Using Homemade Gerbs Creatively

Last post, Making Gerbs (Firework Fountains), I made some homemade gerbs, also called fountains, using either a gold glitter composition or a silver titanium one. These fountains create nice effects, either fired one at a time, or in a “front” with the gerbs in a line, spaced 8-10 feet apart.

One of the things I really love about handmade gerbs is their versatility. In this article I will show you how to incorporate these fountains in some other creative devices:

• I’ll mount some gerbs on a frame to create a waterfall.
• I’m going to show how to make a very simple, beautiful, color-changing spark wheel.
• I’ll recreate the Chromatrope wheel that was described in Mortar Racks, Fusing Techniques, and a Firework Wheel, using homemade fountains to drive it.
• I’ll show how to make a simple set-piece in the shape of a star, using two different types of titanium in the silver formula.
• And a simple line rocket will be assembled.

I totaled up the number of the glitter gerbs and the titanium fountains I need for all the projects I have planned, and I rammed them as described in Making Gerbs (Fireworks Fountains).


I drilled 1/4-inch nozzle holes in all of them except the four titanium gerbs that I have planned for the sample waterfall. I made 3/8-inch apertures in those nozzles so that they spray the silver sparks out more gently.


Also, the glitter gerbs are going to be used in pairs with the titanium ones. The glitter gerbs will burn, and then they will passfire from their bulkhead ends to the nozzle end of the Ti ones. So, I’ve drilled 1/4-inch passfire holes through the bulkheads of the glitter fountains.


When they are going to be used individually, I fuse the gerbs with Visco as shown in the photo above. But when they will be used in devices such as the ones I have planned for this project, I fuse them differently.


I cut some 4-inch lengths of thin blackmatch from Quickmatch or Super-Fast Paper Fuse. This match is doubled and inserted into the nozzle holes of the gerbs.

I screen together, through a 40 mesh screen, a black powder prime composition, consisting of:

Component	Ounces
Potassium nitrate	1.5
Air float charcoal	0.3
Sulfur	0.2
Dextrin	0.1

In a paper cup, I add enough water to the prime powder to create a slurry with the consistency of jam. This slurry is put in a plastic baggie, the top of the baggie is twist-tied closed, and the excess plastic is cut off. I clip a very small corner off of the baggie, and pump the prime into the nozzle holes until they are full.


I finish this priming/fusing off with a dusting of fine black powder granules, and the prime is allowed to dry for a couple of days.

This combination of blackmatch and black powder prime ensures a very positive ignition when the flame from quickmatch fusing reaches the ends of the gerbs.


Now I install paper buckets on the fused ends of all the gerbs, and on the passfire ends of the glitter gerbs. These buckets consist of 4-inch by 9-inch pieces of 40-pound kraft paper glued and rolled onto the ends of the paper tubes, resulting in a double walled bucket.

Traditional fireworks waterfalls use thin-walled paper tubes filled with a potassium perchlorate and aluminum composition, and hung pointing downward. The waterfall I’ll be making with these silver titanium gerbs will be a little different than that.


I was watching a special on Niagara Falls the other day, and I noticed that the water projects horizontally off of the rock river-bed and then gradually arcs over and starts to fall vertically. I started to wonder if something like that could be done with these Ti gerbs.


So, as an experiment, I’m going to mount four Ti gerbs, with the 3/8-inch nozzle apertures, horizontally on a board, 12 inches apart. I’m interested in seeing what sort of effect that produces.


Note: In past articles I’ve shown how Super-Fast Paper Fuse or Fast Yellow Visco can be wrapped with aluminum foil duct tape to produce quickmatch if one does not have access to that fuse.

I was not completely thrilled with the effect this falls produced. Many of the silver sparks burned out flying horizontally before they started to fall vertically. Even with the 3/8-inch nozzle aperture the gerbs still had too much thrust.


The next day I decided to make one gerb without any nozzle at all. I just pressed silver-titanium comp into the tube, and burned it. I was happier with the unchoked tube and would use gerbs in that configuration in the future. The waterfall effect would have been better with 16-foot vertical supports instead of the 12-footers that I used this time.

For the wheel frame, I took a 4-foot piece of 1×2, and mounted a threaded tube through a hole in the center of it. I will later use a 1/4-inch lag bolt to mount the wheel to a vertical support post.



Then I drilled a pattern of holes in the ends of the 1×2, through which I’ll tie on the gerb drivers.

I use waxed string to tie the glitter gerbs to the outer end of the 1×2, nozzle end pointing out. Then the Ti gerb is tied on next to it facing in the same direction. These drivers end up staggered so that the glitter gerb’s sparks do not ignite the fusing of the Ti gerb.

A quickmatch passfire is tied into the passfire end of the glitter driver and over into the thrust end of the Ti one.


I tie the pair of gerbs together to further improve their stability. Additionally, I covered the string ties with aluminum foil duct-tape so that there would be no chance of the ties burning through when the passfire ignites.


Note: In the past, to attach drivers, I’ve used plastic zip-ties, or iron wire, which are both less susceptible to flame damage, but this time I wanted to use the string, which is simpler, less expensive, and lighter.



The completed wheel is now ready to mount to a support post. There is a wood block at the top of the post to space the wheel out and away from the support to keep the wheel from hitting it.

When I am attaching the quickmatch drop-leader to a device which is designed to move, such as a rocket, girandola, or wheel, I always install a “positive disconnect” section. A “positive disconnect” is simply a section in the quickmatch which is designed to burn through and fall away. This is done by exposing, and overlapping bare blackmatch from the ends of two pieces of quickmatch and wrapping with clear packing tape. I then tie the packing tape bucket to secure it in place.

This disconnect ensures that the plastic-and-paper match pipe and the blackmatch string actually detach from the device. I have had moving devices fail to move due to the incomplete detachment of the quickmatch leader. This is a bad thing.

Note: Mounting the drivers at a 45-degree angle to the 1×2, instead of at a 90-degree angle increases the final wheel display’s diameter. It also decreases the thrust that the drivers impart to the wheel, thereby slowing its rotation and making it appear more graceful.

Note: As I was constructing the wheel, I was constantly thinking through the ignition and burn sequences, and imagining all the possible things that could go wrong and could be avoided. The aluminum foil over the string ties was such a counter-measure. In even this small wheel there is a lot of time and effort and I’d really like it to work well. There’s a huge difference in the feeling I have when something works as designed, as opposed to disappointment I feel when it crashes and burns.

I also remade the Chromatrope wheel, this time with homemade gerb-drivers. The ends of the arms on the two spark wheels will have pairs of gerbs mounted on them in exactly the same manner as the simple wheel above. One wheel will rotate clockwise, and the other will move counterclockwise.

Homemade fountains can be arranged in a multitude of ways to create a set-piece, forming letters, a word, or any other design.


I decided to create a simple, 5-fountain, star set-piece to illustrate what can be done with these gerbs.

I used 12-foot 1×4’s to make the framework, and mounted the gerbs with zip-ties and a shim under the nozzle end to slightly point the exhaust out away from the frame. The shim is simply a section of a 1.25-inch ID paper tube.

For this little project I made 5 gerbs with the coarse spherical titanium (CH3001) and 5 with the fine spherical Ti (CH3010). The two effects were dramatically different.

The star on the left, using the coarse Ti, could have easily been made twice as large, and the one on the right with the fine Ti could have been made slightly smaller.

With one last little bit of creativity, I assembled a couple of line rockets. The first one had one driver (this type of rocket makes a nice effect flying into a bonfire as the fire is lit). The second one had two drivers in opposite directions, one burned then passed fire to the other, produced a back-and-forth flight.


In both cases, the gerbs were taped to a piece of PVC plumbing pipe which has the same OD as the fountain tubes.


The pipe is installed on a length of iron wire as the wire is strung tightly between two solid supports, like trees.

In this case, in order to develop enough thrust with the Ti gerbs, I drilled the nozzles with a 3/16-inch drill.

In his book, Introductory Practical Pyrotechnics, Tom Perigrin has some fun ideas for other creative variations on the line-rocket theme. Rat Packs, Jeweled Rats, Pigeons: So many experiments, so little time.

So there you have it. Plenty of ideas on ways to put simple homemade gerbs to use. They don’t make much noise, they are relatively safe, their effects last a long time, they make for instant gratification, and they offer endless opportunities for creativity.

Have fun and stay safe,

Ned

Mortar Racks, Fusing Techniques, and a Firework Wheel

In the last few weeks I’ve discussed making small Cremora fireballs and electric matches to use in a Consumer fireworks display, as well as firing systems and wiring techniques.

I’ve also covered many topics which deserve attention when planning the show and purchasing devices for it.

This week we’ll be looking at the construction of mortar racks from which to fire artillery shells during the show, how to construct a really nice wheel using fountains from the local fireworks store, and some techniques for using various fuses to attach devices together for the display.

Mortars are the tubes with plugged ends that fireworks shells, comets or mines are fired from. Mortars can be made of HDPE plastic, fiberglass, paper, or in some special cases, metal.

The mortars need to be secured in an upright and safe position. This can be done by burying the mortars (guns) about 2/3 of their length in the ground. Here are a couple of shots of some of the large guns that were buried for shows and competition at a recent Pyrotechnics Guild International convention.

Often, especially with smaller guns, the mortars can be securely held in place in racks, either perpendicularly or at an angle. The racks can be constructed of metal, wood, or a combination of the two.

Here are a couple of artillery shell racks made by Brian Paonessa at Skylighter, using Skylighter’s PL3182
fiberglass mortars. One is a fan rack, and the other holds the guns straight up and down.

Here is a shot showing some of the construction details of the fanned rack. Brian has glued and screwed the rack together.

Below is the angled PL3175 artillery shell mortar rack that Skylighter sells. The swing-out feet hold it in an upright position. When using this rack, I drill holes in the feet and drive spikes through them and into the ground to keep the rack from bouncing and falling over.

As you can see in the photo of the PGI racks above, wooden racks can also be held upright by attaching them together with lengths of wood 1×3s, or by pieces of plywood attached to both ends of them. In either case, screws or nails are used to keep the whole assembly upright and rigid.

Care must be taken to avoid driving fasteners into the mortars. In pyro this is known as a “bad-thing.”

Typically, except in the case of fan-racks, racks are set up so that their ends are perpendicular to the front of the crowd. That way, if a rack happened to come loose and fall down, it would not be firing toward the crowd.

Here is another way to secure wooden racks. Screw-eyes are installed into the rack ends, and rebar pins are used to hold the racks in place. Both ends of the racks are supported in this manner, and racks can be erected end-to-end with only one pin between them.

No matter what method is used to erect them, once the racks have been assembled, they ought to be secure enough to withstand a healthy kick with a boot.

In this section I’ll be referring to and using the various kinds of fuse shown in the photo below. Each one serves its own purpose and has its own unique burn-rate. The burn rate of a roll of any particular kind of fuse can vary. So it’s a good idea to cut 10 inches of the fuse off that roll and time it with a stopwatch as it burns to determine its exact burn rate.

American Visco	2.5 seconds per inch
Chinese Visco	1.7 seconds per inch
Fast Visco	0.25 seconds per inch
Fast Fuse	0.1 – 0.15 seconds per inch
Time Fuse	2.2 – 3 seconds per inch
Quickmatch	Instantaneous
Foil-Taped Fast Visco	Instantaneous
Foil-Taped Fast Fuse	Instantaneous

The foil-taped fast-Visco or fast-fuse may be used as excellent substitutes for quickmatch, which is not shippable. I described how to make it in Really Nice 4″ Plastic Ball Firework Shells .

In the rest of this article, I will refer to quickmatch, and you’ll know you can make substitutes for it with the fast-Visco or fast-fuse as described above.

So, I have filled 6 tubes in my rack with an artillery shell, comet, or a mine. If they are to be hand-fired, the shell-leaders (fuses) can simply be left hanging out of the guns, ready to be lit one at a time with a propane torch.

These shell leaders are fast-Visco fuse, and I’d expect a burn rate of about 4 inches per second, which will produce about a 3 second delay between lighting the fuse and the shell launch.

A shell of this size will take about 3-4 seconds to rise in the sky and display its starburst. So if I light the next fuse immediately after the first shell has launched, and so on, I’ll get a nicely paced series of bursts that lasts a total of 18-20 seconds.

If the shell fuse leaders are a bit on the short side and threaten to drop down into the mortars, they can be held in place with a little masking tape. Be sure the shells are all the way on the bottom of the guns, though, to insure proper height when they are launched. A shell that’s not seated solidly on the bottom of its mortar can become a “low break,” which, in turn, can cause fires or injuries.

But, let’s say I want all of these shells to launch at the same time at some point during the show or at the end of it (the “finale”). In that case I’ll chain them all together with a length of quickmatch. Chaining shells simply means attaching their fuse leaders together in a series. If the shells are chained together with quickmatch, and then the end of the quickmatch is lit using a piece of Visco fuse or an electric match, once the flame hits the quickmatch the shells will all ascend skyward in quick succession.

This is done as follows:

• Cut a length of quickmatch as long as the run of mortar tubes containing the shells, plus about a foot. Always use a razor blade or anvil cutters to cut fuse, never scissors.

• Pierce the quickmatch wall with an awl where each shell leader comes out of the top of the mortar, making sure that all the layers of match pipe are pierced and you can see the black match inside.

• Put a fresh diagonal cut on the end of the shell leaders with a razor blade in order to expose the powder inside the leader.
• Insert the shell leader into the quickmatch for an inch or so.
• Use masking tape or aluminum foil tape to secure the shell leader into the quickmatch. I really like the aluminum foil duct tape with the peel-off paper backing. The stuff sticks like crazy, will not gradually come loose over time, and is fireproof.

• Use string to tie the fuse chain down to the rack between each mortar. I like waxed string for this purpose. It makes “threading the needle” with it a breeze. This prevents the first shell from yanking the chain as it is launched, which might pull the rest of the leaders loose from the chain.

Warning: In the past, some folks have used a staple gun to staple quickmatch chains to the tops of wooden racks. More than once, the stapler has created a spark which has ignited the chain and instantly sent shells skyward. This has killed or seriously injured some people. Don’t use a staple gun to secure flammable fuse, nor use one anywhere near pyrotechnic compositions.

The nifty thing about this fusing method, and the following ones, is that they can be applied to fusing rockets set side-by-side in launch tubes, or to fusing cakes laid out in a field or on a piece of plywood. A whole show can be laid out, fused together with a combination of these methods, and fired by lighting one fuse or firing one electric match.

But Wait, There’s More! Maybe I want that nice 3-4 second delay between the shells’ firing that I spoke about earlier. Maybe I want a different delay time, but I want to fire the shells in a chain as in the section above. How can I build that delay in between each shell in the chain?

Near the end of the Pyrotechnica XI article, Traditional Cylinder Shell Construction, Part II, “Finale and Flight Chaining” is addressed. This is a fascinating explanation of “old-time” chaining methods using quickmatch, paper buckets (rolled tubes of kraft paper), string, spolettes and regular time fuse. It’s a valuable addition to my pyro library. In the photo above, there are about 3 inches between the center of each mortar. If I run one of the Visco fuses down the line instead of the quickmatch, and attach my shell leaders every 3 inches, then I will get 3 inches of delay between shots.

3 inches of the American Visco fuse will give me a delay of 7.5 seconds between shells. That’s more than I want, but that might work in some cases. 3 inches of the Chinese Visco will give a delay of 5.1 seconds between shots. That’s more like it. I could go with that, although it’s a bit more of a delay than I really want.

To use Visco for a chain, simply tape the end of each shell leader alongside the Visco fuse as it runs along the tops of the mortars. The two fuses must be parallel to and touching each other for at least an inch of tape. Then tie the chain down to the mortar rack as shown above. Don’t try to run the shell leaders into the Visco fuse chain at a right-angle. You’ll get poor or failed ignition that way.

There is another, more precise, way of incorporating delays into a chain of shell leaders, though. It incorporates sections of cross-matched time fuse, or the hand-rammed spolette fuses that I described in Firework Shells in 2-1/2 Days – Part 3.

The roll of 1/4 inch time fuse that I have burns at a rate of 2.2 seconds per inch. If I use 1-1/2 inches of it between each shell in the rack, I’ll get a 3.3 second delay between the firing of each shell. This is done as follows.

I want 1.5 inches of time fuse delay, and I’m going to split each end of the fuse 1/2 inch for cross-matching. So I cut five, 2-1/2 inch sections of the time fuse. I split each end 1/2 inch with my razor blade, insert three 2 inch pieces of the thin black match that can be found in the fast-fuse or quickmatch, and I tie each end of the time fuse closed with a clove hitch and overhand knot to secure each knot.

Then I make “buckets” out of 3-1/2 inch x 3-1/2 inch pieces of kraft paper, rolled around a 1/2 inch wood dowel, with the edge of the paper glued down. I then tie a bucket on each end of the cross-matched time-fuse pieces, with the knots just to the inside of the pieces of cross-match. Tie the knots very tightly so that hot gasses cannot escape the bucket and transfer over to the next one before the time fuse has burned through.

Now it’s just a matter of making a chain of these bucket time-delays, in similar fashion to the chains that were made above. The first bucket in the chain has a piece of quickmatch coming into it from the ignition source, and a piece of quickmatch coming out of it into which the first shell’s leader is tied or taped. I don’t want a delay before this first shell’s fuse is ignited. This first bucket also lights the first time-fuse delay element.

I bare the black match in the quickmatch for 3/4 inch before inserting it into the buckets. It’s easy enough to clip the buckets a bit shorter with scissors as necessary. It’s just important to avoid cutting into the cross-match with the scissors, and to leave enough bucket so that the knot can be tied without any blackmatch protruding beyond it.

During the chain assembly, it can help to tie each delay down to the rack before assembling the next link in the chain. This helps to insure that the quickmatch pieces leading to the shells are long enough, and are routed away from each other and away from the mouth of a previous mortar, which would lead to a premature ignition.

The chain shown above is designed to be ignited from the left end, to have 3.3 second delays between each shell, and to pass fire from the right end to the next device in the line if desired.

This same type of chaining using time fuse, can be used to link box-cakes to each other. Let’s say I start with the ignition of a cake that has a 30 second burn time, and I want to overlap the next box 5 seconds into the first cake’s time. I’ll put a 25 second delay time fuse and buckets at the ignition point of that second cake. On and on, this type of show can be assembled.

Now for the added bonus section in this article. I find it to be fun and creative to take consumer fireworks items from the fireworks store, and assemble them into larger and more impressive assemblies. Fireworks cone-fountains can be hung upside down in a line to form a waterfall, and they can also be used as drivers in this large wheel. “Drivers” provide the force to make the wheel go round.

Chromatropes are a traditional fireworks display exhibition pieces. They are simply composed of two counter-rotating wheels, each of which is a basic assembly of wooden crosses with the drivers attached at the ends of each arm. They produce the kind of effect shown below.

The device shown above has 8 pairs of crossing fountain-sprays, or 16 drivers. This would be 8 drivers per wheel, and with 1 driver at the end of each cross-member, each wheel would have 4 cross-members. We’ll build a simpler version, with two wheels, each having 2 cross-members and 4 cone-drivers.

Here is an illustration of a chromatrope out of Weingart’s Pyrotechnics.

You’ll notice in both the photo and the illustration that the drivers are mounted at a 45 degree angle to the arms, and will shoot their spray out at that angle. This angle also diminishes the amount of force with which each driver will drive the wheel. I’m going to mount the cone-drivers at less of an angle to increase their force when turning the wheels, since the cones are not as powerful as handmade drivers.

Here’s a very simple pictorial essay on this consumer fireworks model. The hubs that the bolt-axles go through are simply 3 inch long 3/8″ threaded tubes/nuts/washers, available at a hardware store in the lighting department.

I have cut 1-Inch x 2-Inch x 8 foot pieces of lumber in half to produce 4 foot long arms, and I’ve cut steep angles on the ends of each arm.

Then I drill 3/8 inch holes in the center of each arm, insert the threaded tubes, put some wood glue between the arms, and tighten the nuts and washers.

I’ve removed the wrapping paper from the cones and drilled some mounting holes in their hollow bases. I’ve also installed some extra scotch-tape to insure that the fuses are secured in their tops.

I then mount the cones to the arms with iron wire, and I install buckets and quickmatch to fuse them together. I have clipped the cone visco fuses on an angle to get fresh powder exposed, and I’ve glued and tied the buckets to the cones to insure that they don’t slip off.

I’ve assembled a T-support with 4×4 lumber and reinforcements. This insures that the wheels don’t hit the vertical support during operation.

I’ve assembled the wheels so that they are driven and turn in opposite directions. You’d be surprised how easy it is to mess this detail up.

On the day of the show, I’ll tie the two wheel ignition points into one leader so that both wheels will light at the same time.

I always test at least one of the wheels with the cones you want to use to make sure that they are powerful enough to get the wheels spinning once they are lit.

Stay Green,

Ned