Pratt RC ejection system fails me twice at Black Rock!

Pratt RC ejection system fails me twice at Black Rock!

Post by Hawk_Ds » Wed, 31 Jul 1996 04:00:00



Quote:

> At Black Rock 8 this last weekend, I spent quite a long
> time setting up the wiring and electronics for my first-ever
> Hypertek hybrid flight.  I had:

>    PML Tempest (which I now feel is poorly designed)
>    Black Sky timer in the Tempest's nose cone
>    Pratt RC ejection in the electronics bay above the motor
> The poor design of the PML Tempest requires that you either
> A) totally disassemble the rocket on the pad to arm the deeply-
> buried electronics or B) arm the internal electronics before
> you go up.  Silly me: I figure "all the RC stuff is impounded,
> who's going to set this thing off?"
> When everything was ready to go, somebody in the next car over
> keyed their CB as they drove away (we heard them do it).  This
> immediately triggered my RC ejection while the rocket sat on
> my lap.  My added caution thankfully prevented injury, but I
> now had to START ALL OVER wiring and prepping.

> An hour later, I'm out on the Hypertek pad, disassembling the
> whole damn rocket in order to arm everything - out in the hot
> sun.  
> Immediately upon ignition, the Pratt RC ejects again, and my
> first-ever hybrid flight is a large twirling circle of flame.
> Amazingly nothing is damaged, but the flight was an utter flop.
> THe result is this:
> A) The Pratt RC is useless around CB traffic
> B) The Pratt RC is useless around a Hypertek launch system
> C) I wasted a lot of time because I thought it'd be cool to
>    have RC ejection
> D) Next time I'll just use the Black Sky timer, the Pratt RC
>    is not usable for much of what I do at all.  A lot of
>    money down the drain.

> Mark Jeghers--

Mark.

 I'm sorry you had to spend all that money for the useless R/C system. At
LDRS, a realy nice rocket I can't name, sat on the pad for OVER 5 HOURS.
Sat there for at least 4 racks because the dame ejection charge pop'ed
everytime someone breathed. It never even got to fly!

 One of the first things I notice when I got to the field the first day,
was all the Pratt Hobbies control boxes in peoples hands walking around.
My first thought was, "Oh great, stuff will be pop'ing all over the
place."... Sure enough. It got so bad that on the next day, they would
not let you fly ANYTHING untill you turned in all of your control boxes to
the safe area at the RSO table.

 Most rockets, like yours, are not "electronis friendly" yet. It cost more
money to make a rocket that has a simple hatch/door to an electronics bay.
I guess one way to enhance a system like Pratt Hobbies type systems, is
to encode the signal, so that the reciver would know if the signal was
true or false, and sent by you. I believe NASA encryps like this. That
way, no one can tell the Space Shuttle to open the payload doors during
desent! Looks like Pratt type systems would have this already, for what
people are paying for them anyway. What are we talking about here, one chip?
By no means am I an expert. This just sounds like a common sence type of
problem easly fixable by people in the know.

--
Henry Oeser...NAR# 65336. TRA# 4782. NOVAAR #205

"We Need A Bigger Boat..."

 
 
 

Pratt RC ejection system fails me twice at Black Rock!

Post by Mark Jeghe » Wed, 31 Jul 1996 04:00:00


At Black Rock 8 this last weekend, I spent quite a long
time setting up the wiring and electronics for my first-ever
Hypertek hybrid flight.  I had:

   PML Tempest (which I now feel is poorly designed)
   Black Sky timer in the Tempest's nose cone
   Pratt RC ejection in the electronics bay above the motor

The Black Sky timer was set for 14 seconds, based on software
projections, and would serve as primary ejection.  The Pratt
RC would provide emergancy backup ejection.  A Rocketman chute
was used in case of high speed deployment (they claim to
resist shredding by staying shut until the rocket slows down,
and opening gradually).

The poor design of the PML Tempest requires that you either
A) totally disassemble the rocket on the pad to arm the deeply-
buried electronics or B) arm the internal electronics before
you go up.  Silly me: I figure "all the RC stuff is impounded,
who's going to set this thing off?", and I arm it ahead of time
(being careful to not point the rocket at anyone).

When everything was ready to go, somebody in the next car over
keyed their CB as they drove away (we heard them do it).  This
immediately triggered my RC ejection while the rocket sat on
my lap.  My added caution thankfully prevented injury, but I
now had to START ALL OVER wiring and prepping.

An hour later, I'm out on the Hypertek pad, disassembling the
whole damn rocket in order to arm everything - out in the hot
sun.  The Utah guys who brought out and supported the Hypertek
pad are standing around wondering when we'll be ready.  We
finally get set up and launch.

Immediately upon ignition, the Pratt RC ejects again, and my
first-ever hybrid flight is a large twirling circle of flame.
Amazingly nothing is damaged, but the flight was an utter flop.

We theorized that the high frequency electronics which produce
the spark for Hypertek ignition triggerred the Pratt RC.  We
reproduced the condition in a simple test and confirmed it.

THe result is this:

A) The Pratt RC is useless around CB traffic
B) The Pratt RC is useless around a Hypertek launch system
C) I wasted a lot of time because I thought it'd be cool to
   have RC ejection
D) Next time I'll just use the Black Sky timer, the Pratt RC
   is not usable for much of what I do at all.  A lot of
   money down the drain.

Mark Jeghers

 
 
 

Pratt RC ejection system fails me twice at Black Rock!

Post by AVin » Wed, 31 Jul 1996 04:00:00


I was recently involved (as an invited guest) in a rocket launch ad Walt
Disney World in Orlando Florida. These guys launched two large rockets a
day for 7 days straight. Anyways, the rockets used 2 Pratt systems in each
(primary and backup). There seemed to be a problem with frequency scatter
or whatever you would call it. One transmitter would fire other receivers
on different frequencies. They found 2 out of 4 different frequencies that
seemed to play well with each other and used the others in conjunction
with a differnt system. By the end of the week, 3 of the 4 they were using
had quit working completely.

When they were working, there didn't seem to be any problems. A few other
facts to remember before we go: These system are converted garage door
openers; builder, Doug Pratt has been associated with R/C for a while and
is knowledgable;
Doug is a very nice guy and stands behind his stuff; he is working hard to
get the bugs worked out and deals with his customers very well. For the
price you paid, it is probably worth giving him a chance to sort it out
before you abandon his product.

 
 
 

Pratt RC ejection system fails me twice at Black Rock!

Post by Frank J. Bur » Wed, 31 Jul 1996 04:00:00


I agree totally.  I have had only about a 10% sucess rate with the
Pratt system, and now only use it as a third backup, despite being
very experienced in RC planes, and knowing how to place antennas.
I haven't had it go off early, just not go off at all.  Fortunately
I was using my adept as primary, along with the motor.  It is too bad,
really, since it is very nice to have ejection on demand under
certain circumstances.

Frank

Quote:

>At Black Rock 8 this last weekend, I spent quite a long
>time setting up the wiring and electronics for my first-ever
>Hypertek hybrid flight.  I had:

>   PML Tempest (which I now feel is poorly designed)
>   Black Sky timer in the Tempest's nose cone
>   Pratt RC ejection in the electronics bay above the motor

>The Black Sky timer was set for 14 seconds, based on software
>projections, and would serve as primary ejection.  The Pratt
>RC would provide emergancy backup ejection.  A Rocketman chute
>was used in case of high speed deployment (they claim to
>resist shredding by staying shut until the rocket slows down,
>and opening gradually).

>The poor design of the PML Tempest requires that you either
>A) totally disassemble the rocket on the pad to arm the deeply-
>buried electronics or B) arm the internal electronics before
>you go up.  Silly me: I figure "all the RC stuff is impounded,
>who's going to set this thing off?", and I arm it ahead of time
>(being careful to not point the rocket at anyone).

>When everything was ready to go, somebody in the next car over
>keyed their CB as they drove away (we heard them do it).  This
>immediately triggered my RC ejection while the rocket sat on
>my lap.  My added caution thankfully prevented injury, but I
>now had to START ALL OVER wiring and prepping.

>An hour later, I'm out on the Hypertek pad, disassembling the
>whole damn rocket in order to arm everything - out in the hot
>sun.  The Utah guys who brought out and supported the Hypertek
>pad are standing around wondering when we'll be ready.  We
>finally get set up and launch.

>Immediately upon ignition, the Pratt RC ejects again, and my
>first-ever hybrid flight is a large twirling circle of flame.
>Amazingly nothing is damaged, but the flight was an utter flop.

>We theorized that the high frequency electronics which produce
>the spark for Hypertek ignition triggerred the Pratt RC.  We
>reproduced the condition in a simple test and confirmed it.

>THe result is this:

>A) The Pratt RC is useless around CB traffic
>B) The Pratt RC is useless around a Hypertek launch system
>C) I wasted a lot of time because I thought it'd be cool to
>   have RC ejection
>D) Next time I'll just use the Black Sky timer, the Pratt RC
>   is not usable for much of what I do at all.  A lot of
>   money down the drain.

>Mark Jeghers

 
 
 

Pratt RC ejection system fails me twice at Black Rock!

Post by Mike Form » Thu, 01 Aug 1996 04:00:00


{snipped an agonizing report of failed RC ejection system(s)}

Quote:

> Mark.

>  I'm sorry you had to spend all that money for the useless R/C system. At
> LDRS, a realy nice rocket I can't name, sat on the pad for OVER 5 HOURS.
> Sat there for at least 4 racks because the dame ejection charge pop'ed
> everytime someone breathed. It never even got to fly!

>  One of the first things I notice when I got to the field the first day,
> was all the Pratt Hobbies control boxes in peoples hands walking around.
> My first thought was, "Oh great, stuff will be pop'ing all over the
> place."... Sure enough. It got so bad that on the next day, they would
> not let you fly ANYTHING untill you turned in all of your control boxes to
> the safe area at the RSO table.

>  Most rockets, like yours, are not "electronis friendly" yet. It cost more
> money to make a rocket that has a simple hatch/door to an electronics bay.
> I guess one way to enhance a system like Pratt Hobbies type systems, is
> to encode the signal, so that the reciver would know if the signal was
> true or false, and sent by you. I believe NASA encryps like this. That
> way, no one can tell the Space Shuttle to open the payload doors during
> desent! Looks like Pratt type systems would have this already, for what
> people are paying for them anyway. What are we talking about here, one chip?
> By no means am I an expert. This just sounds like a common sence type of
> problem easly fixable by people in the know.

This type of thing is very common in other arenas of RC hobbies. Radios
and recievers use pulse code modulation (PCM) to encode the signals so
they aren't interfered with by other things on that freq. I've seen two
airborne RC planes on the same freq., both with PCM. It isn't recommended,
but it works. I can't believe this isn't implemented in this type of
system, considering the wide range of negative reports of the current
systems.

Mike

--
Mike Forman                                                  NetWorks
Internet Services Manager/Midwest                       616 Jefferson  

913-295-5648                                http://www.cjnetworks.com
"Roger, Odyssey, we copy your venting..."Jack Lousma Apollo 13 Capcom

 
 
 

Pratt RC ejection system fails me twice at Black Rock!

Post by Jerry Irvi » Thu, 01 Aug 1996 04:00:00


Quote:

> I was recently involved (as an invited guest) in a rocket launch ad Walt
> Disney World in Orlando Florida. These guys launched two large rockets a
> day for 7 days straight. Anyways, the rockets used 2 Pratt systems in each
> (primary and backup). There seemed to be a problem with frequency scatter
> or whatever you would call it. One transmitter would fire other receivers
> on different frequencies. They found 2 out of 4 different frequencies that
> seemed to play well with each other and used the others in conjunction
> with a differnt system. By the end of the week, 3 of the 4 they were using
> had quit working completely.

In a target rich environment such as a public show, one is best advised to
use a system that is nearly 100% reliable, not under 50%.  I would have
used internal motor delays for primary ejection and adept for secondary.

Quote:

> When they were working, there didn't seem to be any problems. A few other

This is a truism and completely useless.

Quote:
> facts to remember before we go: These system are converted garage door
> openers; builder, Doug Pratt has been associated with R/C for a while and
> is knowledgable;

So what.

Quote:
> Doug is a very nice guy and stands behind his stuff; he is working hard to

Then he should recall it all.

Quote:
> get the bugs worked out and deals with his customers very well. For the
> price you paid, it is probably worth giving him a chance to sort it out
> before you abandon his product.

Probably not.  Perhaps I will do the world a favor and offer to allow
people to trade in Pratt crapola units for full power expendable J125
motors or something.

Jerry

Keep trying Doug.  But do not rerelease until it works over 90% of the
time or the CPSC will hear about it.

--

Box 1242, Claremont, CA 91711 USA
Opinion, the whole thing.

 
 
 

Pratt RC ejection system fails me twice at Black Rock!

Post by Jim Van Gaasbe » Thu, 01 Aug 1996 04:00:00


Quote:

>In a target rich environment such as a public show, one is best advised to
>use a system that is nearly 100% reliable, not under 50%.  I would have
>used internal motor delays for primary ejection and adept for secondary.

Epcot is a target rich environmnet?  I sure wish we knew that before
we launched there. <g>  Give us a little credit Jerry.  We were well
aware of the environment.

We used timers as the *PRIMARY* ejection trigger.  Motor ejection
charges are far too unreliable in large rockets such as the vehicles
that we were launching at Epcot.  RC was used to deploy secondary
parachutes after we were sure the rockets would land in the World
Showcase Lagoon.

Jim Van Gaasbeck

 
 
 

Pratt RC ejection system fails me twice at Black Rock!

Post by Jerry Irvi » Thu, 01 Aug 1996 04:00:00



wrote, I believe in error:

Quote:
> We used timers as the *PRIMARY* ejection trigger.  Motor ejection
> charges are far too unreliable in large rockets

I think previous threads have soundly concluded that internal delays are
indeed reliable and even more so than timers and ejectors, numerically.  I
also offered the suggestion of a table to make sure the proper delay
collumn is installed in reloadable motors so you need not rely on magic
elves who occasionally make mistakes at the factory.

I strongly recommend internal motor ejections as a primary ejection system.

YMMV.

Mine does not.

Jerry

--

Box 1242, Claremont, CA 91711 USA
Opinion, the whole thing.

 
 
 

Pratt RC ejection system fails me twice at Black Rock!

Post by Darrell D. Moble » Fri, 02 Aug 1996 04:00:00


Quote:

> 1) Are there no rules against arming the electronic ignition systems of upper
> stages off the pad? Upper stages account for the vast majority of life
> threatening accidents in HPR. They could be the death of HPR.

I don't think there are any ironclad rules about this, but maybe their
should be.  I know the safety harnesses are designed to be installed so
that they are mounted through the body tube, i.e. accessible from the
outside.  But, if the safety harness supplied with the kit isn't long
enough to route the jacks through the body tube, rather than get *longer*
safety harnesses, people start cutting corners.  Flying rockets safely
should be the primary consideration of any project, not the additional
inconvenience you have to go through to order or build longer safety
harnesses.

Quote:
> 2) Doesn't the ignition system in question work on a coded signal? It's
> not perfect, but it's better than having your upper stage fire when someone
> else is firing his. This *is* the design, isn't it?

Yes, and no.  The signal is coded to a specific frequency, of which
multiple transmitters of the same frequency are sold.  I think when Doug
went to design this system, he was faced with two scenarios: a) design a
unique system with multiple frequency safeties built in which would
require submission to the FCC for approval, or b) work within the given
product range Ace had to offer which was already FCC approved.  The price
of (a) was obviously much more expensive than (b), probably moreso that
our hobby would have been willing to pay.  So, we got (b).

Personally, I never arm *ANY* system until I am on the pad and ready to
launch.  On my 16 ft. Terrier Sandhawk flown at LDRS, I used two
altimeters, one PST941 time and a Pratt system, and *nothing* was armed
until it was raised into the vertical position.  There is just too much
opportunity for disaster when you have a K550*** off the receiver of
an R/C unit to arm anything earlier.  BTW, to simplify the electronics
spaghetti pit that you can get with that much electronics, I mounted
everything in the upper stage on a single PC-style edge card.  *Voila* no
wires to tangle!

Quote:
> Reminds me of a friend of mine got a vasectomy done at Sears. Problem is that
> every time he gets e***d, the garage door opens :-)

Speaking of garage doors and ECS systems, have you ever had your garage
door open accidentally, with all the door openers in America?  Me
neither.

Quote:
>(Taking a clue from D.M. - I was getting negative again. Sorry.)

I hope you have forgiven me for my comment on CIS, I was out of line.
 
 
 

Pratt RC ejection system fails me twice at Black Rock!

Post by Bob Kapl » Fri, 02 Aug 1996 04:00:00


Quote:

> When they were working, there didn't seem to be any problems. A few other
> facts to remember before we go: These system are converted garage door
> openers; builder, Doug Pratt has been associated with R/C for a while and
> is knowledgable;

Say what? The Pratt systems are built by Ace RC in Missouri, perhaps the only
RC manufacturer left in the US of A. They have always made quality stuff. I
believe the units use the RC channels sandwiched in the middle of the CB band,
and thus are succeptable from CB inteference. This is especially true of
illegal rigs, as they tend to run hi power dirty amps and/or use the RC
frequencies for talking.

Quote:
> Doug is a very nice guy and stands behind his stuff; he is working hard to
> get the bugs worked out and deals with his customers very well. For the
> price you paid, it is probably worth giving him a chance to sort it out
> before you abandon his product.

Nice, yes. I've known him for 20 years, but haven't seen him for a few years
now. But if there are bugs in the system, they shouldn't be on the market. We
wouldn't buy motors form a manufacturer who was still working out the design,
and half of them catoed, would we :-)

        Bob Kaplow      NAR # 18L       TRA # "Abort, Retry, Fail?"

 
 
 

Pratt RC ejection system fails me twice at Black Rock!

Post by Larr » Fri, 02 Aug 1996 04:00:00


Just a couple of opinions here...

1) Are there no rules against arming the electronic ignition systems of upper
stages off the pad? Upper stages account for the vast majority of life
threatening accidents in HPR. They could be the death of HPR.

2) Doesn't the ignition system in question work on a coded signal? It's
not perfect, but it's better than having your upper stage fire when someone
else is firing his. This *is* the design, isn't it?

Reminds me of a friend of mine got a vasectomy done at Sears. Problem is that
every time he gets e***d, the garage door opens :-) (Taking a clue from
D.M. - I was getting negative again. Sorry.)

Regards,
-Larry Curcio

 
 
 

Pratt RC ejection system fails me twice at Black Rock!

Post by John H. Cato, Jr » Sun, 04 Aug 1996 04:00:00


Quote:

> I don't think there are any ironclad rules about this, but maybe their
> should be.

Darrell, check out NFPA 1127 in Chapter 2 (don't remember the particular
paragraph right off-hand) but there is a provision for not arming
ignition circuits in other than a 'launching position'.  That means that
upper stages canNOT be armed until and unless they are in that
'launching position' - which means vertical on the pad.

-- john.

 
 
 

Pratt RC ejection system fails me twice at Black Rock!

Post by Darrell D. Moble » Sun, 04 Aug 1996 04:00:00



Quote:


> > I don't think there are any ironclad rules about this, but maybe their
> > should be.

> Darrell, check out NFPA 1127 in Chapter 2 (don't remember the particular
> paragraph right off-hand) but there is a provision for not arming
> ignition circuits in other than a 'launching position'.  That means that
> upper stages canNOT be armed until and unless they are in that
> 'launching position' - which means vertical on the pad.

Thanks, John, I'll read up on that.  Nice to know I was legal by using my
noodle!  ;-)
 
 
 

Pratt RC ejection system fails me twice at Black Rock!

Post by Jeff Vince » Wed, 07 Aug 1996 04:00:00


Quote:

>Reminds me of a friend of mine got a vasectomy done at Sears. Problem is that
>every time he gets e***d, the garage door opens :-) (Taking a clue from
>D.M. - I was getting negative again. Sorry.)

   Yes, but don't forget that Sears Craftsman warranty -- if your "tool"
breaks, you can get it "fixed" for free.  ;)


Pick one or more: Model Rockets (competition-NERCB) / PCs (even Atari!) /
Papyrus ICR-ICR2-NCR / Who needs a life when you have multiple non-lives?

 
 
 

Pratt RC ejection system fails me twice at Black Rock!

Post by Modem Nak » Sat, 10 Aug 1996 04:00:00


HELLO
ALL!!!!!

In regards
to the
following

Quote:
>>  Most

rockets,
like
yours, are
not
"electroni
s
friendly"
yet. It
cost more
Quote:
>> money

to make a
rocket
that has a
simple
hatch/door
to an
electronic
s bay.
Quote:
>> I guess

one way to
enhance a
system
like Pratt
Hobbies
type
systems,
is
Quote:
>> to

encode the
signal, so
that the
reciver
would know
if the
signal was
Quote:
>> true or

false, and
sent by
you. I
believe
NASA
encryps
like this.
That
Quote:
>> way, no

one can
tell the
Space
Shuttle to
open the
payload
doors
during
Quote:
>> desent!

Looks like
Pratt type
systems
would have
this
already,
for what
Quote:
>> people

are paying
for them
anyway.
What are
we talking
about
here, one
chip?
Quote:
>> By no

means am I
an expert.
This just
sounds
like a
common
sence type
of
Quote:
>> problem

easly
fixable by
people in
the know.
Quote:

>This type

of thing
is very
common in
other
arenas of
RC
hobbies.
Radios
Quote:
>and

recievers
use pulse
code
modulation
(PCM) to
encode the
signals so
Quote:
>they

aren't
interfered
with by
other
things on
that freq.
I've seen
two
Quote:
>airborne

RC planes
on the
same
freq.,
both with
PCM. It
isn't
recommende
d,
Quote:
>but it

works. I
can't
believe
this isn't
implemente
d in this
type of
Quote:
>system,

considerin
g the wide
range of
negative
reports of
the
current

Quote:
>systems.

>Mike

Eeck
sounds
like too
much
money. In
amature
radio and
some
business
band you
can have a
subaudible
tone say
102.7 mhz
on it.
Unless the
reciever
recieves
that tone
it doesn't
break
squelch.  
though
there is
only so
many
encoder/de
coder kits
and people
would be
bound to
pick the
same freq
at least
once or
twice.
Another
idea I
have is
that you
could use
DTMF codes
in the
same way
and say
you had
four
digits or
so you
could set
this up
with dip
switches
and
everyone
at the
launch
using this
sytem
could
choose
different
numbers.

Chris BAR