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Picture of Makeshift gram scale (balancita improvisada)
Hace tiempo tengo ganas de volver a incursionar aunque sea ligeramente en la pirotecnia. Hace unos días pude comprar 1 Kg de NO3K (nitrato de potasio), y me decidí a lanzarme a la tarea. Cuando llegó el momento de mezclar los componentes de la pólvora me encontré con la ligera dificultad de que todos los que han publicado fórmulas insisten en que las proporciones son por peso, no por volumen. De modo que busqué una balanza de cocina que tengo entre mis cosas, pero su rango es hasta 3 Kg, con una división mínima de 20 g, lo cual es demasiado grueso para mi necesidad de proceder a mezclar pequeñas cantidades.

O sea que tuve que interrumpir la tarea de moler y tamizar el NO3K para ponerme a improvisar una balanza con la sensibilidad que necesito.

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Long time I have wanted to return to venture even slightly in pyrotechnics. A few days ago I bought 1 kg of NO3K (potassium nitrate), and I decided to throw myself into the task. When it came time to mix the components of gunpowder I found the slight difficulty that all those who have published formulas insist that the proportions are by weight, not volume. So I looked for a kitchen scale I have in my stuff, but its range is up to 3 kg, with a minimum of 20 g division, which is too thick for my need for mixing small quantities.

So I had to interrupt the task of milling
and sieving NO3K to get to improvise a balance with the sensitivity I need.
 
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Step 1: Specs (especificaciones)

Picture of Specs (especificaciones)
Mi diseño debe cumplir algunos puntos básicos:

1 debe ser factible
2 debe ser fácil
3 debe ser rápido
4 debe ser barato
5 debe tener sensibilidad de alrededor de 2 gramos
6 debe tener poco o nulo rozamiento
7 debe ser fácil de usar

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My design must meet some basic points:

1 should be feasible
2 must be easy
3 must be fast
4 must be cheap
5 should be sensitive to about 2 grams
6 should have little or no friction
7 should be easy to use

Step 2: Decisions (decisiones)

Picture of Decisions (decisiones)
Los 4 primeros puntos determinaron que todos los materiales y herramientas necesarios tienen que estar YA entre mis cosas.

El punto 7 descartó la posibilidad de una balanza de dos platos con pesas, volcando la elección a una balanza a resorte o banda de goma. El resorte tiene sobre la gomita la enorme ventaja de la duración y la constancia de sus propiedades.

El punto 6 elimina la posibilidad de tener articulaciones, palancas, agujas giratorias, etc.

El punto 5 obliga a seleccionar un resorte pequeño, ya sea de compresión, de estiramiento o de flexión.

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The first 4 points determined that all necessary materials and tools have to be already in my stuffs.

Point 7 dismissed the possibility of a twin-pan balance with weights, tipping the choosing to a spring or rubber band
balance. The spring has the huge advantage over ruuber band of duration and constant properties.

Point 6 eliminates the possibility of having joints, levers, rotating stylus, etc.

Point 5 requires to
select a small spring, either compression, stretching or bending.

Step 3: Choosing materials (eligiendo materiales)

Picture of Choosing materials (eligiendo materiales)
Busqué entre los resortes pequeños que guardo en un recipiente transparente con tapa, y encontré algunos candidatos. Pero finalmente me decidí por un alambre de acero plano, debido a que usarlo representa cumplir con el punto 6 de las especificaciones. Podría haber sido un alambre redondo, pero al ser plano presenta algunas ventajas.

Para hacer el cuerpo principal elegí algunos restos de terciado fenólico de 10 mm que me quedaron del carrito plegable para bicicleta.

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I went through the small springs that I keep in a clear container with lid, and found some candidates. But I finally settled on a steel plane wire, because using it is meet point 6 of the specifications. It could have been a round wire, but being flat has some advantages.

To make the main body chose some leftover 10mm phenolic plywood I had left the foldable bicycle cart.

Step 4: Cutting, bending, screwing (cortando, doblando, atornillando)

Picture of Cutting, bending, screwing (cortando, doblando, atornillando)
Al alambre plano de acero le doblé en ángulo casi recto un extremo, a efectos de tener un punto de referencia al atornillarlo. Lo calenté en la hornalla antes de doblarlo, luego lo volví a calentar y lo enfrié con agua

Hice un agujero con el taladro al extremo de un pequeño trozo de terciado fenólico, y atornillé el alambre de acero al mismo mediante una arandela curva, de manera que lo mantenga firmemente en su lugar.

Luego hice un agujero de 5 mm en el centro del pequeño soporte, y lo atornillé al trozo grande de terciado fenólico. Ese tornillo permite girar ligeramente el soporte del alambre para ajustar a cero la balanza.

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Bent in right angle one end of the flat steel wire , in order to have a reference point to fix it. I heated it up on the burner before bending, then turned to heat and cool it with water

Drilled a hole in the end of a small piece of phenolic plywood, and screw the steel wire with a curved washer at the same, so to keep it firmly in place.

Then I made a hole of 5 mm in the center of the small stand, and screwed it to the large piece of plywood phenolic. That screw allows rotate
slightly the wire support to adjust to zero the scale.

Step 5: Adding a base (agregando una base)

Picture of Adding a base (agregando una base)
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Con otro trozo de terciado fenólico hice una base al conjunto, dejando un agujero cuadrado al medio para permitir asegurar el todo a la mesa de trabajo con una prensa manual. Reforcé la unión de la base con dos tacos de madera de sección rectangular, cola vinílica, clavos y tornillos.

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With another piece of phenolic plywood did the base of the set, leaving a square hole in the middle to allow to ensure it to the work table with a hand press. I reinforced the union of the base with two rectangular wooden blocks, white glue, nails and screws.

Step 6: Adding support points (agregando los puntos de soporte)

Picture of Adding support points (agregando los puntos de soporte)
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Decidí que, ya que estaba, me convendría hacer por lo menos dos escalas, una con toda la sensibilidad posible y otra con menos sensibilidad y más capacidad. Arbitrariamente elegí los puntos de fijación de los sostenes: uno en el extremo del alambre y el otro aproximadamente a la mitad.

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I decided that as I was, I should make at least two scales, one with all the possible sensitivity and one with less sensitivity and more capacity. Arbitrarily chose the attachment points of the supports, one at the end of the wire and the other approximately half.

Step 7: Making the calibrations (haciendo las graduaciones)

Picture of Making the calibrations (haciendo las graduaciones)
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Dado que el agua de la canilla no pesa lo mismo que el agua destilada, y teniendo en casa un bidón lleno del agua que destila el aparato de aire acondicionado, usé esta agua para graduar las escalas. Se supone que 1 ml pesa 1 g.

Encontré entre mis cosas dos jeringas usadas de inyecciones, una de 3 ml para la escala sensible y otra de 6 ml para la otra. Me asaltó la duda de que a mis errores de construcción y graduación se podría agregar uno mayor en caso de que las jeringas no estuvieran correctamente graduadas, pero luego me di cuenta de que, para el uso que yo le iba a dar a la balanza, ese error es irrelevante, dado que voy a pesar TODOS los componentes con la misma balanza, y lo que importa son los pesos relativos, no absolutos.

Colgué una bolsita de polietileno del gancho del extremo del alambre, puse en cero el alambre de acero girando ligeramente el soporte del mismo, apreté el tornillo y empecé la tarea de hacer las marcas.

Con cada carga de 2.5 ml el alambre se torcía unos 5 mm hacia abajo. Fui marcando la posición del mismo hasta llegar a los 50 g, o sea que cargué la bolsita de agua 20 veces con 2.5 ml de agua.

Finalizada la escala de mayor sensibilidad, repetí el procedimiento con la de mayor capacidad, llenando 40 veces la jeringa de 5 ml para llegar a 200 g. Con cada 10 ml el alambre bajaba unos 4 mm.

No me resultó nada cómodo ir haciendo las marcas al mismo tiempo que llenaba y vaciaba las jeringas, por eso me quedó todo muy desprolijo, y me vi obligado a pasarlo en limpio una vez terminado. No quedó bello, pero por lo menos se entiende qué es cada marca.

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Since the tap water does not weigh the same as distilled water, and taking at home a full container of distilled water from the air conditioner, used this water to grade scales. It is assumed that 1 ml weighs 1 g.

I found among my things two injection syringes, one of 3 ml for sensitive scale and another of 6 ml for the other. I doubt that to my construction errors could add one more in case the syringes were not properly graded, but then I realized that, to use that I was going to give the balance, that error is irrelevant, because I weight out all components with the same scale, and what matters are the relative
weights, not absolute.

I hung a polyethylene bag at the hook end of the wire, put in zero the steel wire slightly turning its bracket, tighten the screw and began the task of making marks.

With each load of 2.5 ml the wire
twisted about 5 mm down. I was checking the position of it to reach 50 g, it is to say  charging the water bag 20 times with 2.5 ml of water.

Once done the most sensitive scale, repeated the procedure with the other, filling 40 times the 5 ml syringe to reach 200 g. With
each 10 ml the wire down about 4 mm.

I was not comfortable doing the marks while filling and emptying the syringes, so it was all very messy, and I was forced to spend in clean upon completion. It was not pretty, but at least they understand what each brand.

Step 8: Uso (use)

Picture of Uso (use)
El uso de la balancita cumplió sobradamente mis expectativas. No podría asegurar que cuando dice 35 g sean exactamente 35 g, pero estoy seguro de que siempre dará la misma medida para el mismo peso. Aun cargando el alambre de acero con los 200 g de la capacidad máxima, este se mantiene dentro del margen de flexión elástica, es decir que no pierde la forma. Eso me asegura la precisión que yo necesito. Y la ausencia de rozamiento me hace trabajar más tranquilo, solo tengo que tener cuidado de que la bolsita de polietileno donde va el material a pesar no roce la tabla vertical.

Para usar el soporte del medio, o sea la escala de 200 g, tengo que agregar un hilo de coser de unos 20 cm, porque si no la bolsita roza con la prensa de mano que sostiene el conjunto sobre la mesa. ¡TODO DISEÑO TIENE QUE TENER UN ERROR!

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The use of the little scale amply fulfilled my expectations. I could not assert that when it says 35 g they are exactly 35 g, but I'm sure it will always give the same measure for the same weight. While loading the steel wire with the 200 g of maximum capacity, this is kept within its range of elastic bending, ie does not lose the shape. It assures me the accuracy I need. And the absence of friction makes me work more relaxed, I have only to take care that the polyethylene bag where goes the material is not touching the vertical board.

To use the middle support, ie 200 g scale, I have to add a thread of about 20 cm, otherwise the bag rubs the hand press holding the scale on the table.
ALL DESIGN MUST HAVE A MISTAKE!
Grinders for coffee grinder would be the case or better yet a device to grind spices
rimar2000 (author)  Lefrançois2 years ago
Pardon, surely your comment is for another instructable. Anyway, thanks.
Bill WW2 years ago
Excellent as usual, Osvaldo.
Ten cuidado con la pirotecnia
rimar2000 (author)  Bill WW2 years ago
Thanks, Bill. Pirotecnia is very laborious if you have not the components finely grinded, and this is my case. To grind 150 g of NO3K I took almost a day using a porcelain mortar. Sulfur is even worst.

I have only 4 almost finished rockets, I have thought to try them tonight, if it does not rain. The chances of failure are very high.
I purchased this scale for US$16.50, advertised as accurate to 0.1 gram. I used it in an experiment to calculate magnetic field strength versus distance. Hope to post the results of my experiment as an Instructable soon.
Buying a scale is not as much fun as making one as you did.
When I was ten years old we purchased sulfur at the local pharmacy to make gunpowder. We thought the other ingredient was from old electric batteries. Fortunately we were not successful.

Compre esta escala para EE.UU. 16,50 dolares, anunciado como una precisión de 0,1 gramo. Lo use en un experimento para calcular la intensidad de campo magnetico respecto a la distancia. Espero volver a publicar los resultados de mi experimento como un instructivo pronto.
La compra de una escala no es tan divertido como hacer uno como tú.
Cuando yo tenía diez años hemos comprado azufre en la farmacia local para hacer pólvora. Pensamos que el otro ingrediente fue antiguas baterías eléctricas. Afortunadamente, no tuvimos éxito.
scale.jpg
Dr Qui Bill WW2 years ago
I too bought a set of scales like these, i got mine on eBay directly from Hong Kong for about £4.99 postage inc. they are very useful indeed.
Bill WW Dr Qui2 years ago
Yes, but I feel a bit guilty admitting on this site that I did not make it myself!
Dr Qui Bill WW2 years ago
I know what you mean but you cant make everything,  those mass produced items are needed to make the bespoke stuff.

I have reached the age where I work out if the price of an item is to expensive based on how much hassle it would be to build my own version, how safe mine would be and how wrecked I would be from building it, or more importantly if i could even build the thing in the first place. if its under 10 pounds i don't even think i just buy it.

The other point is why waste the fuel money time and hassle of traipsing round stores only to have some disinterested teenager stare at you blankly and ask "whats that?" or "I'll have to go ask one of the older guys".

I think eBay is great, combined with my smart phone and tablet I can order stuff from anywhere.  I feel like Wylie Coyote ordering things from the ACME company,  only these days you click a button and then pace back and forward waiting for the post man.
Bill WW Dr Qui2 years ago
I get most of my "whats that?" questions from my wife

.Bill
rimar2000 (author)  Bill WW2 years ago
Me too, Bill. She ask, I answer, she forget. Tomorrow, same question again.
rimar2000 (author)  Dr Qui2 years ago
HAHAHA!!!

Like "...some disinterested teenager stare at you blankly and ask "whats that?" or "I'll have to go ask one of the older guys...". I get almost every day that response. Not only teenagers, old men/women say it, too.
Bill WW Dr Qui2 years ago
Yes, but I feel a bit guilty admitting on this site that I did not make it myself!
rimar2000 (author)  Bill WW2 years ago
That scale is beautiful and useful!

To get Carbon for gunpowder, the best option is to make a bonfire with pieces of pinewood, wait some minutes and take off the embers. Leave them aside to go out, or just soaking in a bucket of water. In the last case, you must wait 1 or 2 days to they dry. After, grind the pieces (as you can do it) to get a finely ground powder. All this work is easy but a bit boring. My first 4 rockets were fails, but I learned must do some changes.
Fortunate that I did not have all this information sixty years ago!
Suerte de que yo no tenía toda esta información hace sesenta años!

Abrazo y Feliz Navidad y Prospero Ano Nuevo para ti y tu familia.

Bill
rimar2000 (author)  Bill WW2 years ago
Gracias Bill, retribuyo tus buenos deseos para las fiestas y el 2013.
Some sore of motorized ball mill would help with this, i have played around with this using 12mm ball bearings in a sealed metal can, you can get some very fine powders from this, a small 6-12v motor should be enough to run something and i'm sure the rest could be obtained from scrap.

I dont know where i heard this but, I remember seeing something aout how the carbon and sulfur should be milled together to get the carbon to bond to as much sulfur as possible
rimar2000 (author)  Dr Qui2 years ago
I answered this comment above, Dr. Qui.
yoyology2 years ago
I grasped the concept from the first photo, but kept wondering what you were going to use for the reference weights. Water is the perfect answer.

This would also work for "English" non-metric weight systems, since 1 fluid ounce of distilled water weighs 1 ounce. Of course, grams are smaller and therefore more precise.

Excellent work!
rimar2000 (author)  yoyology2 years ago
Thanks for your kind comment, yoyology.
Dr Qui2 years ago
Clever idea for a reasonably accurate gram scale. I look forward to you fireworks Ibles. N03K is on the controlled list here in Northern Ireland even sulfur is quite hard to obtain now, we have to make the best of what can be made from match heads, paper caps and sparklers and that limits you to small bangers.
rimar2000 (author)  Dr Qui2 years ago
Thanks Dr.Qui for your comment and your concern.

My rockets are in "stand by" due to lack of a mill to process some grams of NO3K, sugar, Carbon and Sulfur. Mortar and pestle make the task too sluggish.

Since Saturday I am making a balls mill, but I am having troubles with the motor, it works well but heats after 3 or 4 minutes. Today I will replace it, at least that is my plan. The proximity of the holidays makes everything a bit more complicated. Here in Argentina the school/college courses finish in december, and consequently the parents and grandparents we are forced to attend many long, boring ceremonies related to our children and grandchildren.
Ah Christmas, keeping grumpy men from the sanctity of their sheds for over 2000 years! lol.  whats worse is that you are not allowed to comment on the fact that your related children are tone deaf and have no musical ability yet.


Hopefully the post Christmas left overs will yield some items you can use to build a ball mill.
Smart!
rimar2000 (author)  marcellahella2 years ago
Thanks for the praise, Marcella!
Me encanta lo que inventas.
Idea genial, simple....Enhorabuena!!!
Observo tus instrutables con curiosidad....

Un abrazo desde la Costa del Sol-Malaga
rimar2000 (author)  elgatoandaluz2 years ago
Gracias, elgatoandaluz! Esta noche, si no llueve, probaré los primeros 4 cohetes. Hay altas probabilidades de falla, Ojalá alguno de ellos suba bien.
rimar2000 (author)  rimar20002 years ago
Fracaso total, los 4 primeros cohetes fallaron. Pero eso me dio la pauta de algunos cambios que debo hacer a la construcción, o sea que bienvenidas sean las fallas.
jpalacios32 years ago
totalmente de acuerdo con tus especificaciones de diseno, trato de tenerls en cuenta cuando construyo algo, no es facil reunir todos esos requisitos pero como dice un refran gringo: KISS (keep it simple Sir)................ un abrazo Osvaldo
PD: cuidado con la pirotecnia por favor
rimar2000 (author)  jpalacios32 years ago
Gracias, jpalacios3. Yo a ese principio lo tenía como "Keep it Simple, Stupid". Pero lo cierto es que las cosas demasiado simples suelen no funcionar bien. Por suerte en este caso mis necesidades eran muy elementales, y no tuve problemas.
ChrysN2 years ago
Great design!
rimar2000 (author)  ChrysN2 years ago
Thanks, ChrysN. I am satisfied for the result: ugly but useful. Considering it was done in a hurry, is not so bad.
Phil B2 years ago
Very good and very clever.
rimar2000 (author)  Phil B2 years ago
Thanks, Phil. Your praise is the praise of a MASTER.
ToyMaker2 years ago
This is beautiful. Elegant simplicity.
I have some flat stainless steel from windshield wiper blades and will try to reproduce your design. I don't have ready access to a syringe but coins are very consistent in weight from one to the next. New ones should serve as calibration weights.
Thank you for a wonderful idea.
rimar2000 (author)  ToyMaker2 years ago
Thanks for your kind words, ToyMaker. These flat blades can work very well, I have some of them too. Warn don't exceed the max elastic bending limit, ie the wire don't deforms.

My design is a lot improvable, it raised in middle of a hurry to make some rockets for next Christmas and New Year celebrations.
rncbme2 years ago
I continue to be amazed at your creativeness!
rimar2000 (author)  rncbme2 years ago
"Necessity is the mother of invention", rncbme. The alternatives were "this or nothing". It is working pretty well.

Thanks for your comment.
tholopotami2 years ago
Once again accept my admiration! A physicist like me would be lost in a world of precision limits, elastic modules, non-linearity, mechanical tolerances, stiffness and staff like this before taking the pliers and do what you did!
rimar2000 (author)  tholopotami2 years ago
Well, one of my favorite sayings is "perfect is enemy of good". All my projects have flaws, bugs, and are mostly ugly, but almost all function almost well.

Thanks for your comment!