I think there was a little chamber in the front of the motor...
it was connected to the main propellant chamber through a fitting
containing a little stack of porous disks which could be lengthened
or shortened to change the delay time. When the motor was filled with
propellant (Freon-12), the front chamber would become pressurized with
vapor, and a diaphragm/piston on the front would be pushed forward,
engaging a clamp to hold the nose section on. (I think the clamp was
a dished piece of spring steel, shaped so that when its middle was
pressed forward, tabs around its rim would extend sideways and press
against the I.D. of the forward airframe.)
Once the propellant had been released during thrust, the pressure trapped
in the forward chamber would take some seconds to bleed off through the
"calibrated leak" provided by the stack of porous disks... eventually,
the pressure would fall enough that the clamp would release the forward
airframe and allow it to separate. (I don't think there was any specific
"ejection" per se.)
I never flew one; the above is what I remember
from reading the catalog many years ago.
It is a $10'000 fine for individuals and for companies its $100'000, it
does not matter if its a CFC, HFC, HCFC, They are classing greenhouse gasses
(134A) in the same catergory as ozone depleting substances.
Remember to follow the MONEY!! The EPA has become a self supporting
agency. Its fines and fees support itself. As the ozone depleters
(12,22,502,ect.) run out or companies fase them out the fees and taxes on
new and recycled refridgerants will continue to dwindle. Example R-12 was
well over $50 a pound and is now coming down because there is no demand. So
now the EPA is making very little off of it. So if we now include the new
safe refridgerants we now have a funding source for who knows how long.
Never happen. EPA is too good at guilt-tripping politicians.
No congresscritter wants to risk some opponent/reporter asking
him why he voted to "Weaken Environmental Protections". They've
sure, for a relatively recent agency, carved out an entrenched
Agreed. After our battle with the FAA, our lawyers told us to expect the EPA
to be the next agency with us intheir targets. So they were a little off.
But the EPA seems to be going after all perchlorate sources, so we very well
may be on their horizon.
Bob Kaplow NAR # 18L TRA # "Impeach the TRA BoD"
>>> To reply, remove the TRABoD! <<<
Kaplow Klips & Baffle: http://nira-rocketry.org/LeadingEdge/Phantom4000.pdf
www.encompasserve.org/~kaplow_r/ www.nira-rocketry.org www.nar.org
Save Model Rocketry from the HSA! http://www.space-rockets.com/congress.html
There's a mix of isopropane and butane that has the same pressure
curve as R-12 (and even the same heat capacity per mass) - I think
it's about 80/20 isopropane.
Some fly-by-night repair shops were actually using it in older car
air conditioners a while back - generally without the customer's
knowledge. It works great until there's a leak under the hood,
then it's 'To the moon, Alice!' Several of these guys are doing
time in various places...
Of course, as noted elsewhere in this thread, hydrocarbons are
also greenhouse gases. Never mind that the major component
of greenhouse gas in the atmosphere is water vapor, which
accounts for somewhere around 95-98% of the greenhouse
effect, and is pretty much non-negotiable on a planet that's
73% water on its surface...
Yeah, the EPA specifically lists hydrocarbon blends as "not acceptable
as alternatives for CFC refrigerants" in most applications... and the
compressor manufacturers are singing the same tune. I think it's being
driven by the liability lawyers as much as anything: if you fill your
air conditioner with propane (similar boiling point to R22) and it leaks
and you have a propane fire, they want it to be damn clear that it wasn't
You may be thinking of R22, which has a nonzero Ozone Depletion Potential
rating, but much less than R12: it's still popular for air conditioning
and similar equipment, but is scheduled to be phased out for new equipment
after 2010; although it can be used to service previously constructed
equipment until 2020. R134a is one of the non-ozone-depleting "long term
alternative" refrigerants... even the ones which don't deplete ozone at
all are still considered to be "greenhouse gases".
I'm not sure what the EPA thinks of those circuit cooler" cans that
Radio Shack still sells for testinng electronics... these days they
contain R134a instead of R12.
R-134a is also used as propellant in asthma inhalers. It has zero
ozone depleting potential since it is a hydrofluorocarbon (HFC). All
"big" molecules have substantial infrared cross-sections. The fact
that R-134a is a 'greenhouse' gas, while true, is not particularly
noteworthy - most gases you use or come into contact with are
'greenhouse' gases, this includes the ones you are exhaling (i.e. CO2
and H2O, sometimes CH4), N2O, etc. The famed combustion chemist
Sidney Benson has a few remarks about global warming toward the last
half of this paper that warrant reading:
David - Your description is accurate for the original Vashon design. There
was no active ejection for the parachute, the upper body tube, actually a
paper body tube taped to a short section of aluminum tube for the retention
clamp to grip, would simply fall away, and the parachute would "fall" out.
Estes later redesigned the system. The engine was inserted into a full
length paper tube rocket, much like a normal model rocket. A spring
loaded piston tube that slip fit between the body tube and the motor was
inserted into the front of the rocket. The motor used a thrust ring glued
to the rear of the motor since the piston needed forward clearance. The
retention mechanism was now a rubber bladder in the front section of the
motor that protruded through several round holes in the side of the aluminum
motor tube. The bladder was inflated when the engine was filled with Freon.
The bleed mechanism was internal to the motor and not accessible, probably a
small hole, so the delay was no longer adjustable by changing the number of
paper disks. When the bladder was inflated, it gripped the piston, and when
deflated, the spring loaded piston ejected the parachute.
Although I had both, I never flew the Vashon rockets. I did fly the Estes
version. They were fun, but the performance didn't compare well to regular
model rocket motors.
I still have a couple of each of the Vashon and Estes motors, and the
original instructions for each (but no Freon-12). If anyone wants to see
more detail, I can scan and email the instructions that have detailed
drawings of each system.
It's interesting to note the early use of a piston and a rear motor mounted
thrust ring in the Estes system!
R134a should most likely work just about as well - the vapor
pressures are nearly identical at ordinary ambient temperatures.
(It might be possible to fill the system from cans of the "non
ozone depleting freeze spray" from Radio Shack.)
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