Pneumatic Antenna Launching Systems
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What is Pneumatic Antenna Launching?
Pneumatically Powered (Tennis Ball) Antenna Launching. Pneumatic Line launching is perhaps a more apt description. First we need a line in the trees, then we can pull up an antenna, which in most cases is a long piece of wire. In the launcher pictured above a Tennis Ball is propelled by compressed air, towing a fishing line over the tree. Then we pull up nylon mason twine with the fishline, and finally a wire or heavier line as needed.
Why does anyone need to Launch an Antenna?
It is often more convenient to use existing trees than to erect supports for wire or beam antennas, especially when these antennas are required for temporary or emergency field use. We set up antennas for disasters and drills, camping and contests, practice and fun. With all the applications for Homeland Security there are many potential uses for rapid deplyment. If you have a need to quickly set up antennas in various field situations, or you have some really nice trees in your backyard, you may have a use for Antenna Line Launching.
What is a Pneumatic Antenna Launcher?
It is a very simple system that uses the energy in a pressurized volume of gas (generally air), a valve to release the gas, and a projectile (tennis ball) in a tube that is accelerated by the expanding gas giving it the requisite velocity to pull a light line over the tree.
Why not use a ... (Slingshot, Bow, Rock, Water Bottle, ...)?
We have used many different systems since the 70's to put lines up into trees. Each system has advantages and disadvantages. Throwing an object over a limb is the easiest, but will not reach very high, and there is a significant chance of getting the object stuck. Slingshots reach higher, and Bows reach higher yet. The main problem with all these systems is the projectile. A lead sinker, arrow or crescent wrench can do a lot of damage if it lands in the wrong place. If you are putting a line over a tree in your yard, there are often local ordinances against using slingshots and bows. What is needed is a really safe projectile, and a means for getting it over the tree precisely for maximum safety and effectiveness. If you have a really tall tree, then a Tennis Ball Launcher will allow you to go higher than most slingshots or bows. Even a small Pneumatic Tennis Ball launcher can reach up more than 150 feet, and it is possible to go much higher with the more effective models.
My slingshot/bow works fine, why consider a Pneumatic Launcher?
You might consider a Pneumatic Launcher if you are interested in more Performance or greater Safety. Slingshots and Bows work, but Pneumatics work better. Eric's big launcher can put a tennis ball up over 600 feet high (with no line). The small CSV19 reaches up to 200 feet towing line, and the dimunitive CSV17 goes up more than 150 feet towing line. These launchers are 19 and 17 inches long, respectively, and the heights are measured length of line pulled out. Add about 10 feet to those numbers to get the true height, since the reel is about 10 feet off the ground when launching upwards. You can make launchers go higher, and we have, but the availability of trees that tall and feedlines that long makes it rarely useful. So we scaled the pneumatics back to the smaller sizes. Also be very careful with the slingshot and bow, there are many injuries each year, especially with the slingshots.
If you are going to put up an antenna in the backyard the tennis ball is a lot safer than a lead sinker, and much easier to explain to your neighbor.
Why use a Tennis Ball?
There are three primary reasons to use Tennis Balls: Safety, Safety and finally, Safety. I have read of so many accidents with slingshots each year that I cannot recommend them. A lead sinker flying through the air is potentially an accident waiting to happen. They bounce off the tree, the line snags and the sinker returns on the line rebound, or they get hung up and come sizzling down when the line is pulled, potentially at higher velocity than even the slingshot can impart. The slingshot is not the problem, the projectile is the problem!
A Tennis ball is inherently a fairly safe projectile. They are big so they slow down quickly, limiting the distance they will travel and the velocity they impact with. They are not hard, so they tend to do little damage when they land. It is something familiar so people know what to expect. It is big enough to see fairly well. They are available and inexpensive.
How High will these Launchers reach?
150 to 200 feet of height is easily attained with a Pneumatic Tennis Ball Antenna Launcher while towing a 50 pound test fishing line. It is possible to go much higher with the more efficient or larger launchers, but we have not found suitable antenna trees much over 130 feet tall. So we consider 150 feet to be about optimal.
Are these Launchers Dangerous?
If you've played or watched tennis you know that the serve is (usually) one of the harder hit strokes in tennis. Well, a good serve has more velocity than is required for launching a tennis ball over most tall trees. The ball slows down quickly, and on the far side of the tree (towing the fishing line) it comes down very slowly.
The simplest material for building an Antenna Launcher is Schedule 40 pressure rated PVC. This material is designed for working pressures in excess of 200 pounds per square inch, and the pressures we use are up to 60 or 80 psi. So while the pressures are within design parameters, the manufacturers of PVC pipe and fittings RECOMMEND AGAINST its use with COMPRESSED AIR. If PVC containing compressed air is fractured, it may result in high velocity PVC shrapnel. So avoid breaking it while it is pressurized, and wear safety glasses when using launchers or any power tool. Low and high temperatures make PVC brittle or soft so launchers should not be used in extreme temperatures.
Are these Launchers Regulated? Aren't they Illegal??
The US Federal BATF (Bureau of Alcohol, Tobacco and Firearms) has ruled that pneumatic launchers are NOT Firearms. Some Municipalities have regulations that may affect the use or ownership of Launchers. Such rules are not common, and the ones that do exist usually focus on combustion type launchers rather than pneumatics. Check with the local authorities to be sure. Note that slingshots and bows are generally illegal to use in residential areas, parks, campgrounds, etc.
How much does a Pneumatic Antenna Launcher cost?
The materials for a launcher cost between anywhere from about $60 on up, plus a fishing reel, some line and a few tennis balls. If you have leftover parts from a lawn sprinkler project it may be much less... Launcher Kits are available for under $100.
How hard is it to build a Launcher?
It depends on the model, and it ranges from fairly simple to quite complex. If you can cut and glue PVC and thread pipe fittings together you can build the simple models. Some require drilling and tapping a hole or two in the plastic, some need a little soldering. Kits are available for some models, so the hard parts are already done. The time required varies from a few hours on up. The more complex designs may require a friend with a lathe to machine some PVC. Generally speaking, as size/weight/cost go up, so does performance. A low performance design might require 80 psi to launch 150 feet high, whereas a higher performance design might do the same job at 25 psi. Choose a design that matches your construction ability, budget and size requirements, and the trees you need to launch over.
What kind of Pneumatic Antenna Launcher should I build?
Eric (WD6CMU) and I (Alan WB6ZQZ) have been experimenting with Tennis Ball Launchers since 2002. We have built nearly a dozen different models, and I have written software that analyzes and predicts performance. A couple had insufficient performance, and some others had excess performance. (Excess performance is not always a problem as it does allow operating at lower pressures, but it may mean that the Launcher is larger and heavier than it needs to be.) We seem to be settling on about sixteen inches of barrel length, a 1" sprinkler or 3/4" pneumatic valve, and approximately 60 to 100 cubic inches of air storage. This produces a launcher that weighs in the neighborhood of five to seven pounds, and produces sufficient performance at about 40 to 60 psi for most launches. The barrel material is 2.5" schedule 40 PVC, into which a tennis ball fits very snugly, or 2.5" SDR21 PVC into which they fit nearly perfectly.
To get specific I will mention some of our models.
The CSV19 and its smaller sibling the CSV17 are fairly simple to build, and are available in kit form. This may be the best compromise and we provide the most detailed information on building this unit, as well as partial and full kits of prepared parts.
The U37 and DU36 U valve models are simple to build but are a bit larger than some of the newer designs. The original QRP Quarterly article describes building the first (electric) version of this model (U37) in some detail and the pdf is available. It was designed to fit between the wheel wells of a Toyota 4Runner and is 37" long. I later modified this to pneumatic triggering and it became the DU36. It will not fit in the Rubbermaid(tm) tote boxes that we use for our newer designs. I don't recommend these launchers for antenna work - they are too large and look like a bazooka..
The Field Day 2003 Special is not hard to build and does not require exotic tools. It is a bit larger and heavier and more expensive than the newer smaller models. There are some pictures and info here for the Field Day 2003 Special. It also will not fit in the Rubbermaid tote due to the overall length. I no longer recommend this launcher due to the large size.
The QE19 Quick Exhaust Valve design is the simplest to build and is fairly lightweight and small but requires a bit more air pressure to operate. The 3/4" Quick Exhaust valve limits the airflow somewhat, but it does reach up to 150 feet of height at 70 psi, and it can safely take 100 psi. Due to all the brass parts the cost is somewhat higher as well, but there is no need to bore, drill or tap PVC so construction is straightforward and few tools are required. This is a good choice for simplicity of construction.
Eric's Trident design utilizing the soda bottle pressure chamber is the lightest but has some difficult to make threads, and the pressure needs to be kept low to protect the chamber.
The DV19 Dual Valve is complicated to build but does not require exotic tools. It has very high performance. Due to the high parts count the cost is on the high side and the weight is high also. It still fits in the Rubbermaid tote, but nearly fills it up. The high performance allows reaching tall heights at low air pressures. I do not provide detailed instructions on building it, but there are several photos in the Tale of Two Launchers page. This launcher is heavy, complicated and expensive, and more than necessary for antenna work.
The DFTV19 Turbo Valve requires a lathe to make the parts. It also provides very high performance. Due to the custom made parts the weight is quite low and the cost is low but the effort required is high. It is more than required for antenna work.
The Spud Tech TB500LP is a commercially available launcher. It is a bit larger and heavier than our current models but should do the antenna launching job well.
The PADS17 Pneumatic Antenna Deployment System
What is a Pneumatic Antenna Deployment System?
This is the name for the Launcher-in-a-Suitcase shown above. This scaled-down launcher fits nicely into this hard case. The launcher and hard case are available on the order page. Also shown are a pair of Twine Reels containing 500 feet of nylon twine. They are available in 270 foot lengths as well. The grey cylinder near the bottom center of the photo is a bicycle type CO2 tire inflator. It can be used with a number of different capacity CO2 cylinders. Using the low-cost 12 gram cylinders produces enough pressure for one good launch per cylinder. Also in this case, but not visible is a 12 oz Paintball CO2 cylinder stored inside the barrel, along with two tennis balls. The CO2 pressure regulator is behind the right end of the ramrod. There are a total of six tennis balls in this photo, two hidden in the barrel and one hidden inside the reel on the lower left. The reel on the lower left is a prototype we are working on. It may be available later if it meets our requirements. Just behind the launcher's trigger is a bag of 12 gram CO2 cylinders. See the PADS Web Page.
What about a Ball-valve type launcher?
The simplest pneumatic launcher is a pressure storage chamber, a barrel, and a ball valve in between. These are not particularly suitable for antenna launching because the performance is dependent on how quickly the valve is opened. Additionally, opening the valve manually disturbs the aim, so it will be difficult to make it go where desired.
What about a Combustion powered launcher?
Combustion type launchers (also called potato cannons) use lighter fluid, spray deoderant, propane or some other fuel in a closed pipe chamber behind a projectile with an ignition source to trigger it. In addition to some safety concerns, combusion launchers may produce somewhat inconsistent shot-to-shot performance, which makes them difficult to use as a serious Antenna Launching tool. They also misfire occasionally and are more often regulated than pneumatic systems. Let's not use them for Antennas!
How Small and Light can an Effective Pneumatic Antenna Launcher be?
First, I'll define 'effective' as any launcher that can toss a 4 ounce tennis ball to a height of at least 150 feet towing a fishing line. That is pretty adequate for our purposes.
The smallest launchers that meet this criterion that we have built are the Compact Low Cost Sprinkler Valve Antenna Launcher and the Quick Exhaust Valve Launcher. At about six pounds, these are small enough to fit into a Rubbermaid tote box, or less than 19 inches in length. There is plenty of room left in the tote box for line, antennas, feedline, and other equipment.
The CSV19 Compact Low Cost Sprinkler Valve Antenna Launcher is assembled from plumbing parts most of which are available from local plumbing or home improvement stores for under $100. Some machining is required to make them fit together as shown above. The dark grey barrel is SDR21. Schedule 40 also works, but the ball is very tight. SDR21 fits better but is harder to find. This is the lowest cost simple to construct launcher I have designed. The link above has fairly complete construction instructions. The collection shown above is shown complete with Saunders Zip Reel with yellow Spectra type synthetic line, and a couple of prepared Tennis Balls sitting on a Rubbermaid 10 gallon tote. The gear fits into the tote with plenty of room to spare.
QE19 Photo
The QE19 Quick Exhaust Valve Launcher is the smallest and lightest of my launchers. It is based on an industrial quick-exhaust air valve (the silver item above). This is the easiest launcher to build, but due to the industrial and brass parts costs somewhat more than the model above, about $100. The link above has construction information. This launcher is sitting on top of one of the Rubbermaid (tm) 10 gallon tote boxes that I use to carry equipment to field. There is room for lots of gear in there in addition to the launcher.
The lightest launcher we've done to date for Tennis Ball Antenna Line Launching is Eric's Trident which uses soda bottles for the air pressure reservoir and weighs a litte less than five pounds. Eric also came up with a nice mount for an archery fishing line reel that fits around the barrel and feeds line very smoothly. Check out Eric's website at www.qsl.net/wd6cmu for his Saunder's Zip-reel mount and Trident Launcher.
The Launcher on the left is the Quick Exhaust model, here shown in the 28 inch configuration with a spinning reel mounted just below the forward end of the barrel (hard to see against the foliage in this photo). This photo was taken before it was shortened to the 19" version shown above. The two launchers in the photo were used on Field Day 2003 to put up numerous antennas. Field Day is an Amateur Radio 'Emergency Drill' essentially, setting up and operating in field conditions for a couple of days. It is a lot of fun and a good test of our equipment and technique, both radio and Antenna Launching.
More Pneumatic Antenna Launcher Examples
High Performance in a compact package: DV19
This model packs a pair of one inch sprinkler valves in to a Rubbermaid sized tote package. It doesn't take much pressure for this unit to reach 150 feet of height! Building this is quite a challenge with all the plumbing parts packed in tight. There are the two 1" sprinkler valves, a quick exhaust valve trigger, two check valves, a paddle trigger valve, and some specially adapted (shortened) PVC fittings. It was made with fairly minimal tools - a drill press and a belt sander, plus a radial arm saw. None of these tools are absolutely required - this design can be made with hand tools. It is a bit heavy, around 10 pounds. As shown below it includes the Saunders Zip Reel and a removable barrel extension that improves the efficiency of the launcher. For more info on this launcher see A Tale of Two (Compact) Launchers.
DV19 Photo
Ultra Performance in a Compact Package: DFTV19
This six pound model packs a tremendous capability in a very lightweight package. It fits in the Rubbermaid containers as well. The Darn Fast Turbo Valve is a 1.2" ported homemade piston valve with a self-venting and turbo actuation features that make it low cost, light weight, and incredibly effective. The only disadvantage to this design is the requirement for precision machined parts in the valve. I purchased a small lathe (www.Grizzly.com) and made them with no prior machine shop experience, so it isn't all that hard. More info is available in the The DFTV Story.
DFTV19 Photo
More Examples can be found via links in the "More Information" section below.
How is Launch Pressure developed?
The pressures and volumes involved are similar to a bicycle tire, so automotive or bicycle air pumps are just about right. The portable 12 volt electric ones are great. They run from a car battery or are even more portable with a Gel Cell. Hand or foot pumps work well also, and have the benefit of a good aerobic workout. Some folks use CO2 systems which are very convenient at greater cost. I recently have been testing two CO2 systems - a Paintball cylinder and regulator, and a Bicycle tire filler using 12 gram cylinders. CO2 systems cost a bit more to own and operate, but they are pretty amazingly effective and fast.
I tested a 6 gallon compressed air tank recently and starting with 100 to 110 psi was able to get about 15 shots at 50 psi from it with the CSV19 launcher. The smaller chambers on the CSV17 and QE19 would get even more launches per fill.
Here is a portable battery powered filling station similar to the one I have. This has become a favorite for charging the launcher. It takes about one minute. Mine has a 12 volt 17 amp gel battery and a compressor and was under 50 bucks at Harbor Freight tools. After you launch the antenna you can hook up to the 12 volt gel battery and run the station!
Jumpstart Box Photo
Detailed Antenna Launcher Construction Articles
The Compact Sprinkler Valve and Quick Exhaust Valve models have fairly construction details on their web pages. I wrote a complete construction article on the TBL-U37 pictured above (lead-in photo and electric actuated above). It was published in the QRP Quarterly magazine, Spring 2003. A pdf version is available here. Note that changing to pneumatic actuation makes a large performance improvement in this launcher. A similar launcher that has good performance is the Field Day Special. Information on this model is available on the Modelling page.
Can I buy an Antenna Launcher already built?
Joel has a premier website and builds launchers: The SpudGun Technology Center. He sells components and complete units. Look under his "Launchers, Low Power Pneumatic" links. His TBL500LP with a 24" barrel and 12" by 3" chamber is about the right performance level and size. (Disclaimer - I have not used any of his launchers.)
We can also build launchers, see the order page for details.
Recent Progress
I am still working on a Compact Coaxial valve launcher. This project started quite some time ago but has been building steam and most of the parts are made. I still am working out a few kinks before final assembly but that should begin soon. The flow of this valve is six times the flow of a 1" sprinkler valve, so the performance should be impressive. I don't expect this launcher to be easy to reproduce due to all the components and machining required. It will show us what can be accomplished in a small overall length package. (note this work is again on hold. 5/05)
CSV19 Kits - I have Kits for the CSV19 launcher to help you get a quality Antenna Launcher going with less effort and fewer tools.
The Mini CO2 Charging System is working quite well. I have been using 12 oz paintball CO2 cylinders with it, and getting lots of launches (approx 20) from one $3 fillup. It gets a bit cold if it is used in cool weather, but it has not been a problem at the low rate of launches that we usually need. This is certainly not a required Antenna Launching accessory but it is extremely convenient. Several tests conducted have not found much difference in height between CO2 and air at the same pressure. We have added this to our new Online Order Form.
The Berkeley Gorilla line has been reaching about 20% higher height than the previous Dacron twisted kite line. I suspect that the lines work best when new, and as they get a bit fuzzy the height is reduced due to drag. I got 35 pound test Gorilla Line at Wallmart, but next time I think I will follow Eric's lead and get the 50 pound test variety.
11/04: Finally found SDR21 barrel material! It is thinner, lighter and rated to 200 psi instead of the 300 psi that 2.5" schedule 40 is rated for. It weighs about a half pound less in a 16" length, so it will be noticeably lighter than the schedule 40. Eric did some testing and it helped the launch height at low pressure but made no difference above 100 feet or so. Drop me an email me if you are interested in some 2.5" SDR21.
I have really been enjoying the CO2 system. I get about 30 shots from a 12 ounce paintball bottle. That is more than we used on Field Day this year, and we put up a lot of antennas.
7/04: How would you like to pressurize your launcher in 5 seconds with a several pound 'charger' that you can carry around with you or even mount to the launcher? I'm working on a couple of different systems for this, all based on CO2. The key to this is two things - refillable paintball CO2 cylinders and a top quality pressure regulator. Since CO2 is around 800 psi we need a pressure regulator for safety and practicality. The Low Pressure (0-300 psi) version of the Palmer Pursuit Female Stabilizer is designed to mount directly on the paintball bottle screw threads and regulate the pressure. It is available in a number of configurations, the most convenient of which has a schrader tire filler valve directly mounted. This is plug and play CO2! You order the 'tire stabilizer'regulator and one or more bottles from Palmer Pursuit, take the bottles to the local paintball CO2 filling station to get it filled, screw on the regulator and start filling your launcher. The small launchers we are using currently get about 2 to 5 launches per ounce of CO2, so a 12 ounce CO2 bottle will give you about 25 to 60 launches. You can get up to 20 or even 24 ounce bottles for more capacity, and of course can have several bottles on hand. I selected the 12 ounce as a good compromise between size, weight and capacity, though the the 20 ounce was very tempting as well. The 8 or 9 ounce bottles are really convient and small, so you have to decide! The cost for CO2 around my area comes to about ten cents per launch. I'm still going to use a compressor for my megalaunching testing sessions, but when doing actual field antenna work it is quite inconvenient to have to trudge back to the compressor each time. It is also safer to pressurize right at the time of the launch, and minor leaks are not so much of an issue. In addition, the whole launching system, including the CO2 system will fit into the Rubbermaid tote along with the launcher.
6/04: My Turbo Valve launcher is leaking again. Based on this, I can't really recommend using cyanoacrylate with PVC. It seems to get a good joint, but fails later. I had only used the CA to seal some leaks, but it failed even to do this on a reliable basis. My first repair of the repair with epoxy has been 85% effective. I think I will have to set up to use vacuum to draw the cement into the cracks for a better result.
Field Day 2004 was a great workout for the launchers. We used three of my launchers and Eric's Trident (but using only one bottle) and put up two HF beams, a 40 meter sloper and a multiband inverted Vee. Eric's CO2 system worked well. My little compressor took longer and made more noise. Have to check into a CO2 upgrade... We shot some video and are deciding what to put on the websites...
The Dacron kite line seems to grab too much air and have too much friction on the tree. I'm going to look into the higher tech fishing/kite lines as they do seem to perform better.
Where can I get More Information about Pneumatic Antenna Launchers?
There is a lot more info on the web. Most of it is not directly Antenna Launching related, but much can be learned there that is applicable. If you find the information on this website useful and have a website of your own, please include a link to this page to help others find it. If you have related information and want a link here on my page drop me an email!
- The Rest of the Story (Antenna Launching)
- Visit the Antenna Launching Discussion List
- Join the Antenna Launching Discussion List
- Constructing a Compact Low Cost Sprinkler Valve Antenna Launcher
- The Pneumatic Antenna Deployment System
- A Tale of Two (Compact) Launchers
- Constructing a Compact Quick Exhaust Valve Antenna Launcher
- The Darn Fast Turbo Valve Antenna Launcher
- Launcher Performance Data (Measured)
- my original Antenna Launcher Article (QRP Quarterly Spring 2003)
- Pneumatic Launcher Calculations
- Eric's Launchers and Reel System
- Eric's Trident Launcher
- Joel's SpudGun Technology Center has a wealth of info, parts, and complete units for sale
- Mark's Antenna Launcher
- Other Launcher Construction Websites (Not necessarily Antenna oriented)
- Advanced Spuds
Or Search the Web:
The following links perform Google web searches with various arguments that produce lots of hits for this topic.
Compressed Air Cannon
Tennis Ball Launcher
Tennis Ball Cannon
Pneumatic Cannon
Spud Gun
Spudgun
Spudgun technology
Spudlaunch
Backyard ballistics
Aircannon
CategoryAntennaLaunching
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