Tuesday, September 9, 2008
Multi shot barrages (cakes) come in many sizes and shapes. Do not underestimate the power of this group of fireworks. Careful attention to detail is required when setting these up.
They can produce considerable forces when firing. For this reason they must be placed on stable and flat ground. Where this is not achievable, wooden boards may be required to form a firm base. These are held in place with stakes and Straps or Ties. This provides a firm base for the firework to recoil against, thereby reducing the possibility of distortion or breaking internal fuses thus breaking the fuse chain, or misdirection of projected pyrotechnic items. They can also be buried to half their depth in soil or sand if required.
Make sure that they cannot topple over and secure them to two or three stakes set around the box with straps or ties. They should be slightly angled away from the spectators and the underside of the box packed out with wooden boards.
The larger cakes are already wrapped in plastic but it is good practice to further protect them in damp or wet conditions at fireworks displays.
The fuses on the Chinese cakes can be unreliable and should be replaced with green delay fuse (PIC). Insert some quickmatch with the end bared directly into the first tube of the cake to replace the original fuse, and connect a length of green delay fuse to this. Some cakes are susceptible to blowing up if badly constructed.
Remember – a barrage cake may have as many as twenty or thirty 2.5” (65mm) shells in one box!
Placing and loading mortars
As a Rule 1st Galaxy Fireworks Ltd use racking systems for 2.5” (65mm) – 5” (130mm) Mortar Tubes, these Racks can fix together to form a solid structure. Or where safety requires distances between them, we can stake them in Two Places (at opposing diagonal corners). These are placed long ways onto the crowd, ensuring that they cannot fall over in that direction.
Larger Mortars are secured With Three Large Stakes, they can either be buried to cover the Shell itself, e.g. a 6 inch shell would be placed in a 6 – 8” hole, thus the shell is set slightly in the ground. This offers both a stable surround, and some protection should the delay blow, and the lift charge and break fire within the tube at the same time. Sand bags can also offer protection from such an occurrence if used to surround the base of the tube.
Stakes: The use of stakes, preferably strong wooden, or purpose made racks are the only practical methods of safely setting up mortar tubes
Ensure that stakes are driven firmly into the ground before the fireworks are attached to them.
All stakes must be angled by no more than 15 degrees away from the crowd, depending on site conditions
Where stakes are used to obtain a fan effect, from Roman Candles for instance, then these must not lean over from the vertical by more than 15 degrees, i.e. 30 degrees between the two.
Where Set Pieces are secured to a stake(s), attach them to the rear of the stake. This applies especially to shell tubes and Roman Candles. The only exceptions to this rule are Wheels which will be on the front of a pole but this will still be secured to the rear of a stake.
Make sure that the fireworks are firmly attached to the stakes using string, nylon cable ties or straps. Each one must have at least two separate fixings at the top and middle points. Larger fireworks will require more. Do not over tighten nylon tie fixings as this may cause a restriction in the tube.
Stakes must not extend beyond the opening of the firework and care must be taken not to split open the top of the stake. Good quality, not split, 50mm x 50mm wooden are recommended for most fireworks although lighter gauge stakes may be used on the small candle boxes, Steel angle iron stakes are ideal as long as they are not too flimsy. A selection of lengths will be required for the different size fireworks.
Make sure that the ties are not too tight. This could restrict the bore of the firework, particularly candles.
It should be stressed that the procedures and information set out in this course are to be strictly adhered to.
A shell is launched from a mortar tube. These are made to withstand the pressure created when the lifting charge explodes. It is therefore essential that the following initial considerations are taken into account.
• Is the tube in good condition and dry and that the bung is firmly in place
• Is the tube the correct size for the shell
• Is the tube long enough
• Is it made from a suitable material
All tubes should be carefully checked to make sure that they are not damaged, damp or obstructed in any way.
The shell must be a good fit in the tube. If it is loose the effect of the lifting charge will be to partially bypass the shell and produce insufficient pressure to lift it high enough into the air. This can result in a “low burst”.
If it is too tight there is danger that the shell will not clear the tube when the lifting
charge detonates, resulting in the tube being split and the shell exploding at or near ground level. This can result in a “low burst”. This will also make the likelihood of fragments from the tubes an additional danger.
This is particularly important when using top fused shells as the connecting fuse
between the delay and the bursting charge may be damaged. This will cause the
shell to explode but not the lifting charge.
It is important that mortar tubes are made of materials that will not fragment.
Suitable materials are cardboard / fibreboard, high density polyethylene, heavy duty UPVC. If in doubt then don’t use them.
NEVER use tubes constructed from steel or hard brittle plastics such as drain pipe.
Fibreboard tubes that become wet lose a great deal of their strength and will not recover. Always ensure that tubes are protected from the weather and stay dry. Shells to be put into plastic tubes are best put in a poly bag first – plastic sweats!
Shells generally range in size from 2” (50mm.) to the massive 16” (400mm.) finale shell. Common sizes are 3” (75mm.), 4” (100mm.), 5” (125mm.), 6” (150mm.),8” (200mm.), 10” (250mm.), 12” (300mm.). Single tubes are generally used for 150mm. shells and larger.
Before loading the shell, make sure that the tube is empty.
The shell should be a comfortable sliding fit down the whole length of the tube and must rest at the bottom. Make sure that you are using the correct size tube for the shell. Check that the shell is the correct way up. Sometimes the string loop on the shell can break away causing the shell to hang upside down. Do not remove strings.
Setting up mortar tubes
Where mortar tubes are not available in specially constructed racks, they must be secured to a stake that is driven well into the ground or an appropriate steel or timber frame. A small piece of timber must be inserted between the tube and the ground to transmit the force of firing. Otherwise the base of the tube could be blown off.
The tubes must be positioned at a safe distance from the spectators in the event of a tube failure. The firers must wear the correct PPE and allow sufficient time to get to a position of safety.
They must be fixed in at least 2 separate positions using straps, nylon ties or strong sisal string and the tube must be positioned on the far side of the stake, angled away from the spectators. Check that there is sufficient room between tubes or tube racks.
Make sure that the tube is completely clear of debris from the previous display
firing before lowering the shell into it.
The shells are lowered into the tubes using the long fuse. Handle them with care, they are fragile. The larger shells (10” and upwards) may have a string for lowering. The fuse is not strong enough to lower these. Some shells need the string to assist flight.
The lifting charge is usually contained in a paper cone at the bottom of the shell. This may not be obvious when using plastic shells so check that they are the right way up!
The shell should be a comfortable sliding fit down the whole length of the tube and must rest at the bottom. Make sure that you are using the correct size tube for the shell.
Shells with ancillaries / tails & some double break shells may have a protective wrapper over the top of the additional ignition point. These are for protection during transit and must be removed before inserting into the tube. Often coloured red.
If it does not slide in – DO NOT FORCE IT.
NEVER RE-LOAD A TUBE DURING A FIREWORK DISPLAY
If possible set up the Finale first, protecting it from possible sparks from other pieces by setting up and covering with aluminium foil.
Cover each piece with foil or plastic bags, as necessary.
Monday, September 8, 2008
Shell Batteries / Shell Strings
These are generally used for 75mm. and 100mm. shells fired in sequences. They are usually used in groups of 6 shells for 75mm, and 5 for 100mm.
Such sequences are normally placed in racks specially designed for the purpose.
This allows the shells to be fused together, normally with a time delay between each shell using green PIC. Certain Maroons must not be placed in racks. Always load into individual tubes.
The racks must be secured using wooden stakes or steel pins. If using steel pins
(road pins) or angle irons, then the sledge or club hammer must be protected from the pin to avoid sparks - a piece of cardboard or wood should be sufficient for the purpose. Non- ferrous hammers are available, but are extremely expensive and difficult to procure. If setting up close to where other fireworks have already been prepared, consider placing all the stakes out before fixing the tubes.
Make sure that all fuses are protected whilst securing the stakes and that the racks are angled away from the spectators.
All match fuses must be secured to the top of the mortar tube to prevent it being lifted off by an adjacent shell when fired. This can be difficult to achieve on plastic tubes as they tend to stay damp. In such cases wipe them dry with a rag or paper towel beforehand.
To secure the shell leaders (quickmatch leaders) to the racks use wooden battens tied down using nylon zip ties to pinch the leaders onto the rack frame. You can also use a zip ties on individual leaders, but when using a larger number of shells this is fiddly and time consuming so the former is usually preferred. Another method is to tape the leader down, but this is usually a last option and used if zip ties etc run out as the tape tends not to stick to the racks, but is useful when attaching leaders to the cardboard tubes, simply ensure the surface is as clean as possible giving the tape chance to stick well.
Never use a Stapler to secure shell leaders onto a wooden frame; this can result in premature ignition.
This applies to both batteries and single tubes as the quickmatch fuse can blow itself out when bent over the edge of tubes.
It is important to ensure that the brown paper quickmatch fuse is completely inside the mortar tube and covered as it is particularly sensitive to damp.
The paper fuse will need to be joined to a length of waterproof quickmatch which can be left outside the tube.
Some shells may be pre-fused at the factory. They must not be carried in the tubes in vehicles but unloaded before transport and re-loaded at the display site.
Maroons and Mines
Treat as for shells. Never put maroons in racks. They contain flash powder and if one blows the blast will destroy the whole rack.
As a rule Britannia Fireworks do not use Single, Large Rockets in our Displays, but on occasion we are requested to do so. If the site is suitable etc.. we take into account the following :-
The major consideration when setting up rockets is that the empty tubes and sticks will not fall onto spectators. It may seem obvious but the crowd are going to be looking up into the sky! This is where the debris will come from.
Before any firework display it is vital that the wind direction is checked. This is particularly important when considering where to fire rockets. We have already made reference to the fact that rockets turn back into the wind. Plenty of space is required to fire them and an adequate “fall out zone” must be available.
Rockets should be set up in racks specially designed for the purpose. These can take the form of steel tubes welded onto a frame. One alternative is to construct a timber frame made from 1 ½ “ x 1” timber (38 x25mm). The sticks can then be dropped into such suitable guides as large screw eyes, saddle clips, staples of 12mm. diameter or plastic tubes set into spring clips.
Check first of all that the stick of the rocket is firmly fixed to the body and that the stick is not broken or split. Make certain that the rocket is free to rise with no obstructions.
Most rockets have fuse caps. These must be removed for fusing but delay this as long as possible to avoid damp. Rockets are very often fired in a sequence and will therefore need to be fused together. Use green fuse and secure this with tape to each rocket fuse. Be careful the green fuse does not fall away from the rocket as it burns.
Remember to remove all plastic waterproofing before firing rockets!
Rockets – Flights
These are smaller rockets which are fired in groups of 10 or more at the same time and may be fired from a metal cone, an 8” (200mm) tube or a specially constructed box.
Flights are fitted with instantaneous match fuse, unlike their bigger brothers which have delay fuses.
The method for fusing flights is to ensure that all of them fire together. A length of brown fuse or more commonly quickmatch is attached to two rocket fuses and a piece of green fuse is finally attached to the brown or quickmatch to act as the delay fuse. The spread of fire from each fuse will ensure that they will all fire simultaneously.
Roman Candles, single
These fireworks must be securely fixed to a stake using at least 2 ties, or set firmly in sand or earth. It is important to make sure that they cannot topple as the balls of fire and effects are thrown to a considerable height. When using wire, care must be taken so as not to over tighten and restrict the bore of the tube.
These are very often used in pairs or groups of three to create spectacular effects in fans. In this case they should be fixed as before to specially constructed frames which are in turn attached to stakes. They should be angled away and fixed on the side furthest away from the spectators. If frames are used it will determine the angle of the candles automatically, but if in sand or earth then the maximum permitted angle from the vertical must be no more than 15 degrees.
Candles are fused together using quickmatch. The end of the quickmatch is exposed and is inserted into the open end of the candle. A further short length of black match is used in the end of the candle to aid ignition. All fuses are then secured to the candle using tape. All fuses are then brought to a central point and a 5 second delay using green fuse is finally connected.
Bundles of candles
Small Roman Candles can be tied together to form a bundle of 7 or 19. The bundle is tied together using strong tape or wire provided it is not too tight. These are then secured to a stake or special frame as previously described.
They are fused together by exposing the fuses and laying a generous quantity of black match over the top of them. A delay fuse is attached to the black match and then the top is completely covered with tape to waterproof the items, leaving only the green delay fuse exposed. These can also be linked to others.