Fuse Types, Characteristics and methods of Joining: Part 3

GREEN PLASTIC IGNITER CORD

This fuse burns slowly, at about 25mm (1inch) per second. It is normally used to provide delays at ignition points and in sequences. It sometimes serves as the initial point of ignition for the fireworks.

Connecting green to green is done by twisting 25mm. or so and taping, green to quickmatch by inserting at least 25mm into the core and taping, quickmatch to green by stripping the plastic sleeve (to aid the transmission of the flame use tape wrapped around the plastic sleeve which when pulled back reveals the brown core) and inserting the incendiary into the central core of the quickmatch and then tying with a cable tie if required and/or tape.

BROWN PLASTIC IGNITER CORD

May be worked in a similar fashion to green, however it has a considerably faster burning rate and to avoid confusion should be kept away from the general fusing process unless specifically required.

Other Fuse Joints (Spanish Delays and Pressed Delays)



You can either have a fuse join that finishes at the delay in which case simply reveal 25mm or so of the Quick Match, place this is the end and secure using a cable tie or string. If you wish to join a number of varied time delays together to create several delays from one line of Quick Match then fold the quick match over and cut the end to reveal the internal fuse as shown above.



Once you have done this place the double strand in (exposed end first) and secure in using a cable tie or string.

These fuses can be used to provide delays between sequences of various items or used as a method of delaying shell in the same way as using PIC. Delays are generally more accurate but are more costly, but the benefits can out way when firing to music etc. You must also remember that pressed delays in particular can burn quite viciously and this must be considered when securing them down due to unwanted burning to surrounding fuses, other items and even wooden racks

Safety Considerations When Fusing

The following points must be taken into consideration with regard to fusing before you arrive on site:-

Fusing away from the workshop may only take place on the site of the display,
even though more than one day may be required to prepare the fireworks.

If the weather is poor and you require shelter, fusing may only take place inside a tent or cover of light fabric material or vehicle with a light fabric roof – never in a building.

Only use proper supplied cardboard / fibreboard tubes, high performance
polyprene or UPVC tubes for mortars and shells. Never use steel pipes or
lightweight drainpipes (they also sweat).

Handle quickmatch with care. Cut off what you need and put the rest of the bundle back into the storage container.

When joining quickmatch avoid cutting the incendiary cores. Where cuts must be made, only sharp scissors, nips or very sharp knife may be used. Do not tear fusing apart.

Keep all fusing dry and generally consider total waterproofing of the fireworks display. Bases of buried cardboard tubes should be bagged, open ends of tubes covered with foil or bags secured with rubber bands or tape, cake boxes covered with polythene, flights with thin aluminium foil (which must be taped down to prevent it being dragged off with the first rocket), candles wrapped with polythene etc.
Remember to remove waterproofing from rockets before firing!

Secure all joins so that they cannot be snatched either by accident or during
ignition.

Never use staples to secure fusing. Always use battens with cable ties or the cable ties themselves tape to secure them to the Shell Frame, tape can also be used (gaffer tape) but tends to be less reliable and the PIC can rip stopping the sequence

Do not set green cord along a surface and then cover in tape as it will burn more quickly.

Keep the work site tidy.

Fireworks Families & Types Part 2

Illumination Pots, Bengal Flares, Lances & Portfires

The compositions used are designed to be slow burning and are contained in light paper cases which burn away with the contents. The commonest encountered are the good old garden volcano, Portfires which are used for ignition purposes, and Lances which are used for making up “Good Night”s etc. Others can be illuminating or strobing, with a duration of anything between 60 seconds and 6 minutes.

Roman Candles

A more complex firework consisting of a tube containing pyrotechnic units alternating with propellant charges. When fired, the units are thrown into the air in sequence from top to bottom. Different effects are obtained by using successive units of varying colour and form. They may also produce sound effects during their trajectory, including a report at the end. Between successive projections, the candle may emit coloured sparks or flame directly from the body.

They are made up to 60mm calibre and can send stars up to nearly 200 ft. The candle must therefore be securely fastened to a stake or candle frame.

It should be noted that as each successive star has further to travel up the case of the candle, it takes longer to exit the tube and is therefore subjected to the lifting charge for longer. The quantity of gunpowder has to be progressively decreased to achieve the same height. Do not use damaged candles – there could be a blow out.

Whilst the styles or effects of roman candles have remained more or less unaltered throughout their history, there have been alterations in the method of activity of achieving the delay between the successive stars.

a) The original Ruggieri design utilised green mix gunpowder and these candles will emit showers of sparks between successive stars. It should be noted that with the exception of any tube products that may be used, all the products are consumed and there is little or no fallout.

b) Typical Chinese candles are used in vast quantities in the fireworks industry. Here a continuous fuse runs down the side of the tube and is designed to burn for the duration of the candle. The delay between successive stars is achieved by alternating them with loose plugs of potters clay. During the course of even a modest display, a considerable amount of clay is thrown into the air. Beware!

c) In recent Years 1^st Galaxy Fireworks Ltd have been using “Typical” Chinese Candles manufactured using similar ideas to the “Ruggieri Technique”, and showers are emitted between each shot, this has enabled slightly better timing and larger stars etc.

d) To overcome the problems of achieving synchronised firing, there have been two developments, the earliest being the substitution of the green mix delay with a felt plug with a pressed delay in the centre. These felt plugs return to Earth unburnt.

Shells

A firework shell is a hollow projectile containing an explosive charge. In Western Europe and the USA the shell may also have an attached lifting charge. It must be remembered that this practice is by no means universal and the presence of a lifting charge would not be considered a defining characteristic by firework technicians. (The presence of a propellant charge is considered a defining characteristic of a rocket!)

The shell is projected from a mortar tube by a charge of gunpowder (the lifting charge) to burst high in the air with whatever effect is incorporated in the shell.

The mortar tube may be made from cardboard, fibreboard or specific types of plastic.

The shells may be made from paper or plastic and are either spherical or cylindrical in shape. It is much easier to contrive multiple breaks or bursts with a cylindrical shell, whereas the spherical shells are required to produce spherical bursts, chrysanthemums, peonies.

Shells which explode with a loud report are called maroons or salutes

The diameter of shells used at 1^st Galaxy Fireworks Ltd are generally anything from 2” to 12” and come in two types:-

a) Bottom fused and

b) Top fused

Bottom fused shells have their lifting charge ignited first. This in turn ignites a delay fuse to the bursting charge.

Top fused shells are fitted with a delay fuse to the bursting charge with a secondary instantaneous fuse to the lifting charge. These are perhaps a little more reliable as there is less risk of the delay fuse being blown out. These tend to be more cylindrical in shape. Care must be taken when installing top fused shells to avoid damage to this lifting charge fuse. It is also essential to ensure that the shell, as with all shells, is inserted into the tube the right way up. Damaged shells should not be used.

Shells can be extremely dangerous if they are not handled and fired in the approved manner. The exit velocity of a shell from the mortar tube could be in excess of 200 mph!

To appreciate the height and effect of a shell, the following can be used as a rough guide

If ‘x’ is the calibre of the shell in inches,

The delay to full height is ‘X’ seconds,

The height reached is ‘X’ x 100 feet,

The spread of burst is ‘X’ x 10 metres.

This will not always apply, however it can be used as a guide for most shells.