By the way of exception today the video is in Finnish
and for the 3 watchers who don't understand Finnish
there will be subtitles.
But let's talk about the cannon.
I guess at first it's quite good to tell why?
In the year 2005
in the summer camp of Finnish Amateur Radio League
in Räyskälä, Loppi
we were watching when
OH9NB from Northern Finland
aged gentleman was introducing
his small handheld tennis cannon
shooting the antenna wires to the trees
We were quite surprised about this
how high the ball flew with so small cannon and low pressure
So we decided to challenge each other.
In 2006 at the next camp in Turku
we would see who could set balls to fly the highest
3 teams signed up and two of them really made something
Me and Teemu OH7KAA.
Teemu's cannon was compact and nice looking
but the pipe was too small for a tennis ball.
And it didn't compete this in power either
Then back in 2006 in the summer camp in Turku
we shot anything that we could use as a target
CD drives, beer cans
though filled with water
and garden gnomes!
They were a big hit.
We made output speed tests with a high speed camera
But... let's talk about the cannon itself.
In the first phase in the summer of 2006
I built the actual cannon
Here the most of the grey stuff is the original cannon
for which I built the stand in last year, 2016.
About the technology of the cannon I would say
basically this is purely pneumatic
A big tank with the volume of
over 60 but less than 70 liters.
made from 320 millimeter compressed air cylinder
tube, endings and bolts
The air will be compressed to the tank, nominally max 10 bar
but i have tested 11 bar.
And the next after the tank there is
if I remember right, an Italian manufactured
a little slantwise machined valve
This is a little difficult to show outside
there is a film
that drives a plate in the end of a small piston inside the valve
The plate needs pressure behind it that it stays closed
so this structure is a little hazardous
But there are some extra security arrangements
to make sure that the valve stays closed in all cases of use
This is not optimal as a valve
In many smaller cannons there are better fitting valves
like sprinkler valves etc.
And there are plans to change the valve in this cannon too.
But this is here because it was found easily
From my previous employer and it didn't cost much
The valve has lasted thousands of shots.
If you could call this a pneumatic cannon, whatever
The tube is from a pneumatic cylinder too.
63 millimeter inner diameter
and 3 millimeter wall thickness.
Well anonized aluminium.
Very smooth inside
and no scratches yet even it has been in heavy use
The tube is 1.5 meters long.
I still haven't found a perfect solution for targeting.
There is a laser pointer on top of the tube
that emits a red point
is a working and visible solution indoors
But when shooting outside when the sun is shining
there's no hope to see the spot
especially when the user is a little blind.
Better idea for targeting
and less dangerous to the eyes than a high power laser
There is a camera installed under the tube.
The idea is good, but
this particular camera lacks autofocus etc.
There is no auto iris which causes that
lightning conditions or distance of the target changes
or anything else changes, you must adjust the camera again.
This should be replaced with some better solution
But anyway the camera and a screen is the best solution
for shooting with this kind of a gizmo.
And about the pneumatic system
There are separate control pressure tanks
where practically there is the same pressure as the feeding pressure
And they are separated from the pressure of the main tank
because that when shooting with a low pressure
the valve will work correctly.
And there are some security arrangements for that
the cannon discharges if the control pressure is lost
The adequacy of the control pressure has been secured
with several separate valve solutions
These are a little difficult to describe
If there is a leak in the control pressure system
and there is some pressure in the main tank
The air can flow from the main tank to the control side
There can't be much lower pressure in the control side.
There are several other security arrangements
eg. for losing the electric power
In the end of the main tank
there is a separate modified valve
that is separately kept closed with electricity
So in case of power loss or press of emergency stop switch
a controlled discharging of the pressure will happen.
and the cannon will be in harmless state relatively fastly
This little chunk of steel
on top of the cannon is because of
the weight distribution of the structure is not good.
Because the tube is long and there is many extras
this is front-heavy.
And because the control motors etc are not very big
that causes some problems.
Because of that there is some weight added for balancing
With the new tube that is coming, a 4.5 meter one
that you will see later
there will be need of much bigger balancing weights.
But there will be another challenges for installing them
because the stand is designed so that
it is possible to shoot directly upwards
and even a little backwards
and because of that when the cannon is turned upwards
the back of the cannon
and the stand have just a few centimeters of space between
So the extra weights must be installed here under
or over the top or better both.
About the structure... this is a quite high fork.
which of course causes some unfavorable forces
And the principle of design was that
it is possible to shoot directly upwards
and as a compromise the weight balance was tried to
it can be used horizontally too
so the fork became relatively high
It should be even a little higher but it causes different problems
On the stand down there
this big disc in the middle
this one with the holes on the outer edge
the disc is originally manufactured
for an end cap to a steam pipe or other industrial tube
so the holes on the outer edge were there already
I got it from a local scrap yard
with a price of scrap iron
and it was processed to a hub
The hub around which the cannon turns
is from a tractor trailer
a trailer axle hub
Quite robust
but it has been in mind that it could be bigger
Then if we look at the turning solutions
there is a pulley wheel over 40cm of diameter
This was originally for two belts or how you say, a V-belt
Originally manufactured but later it has been lathed
to fit one wide belt
and there is now a toothed belt matched to fit
You can buy this as a piece goods
and it has steel wires inside
in the toothed surface
This is used eg. in train doors
This withstands very hard pulling
and use for a long time
Is it hard enough in this use is a different question
And the turning back and forth
horizontally and vertically is done with these
Dunkelmotoren GmbH manufactured
24 volt 50 watt
little DC motors
and behind them both
in vertical and horizontal turning
down here
the both have this kind of three phase planetary gears
which have the gear ratio of 1:162
so the gear rate is quite huge
and because of that a quite big torque is possible with small motors
The cannon turns nicely and there is power enough
but there should be more power in vertical turning
Erm.. what could I say more
These are DC motors as I said
There could be or it could be better to use stepper motors
but I must be satisfied with this solution
These motors were found just from trash
And better motors would cost quite a lot
And this project has taken money enough
so I must be satisfied with this
to this which we have now
There should be some kind of a feedback circuit
because it could be possible to monitor
or automatize the turning and maybe even with a computer
maybe with and Arduino or
some else for controlling the cannon
But they are long lasting future projects
there is plenty of time available in the world.
The cannon is now 11 years old
and it took 10 years to get any kind of a stand
so we are quite far now
And about the stand structure
the horizontal turning angle
is maybe about 270 degrees
It is limited mainly because of
cables and the tubes
and these yellow cords
and that the belt is not
and endless loop but
it is mounted in this big wheel in the middle
on the front side
but the turning angle is more than large enough
There is similar limitation on the vertical turning
it can be turned about 20 degrees backwards
and the tube can be turned down so that it touches the ground
so to that direction the angle is large enough.
Because this kind of a narrow stand
would not stand for very long itself
it is equipped with
with removable legs
this kind of
supporting legs. Let's install one to its place
In the bottom of this supporting leg
are big steel chunks welded
Pieces of steel that match
this steel pipe fitting
to the pipe in the cannon stand
Like this
In this phase we can see that
there is a steel piece going
into the pipe
It must be pushed in the end
and after that securing with a cotter
that makes sure that the leg can't escape
With four legs the cannon will be supported so that
it will not wobble, fall or move from its place
It should be mentioned that when shooting
some heavy projectiles
like in the wintertime
two kilogram concrete projectile
even this equipment weighs over 300 kg
slided on the concrete floor
more than ten centimeters
so there is relatively big recoil
though the metal feet on the concrete are little slippery
And then let's introduce the control desk
First open the door
Here we have
shortly explained
firstly
Nice controlling joystick
there is a connector for it and it's another story
But there are the connectors
for all for the cannon, eg. here is
the cables for the cannon. Here are the motor controlling
which is a Speakon connector
and then several Neutrik XLR connectors
and these are selected so that miswiring is impossible
Four pneumatic connectors for
the meters on the control desk
There are four thin pneumatic hoses
and we get the information of the pressure
in the main tank, control tanks and feeding and the tube
So there is an underpressure meter as well.
which is unfortunately a little bit damaged just now
And about the other connectors
there is a CEE connector that is widely used in Europe
16A plug where the mains is brought
if needed
Practically when shooting with the cannon
and only shooting and turning, the battery power is enough
You will see the batteries on the other side
The 3 phase connector on the right is
this is for the vacuum pump mentioned earlier
That is why there is 3 phase connectors installed
On the upper side of the cabinet there are several normal
grounded 230V 16A sockets
for to connect several things
This is the main switch of the 24 volt subsystem
and the handle for it is here
So it goes
So there are the most important things from this side
Let's see the other side
Wait a moment, I will turn around this orchestra
Let's inspect this side
A couple of words
Firstly, one piece of
contactor or relay, whatever you want to call it
which operates as an emergency stop
switch off. When the control voltage is gone, everything stops
Next to the relay there are two DC motor drivers
One for the horizontal and one for the vertical turning
On the right there is a 230V mains power to
24 volt subsystem power source
and next to it 24V to 12V DC-DC converter eg. for the camera
All the cables for the cannon under this terminal block
the cables here
these cables here are for the external joystick
All the others
these are for the motors, these for the cannon
are in the grey baquette of the cannon
there are some controls and reservations
The system uses 24 volt
and of course it's equipped with batteries
Two Panasonic 38 Ah lead acid batteries.
And then let's quickly see the control desk
First. The emergency stop switch
By hitting this emergency kill switch down
the movements of the cannon are immediately stopped
It can't be turned or triggered
if this switch is down. It also causes
discharges the pressure controlled
And then let's look at the meters
The feeding pressure meter that tells how big pressure is
coming from the compressor
And the next meter is for control pressure
practically and usually shows the same pressure as feed
except when pressurizing the tank
when it is typical that control pressure is stable and feeding is low
during the pressurizing
The meter named as the cannon tells
the pressure in the main tank
The last meter has been plusminus 1 bar meter
Then the signal lights
This green light tells that the cannon is switched on
And the red light here, which is by the way a LED too
tells that the cannon is ready for shooting
which needs the key
Here is a key operated switch for
making sure that no one can shoot
and the cannon can't be turned
without the key
The next switch here is
This can be used for pressurizing
or optionally empty the air tank without shooting
In the middle position the valve is closed and nothing happens
The next one is for the vacuum pump control
so this switches on the power to the socket in the cabin
And the next switch is for the targeting camera
control. Here we can switch on the camera power
And then the targeting laser switch
And the next one is a switch that does nothing
This is for future expansion
On the lower row there are several switches
and most of them are for future use
Reservations for several systems
Here is the slow drive switch
and by pressing it the motors will
be in slow mode and more accurate targeting is possible
And then on this side is
the shooting switch
and next to it is the joystick for controlling the turns
Today we had this introducing video that became very long
hopefully you enjoyed it.
And in the end of this video there will be a tradition
Thank you and apologies
All you who have followed tennis cannon videos last months
might have noticed that in the end of the videos there is
there has been a program number
about destroying an IKEA Lack table
This day is not an exception
but thanks to little cute foals
there will be no shooting
So I must use my imagination and other methods
and there are plenty!
So!
In today's program
an IKEA Lack table again
and a plastic flower that has found out to be very tough
I have planning for a while that a tail lift
can be used for destroying that and now we are testing it!
Let's see as they say
It's still in awkward good condition
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