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Day 124 - Boom and Chase cams
Burnt grass at Doonside is slowly growing
back. It's easy to find rockets now.
Chaser and chasee rockets set up. We used
the old and the new launchers.
Looking back towards the parking area.
Arming servo timers.
Documenting flights.
Both rockets were launched at 110psi.
Rockets landed well away from trees.
Both rockets landed fairly close.
Downloading video from the camera.
First flight.
Fourth launch, the rockets went almost
simultaneously.
It's a drag race, and the wrong rocket is
winning.
They both used 900mL of water and a 9mm
nozzle.
Grass shoots are starting to spring up.
Without the long grass the landings are a
little harder.
Panorama from flight #3.
Just after burnout on flight 2.
Launch sequence of both rockets.
The third flight was very good, and showed a
good close-up of the other rocket.
The air pulse is starting.
Ready to go for flight #4.
All rockets returned safely.
On the fourth flight the chasing rocket flew
ahead of the camera one so all we got was a
water column.
The last flight gave us a good longer look
at the flight of the second rocket.
Setting up the boom cam under the pyro
launch rails.
Controlling the rate of rotation remotely.
Boom cam set up for the water rocket launch.
About to launch.
Date:9th
September 2012, 8:20am - 1:00pm
Location:Doonside, NSW, Australia
Conditions:5 - 15km/h , mild ~20C, blue
skies
Team Members at Event: PK and
GK
Today was a beautiful day for rockets with
blue skies and little breeze. We only
brought a couple of small rockets with us
because we wanted to try filming from a couple of
different camera angles. Since our last
visit to Doonside there had been a big grass fire which
cleared away all the tall grass. Small green shoots have
now started coming out
so it looks like someone has mowed the
whole field. This makes it really easy
to find rockets but also makes it for harder
landings.
Chase Cam
We wanted to try the classic chase cam
camera angle
with one rocket flying just ahead of another
and the first looking back at the
second. We had tried similar footage a
few
years back, but the camera was
looking
sideways. This time we just taped the camera
to the side of the rocket so it could look
straight down rather than out at an angle.
We positioned the two rockets about 50cm
apart and used the one hose with a splitter
to supply air to both rockets. We also used two
separate strings to launch the rockets. This
way we could control the delay between the
rockets.
The rockets were filled with 900mL of water
and launched at 110psi. We did 5 double
launches all together and all flew well and
landed without problems. One of the
batteries came loose on impact during one
landing and so we had
to take the nosecone apart and reattach the
battery.
Here is a video
of the flights and the views from the chase
cam.
It was difficult to try to decide how much
of a delay there should be between the
flights as too short a delay meant that the
second rocket could fly out of view sooner,
and a longer delay meant that the second
rocket would be fairly small in the field of
view. So we tried several different delays.
On the fourth flight the rockets launched
almost simultaneously and the chasing rocket
was out of shot very early. The best
sequence was on the 5th flight.
Boom Cam
The boom cam is simply a
high speed camera mounted at one end of a
boom with a pivot point at the other end of
the boom. The camera is pointed back towards
the pivot point. The rotation of the boom is
controlled remotely using a pulley and
string. At first we wanted to drive the boom
electrically using a motor and gearbox, but
the hand controlled movement gave you more
control over position and rate of rotation.
Because the camera is
pointed back towards the pivot point the
subject matter needs to be centered on the pivot
point also. A couple of the launch rails at
Doonside overhang the
mounting pole which allowed us to position the
pivot mechanism directly underneath the
launch rail and point the camera up at
the rocket.
We filmed a few launches of
the smaller pyro rockets taking off. These
turned out quite well, although on the first
one we were a little too slow with the
rotation.
On the third flight,
something went wrong with the camera and it
didn't record the file properly. It was a
pity because the rocket CATOed on the pad.
It would have been good to get a video of
that. The camera just did not want to turn
off so we had to pull the battery out.
After that we also set up
the boom next to the small water rocket
launch pad and ended up getting pretty good
video of that.
Here is a video of the boom cam:
The idea is to try to
eventually get a "bullet time" like effect
with the single camera although the boom
needs to be rotating a lot faster. The
higher frame rate and faster shutter speed
should allow us to get closer to the ideal
effect, although you can't quite get the
"frozen in time" look with this kind of
set-up. In order to get the high speed
rotation we would need the boom to spin
continuously in order to build up the speed.
Ideally for this the pivot point should have
the launcher incorporated into it.
We were very happy with the
rocket performance as well as the video
shots we got from the flights. It's always a
bonus when you don't have to do repairs at
the end of the day.
