Compressed-air powered nets help

[Chris Snook-3]

Has anyone on this list any experience with building/using compressed
air-powered cannon nets?

I am trying to build a couple of compressed-air powered cannons for a
small scale cannon net ( 6 m x 3 m, weight 800 g ) and have some questions.

1. What typical air pressures are used?
2. What size and weight of projectiles are used for what net size?

Any help will be appreciated.

Chris Snook,
Charleston, SC

subscription options and posting rules can be found at the BirdBand web site:
http://www.geocities.com/RainForest/6549/birdband.htm

[Michael Lancaster]

For a net as small as this an elasticised system will suffice. The
trajectory is however not very high and needs to be adjusted by stretching
the elastic over a pole to give initial lift.  We were catching small
passerines.

I think BTO (UK) have designs. I was involved with one of these several
years ago and it worked fine and was much larger than your proposed net. I
cannot remember details I am afraid.

Barry
M B Lancaster
Currently, Addlestone UK
----- Original Message -----
From: "Chris Snook" <snook_c@...>
To: <BIRDBAND@...>
Sent: Wednesday, November 11, 2009 5:53 PM
Subject: [BIRDBAND] Compressed-air powered nets help

> Has anyone on this list any experience with building/using compressed
> air-powered cannon nets?
>
> I am trying to build a couple of compressed-air powered cannons for a
> small scale cannon net ( 6 m x 3 m, weight 800 g ) and have some
> questions.
>
> 1. What typical air pressures are used?
> 2. What size and weight of projectiles are used for what net size?
>
> Any help will be appreciated.
>
> Chris Snook,
> Charleston, SC
>
> subscription options and posting rules can be found at the BirdBand web
> site:
> http://www.geocities.com/RainForest/6549/birdband.htm 

subscription options and posting rules can be found at the BirdBand web site:
http://www.geocities.com/RainForest/6549/birdband.htm

[Phil Prosser-2]

Compressed-air powered nets have also been called "phut" nets (from the
sound they make); this might help your research.

But elastic power is probably simpler and better for a net of the sort
of size you're proposing.  We've used an elastic-powered "whoosh" net
(also onomatopoeically named) up to 5 by 15 metres, powered by four
elastics to catch Anser geese.  We've also routinely used smaller ones
to catch passerines - they can be set to fire VERY fast indeed.  I have
a document with some technical details which I'll send you off-list if
you like.

--
----------------------------------------------------------------------
Dr Phil Prosser
Wildlife Ecotoxicologist
The Food and Environment Research Agency
Sand Hutton, York YO41 1LZ

subscription options and posting rules can be found at the BirdBand web site:
http://www.geocities.com/RainForest/6549/birdband.htm

[Jack Clinton Eitniear]

An elastic powered net used to capture caracara was detailed in an article published in the Journal of Field Ornithology a number of years ago. A search of articles in that journal might be fruitful.

Jack Eitniear
CSTB inc.
"We will be known forever by the tracks we leave" Dakota Indian Saying


--- On Thu, 11/12/09, Phil Prosser <phil.prosser@...> wrote:

> From: Phil Prosser <phil.prosser@...>
> Subject: Re: [BIRDBAND] Compressed-air powered nets help
> To: BIRDBAND@...
> Date: Thursday, November 12, 2009, 6:13 AM
> Compressed-air powered nets have also
> been called "phut" nets (from the sound they make); this
> might help your research.
>
> But elastic power is probably simpler and better for a net
> of the sort of size you're proposing.  We've used an
> elastic-powered "whoosh" net (also onomatopoeically named)
> up to 5 by 15 metres, powered by four elastics to catch
> Anser geese.  We've also routinely used smaller ones to
> catch passerines - they can be set to fire VERY fast
> indeed.  I have a document with some technical details
> which I'll send you off-list if you like.
>
> --
> ----------------------------------------------------------------------
> Dr Phil Prosser
> Wildlife Ecotoxicologist
> The Food and Environment Research Agency
> Sand Hutton, York YO41 1LZ
>
> subscription options and posting rules can be found at the
> BirdBand web site:
> http://www.geocities.com/RainForest/6549/birdband.htm
>

subscription options and posting rules can be found at the BirdBand web site:
http://www.geocities.com/RainForest/6549/birdband.htm

[bom]

Hi Chris

Lyndon Kearsley was collecting a lot of details on this type of net a
few years ago. Perhaps he would be a good source of information.
Regards

barry


Chris Snook wrote:

> Has anyone on this list any experience with building/using compressed
> air-powered cannon nets?
>
> I am trying to build a couple of compressed-air powered cannons for a
> small scale cannon net ( 6 m x 3 m, weight 800 g ) and have some questions.
>
> 1. What typical air pressures are used?
> 2. What size and weight of projectiles are used for what net size?
>
> Any help will be appreciated.
>
> Chris Snook,
> Charleston, SC
>
> subscription options and posting rules can be found at the BirdBand web
> site:
> http://www.geocities.com/RainForest/6549/birdband.htm
>

--
Barry O'Mahony
Cork, Ireland

subscription options and posting rules can be found at the BirdBand web site:
http://www.geocities.com/RainForest/6549/birdband.htm

[Wes Halton]

Hi

About 15 years ago along with an engineering colleague of mine we developed a
prototype compressed air net that was showing some promise but we had problems
with the valves remaining airtight when in use in the field.  

I cannot remember the exact measurements and weights but the net we had was of a
similar size to the one you are using possible a little larger.

Anyway some vague details you may find interesting.

The air reservoir was approx 1.75 litres and the air pressure was  over 180  and often
up to  220 psi.

The missile and launch tube were made of plastic kitchen waste pipe which over here
in the UK is sold in 2 sizes  1.25" and 1.5" od. The smaller size fits snugly inside the
larger one. Our missile was the outer tube, ie it fitted OVER the barrel not inside it
like cannon nets.

 The release valve was a simple 1" diameter ball valve which was spring loaded so
that it would remain open until it was connected to a solenoid release mechanism  
which would hold the valve closed until the solenoids were switched to "fire"

The missile was approx 15" long and had a metal nose cone of approx 4oz weight ( I
think!)  at the tail end of the missile we used some rubber inner tube off a cycle that
would form a seal between the two different sizes of tube being used. In practice this
did not seem to be necessary !

The first time we fired the system there was an almighty "POP" as the missile was
launched and since we knew the missile velocity would be slower than usual cannon
nets we decided we needed to muffle that somehow as it would scare birds before the
net had settled. After trying several methods we tried filling the launch tube with
water (just the tube not the air reservoir !)We then did a test fire and scared ourselves
to death !  The velocity of the missile was greatly increased maybe 5 or more times
more powerful,  In fact firing a missile untethered it would easily travel over 150
metres, in addition the exhaust noise was almost negligible

My friend had a really thick hawthorn hedge at the bottom of his garden, some 20
yards from our test launching pad (really a picnic table). We  fired tethered missiles
for safety purposes and after a few days we had all but obliterated a section of the  
hedge .  We were firing the missiles like kids with a new toy! Our method for testing
different barrel lengths, missile weights etc was rather crude. We had strong rope
attached to a water container and the other end of the rope was fastened with cord to
the missile. The overall length of the rope and cord was a few feet less than the
length of the garden. Every time we fired the water container was put on a chalk line
and we just observed how far the container had jumped when it was stopping the
missile in flight. Simple but it did work !

 We took some video footage of a net being fired using the air power and some of a
normal cannon net.  Although the net sizes were different it was obvious that the air
net was actually faster in flight than a cannon net. This was mainly due to the fact
that when a cannon is fired, because the "front" of the missile is pushed down the
cannon it  has to start  travelling backwards and  then somersaults in the air once
there is some tension in the attached rope. In fact the cannon missile travels in a very
erratic manner until the weight of the net stabilises its direction. The videos when
slowed down showed that a tremendous amount of energy is wasted in cannon net, it
was actually scary to watch, if ropes should snap on a cannon net then the missile
could go anywhere  within 60 degrees  in any  direction from the intended trajectory

The air missiles had the net cords anchored at the tail end of them, this was only
possible because as described earlier the missile is on the outside of the launch tube.
With the cord being attached like this the missile is travelling in the right orientation
from the outset, and wastes no energy tumbling through the air as a cannon missile
does.

We experimented with various lengths of missile and launch tube but the firing range
wasn't much different, unless the tubes became excessively long. The important
factors are the volume of air that was available along with the psi when ready to fire.
The other important thing is the valve size, anything less than a 1" valve did not
allow air to escape fast enough to power the missile.  I seem to remember that we
initially worked on a principle that the reservoir should be twice the volume of the
launch tube, but this wasn't as important once we added the water to the system.
There shouldn't be any bends in the system either  as that can reduce the effective
force of the air.

The were a couple of reasons we stopped development of the device, one was the
short life span of the valves. In field use the nylon seals soon became contaminated
with sand etc so they leaked at an alarming rate, which meant that realistically new
valves should be used with each fire .. not exactly a cheap method !

The other was that we had wanted the unit to be an intermediate device between
whoosh nets and cannon nets.  When we demonstrated the system to staff at the BTO
there was some concern that it could potentially catch as many birds as a cannon net,
and would thus require special licensing which was not what we had set out to
achieve !


Hope this helps !

Wes


On 11 Nov 2009 at 12:53, Chris Snook wrote:

> Has anyone on this list any experience with building/using compressed
> air-powered cannon nets?
>
> I am trying to build a couple of compressed-air powered cannons for a
> small scale cannon net ( 6 m x 3 m, weight 800 g ) and have some questions.
>
> 1. What typical air pressures are used?
> 2. What size and weight of projectiles are used for what net size?
>
> Any help will be appreciated.
>
> Chris Snook,
> Charleston, SC
>
> subscription options and posting rules can be found at the BirdBand web
> site:
> http://www.geocities.com/RainForest/6549/birdband.htm

----
email :- weshalton@...
Tel :- Home 01204709302
        Mob [phone]

subscription options and posting rules can be found at the BirdBand web site:
http://www.geocities.com/RainForest/6549/birdband.htm

[John Woodcock]

We've been using nets powered by bungie cords (rubber tie down cords) to capture birds on the ground i.e. CAGU, HERG, RBGU

John Woodcock, Program Coordinator
Thunder Cape Bird Observatory
phone: [phone]
http://www.tbfn.net/tcbotbfn.htm 
johntbaywoodcock@...
http://www.saveoursongbirds.org 

Mailing Address: 350 N. Harold St., Thunder Bay, Ontario, Canada, P7C 4C6

"You belong to Nature... not it to you." Grey Owl 1888-1938



 

> Date: Thu, 26 Nov 2009 07:27:26 +0000
> From: weshalton@...
> Subject: Re: [BIRDBAND] Compressed-air powered nets help
> To: BIRDBAND@...
>
> Hi
>
> About 15 years ago along with an engineering colleague of mine we developed a
> prototype compressed air net that was showing some promise but we had problems
> with the valves remaining airtight when in use in the field.
>
> I cannot remember the exact measurements and weights but the net we had was of a
> similar size to the one you are using possible a little larger.
>
> Anyway some vague details you may find interesting.
>
> The air reservoir was approx 1.75 litres and the air pressure was over 180 and often
> up to 220 psi.
>
> The missile and launch tube were made of plastic kitchen waste pipe which over here
> in the UK is sold in 2 sizes 1.25" and 1.5" od. The smaller size fits snugly inside the
> larger one. Our missile was the outer tube, ie it fitted OVER the barrel not inside it
> like cannon nets.
>
> The release valve was a simple 1" diameter ball valve which was spring loaded so
> that it would remain open until it was connected to a solenoid release mechanism
> which would hold the valve closed until the solenoids were switched to "fire"
>
> The missile was approx 15" long and had a metal nose cone of approx 4oz weight ( I
> think!) at the tail end of the missile we used some rubber inner tube off a cycle that
> would form a seal between the two different sizes of tube being used. In practice this
> did not seem to be necessary !
>
> The first time we fired the system there was an almighty "POP" as the missile was
> launched and since we knew the missile velocity would be slower than usual cannon
> nets we decided we needed to muffle that somehow as it would scare birds before the
> net had settled. After trying several methods we tried filling the launch tube with
> water (just the tube not the air reservoir !)We then did a test fire and scared ourselves
> to death ! The velocity of the missile was greatly increased maybe 5 or more times
> more powerful, In fact firing a missile untethered it would easily travel over 150
> metres, in addition the exhaust noise was almost negligible
>
> My friend had a really thick hawthorn hedge at the bottom of his garden, some 20
> yards from our test launching pad (really a picnic table). We fired tethered missiles
> for safety purposes and after a few days we had all but obliterated a section of the
> hedge . We were firing the missiles like kids with a new toy! Our method for testing
> different barrel lengths, missile weights etc was rather crude. We had strong rope
> attached to a water container and the other end of the rope was fastened with cord to
> the missile. The overall length of the rope and cord was a few feet less than the
> length of the garden. Every time we fired the water container was put on a chalk line
> and we just observed how far the container had jumped when it was stopping the
> missile in flight. Simple but it did work !
>
> We took some video footage of a net being fired using the air power and some of a
> normal cannon net. Although the net sizes were different it was obvious that the air
> net was actually faster in flight than a cannon net. This was mainly due to the fact
> that when a cannon is fired, because the "front" of the missile is pushed down the
> cannon it has to start travelling backwards and then somersaults in the air once
> there is some tension in the attached rope. In fact the cannon missile travels in a very
> erratic manner until the weight of the net stabilises its direction. The videos when
> slowed down showed that a tremendous amount of energy is wasted in cannon net, it
> was actually scary to watch, if ropes should snap on a cannon net then the missile
> could go anywhere within 60 degrees in any direction from the intended trajectory
>
> The air missiles had the net cords anchored at the tail end of them, this was only
> possible because as described earlier the missile is on the outside of the launch tube.
> With the cord being attached like this the missile is travelling in the right orientation
> from the outset, and wastes no energy tumbling through the air as a cannon missile
> does.
>
> We experimented with various lengths of missile and launch tube but the firing range
> wasn't much different, unless the tubes became excessively long. The important
> factors are the volume of air that was available along with the psi when ready to fire.
> The other important thing is the valve size, anything less than a 1" valve did not
> allow air to escape fast enough to power the missile. I seem to remember that we
> initially worked on a principle that the reservoir should be twice the volume of the
> launch tube, but this wasn't as important once we added the water to the system.
> There shouldn't be any bends in the system either as that can reduce the effective
> force of the air.
>
> The were a couple of reasons we stopped development of the device, one was the
> short life span of the valves. In field use the nylon seals soon became contaminated
> with sand etc so they leaked at an alarming rate, which meant that realistically new
> valves should be used with each fire .. not exactly a cheap method !
>
> The other was that we had wanted the unit to be an intermediate device between
> whoosh nets and cannon nets. When we demonstrated the system to staff at the BTO
> there was some concern that it could potentially catch as many birds as a cannon net,
> and would thus require special licensing which was not what we had set out to
> achieve !
>
>
> Hope this helps !
>
> Wes
>
>
> On 11 Nov 2009 at 12:53, Chris Snook wrote:
>
> > Has anyone on this list any experience with building/using compressed
> > air-powered cannon nets?
> >
> > I am trying to build a couple of compressed-air powered cannons for a
> > small scale cannon net ( 6 m x 3 m, weight 800 g ) and have some questions.
> >
> > 1. What typical air pressures are used?
> > 2. What size and weight of projectiles are used for what net size?
> >
> > Any help will be appreciated.
> >
> > Chris Snook,
> > Charleston, SC
> >
> > subscription options and posting rules can be found at the BirdBand web
> > site:
> > http://www.geocities.com/RainForest/6549/birdband.htm
>
> ----
> email :- weshalton@...
> Tel :- Home 01204709302
> Mob [phone]
>
> subscription options and posting rules can be found at the BirdBand web site:
> http://www.geocities.com/RainForest/6549/birdband.htm

     
subscription options and posting rules can be found at the BirdBand web site:
http://www.geocities.com/RainForest/6549/birdband.htm