Sciencemadness Discussion Board - Simple shielded lever press

Simple shielded lever press

markx - 28-9-2014 at 14:31

Any attempts to in depth investigations in the field of energetics cry out for the help of an appropriate pressing device. I have seen and heard of some pretty horrendous practices being executed regarding this matter...starting from unshielded bench vise and ending with a charge being hammered into containment. So in hopes of setting a humble example in a more appropropriate direction (far from perfect though) I went forth and constructed a simple shielded lever press. Perhaps it can serve as an inspiration to fellow experimenters involved in the field:

As can be seen on the pictures, the whole pressing assembly is enclosed in a steel barricade that shields the user from the worst primary shrapnel effects and directs the energy out the front of the device in case of a mishap. Granted, one can still recieve an injury, but at least the energy can be partly dissipated and redirected by the simple shielding. Please feel free to share your ideas on how to improve the design...

APO - 28-9-2014 at 16:28

Very nice work markx.

Bert - 28-9-2014 at 17:25

Excellent. The BEST time to think about safty equipment is BEFORE the accident!

A load cell under the loading block assembly or other means to calibrate force applied would be a useful feature.

markx - 28-9-2014 at 23:46

Quote: Originally posted by Bert

Excellent. The BEST time to think about safty equipment is BEFORE the accident!

A load cell under the loading block assembly or other means to calibrate force applied would be a useful feature.

A load cell would be a very useful upgrade...I've been thinking about this option myself, but have not found a reasonably simple and affordable means to realise it so far. Instead I opted for a set of precalibrated loading pins to get desired compaction rates. The action of the press is limited by the shield touching the base and hence always stops at the same height from the base of the load compartment. Therefore the density can be regulated with either the lenght of the loading pin (if charge mass is kept constant) or the charge mass (if loading pin lenght is kept constant). I suspect the option where charge mass is kept constant is preferable for comparative reasons and a matching set of loading pins is an easy and dirt cheap option to realise. It just involves the ability to solve a simple equation system and a stock of round bar of choice (hardwood is preferable, I would avoid metal as far as possible):

V=3,14* r² *h
V=m/density
L=H-h

Where r is the radius of the load, V is the volume of the load after pressing, h is the height of the load after pressing, m is the mass of the load, density being the desired compaction after pressing, H being the height of the loading compartment in fully closed position of the press and hence L being the required load pin lenght.
By choosing the desired mass and density of the charge, one can simply calculate the loading pin lenght. For a particular mass/density combination the pin is universal and can be used for different substances. That is if the applied force is strong enough to drive the press to a fully closed position....common sense and selfpresevation instinct should be the user's best allies at that point

P.S. I strongly advise against the pressing of primaries on top or the secondary to create a joint compound device. Apart from suicidal danger levels this practice seems to give surprisingly bad results as far as primary material economy goes with SADS. I have not tested on other primaries, but small scale tinkering with PETN SADS combo gave frustrating failures at even the ratio of 0,8/1 of sads/petn by mass with PETN density of 1,2g/cm3. Simply put, 80mg of best quality double salt was unable to initiate 100mg base charge and kept persistantly pulverising it. For comparison, 40mg of the same primary on separate carrier with some loose base inbetween the secondary and primary carriers gave confident initiation every time....makes one wonder.

[Edited on 29-9-2014 by markx]

markx - 29-9-2014 at 14:04

A small additional feature to go with the press for constructing separate primary carriers...again, perhaps for inspirational purposes:

The snapshots portray 75mg SADS units to go with secondary carriers of choice. I could actually use less primary material per unit, but for the sake of structural integrity with that particular diameter (4,5mm) the 75mg was about the minimum that could be used without the disc becoming too thin and structurally unstable. Notice the wooden loading pin....I would strongly discourage the use of any metals pins in primary compacting practice.

[Edited on 29-9-2014 by markx]

roXefeller - 30-9-2014 at 02:40

Given your postscript in the earlier post regarding economy of SADS, what do your secondary carriers look like alone and assembled with the primary carriers?

markx - 30-9-2014 at 03:58

Quote: Originally posted by roXefeller

Given your postscript in the earlier post regarding economy of SADS, what do your secondary carriers look like alone and assembled with the primary carriers?

You can see one assembled unit on first picture on top of the press base (it is acutally a dummy unit with no charge in it). I constructed it with inert materials to check the functionality of assembly procedure. The fuse is inserted into the primary carrier and fixed with pvc tape. I usually add a plastic straw that the fuse extends through....for convenience of handling. The secondary carrier is the foil tube with the main charge pressed into it. One can also be seen on the press pictures beside the loading pin.

In earlier design I had the primary carrier filled with a pyrotechnic delay mixture for added structural integrity. Then a part of the delay was removed from the end of the tube and replaced by a quantity of primary. It allowed to vary the primary charge mass with no limitations. The downside was complicated and time consuming assembly...just way too much tinkering around with small things. To be honest, the hollow design is not very sustainable against mechanical influence and it does not allow the charge mass to be much below 75mg without falling apart. So I guess I will have to find a suitable delay mixture that I can press into the primary carriers hollow part after the energetic...this would add structural integrity and again allow for smaller amounts of primary to be applied with basically no limitations and still be quicker to assemble. Any ideas on what kind of delay mixture would be the best for this application? I have used the rocket candy type of mix with iron oxide as catalyst before, it performed pretty good, but perhaps someone has a better proposition...

[Edited on 30-9-2014 by markx]

Praxichys - 30-9-2014 at 04:27

Excellent work! How did you make the foil tube? They look very uniform. I had assumed up until I read your last post that you had found some sort of casing that is perfectly suited for the job. I have been looking for deep-drawn brass or aluminum casings for a long time.

markx - 30-9-2014 at 04:52

Quote: Originally posted by Praxichys

Excellent work! How did you make the foil tube? They look very uniform. I had assumed up until I read your last post that you had found some sort of casing that is perfectly suited for the job. I have been looking for deep-drawn brass or aluminum casings for a long time.

Yeah....no luck with finding suitable prefabricated casings. I have seen some deep drawn sample holder cases for chemical analysis apparatus, but these cost an arm and a leg and are not of suitable dimensions. Best bet is to roll your own and it is really simple. Just cut strips of heavy foil, roll around a loading pin of suitable dimensions, crimp the end and place into end forming cavity, tap with a hammer and slide the case off the pin. Sure it takes some time to tinker with this, but I find that it is the simplest and easiest way to do it. Best part is that you have the possibility to choose any dimesions needed and can design all parts to fit together properly from the beginning on.

Bert - 30-9-2014 at 09:11

If chemical compatibility with Copper is not an issue-

Many sizes of ready made swaged Copper cups

Praxichys - 30-9-2014 at 12:21

Wow Bert, that is an excellent find... but you took me on an awesome online shopping journey ending in these wonderful things:

http://www.aliexpress.com/item/50pcs-lot-Thermocouple-RTD-6-...

http://www.aliexpress.com/item/20pcs-lot-Thermocouple-RTD-DS...

http://www.aliexpress.com/item/Free-shipping-Thermocouple-RT...

Perfect stainless steel initiator casings! Cheap and just the right size. They come in all shapes and sizes but I have yet to find a US supplier. Free shipping from China at the ~$0.60/pc level.

markx - 30-9-2014 at 23:02

Them stainless tubes look really excellent! But seem quite thick walled...accidental shrapnel from something like that can be very hard to contain. Even with a metal shield.

Bert - 1-10-2014 at 06:44

The stainless steel capsules are pretty- Maybe a little short and narrow, but look nice. I might order some for use in fabricating movie props! But not for actual use, I see a couple of problems there.

Stainless steel is a hard, tough material. Fuses or electric match head installation requires crimping the mouth of the capsule- This material might well be harder than a standard non sparking fuse cutter/cap crimper.

The thermocouple capsules are 6mm OD and unspecified ID, in my experience 6mm OD capsules will not be sufficient ID for crimped in standard 1/4" fuse, and is marginal for the "shroud" of commercial electric matches-

It is usual for capsules to be formed with a concave profile at the base charge end. With Copper or Aluminum, this contour may easily be pressed in. Stainless steel, probably not so easy!

When using markx's device, it might be sufficient to place an appropriately sized ball bearing in the bottom of the capsule holder before pressing the base charge into the capsule. Sufficient pressure to consolidate such base charges as PETN/RDX/MHN to maximum practical density could result in a nice hemispherical concavity at the output end of a soft copper capsule, and most probably in Aluminum- Thus producing Munroe effect at final output... Don't leave anything on the table, get every bit of performance you can out of your initiator!

markx - 1-10-2014 at 07:08

I was just thinking about the possibility of inducing Munroe effect in the primary carrier stage....perhaps changing the contour of the straw holder base to a hemisphere or conical geometry would allow for a shaped charge like effect in the primary stage, thus giving better initatiation ability and perhaps even material economy. So much testing to do....so little time!

load

Laboratory of Liptakov - 1-10-2014 at 11:57

Do you think something like that? Also, think about it. In research detonators type NPED.
LL

markx - 1-10-2014 at 13:44

Quote:

Do you think something like that? Also, think about it. In research detonators type NPED.
LL

Well, yes, something along these lines....
I guess with initiation systems the goal is to make it simple, reliable and safe. The cruel reality of the "Great Architect" seemingly lets us choose only any two options out of the three.
Simple and reliable: with primaries....not safe
Simple and safe: NPED designs...not reliable
Safe and reliable: Bridgewire systems...not quite so simple

But I always try to find joy in attempting

NPED

Laboratory of Liptakov - 2-10-2014 at 10:25

Safe and Reliable and simple detonator: This is the Holy Grail of fireworks. Way to the Holy Grail is a big challenge. Secondary and tertiary explosives have long been a safe, reliable and simple. (some) Detonator not. Detonator is key. I'm working on it for 2 years. I am at the stage: Very simple and safe.
LL

Energetic Einstein - 2-10-2014 at 15:18

Quote: Originally posted by Laboratory of Liptakov

Safe and Reliable and simple detonator: This is the Holy Grail of fireworks. Way to the Holy Grail is a big challenge. Secondary and tertiary explosives have long been a safe, reliable and simple. (some) Detonator not. Detonator is key. I'm working on it for 2 years. I am at the stage: Very simple and safe.
LL

Maybe you should create or post on a NPED thread on your findings. That way it doesn't clutter this thread. Also a design can sound good in your head. Its when you put it on paper, and present the paper to those who have a greater knowledge on that topic; Is when you find the positive and negatives about your design.

roXefeller - 2-10-2014 at 15:39

He did post about it, at least enough to tease without disclosing enough to criticize. He seems to assert that he's found the holy grail without showing it. Maybe we can goad him into talking.

Do we want to start an NPED/blasting cap design thread?

Bert - 2-10-2014 at 17:52

If someone wants to organize their information, document references and kick off a new thread, I would be happy to edit the appropriate posts of this thread into it- Or merge them with one of the existing NPED threads.

Both topics (safety in pressing, NPED cap design) are EXCELLENT places for members to put in some research. They are related... But should have their own threads, for the sake of simplicity in accessing their information. Too many long, tangled threads here already!

[Edited on 3-10-2014 by Bert]

markx - 16-3-2015 at 09:39

I was bored to go out and perform the pointless spring chase after girls this past weekend and decided to relax and tinker about in my workshop a little instead of throwing time and money into the wind and across the bar in the night clubs. Conceived a fuse/cord/tube cutter for the purpose of making primary carrier cases and other energetics related contraptions:

LOL...this has to be the most "dildoesque" piece of equipment that I have ever come up with

But it rather appeals to my distorted sense of humor and performs damn clean and repeatable cuts....

aga - 16-3-2015 at 12:58

A Load Cell would work best for compression force measurement, although there are mechanical means, such as using a simple see-saw under the bottom block with a vertical scale on the other side of the see-saw.

Rig up some super heavy duty 'spring' (e.g. a block of PVC or very dense rubber) under the block-end of the see-saw and the scale will move up/down as you apply/remove compression force.

The length of the see-saw arm on the scale side will alter the sensitivity.

Obviously add a pointer somewhere, and best of luck calibrating it !

Fulmen - 16-3-2015 at 13:30

When it comes to measuring force: Have you thought about what happens if a charge goes off? A well designed tool should not only protect the user form damage but also itself.
My suggestion would be a torque-wrench as a handle since they work as a "safety release".

aga - 16-3-2015 at 14:42

Quote: Originally posted by Fulmen

a torque-wrench as a handle since they work as a "safety release".

How would that work ?

You're right though, if the charge goes off, then the handle will seriously wish to go Up at high speed. Perhaps a Ratchet system would help prevent this ?

Reminds me of the Correct method for crank-starting an old car : never put the thumb around the handle.

markx - 16-3-2015 at 15:41

A torque wrench would only work as a safety release as long as the detonation has not happenened yet by alerting the user from applying too much force yet not really preventing one to do so on will, but not really at all in the case of one happening despite it. I would like to point out that there already is a physical pressure limiter built into the press by the shield touching the base and limiting the travel and force applied by the loading pin. If one does not deliberately choose to apply axcessive force by selecting the loading pin of wrong lenght, then it is not possible to do so. And I never press primaries on top of the secondary as is usually practiced with the design of the compound cap, nor do I encourage anyone else to do so, but instead use a separate primary carrier for that purpose. I've always felt a strong discomfort towards this practice in amateur setting. Nevertheless there are still countless ways for things to go wrong and I have to admit my inability to prevent this from totally happening. The only choice for that would be to abandon any practical experimentation in the field of energetics, I guess...

Hennig Brand - 16-3-2015 at 15:49

Combination metal phallus and precision tubing cutter, of course it is painted green though which disguises its true form a bit.

In all seriousness you did do a nice neat job of building it and it looks like it works well. Good job!
I think I will stick with a utility knife and a wooden cutting board, but you do have the capability of making a lot of precision cuts very quickly and easily which could be a real advantage to anyone making large numbers of cuts at a time.

markx - 16-3-2015 at 16:18

Quote: Originally posted by Hennig Brand

Combination metal phallus and precision tubing cutter, of course it is painted green though which disguises its true form a bit.

I tried the knife and brasilian pine board method, but achieving repeatablility and a staight cut drove me to drink....which, given my unrestricted access to unlimited amounts of highly purified palatable alcohol, seemed like a really bad set of circumstances...hence the camoflaged green metal dick with a precision blade

Fulmen - 16-3-2015 at 23:03

First off: Nice work. But think about what happens if something goes off. It will push the lever you're holding upwards with tremendous force, are you sure you'd like to experience that? As a minimum I'd add a long wooden handle sized so it'll break, that must be better than trying to hold down the entire blast.
A proper torque wrench "releases" once the proper torque has been reached. So not only would it limit the force applied but also "give" if a detonation occurs. It would also produce a repeatable force without staring at a gage, a great plus for repeated work.

markx - 17-3-2015 at 01:34

Quote: Originally posted by Fulmen

First off: Nice work. But think about what happens if something goes off. It will push the lever you're holding upwards with tremendous force, are you sure you'd like to experience that? As a minimum I'd add a long wooden handle sized so it'll break, that must be better than trying to hold down the entire blast.
A proper torque wrench "releases" once the proper torque has been reached. So not only would it limit the force applied but also "give" if a detonation occurs. It would also produce a repeatable force without staring at a gage, a great plus for repeated work.

The wooden handle is a very good idea! I did see Hennig's press in one thread and it was entirely composed of wood if I remember correctly...a nice safety release if properly shielded against high velocity shrapnel.
I've been thinking about it a lot in terms of what happens if a charge does go off in the compartment and swings up the back of the handle. It can easily break ones hand or worse. An even scarier scenario would be if the back of the handle is is held down with enough force to cause the bolt in the front end to break instead and then the handle and the shield swing up from the front and towards the face of the user....
Another danger is the loading pin...if a metal one is used then this thing becomes a deadly high energy projectile that can penetrate the top of the shield and lever. A wooden pin is hence the preferred choice, it will shatter and dissipate the energy in case of a mishap.
Taking all of that into account I never stand directly behind the press while compacting a load, but rather on the side, nor lean over it while applying force.

[Edited on 17-3-2015 by markx]

aga - 17-3-2015 at 03:11

How about a 30 foot long wooden handle

Hennig Brand - 17-3-2015 at 11:02

A hole right through the lever could maybe be made which the loading rod could fit into. The pin (bolt?) holding the loading rod to the lever could allow the loading rod freedom to move (pivot point) as well as act as an effective shear pin if its size and strength were properly selected. The pin could be made to be the weak link. Just keep your body away from above the loading rod during pressing, since it could end up traveling at very high velocities in the upwards direction.

[Edited on 18-3-2015 by Hennig Brand]

markx - 19-3-2015 at 11:40

Yes, the pivot point under the lever for the loading pin is a very good suggestion...I've was thinking of implementing that part, but since this press was meant for sub gram quantities of secondary and the stroke of the pin is quite negligible, I opted for just a slot in the lever.
I guess common sense, a healthy selfpreservation instinct and no time pressure are the energetics experimeter's best allies. I find that sometimes overengineered safety features can to make the process very uncomfortable and provoke mistakes. But by far the rushing of things is a surefire way to a disaster. Hence always take ample time to prepare and think through all operations before commencing with an experiment.

aga - 19-3-2015 at 14:57

Wise words.

Perhaps a few unmanned experiments would be worthwhile to determine the safest design ?

Edit:

Rig up a press design with whatever, and stick a bucket on the end of the lever.

Use a Hosepipe to remotely add water to simulate the pressure.

If the bucket survives an explosion with it's water intact, a human operator should, as we're more-or-less the same thing.

[Edited on 19-3-2015 by aga]

Hennig Brand - 20-3-2015 at 18:32

The end of the lever could have a handle which pointed straight down and was round and relatively smooth. If detonation occurred during loading and the lever flew up quickly the handle would be pulled from the operators grip rather than seriously injuring him or her. Just don't hold your head or body over the lever when pressing.

markx - 21-3-2015 at 04:31

Quote: Originally posted by Hennig Brand

The end of the lever could have a handle which pointed straight down and was round and relatively smooth. If detonation occurred during loading and the lever flew up quickly the handle would be pulled from the operators grip rather than seriously injuring him or her. Just don't hold your head or body over the lever when pressing.

Ya...how long do you estimate would it take for me to stop jerking down on that handle end and start pushing on the lever instead

? I would also have to weld sharp spikes on and around the lever to prevent that from happening

Hennig Brand - 21-3-2015 at 10:38

Ok, I get the sense you think it would be very difficult to use.

Yeah, you could be right. However, with the right mechanical advantage (long enough lever) it wouldn't need to be that hard. Not as convenient you are right.