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Day 69 - FTC Rocket
The T-8 FTC deployment mechanism main
components.
Detail of the electronics bay
Latch mechanism in the latched position.
Latch mechanism in the open position.
Spring loaded nosecone section
Another view of the nosecone.
Payload section ready to be fitted to the
top of the FTC rocket
Reverse view of the payload section.
Deployment mechanism attached to the top of
the FTC rocket.
Detail view of the fins. The fins and glue
still need a final coat of paint.
Date:9th
November 2008
Location:
Workshop
Conditions:Pleasant
Team Members at Event:
GK and PK
FTC Rocket
It's been quite a few months since we
started work on the FTC rocket. We usually
worked on it when
we had a bit of spare time while working on
the other rockets. Our FTC rocket is based
on a T-8 FTC tube.
Body
The body is made from a 0.36mm wall thickness
FTC. We've wrapped it with one layer of
glass fiber strapping tape. It has about 1
L capacity.
Nozzle and End cap
We made an end-cap out of some PVC we
had on hand and the nozzle is based on a
15 mm Gardena nozzle. The one we bought
from the local hardware store came with
an outside thread. We machined an
adaptor with a matching thread that fits
snugly inside the FTC. We then epoxied
the nozzle inside the adaptor. The seal
for the end-cap and nozzle is provided
by an o-ring that sits against the FTC.
Just behind the o-ring is a groove that
allows us to shrink the FTC into it to
hold the end-cap and nozzle in place. We
borrowed this technique from
Urie's water rockets.
Fins
The fins are made of 3mm plywood. The
Dremmel tool came in really handy in cutting
these out. We tried to glue them directly to
the outside of the FTC but the PL does not
hold well to the strapping tape. We have
instead attached them to a split sleeve made
of FTC and taped that to the body. This lets
us remove the fins and place them on another
FTC rocket.
In order to secure the fins a little better
than just glue, we essentially sewed them to
the sleeve with 4 loops of wire.
Payload Section
The payload section contains the parachute,
flight computer, batteries and altimeter. We
went with a split nosecone for the
deployment design, as it meant we would not
have to be pushing the parachute out of the
thin tube. The nosecone can be made longer
or shorter depending on the parachute size
requirements.
Several weeks ago
Tim Chen had discussed with other forum
members a similar spring
loaded "clamshell" design for an
FTC rocket, but no specific
diagrams or photos are available of
his design.
The nosecone is made from the plastic end
cap that comes with the FTC and a half a
plastic Kinder Surprise egg. mmmmm ....
chocolate ....
The two halves of the nosecone (shells) are
made from another piece of FTC.
The hinges at the top of the nosecone are
made from two strips of ripstop nylon glued
to either side of each shell and wedged
between the nosecone and FTC end cap.
The two shells are spring loaded to open
when deployed. The spring is made from a
piece of PET plastic from a regular bottle. This
also acts to help get the parachute out of
the shells. The plastic is just attached
with a couple of wires.
The shells overlap the main payload section
and are held in place by a latch mechanism
made from a paperclip. This latch mechanism
is operated by a small RC servo motor which
in turn is controlled by the flight
computer. We had to make up a smaller
version of the flight computer to fit inside
the FTC.
All the components inside the main payload
section are attached to a piece of Coriflute
material. This lets us slide the entire
mechanism out of the payload bay.
Having the servo horn stick out the side of
the FTC tube is not ideal aerodynamically
but sure makes it easy to setup and lock the
nosecone in place. With a smaller servo we
could place the entire mechanism inside the
FTC.
Coming up
We still have a bit more work on this rocket
before it is finished but we hope to launch
it at the next NSWRA launch day. We should
have it complete for the NSWRA open day.
We will launch this rocket from our medium
launcher fitted with the 15mm release
head and a 1200mm long launch tube.
The launch tube will act as the guide rail.
The first flight is likely to be around
160psi to evaluate the rocket's performance
before trying at a around 200psi on the next
launch.
