Shell Barrages – “Cake Boards”
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.
Shells
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.
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