My biggest problem is in finding parts. I've never seen an
FTC (fluorescent tube cover) and PVC pipes only come in a few sizes. But I guess that
makes it more fun always trying to come up with alternative solutions.
CURRENT CHALLENGE
After many frustrating attempts to build a crushing sleeve-type staging device, I had this
thought of using the Clark Cable
technique backwards (inwards?). Anyway. The idea is to have the cable ties grab the 2nd
stage (the top bottle, the sustainer) from within, locked in place by a piston that gets
pushed up by the pressure difference between the two bottles.
I´ve called this thing "Candiru" which is the name of a terrible tiny fish
from the Amazon region. The indians are scared to death of this fish, much, much more than
the "Piranhas". It senses the smell of urine and feces and it swims right
towards their origin, making its way into the respective canal. Its scales are hard and
sharp, making it easy to get in but impossible to come out. They are deadly!
My attempts at building this device is enormously hampered by my own incompetence in
working with machines, tools, etc. To make matters worse, I haven't been able to find
suitably-sized pipes to fit my original plan. Rats! I suppose one could use a lathe or
something to get to the proper diameters.
If you guys could brainstorm about this idea I think it would be an interesting
addition to our supply of rocket-related gadgetry. This is what I've accomplished so far:
This is a picture of a prototype. You can see the
piston (in white) locking the bottle in place. At the bottom end you can see the PVC cap
with a length of threaded lamp rod, which would be used to fix the assembly on top of the
1st stage (the bottom bottle, the booster), à la Robinson Coupling.
On top of the cap I've placed a section of 32mm PVC pipe to function as a ledge onto which
the bottle rests. You must have a couple of these hoops in different lengths to accomodate
the various tapering shapes of bottles.
The "piston" was made with the body of a ball-point pen.
These are the main parts:
(left to right) 3 different hoops of 32mm PVC pipe to use as ledges; ball-point pen
modified to serve as piston; the "grabber" assembly - 4 cable ties squeezed and
glued between the 25mm and 15 mm pipes; the PVC cap with the threaded lamp rod installed.
I like the way Paul Grosse
draws his rocket plans. They inspired me to draw these:
|
At left, the
piston is down, allowing the cable ties to come close to each other and freeing the
bottle. At right, the piston is held up by a greater pressure from the booster, preventing
the ties from moving and locking the sustainer in place. |
The most important thing here is this: I HAVEN'T TESTED IT YET. So that
you know.