Important Launch Tip! (and crash picture)
Warren
"teachable moment" is instructor-speak for seizing the opportunity to
convert a negative experience into a positive learning experience.)
I suffered a rather impressive, and before now unexplained, crash right
off the launch rod at February's Maryland Tripoli launch. Just recently,
a roll of film was developed that caught the launch of my "X-Calibur"
and finally revealed the reason for the crash.
If there is anyone out there who doubts the importance of _firmly_
staking down the wires from the launcher, go to:
http://patriot.net/~warrenp/xcaliburcrash.htm
and check out the photo.
I hope this helps someone else out there to avoid what happened to me.
... Warren
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Have you ever noticed that those instruments designed to detect
intelligent life in the universe are all pointed AWAY from Earth?
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
JDcluster
preach to people not to tape the igniter to the rocket . If so make
double sure you
tie the leads to the pad .
Jeff
--
"If it doesn't fly straight: stick a bigger motor in it we'll make it
fly straight "
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Jeff Davenport
http://www.users.nac.net/jdcluster/JDindex.html
METRA B.O.D & Web Master
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TRA: 4486 L3
NAR: 63238 L: coming soon
Paul Stevens
Is this a potential problem with smaller rockets using Estes engines?
On the last flight of my Estes Skywinder, I noticed some instability
just as it cleared the launch rod. It wobbled for the first ten to
fifteen feet, then stabilized. I've been trying to come up with all
the possible explanations (loss of clay from the nose cone, the rotor
mechanism snagging the launch rod, etc), but hadn't thought about the
ignitor wires.
I've never staked the wires, since it hadn't occured to me that the
ignitor might not blow out of the motor on ignition.
--
Paul Stevens
Sleeping Dragon Forge
http://www.geocities.com/Heartland/Lake/7316/index.html
Jim Yanik
<3B3F40D0...@bellsouth.net>:
I believe that it's more of a problem with the composite motors,that have
the igniters inserted far up into the motor,and some people taping the
igniter to the nozzle or motor case to insure proper placement.Some
igniters are barely small enough to go through the nozzle,too. That's not a
problem with Estes motors,which are end-burning grains.
--
Jim Yanik,NRA member
remove X to contact me
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Paul Stevens
Thanks for the clarification.
I think I'll start wrapping the igniter wires around the leg of the
launch pad. Ol' Murphy shows up often enough...
DCastle872
parts that trail the motor. I had leads catch once on a poorly designed
scratch built model that used tubes for stabilization..that were attached to
the body tube by long struts and trailed behind the rocket by about 6 inches.
The leads caught and at about 15 feet up they took up the rest of the slack and
caused the rocket to have a spectacular cartwheel and crash.
Front motor gliders are also at particular risk.
Dan Castle
NAR 77391
CMASS Member
Mark Saunders
Tripoli. 8^)
Best regards,
--
Mark Saunders, KJ7BS
Glendale, Arizona
NAR 78825 L1
SSS
Warren <war...@patriot.net> wrote in message
news:3B3F17...@patriot.net...
GCGassaway
Thsi reminds me of an accident i saw 9 years ago.
In 1992, Jay Marsh flew a 1/66 Saturn-IB boilerplate that mysteriously pitched
hard over at liftoff, flying horizontal and crashing about 200 feet away. It
had made several great glights before, so seeing it pitch like that was a huge
surprise. Was a mystery for awhile. Not sure how we realized what happened, if
it was video or if it was the launch lead wires laying on the ground 180
degrees away from the direction the model pitched, the leads many feet away
from the pad (I think the leads were the clue and video confirmed it).
The lead wires got carried by the model, for a bit, thne stretch to their limit
and yanked on the tail to make it pitch like that, and then let go. It was
bizarre since that was not a clustered flight where perhaps an unignited engine
might be the culprit. It was a single E30 engine in the 1st stage. But the red
cap holding the copperhead to the extended nozzle didn't pop off, it melted a
hole in the bottom of the red cap and stuck to the nozzle, which trapped the
copperhead's leads between the extended nozzle and the red cap. And the
Aerotech ignitor clip had a deathgrip on the copperhead.
But of course it can also happen to any model where the ignitor leads are
securely attached to the motor in some way. And for clustered models you pretty
much have to plan for it to happen. I've seen several photos of flashbulb
ignition models where the "bundle" of bulbs and wires trail up with a rocket
when one or more engines didn't ignite or was late to ignite. Had a few like
that myself but fortunately the launch control leads themselves didn't go up
with the model, just the flashbulb bundle.
A good precaution is to not just secure the leads directly under the model, to
the pad or ground right under, but to use clips to attach to the ignitor that
can slip free as the rocket goes up (much as I hate to use the term in light of
that NBC "game" show... the "weakest link" approach)
Also a few accidents with gliders. Adding an umbilical rod or post to hold the
leads helps a lot in keeping the clips from grabbing the glider.
- George G.
Paul Stevens
>
> Jim Yanik wrote:
> >
(snip)
> > >
> > >Is this a potential problem with smaller rockets using Estes engines?
> > >
> > >On the last flight of my Estes Skywinder, I noticed some instability
> > >just as it cleared the launch rod. It wobbled for the first ten to
> > >fifteen feet, then stabilized. I've been trying to come up with all
> > >the possible explanations (loss of clay from the nose cone, the rotor
> > >mechanism snagging the launch rod, etc), but hadn't thought about the
> > >ignitor wires.
> > >
> > >I've never staked the wires, since it hadn't occured to me that the
> > >ignitor might not blow out of the motor on ignition.
> > >
> >
> > I believe that it's more of a problem with the composite motors,that have
> > the igniters inserted far up into the motor,and some people taping the
> > igniter to the nozzle or motor case to insure proper placement.Some
> > igniters are barely small enough to go through the nozzle,too. That's not a
> > problem with Estes motors,which are end-burning grains.
> >
>
> Thanks for the clarification.
>
> I think I'll start wrapping the igniter wires around the leg of the
> launch pad. Ol' Murphy shows up often enough...
>
I think I've found my problem. This afternoon was my first launch
since the wobbly launch of the Skywinder. While putting the rocket
on the rod, I noticed it dragged as it went down. Residue, from
the motors on previous launches, had built up on the launch rod
and caused friction to slow the rocket down (until it cleared the
rod).
A few seconds with some fine sandpaper (and a mental note to do this
in the future) solved the problem.
Kevin Rich
melted through and the copperhead still dangling. When I went to hook up
my next rocket..... I suddenly realized what the little object I had seen
flying off the first rocket had been. The copperhead clip had pulled
cleanly of the lead clips and went along until G's,, exhaust or wind
resistance knocked it off. Goner......... had to get another one. I think
I will tie this one to the pad!
--
Kevin
TRA # 8732 Lvl 1
FAA Senior Parachute Rigger
Bob Ellis
Don't use sandpaper, it will just crud up before it gets
most of the residue off. Instead get a green or brown
kitchen scrubbie and spray the scrubbie with WD-40 or Simple
Green. (Your choice, just depends on how you want your hands
to smell.)
If you're still using the Estes two piece aluminum rod,
don't bother to clean it, go to a hobby or hardware store
and get a piece of 3 foot long, 1/8th inch stainless steel
rod (piano wire). It won't bend, is stiffer, easier to
clean and you won't have a rocket hang up on the joint in
the middle of the rod (another possible cause of wobbly
launches).
Keep the aluminum rods, they come in handy when you are
putting on two piece launch lugs. Wrap tape around them at
the point where launch lugs are going to be, make the tape
just thick enough to hold the lug in place. Then slide the
lugs on, over the tape and glue the lugs down. It keeps the
lugs exactly aligned and the rod makes it easier to get
lined up straight on the body tube.
Bob Ellis
Paul Stevens
>
> Paul,
>
> Don't use sandpaper, it will just crud up before it gets
> most of the residue off. Instead get a green or brown
> kitchen scrubbie and spray the scrubbie with WD-40 or Simple
> Green. (Your choice, just depends on how you want your hands
> to smell.)
>
> If you're still using the Estes two piece aluminum rod,
> don't bother to clean it, go to a hobby or hardware store
> and get a piece of 3 foot long, 1/8th inch stainless steel
> rod (piano wire). It won't bend, is stiffer, easier to
> clean and you won't have a rocket hang up on the joint in
> the middle of the rod (another possible cause of wobbly
> launches).
>
> Keep the aluminum rods, they come in handy when you are
> putting on two piece launch lugs. Wrap tape around them at
> the point where launch lugs are going to be, make the tape
> just thick enough to hold the lug in place. Then slide the
> lugs on, over the tape and glue the lugs down. It keeps the
> lugs exactly aligned and the rod makes it easier to get
> lined up straight on the body tube.
>
> Bob Ellis
>
Thanks for the tips.
Bob Kaplow
> Absolutely it's a potential problem, in particular with models that have any
> parts that trail the motor. I had leads catch once on a poorly designed
> scratch built model that used tubes for stabilization..that were attached to
> the body tube by long struts and trailed behind the rocket by about 6 inches.
> The leads caught and at about 15 feet up they took up the rest of the slack and
> caused the rocket to have a spectacular cartwheel and crash.
>
> Front motor gliders are also at particular risk.
You can say that again. Especially when you launch off a single rod, with
the glider half way up the rod, and the clips stretched to meet the glider.
For a better solution to this problem see the RMR FAQ part 8 on lauching BGs
and build a Power Tower launcher, a very simple glider pad.
Bob Kaplow NAR # 18L TRA # "Ctrl-Alt-Del"
Kaplow Klips & Baffle: http://www.nira.chicago.il.us/Leading_Edge/MayJun00.pdf
NIRA: http://www.nira.chicago.il.us NAR: http://www.nar.org
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Bob Kaplow
> But of course it can also happen to any model where the ignitor leads are
> securely attached to the motor in some way. And for clustered models you pretty
> much have to plan for it to happen. I've seen several photos of flashbulb
> ignition models where the "bundle" of bulbs and wires trail up with a rocket
> when one or more engines didn't ignite or was late to ignite. Had a few like
> that myself but fortunately the launch control leads themselves didn't go up
> with the model, just the flashbulb bundle.
Reminds me of the first of 2 fires we had at NARAM-33, the first NARAM to
fly HPR. The HPR pad was in an area where we had cleared out tall weeds all
around the pad. Will Safford (there's a name that hasn't been on RMR for a
LONG time!) had a humungus HPR cluster with lots of flashbulbs. The rocket
took off, but pulled up on the clip leads. The relay must and finally
separated the leads from the rocket, but acted as a pivot point, throwing 12
very hot bulbs 180 degrees opposite the pad from the relay, to an area that
was not cleared. Fortunately we saw the smoke quickly, and dispatched Indian
pumps and had the fire out before we burned more than a few square feet.
I'd recommend keeping the relay box as close to the pad as possible, both to
shorten the wires, and to prevent them from being flung, and to insure that
any torque they might apply to the model is in the line of flight.
Tirran
>If you're still using the Estes two piece aluminum rod,
>don't bother to clean it, go to a hobby or hardware store
>and get a piece of 3 foot long, 1/8th inch stainless steel
>rod (piano wire).
Umm... piano wire isn't stainless steel. I've cleaned far too much
rust off my old one.
OTOH, as long as you do keep it clean, piano wire is wonderful for
launch rods. It's smooth, it's straight, it doesn't bend or flex much. Real
stainless has its good points, but it's softer than it should be for a
decent launch rod.
Tir'
Bob Ellis
much better than the Estes aluminum two piece rod. I also
prefer the piano wire, a little bit stiffer and easier to
find, you just have to clean it a little better. Most
people refer to them more or less interchangeably.
Bob Ellis