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RTV and the I110 PVC-NO Hybrid Motor
"I am sure the air in
heaven must be this wonder working gas of delight". -
Poet Robert Southey on Nitrous
| I (in this case, I being Rick) shelled out a few
bucks and invested in the new West Coast Hybrids I-Motor
system. Consistent with RTV Ideals, the reason for
purchasing this equipment is to get more bang (Whoosh?)
for the buck. The cost of the casing is comparable to an
AP motor, but the consumable reload is a fraction of the
cost of AP. Ground support equipment, which can get
expensive, is a non-recurring cost that can be spread
over a number of flights and/or users. Even when figuring
in the amoritization of the investment in ground support
equipment, I estimate that I'll break even before I've
made 10 flights. |
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| I recently had the opportunity to use
this motor at The G. Harry Stine Launch 2002, in Rainbow
Valley, AZ. Click
here to see the launch report 
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| As you can see, This motor is extremely
long, and purple!. It measures 38 mm in diameter and 24
inches long, So it's going to be a little difficult to
fit into a Loc Minnie Mag!! |
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This is the fuel grain used in the WCH Motor. It is a
solid cylinder made from PVC. Totally inert! (Take that!
BATF!) What's more, unlike RATT or Aerotech Hybrids,
no Pyrogen is required for ignition.
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| Ignition of the motor is made possible by using FFG
Black powder mixed in a petroleum based inhibitor fluid.
This makes it burn, rather than bang, and sustains the
combustion long enough to ignite the PVC Fuel, burn
through the supply tube and release the NOX reaction.
Cool, huh?! To the right is the Graphite Nozzle.
Supposedly it can be used up to five times before
requiring replacement. The internal geometry is rather
crude, however. Perhaps future optimization of the nozzle
design may boost the thrust output of the motor.
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| To keep all this organized I put it all
in a 26 inch Plano tool box I got on clearance at WalMart.
It barely fits. I also keep all the small parts neatly
arranged in small Plano Stowaway organizers I got very
cheaply, also at walmart (Hint go to the fishing section
and look for bulk packs for $5, there is not a better
deal. The future of Hybrid Motors is promising. Unlike
solid fuel motors, anyone with sound technical
knowledge and access to a machine shop can design, build,
experiment with, and produce hybrid motors. That's why of
the five hybrid manufacturers currently offering
products, three of those are essentially back room
operations. With the continuing restrictions on solid
propellants, hybrids may well be the future for high
power rocketry.
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| Assembling the WCH I110 |
The assembly is a snap. There are several
steps, but no tricks. Therefore, we won't bore you with
details here
(here is
a step by step checklist
- and here is a list of
tools and supplies), The following are a few pictures from the
assembly process:
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Inserting the supply tube
into the injector
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Fastening the supply
tube in place
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the black powder charge prior to installing the paper cap
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Here is the business end of the I110 installed in
Brad's TEDMAPOD. Note that the motor clamps are clamping
directly on the graphite nozzle. We we would not normally
recommend doing so. |
| Flying the I110 |
Andy Woerner verifies all fill connections are working
properly |
As far as hybrids go, launching the I110 is pretty
easy. Insert the ignitor attach to the nitrous supply
system, and stand back. The hardest part is to witness
the evidence of nitrous venting, which tells you the
tank, is full, fortunately, we had the infamous Andy
Woerner to spot for us. so the flight went off without a
hitch. The WCH I110 has the flatulent report
characteristic of hybrids. The flame produced by the PVC
grain is almost imperceptable. Nonetheless, the motor had
sufficient thrust to push this six lb. rocket to 1200
feet.
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| Post Launch Examination: The
I110 is incredibly easy to clean up, as long as you
remember to grease the charge pocket in the piston. There
is no residue left in the tank, or the combustion chamber.
be careful not to introduce dirt while pushing out the
internal components.
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The picture above is the fuel grain after cutting it in half. As
you can see, most of the fuel consumption occurs near the center
of the fuel grain. At the point of the arrow the grain is
consumed to half of its original thickness. Before cutting the
grain I weighed it and compared it to an unspent grain. Turns out
that about 34% of the PVC material is consumed in a single firing.
It's tempting to want to reuse the grain, but burn through would
certainly occur on a second launch.
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Click
[HERE!] to view an interactive 3D cutaway model of the WCH I-110 Motor. You will be able to view the key components as well as rotate and zoom. More fun than a barrel of monkeys.
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| About
Nitrous Oxide This gas was discovered in
1793 by British Clergyman Joseph Priestly, who was simply
trying to find a better way to preserve his county fair
pickles. It worked only slightly better than his prior
method of dipping the cucumbers in Mercury. However, he
was sufficiently intrigued with his discovery to show it
to off his nefarious friend Humphrey Davy, which was
really a bad idea, since Davy had already sabotaged
Preistly's exclusive patent rights to Oxygen years
earlier.. Davy hijacked Priestly's discovery and took it
back to the Pneumatic Institute of Bristol .
There he delighted his posse by slipping the gas to
unsuspecting patients, who then went about in a drunken
stupor. Thus NOX was dubbed "Laughing Gas", but
not for the effect on patients; but on the observers.
Nitrous soon became the inebrient of choice at 18th
century Rave Parties.
Nitrous went on to many legitimate uses, most
notabably the production of whipping cream for drug store
soda fountains. Nitrous for industrial use has been
"denatured' to discourage recreational use, i.e;
Sulfur Dioxide is added to the gas to "induce
vomiting", which makes us wonder what it is that
Mark has been eating lately.
It's
true! You can read all about it here
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Caution!!
Nitrous Oxide as used in Hybrid Rockets is highly
compressed into a liquid. Venting of Nitrous
through a Nozzle or Orifice will create a Super
Cold Spray that will Freeze Human Tissue on
Contact.
So Don't Get Stupid, Wise Guy!
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The Rev. Joseph Preistly, inadvertant
creator of the Mosh Pit.
No relation to Jason Priestly
The result from a night of Nitrous Free-basing
is never pretty
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