob which allowed me to determine exactly where the fall hammer would land and position the anvil and punch assembly
accordingly. Simply because of availability, 13/16 inch soft steel round stock was used to make the anvil and punch (roller bearing would have been
preferable and possibly in smaller diameter). A wooden holder was made for the anvil and punch with two large vent holes for explosive gases and flash
to escape from. The bottom end of the 13/16 inch anvil sits on the large blacksmith's anvil below.
This test was a quick and dirty test in a number of ways. It was in large part an excuse to test the apparatus. The ETN used for the ETN test was of
unknown purity and not freshly made; it was removed from a section of detcord which was made over 3 years ago and was a very fine powder. From earlier
testing of the machine, I knew about were the starting height should be for this sample of ETN. The sensitivity of the ETN tested seemed
uncharacteristically low. The test will be repeated when a freshly made, recrystallized, sample of ETN is available. Also, as has been discussed
before, wrapping the sample in aluminum foil does effect the results, at least to a small extent, as it is soft and will absorb some of the force of
the blow. The height was increased by 2 inches after each no go test.
Results (2.85kg Fall Hammer and 13/16 Inch Punch and Anvil):
ETN Powder
22 inches - no go
24 inches - loud bang
Tetrolite 50/50 Co-precipitated/Granular
24 inches - no go
26 inches - loud bang
Tetrolite 50/50 Cast
26 inches - no bang but smell
28 inches - no bang but smell
30 inches - small snap, a lot of smoke and smell
Here are a few pictures of the apparatus:
[Edited on 20-12-2014 by Hennig Brand]Bert - 20-12-2014 at 07:46
I continue to be impressed with your testing program.
I spoke about drop tests some time back with a manufacturer of industrial testing & quality control equipment. They did indeed use an
electromagnetic drop mechanism. The rig also automatically reset, logged heights of tests, all the tech did was set a new anvil plate & sample in
place-
It was HIDEOUSLY expensive, came with a nice software suite though.Hennig Brand - 20-12-2014 at 08:53
Thanks, good to know I was on the right track with the electromagnet as well. Much better electromagnets can be made or bought. I watched a professor
pick up a ca. 120lb girl off the floor, who was holding a handle or sitting in a harness attached to a steel plate, using a small round electromagnet
(ca. 2-3 inches in diameter) powered by one, 1.5V, D sized battery in a first year electrical engineering class. The magnet he used was rated for up
to 500lbs, IIRC, and was obtained mail order from a scientific supply company. I think they went for about $100 the last time I checked. The professor
told me the same D battery had been used for about 5 years to do the class demonstrations. Those designs are much more highly optimized than the one I
made from an old transformer, but the one I made does the trick (at least for this application). Making a highly optimized and powerful electromagnet
has been on my to do list for a while.
[Edited on 20-12-2014 by Hennig Brand]
hammer
Laboratory of Liptakov - 20-12-2014 at 14:33
I have this idea. Why use a plumb line? Motion in the picture. Replaceable paper tube. Small window for precise adjustment and control before the
test. The paper tube is a plug-in. Not too much force. Not too freely. In short, just right. I suggest pipe inner diameter of about 15 mm. If it
blows, the paper will be destroyed. But if not, it can be used again. On the right in the picture is a simple version without solenoid. Plastic pipe
with a diameter of about 50 mm or 2 inches........LL
Hennig Brand - 20-12-2014 at 15:24
The plumb line is only used to position the anvil under the hammer then it is put up out of the way during the test. So in your design the anvil,
punch and hammer all fall onto the main anvil below? All of the commercial designs that I have seen have a track or guide of some sort on either side
of the hammer, which has advantages. For starters, it guides the hammer to the target and the hammer doesn't need to be picked up off the ground
either. The free fall design has some advantages too, however, it is simpler and cheaper to build, one can be sure that there is no resistance to
motion other than wind resistance during the fall as well. I think your plastic tube idea could probably work, not sure about the release mechanism
though. I wanted a true falling hammer and I wanted it simple and I suspected that if I got into shoots and tracks and things that I could easily get
into problems with friction unless I went complicated or expensive (tracks). The solution to not having to aim the hammer every time is to build a
better stand for the apparatus. The stand could have been made with two vertical members, like in Markx's design and most commercial models, which
were carefully made as close to perfectly vertical as possible and well fixed in that position. With this setup, no matter what height the hammer was
put at it would always hit more or less the same place every time (gravity is a wonderful thing; very reliable). Even one vertical member could be
used but it would need to be made to more exacting standards than I made mine. This is only a prototype model.
Laser Plumb Line
Ok, I just thought of a nice solution to the hassle of the plumb line. The plumb line I am using now must have its length adjusted nearly every time
the hammer height is adjusted and being so long it can be a bit unwieldy to work with and a bit of a bother to make steady. I have been thinking of
how to use a laser level or laser pointer in some way that would be more convenient but still be as reliable. I kept discarding ideas because most of
them seemed less reliable and less accurate compared to a plumb line. A laser plumb line though incorporates the good points of both the laser and the
plumb line and loses most of the negative attributes of the regular plumb line. It can be made much shorter and never needs to be adjusted for height,
since the laser beam can travel the distance and mark the landing spot. Since the plumb line is shorter, it is easier to steady and also easier to put
up out of the way during tests. I found the attached picture of one online.
[Edited on 21-12-2014 by Hennig Brand]
nice work
Laboratory of Liptakov - 21-12-2014 at 15:34
OK results are important and these are at the top. Tetrolite granules cast and are less sensitive than ETN. That's the main thing. All three samples
have low sensitivity. That's good, nice work .......LLHennig Brand - 21-12-2014 at 18:33
Thanks, I expect that the sample of ETN powder I tested was less pure and more insensitive than it should be however. You are right though, tetrolite
both granular co-precipitated and cast is definitely at least a little less sensitive to impact than ETN which is an important thing to know.markx - 21-12-2014 at 23:33
Excellent work, Hennig!
The ETN sensitivity really seems very low, a characteristic result for a fresh recristallised and purified sample would lie on the order of 30-40cm
drop height which translates into about 10-15 inch. At least it does so on my particular drop test machine. Then again the results of drop test may
vary quite significantly between different machines depending on construction, materials, placement and substrates. Hence it is hard to compare the
values from different testers, but comparing the relative differences of samples tested on one and the same apparatus should give a better
perspective.
Perhaps you could also incorporate a mechanical failsafe for the electromagnet in case the power circuit should fail or become damaged for some
reason. Electromagnets are strong, but the only thing keeping the hammer from falling is the electrical current...one bad solder joint or damaged
switch and a premature drop is the result. There is no real danger of a serious injury if the sample weigths are kept normal, but the effect of
thescare that the noise from a 3kg hammer hitting an anvil accompanied by the possible detonation of the sample can give you is quite enough for me to
incorporate some preemptive measures into the system.
Also building a basket around the anvil to catch the falling hammer after if has hit the target is really convenient....and prevents the thing from
landing on your toes after every test
Thank you. Yeah, that ETN is very likely much too insensitive. The ETN used to make the tetrolite was from a much more recently made batch. I built
the apparatus in a bit of a hurry as well, so I should go back and carefully check that the anvil and punch surfaces are really flat and smooth and
actually flush with each other. The aluminum foil probably shouldn't be used either, but I would need to test to see how much of a difference going
without it would make. A basket to catch the fall hammer would be convenient for sure. I have a procedure which I think is fairly safe though. The
sample is placed on the anvil and lined up under the hammer release. The hammer is put in place last and then a bit of downward force is placed on the
hammer by hand to be sure that it is really secure. The position of the anvil is verified with the plumb line before the line is moved out of the way
for the test. Currently about 15 feet of speaker wire (copper pair) is used which allows me to be well away from the apparatus, and behind cover if
desired, when the current flow is removed from the magnet.
Battery Backup Failsafe
Some of the old backup lighting systems, security system and things had a very simple battery backup system, so I was told by a technician years ago,
that used a single diode. I have used the following concept several times in the past. If the AC power, or power supply, fails for whatever reason
current will immediately start flowing through the diode from the battery when the voltage on the cathode side of the diode drops below that of the
battery by about 0.6V (for a silicon diode). This is a very simple circuit compared to many modern battery backup systems, without some of the
advantages, but it is very reliable, simple and cheap. I made a little sketch with paint to illustrate the concept. Of course a mechanical failsafe
could also be used, with or without the battery backup.
[Edited on 22-12-2014 by Hennig Brand]Hennig Brand - 23-12-2014 at 15:50
It just occurred to me that what I need are adjustable feet for the fall hammer apparatus. The vertical member could maybe have been positioned closer
to perpendicular the base, during assembly, but the truth is almost no floor or ground is perfectly level anyway. A way to quickly make adjustments to
make the apparatus level would be a good addition. This would reduce the need to make adjustments of anvil position below the fall hammer whenever the
height was adjusted.
[Edited on 24-12-2014 by Hennig Brand]Hennig Brand - 30-12-2014 at 19:22
Here is an alternative to an electromagnet for the drop hammer device. It is a permanent magnet inside a light casing for picking up iron, steel and
other magnetic objects. A spring is inside which holds the magnet against the thin non-magnetic bottom plate. When the handle, which is attached to
the magnet by a rod, is pulled the magnet comes away from the plate which releases any objects magnetically coupled. If a suitable commercial model
could not be found, to hold up the fall hammer used, one of these could be built or the magnet in a commercial model could be replaced with a more
power magnet. Before I built the electromagnet I was playing around with a car speaker magnet. These speaker magnets are often extremely strong and
have no problem holding up a hammer head of several kilograms. Some sort of lever or pulley arangment, above the permanent magnet assembly, could be
used to change the direction of force and possibly provide mechanical advantage allowing the hammer to be released from a safe distance by pulling a
thin cord.
[Edited on 31-12-2014 by Hennig Brand]Hennig Brand - 2-1-2015 at 12:37
Results (2.85kg Fall Hammer and 13/16 Inch Punch and Anvil):
ETN Powder
22 inches - no go
24 inches - loud bang
Tetrolite 50/50 Co-precipitated/Granular
24 inches - no go
26 inches - loud bang
Tetrolite 50/50 Cast
26 inches - no bang but smell
28 inches - no bang but smell
30 inches - small snap, a lot of smoke and smell
A freshly made and recrystallized from methanol sample of ETN was just tested three times and the average fall height which resulted in initiation was
15 inches using exactly the same testing method and apparatus as was used for the earlier testing. The temperature in the building where the testing
was done, this time and last, was below zero Celsius which could have at least partially resulted in lower values for sensitivity. Since the tetrolite
was made with ETN that was only a month or two old and was recrystallized and well stored, it is safe to say with a high degree of certainty that
tetrolite, either co-precipitated or cast, is significantly less sensitive to impact than straight crystalline ETN.
etn
Laboratory of Liptakov - 2-1-2015 at 14:07
This is an interesting change, but it's still pretty good sensitivity. Clean fresh ETN, hammer almost 3 kg, height 38 cm, it is still good ......LLDornier 335A - 7-1-2015 at 13:12
I got an idea about another melt-castable based on TNT. It could maybe be called "hexolite", but not from mannitol hexanitrate. The much more potent
and denser oxidizer hexanitroethane should give a slightly better bang. 63.4% HNE and 36.6% TNT is oxygen balanced and should be possible to cast
safely, at least with some care. A similar but non-cast mixture with HNE and tetryl was tested in an old thread found here
The downside would be that the mixture can prove to be quite sensitive. Pure HNE is like PETN, but a mixture with a fuel will likely be more
sensitive; that's at least the case with TNM-based mixtures.
Calculated performance at 1.77 g/cc:
DCJ: 9000 m/s
PCJ: 363 kbar
Energy content: 7.21 MJ/kg (about 30% higher than HMX)markx - 8-1-2015 at 02:42
Perhaps coprecipitation from a common solvent or solvent system could also yield interesting results with some combination of energetics....and likely
be a safer practice compared to melt casting. I do not particularily like the idea of melting together highly potent substances...Hennig Brand - 8-1-2015 at 10:23
Hard to ignore the great ease with which very well incorporated mixtures can be cast at high density and with great uniformity however. The advantages
for shaped charge applications, for instance, are tremendous. Pentolite is a very common melt/cast mixture that is used both militarily and
commercially and all reports I have seen would indicate that it is fairly safe to work with. Tetrolite (ETN-TNT) can be melted below 50C using hot
water much below the boiling point. As long as open flames, or other intense localized heat sources, aren't used the melt/cast process should be
fairly safe in my opinion. I have several samples of tetrolite which have been sitting around for a month or so, both co-precipitated and melt/cast,
and so far there appears to be no signs of decomposition. The melt/cast samples have been re-melted and cast several times too. I do proceed with
caution though when working with such things.
