The prologue...

Even for the amateur pyrotechnic enthusiast, there will quickly come a realisation that a safe and reliable fuse is not only an essential piece of kit for successfully setting off fireworks predictably, but that they are the most underappreciated part of any firework.

Not only does a safe fuse greatly reduce the risk of injury and damage but it’s crucial for the timing of both simple and complex pyrotechnic firing arrangements. Even in the most complex electrical firing systems used by professional pyrotechnicians, after the ignition of a firework begins all subsequent timings within that firework will be dependent upon a chemical fuse of some kind burning at a set rate.

There are many types of fuse with different properties designed to fulfil different requirements. Arguably the most important of these (at least in the beginning) to the budding enthusiast is the fuse used to initially light a pyrotechnic device. This type of fuse is often referred to as “safety fuse”, “cannon fuse” or most commonly of all “visco fuse”. There are many places where restrictions on the sale of fuse prevents (or makes it difficult for) a pyrotechnic enthusiast to obtain fuse. Even where you can purchase fuse you might be looking to pay a relatively high price for a short length of fuse. Whether a commercial fuse is available to you or not, there are many good reasons for making your own fuse, such as:

• After the initial cost of materials, production of homemade fuse is often much cheaper than buying fuse.
• You can tailor the fuse to the specific requirements you have for a given application i.e. burn rate, fuse dimensions etc.
• You can have fuse “on tap” whenever you want it.
• Having the satisfaction of making the fuse yourself – after all, the whole reason you’re making fireworks in the first place instead of buying them (fuse and all) is because you appreciate having put in the effort to understand the processes and get it right for yourself.

Therefore, many amateur enthusiasts look towards producing their own fuse – with a greatly varying degree of success depending on the type of fuse they’re trying to replicate. The most desired option is to try and make a visco style fuse. This is because a visco style fuse offers the greatest benefits to the user. Other fuses like black match and fuse paper can produce the desired results in some cases, but these are not waterproof, may have an inconsistent burn rate and can fail to continue burning in a confined environment. Visco style fuse has none of these problems.

Unlike some homemade fuses, in order to make a consistent product of the visco type there needs to be a standardisation of the production process and this can only be done using some form of mechanically driven machine.

The designs of machines which produce visco style fuse can vary greatly depending on the needs and constraints of the user. Although there is a lot of information on the internet with all manner of details regarding the construction and design of visco machines, these tend to be incomplete.

For the average enthusiast the production of fuse will be a relatively low level affair requiring only a few feet per time as opposed to an industrial scale operation. There are many devices which others have made which work beautifully, but unless you’ve got access to a workshop and a fair amount of technical knowledge these devices might be beyond the fabrication skills of most beginners and tend to put people off.

My specific needs as an amateur enthusiast for a visco machine was a device that was:

• Compact, and so easily stored.
• Easy to construct.
• Cheap to build.
• Easy to operate.
• Quiet.
• Could produce small to medium lengths of fuse easily and quickly.
• Hand powered – reducing complexity, cost (both of materials and in operation) and noise.

This in turn would need to produce a fuse that:

• Had a consistent burn rate.
• Was reliable – i.e. it would continue to burn in confined spaces, such as the exhaust port of a rocket nozzle.
• Could be waterproofed.
• Would be strong enough to withstand pyrotechnic charges (such as those in lift charges and break charges) but still be flexible enough to cope with a certain amount of manipulation.

The eBook available here details the construction and use of the machine that I eventually made. It fulfils all of the above requirements for both the machine and fuse produced. The finished machine looks simple, and to be fair, that’s the point. It took a long time to make a model which would meet the criteria listed above yet be as simple as possible and use readily available materials. The less complicated a system the less there is to go wrong with it, and anyone who has battled the trial and error of getting a visco machine to work will testify that the fewer times you have to thread the “dies” the better!

The model produces fuse at the rate of 3 feet per minute and the fuse itself has a diameter of 2mm with a consistent burn rate of 0.7cm/sec, even underwater, and can be seen in action in the video below.