Ramming[]
From PyroGuide[]
Ramming
Ramming a rocketFor anyone wishing to progress beyond making items such as bangers or salutes, it is necessary to become familiar with the techniques of consolidating pyrotechnic compositions in a tube. Known as charging or ramming, the oldest and most common method is done by hand with a mallet and drift. This technique is easy to learn and can be used for making such items as rockets, fountains, gerbs, spolettes, saxons, and drivers. The process is still widely used in large scale manufacturing plants and in many instances is a faster and definitely cheaper method of loading composition than trying to use small hydraulic press. It is especially versatile when making up prototypes or small numbers of devices. A major drawback to hand ramming is that it is unsuitable for friction or shock sensitive compositions, such as those used for strobe or whistle rockets.
Mallet - Generally wood, rawhide or rubber "dead blow" mallets work best. A broad face is preferable and the mallet should be large enough that its weight does most of the work, rather than your arm. Avoid steel carpenter or machinist's hammers. Some people like a round mallet of the type woodworkers use for striking chisels.
Rammers or Drifts - These are simply rods or dowels made to fit the internal diameter (I.D.) of the tube being loaded. They should be an easy slide fit without binding on the walls of the tube. If too loose however, the surface of the powder will not be properly compacted near the tube walls. Suitable materials include wood, brass, stainless steel, aluminium, and some plastics. Each material has a different "feel" when ramming. Plastic, such as PVC rod, has limited use and has a very spongy feel when struck. However, it is cheap, easy to cut and holds up well. Wood is also cheap and easy to cut and shape. Hardwoods, like birch or maple, have a fine, even grain and have a more solid feel than plastic. Wood is simple to reduce in diameter without complicated machinery if a slightly looser fit is required. It is soft enough that if the face of the rammer accidentally strikes the spindle used to form a clay nozzle, there will be little or no damage done to the spindle (which is usually metal, and can be costly to replace). There is less chance too of accidentally causing any powder to ignite if pinched between spindle and rammer. Metal rammers made from brass, aluminium, or stainless steel have a very nice, heavy, solid feel, but may be expensive and hard to machine without a lathe. Brass is especially nice to use in small (3/8" or less) diameters, when wood is not rigid enough. Wood is fine for most other instances, and is an inexpensive way of building an inventory of rammers in different diameters and lengths. Steel should not be used because of spark hazards.
Ramming Post - In order to get even, solid consolidation of material, a suitable support surface is needed underneath the item being loaded. There is nothing worse than trying to ram on a weak or springy surface. Ideally, the ramming surface should be a post with a smooth level top held upright by being buried part way in the ground. The actual top does not need to be more than four to six inches square. It should be as heavy and solid as possible. Material can be wood or cast concrete. If a portable post is desired, it can be a section of railroad tie, a section of 6x6 beam, or a tall box made of plywood and filled with sand. A cap made from medium density fibreboard (MDF board), solidly attached to the top of the post makes a great smooth surface that is easy to brush clean. Avoid cracks or crevices in the post where loose powder can collect. Always separate the ramming surface from whatever table or surface is used to hold the powder being rammed. If this is not done, the vibrations from the ramming process will tend to separate the components of the unused composition. The arrangement of post and table should be of a convenient height and layout such that all tools, powder, and finished devices have a designated location to make the ramming process go smoothly. Having tubes and drifts rolling off the table interrupts the flow of work and increases chances for accidents. Locating everything within easy reach will make the work go much more quickly with fewer mistakes.
Tubes - For the most part, parallel or convolute wound tubes are used when hand ramming compositions. A convolute wound tube is made by wrapping a single sheet of paper around a metal mandrel. The mandrel's diameter is the required internal diameter of the tube. The length of the paper when rolled up completely will determine the wall thickness of the tube. Convolute tubes can be machine rolled or hand rolled if an unusual size is needed. Generally, heavy walled tubes are used in order to withstand the blows from the ramming process and to keep the tube from splitting. Thinner walled tubes can be used also if properly supported in sleeves and molds (this will be covered more thoroughly in another article). Purchased tubes come either cut to length (with nice square ends) or in longer sections straight from the rolling machine (which you can cut the length needed). Unless one owns a lathe to make a clean cut, a chop saw with a fine tooth blade will give a good square, albeit somewhat fuzzy, end.
Clay - The most convenient and widely used method for plugging tubes and making nozzle orifices is to use dry powdered clay. Bentonite clay works well, as is, for most applications. Many people like to treat the clay with additives such as wax, various oils, or graphite to cut down on dust and to facilitate its loading and packing qualities. It is also possible to use kitty litter.
Pyrotechnic Compositions - Hand ramming as opposed to pressing with pneumatic or hydraulic presses, can be more dangerous when utilizing mixtures that are friction and shock sensitive. Black powder based formulas used in fountains, gerbs, and rockets are generally safe, although the inclusion of metals such as titanium should be treated with caution and respect.
Safety - Any loading and ramming of pyrotechnic devices should be done in a remote area, preferably outdoors in an area protected from the wind. Powder in the area should be limited only to the material being used and in uncovered amounts not exceeding one or two pounds. A good quality dust mask should always be worn when hand ramming, as there will always be dust floating in the immediate area. Follow all standard safety rules concerning static, sources of ignition, etc., which one adheres to when working with any pyrotechnic process.
References[]
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