Air-Lifting Revisited

[patsroom]

This is a follow-on to the original Air Lift post with a few ideas I had about making it possible, if not practical.

 

Air Lift re-visited, Air launching shells Last entry 16th Sept. 2008 by Arthur

 

I became interested in the ideal of aerial lift without a powder charge as I read the Air-Lifting subject in the Cannon forum article. I seen that it was not carried very far to a possible end. Hence, this became my cue as to see if I could add something of value to the forum.

The ideal that springs to mind would be the use of a piston.

They say a picture is worth a thousand words, sooo I'm figuring this should be about 14,000 of them.

The areas to address will be building a device to aid in launching, igniting and the safe return of a re-useable launch piston.

Shell building, fusing and priming will not be included unless there is something new to add to these areas that needs to be refined for this project.

 

"I've been surprised by the odd insert case hitting me on the firing site but I do NOT want to feel an AA cell (0.5 cal?) battery/bullet descending from 1000 feet."

Safety first:

Arthur carried a good point about falling rubbish in that article. It is something that is included in most fireworks that are fired skyward. Care should be taken to reduce possible strikes whether it concerns person or property.

So as it goes for the falling batteries, which are placed inside of one of the a piston's halves, which in turn is a falling object we should therefore include a parachute to slow the return to earth. Seeing the drawing of the two halves of the piston hanging from the parachute in the first set of drawings is petty much self explanatory. If someone was to need more information, most rocket sites can explain the process in better detail. So I will not be touching that subject very much as well.

 

Piston

Starting with one of the piston halves, slide into the other it should fit loosely. Both sleeves of that same piston have their outer ends covered. The diameter and height will have to be determined by the individual that is building one of these for his Air-Cannon. It should be as light as you can build to help reduce needed energy to propel the shell to height. Weight also will allow more height to be gained by the piston itself when launched. This is something that we may not want. What we want is for it to be robust enough that it will survive repeated launchings. And easy enough to quickly reset for another firing.

To make the piston roll a newspaper to to inside diameter you want of the smaller of the two piston sleeves. Roll on the outside of this a layer of wax paper, tape it down. Next roll a strip of paper just like making any tube with paste, to the height of the piston until you reach the thickness needed, leave to dry. Then after it is dry make one or two wraps of wax paper over this tube. Once this is done roll the outside piston to size with your paper. Once more you need to let it dry completely. That will make two tubes capable of freely sliding into each other. Remove from the form and trim to size.

To make the curved socket fitting you could use half of a hemi that is a larger size of the shells being used or even lay one up out of paste and paper. The bottom end plate should be heavy enough to withstand the air pressure. Attach the end cover plates to finish the piston sleeves.

Ignition Chamber

In the upper half of the piston sleeve inside the cup is a receiving hole, that must be large enough for the fuse to slide into and out of the ignition tube easily without hanging-up. The tube that the fuse needs to slide into is located inside the ignition chamber, which is located in the bottom half piston sleeve.

The bottom piston sleeve should be well made with a hole that is off centered from ignition chamber in the end plate. The purpose of the hole is to provide air pressure into the switch housing. This switch has to be custom built for use in the the housing. (I do not believe that it will be that hard to do).

The ignition chamber should be glued in well, as well as sealed with the exception of the fuse entry area at the mouth on top it well also be the point of exit for the four strings that will be use to secure everything (shell,upper and lower piston sleeves). See the drawing above and the one below.

The piston and the shell are not to separate until the fuse has been lighted and the complete shell with piston has cleared the mouth of the Air-Cannon. When looking at the drawing above it shows the location of things.

More Safety

One of items shown is an optional (as in if you wish to add) dis-carded music device, the type that is found in musical cards and the likes. Make a card board sleeve for it and glue it in a out of the way spot in the bottom piston sleeve. Its purpose is to make a sound so that when loading the shell if the switch fires, igniting the fuse you have time to prepare and move to safety. I would think that the loudest one you can get would be of help. The second point of the music device is to help locate it in the dark. Speaking of locating the piston in the dark - it should help if it is painted with glow-in the dark paint or even place a small LED circuit inside.

 

Igniter

Okay, now we come to the Igniter. It is the Christmas Bulb type with the leads as long as needed to work with. The filling charge for priming is black powder or users choice.

The Igniter unit slides into the casing in the bottom piston sleeve, and is held in place by fiction only. This way it is easily removed after use and replace with a new one.

The electrical connection is just J hooking the two wires together so they pull on each other, then tape them with masking tape and aluminum foil insert. Cut the tape and foil to size then lay the foil in the middle of the tape.

Fold the tape over and do the same for the other one. Now place one of the taped connection on top of the other and use a paper clip to secure the wires this also helps make a better contact. You will want to be sure that the bare wires are well covered by the tape so there is no short.

 

Pressure/G-Switch

Remember earlier I wrote about building a simple switch, well here it is.

This is design to act like a pressure switch when the release of air moves the batteries up to make contact, or act a G-switch from the forces of launching. So if one does not work the other is to increase the odds and make the needed contact connection.

Using some of those 1.5 volt hearing aide batteries, take one of them and solder a contact to the bottom of it. Then press two batteries into a single unit. Use black electrical tape (the smooth plastic kind) and wrap the batteries until they fit loosely in the switch housing tube. Remember to leave some extra wiring for movement as this will act as a piston. Place the battery unit into the switch housing check for a 3/16 movement then glue the end plug. Be sure to check for the movement.

For the other contact end, use a piece of copper wire or rod about 1/8 or 3/16 of an inch in diameter and about 3/4 of an inch long. Solder the wire at one end, laying both so they are going in the same direction. When cooled wrap with paper about half of the length of the contact rod until it is about to fit as the batteries did. Finish the outside wrap with black plastic electrical tape for an nice sliding action without binding.

Make note not to stretch the tape when using it. What will happen is the tape will retract and leave a sticky area where it was at.

Before the final fitting insert a spring of the proper tension or use a foam core, slipping the contact right behind it and gluing an end piece in place. Remember to leave some extra wiring for movement as this will act as a piston.

When using the foam be sure to punch a hole through the center for the contact to fit though.

Just pushing a shell and piston into the launch tube should not be able to fire the igniter if it does increase tension in the spring with a few spacers and what have you.

One other thing use a push rod to push the shell into the launcher hold it lightly in your hand as you seat the shell and piston.

 

Tying It All Up

When placing the piston together be sure to thread two string though the igniter unit place the igniter in the bottom up to the string, and friction fit into the tube that holds it in place. Connect the wire in the bottom piston half. If using a parachute pack it into place, protect from the igniter blast with wadding.

Slide the top half into place followed by the shell with the fuse going into the receiving hole in the tube that is holding the igniter. The fuse should be pre-primed with BP slurry and ready to go. Seat the shell fully into the cup on the top piston, using the light sewing string wrap up around to the top and tie. A drop of glue will hold it in place.

All that the sewing string is doing is holding the piston halves together and the shell on top in place. It is not robust enough for rough handling.

When the igniter lights it will burn the sewing string into, letting the piston fall from the shell. At the time of release the piston should fall apart letting the parachute out to inflate to full size and return to earth.

(Well, in theory it does, anyway!)

[TheSidewinder]

I helped this member post this information, and a quick read intrigued me.

 

Although it looks feasible, I don't have the time or facilities to test this.

 

Members are welcome to do so, and add any observations that may have.

[NightHawkInLight]

That there is a post! Ha actually, sorry but I didn't have the time to read more than half of it. One challenge to overcome so far as I can tell is how to keep the parachute from being destroyed by stars. It would need to be reusable if this idea were to be practical.

 

Though the musical card device is a good idea for safety, I also am imagining 1,000 of them raining down annoying the county . I suppose the humor in that moment might be worth the annoyance...

[Arthur]

I can see that it is possible to do air launch, but if you have to use a complex sabot arrangement then there is actually more litter in the field, and it is complex litter! The concept of making a shell with a delay fuse and a socket for fitting an igniter is interesting. However air lift is good for installation shows but not for one night stands -which is the majority of the fireworks business.

[firetech]

Cool idea. But why?

[patsroom]

Cool idea. But why?

 

 

I am glad to see that some have posted with questions and with their inputs so soon.

 

To answer "why?" There was an artical in the cannon forum with a last posted date of 16 Sep.08 about using a spud gun type launcher. The best answer why is - I became interested in the semi-finish fashion of that forum as they had not found any real solution.

 

This is not a sabot that re-sizes the cal. of the shell being lifted, what it does is push from the bottom of the shell by use of a piston.

 

And for the parachute being damage I think the piston will open up quite soon after leaving the tube and with so much drag that it should not gain enought height as to be in danger of the stars.

I thank all of you for your replies. 8)

Edited September 17, 2009 by patsroom

[Arthur]

While an air lifted shell may save on lift charge it does mean that every mortar needs a large and expensive solenoid valve and a supply of compressed air from a big reservior able to supply a big pulse instantly.

 

If every mortar needs a solenoid valve at say $100 there has to be a very important saving somewhere else. Plus if each tube has a valve that's a lot of extra racking to protect all the critical valves.

 

As there is a massive saving of explosive content so a reduction in NEQ so an easing of transport regs, there must be a reason why air lifting is not common place! I suspect that the increased cost and complexity of the mortars and racks is one good reason.

[TheSidewinder]

While this may not be practical on a scale other than "small", I thought the idea was intriguing. And it DOES look to be possible.

 

Litter would be non-existent, PROVIDED you clean up after yourself.

 

It's a lesson in theory, rather than practical application. But if anyone ever does tackle this, I'd love to see the results!

[Arthur]

The idea is very valid for fixed instalations where you can have a compressor and several receivers and lots of fixed piping and valves. Disney with 365 + shows a year is a prime example. Occasionaly a show needs shells launched when there isn't cover for the lift noise so air lift may help there.

 

However in reality Disney do not exclusively use air lift and AFAIK no-one else uses air lift or has the racks.

 

As a reality check a 3" pro use GRP tube in the UK is about £3, Add a solenoid valve and the tube itself goes up to about £50, and you need 500 of them to make a show!

[patsroom]

I hope this will show that the ideal does have its supporters

5339741_Precision_fireworks_display_syst.pdf

Edited January 10, 2010 by patsroom

[dagabu]

I hope this well show that the ideal does have its supporters

 

I was going to say...

 

I was watching a Discovery Channel show about Disney world fire works and it got me thinking so I called my son that lives close to the Orlando park and asked him to look into it. He told me that a lot of their guns are air powered so that only the break is heard.

 

I have no way of checking the validity of thei claim but the patent is for Disney so it may very well be so.

[patsroom]

You will find most of my post for a while to be short, and that they will be accompanied by a pdf. But I will check in from time to time.

The_Brain........._I_know_Pinkie_its__a_big_Place..........pdf