Rocketman flanged aft closure Q.

anybody know if this is considered modifying the motor under NAR rules? DR Rocket's hardware is licensed by aerotech and is ok to mix with AT load or
parts, but Rocketman's does not say anything, TIA, Le
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My understanding is that any new hardware requires testing by TMT. It DEFINATELY WOULD VOID the AeroTech warranty, since we have not authorized third party manufacturing of compatible components to this manufacturer, nor have we supplied the actual dimensional drawings of detail parts which govern the proper tolerances required. Using an existing part as reference, (Oklahoma blueprint) is not acceptable by any means. The basic concept is good, but the execution is poorly planned.
Robert

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Didn't the blueprints used to be posted to the web site? I've still got my hard copy from 1990.
    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
    26-October, 2001: A day that will live in infamy     Support Freedom: http://www.indefenseoffreedom.org /
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kaplow snipped-for-privacy@encompasserve.org.TRABoD (Bob Kaplow) writes:

Got an email from Gary pointing out that the blueprints posted / distributed were NOT the fully detailed blueprints licensed to Dr Rocket. I've also seen cloned hardware that clearly lacked some of the obvious safety features of the factory approved casings.
    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
    26-October, 2001: A day that will live in infamy     Support Freedom: http://www.indefenseoffreedom.org /
    Voting for "the lesser of two evils" is still voting for evil.
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On 30 Oct 2004 22:50:56 -0500, kaplow snipped-for-privacy@encompasserve.org.TRABoD (Bob Kaplow) wrote:

Which safety featuers? Who maakes them? People should watch out for that.
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The unauthorized clones I saw had no brand or even anodizing on them. It was nothing more than aluminum tubing of the right size with threads of the right pitch. Some were bought from a vendor, but I don't know who. Others were made by locals, and used at TRA launches (not EX).
    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
    26-October, 2001: A day that will live in infamy     Support Freedom: http://www.indefenseoffreedom.org /
    Voting for "the lesser of two evils" is still voting for evil.
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On 31 Oct 2004 06:54:43 -0600, kaplow snipped-for-privacy@encompasserve.org.TRABoD (Bob Kaplow) wrote:

As far as I know, anodizing is not a safety feature.
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Correct.
--
Joe Michel
NAR 82797 L2
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Phil Stein wrote:

Neither is the brand marking.
Details of the machined shape at the bottom of the thread may be, though... there may be features that provide for controlled failure patterns under accidental overpressure, or that prevent stress concentrations that could cause the tube to crack open under normal operatng pressure.
-dave w
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On Sun, 31 Oct 2004 10:44:43 -0800, David Weinshenker

I can't imagine how anyone wouldthink this has anything to d with safety.

There isn't anything special about the shape below (or above) the threads. In fact if you look at any size casings, there isn't anything to make it fail in a soecific way. Also if you see these fail it's apparent.
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says...

There is nothing mysterious, magical or special about those rear closures. Take chunk of aluminum, add threads, drill hole. Add knurls if you want to get fancy. Of course, that doesn't support anyone who can do it themselves, so add a pinch of the mysterious and wah-lah, institutionalized protectionism in a flash.
Controlled failure pattern? AT failure pattern is usually to open up like a steamed burrito.
--
Tweak

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On Mon, 1 Nov 2004 11:07:29 -0500, Tweak

You mean it's not a squished banana?
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snipped-for-privacy@ArielSystems.spamsks.net says...

More like a over-nuked hot dog.
--
Tweak

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Tweak wrote:

Come to think of it, is "ends popping off" really that much less hazardous a failure mode than "tube splitting open"? I can see that the latter might be a concern with a brittle casing, but it should be comparatively benign with a tube material that will "unroll" instead of "fragmenting". (Benign for the observers, that is... the airframe may well be toast in any case.)
-dave w
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says...

What I usually see is the complete destruction of the rocket, regardless of failure mode.
When the end cap does come off, the motor usually shoots through the rocket, like an alien coming out of it's belly through it's nose, obliterating everything in it's path. Centering rings, nose cone, electronics, 1/2" stainless hardware...nothing stands in the way of one of these beasties. Henceforth, I will refer to these nasty occurrences as Alien CATOs.
When the case ruptures, fins go flying and the bottom of the rocket usually takes the brunt of the damage. I personally would prefer a burrito CATO for my rockets, as the destruction isn't usually quite as absolute as the alien CATO. These CATOs just don't seem as violent as the Alien variety.
I have only seen one or two cases where the motor extinguished itself when the end closure came off.
I think the distance table is quite enough protection for rocketeers regardless of failure mode.
--
Tweak

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Tweak wrote:

I saw one of those, very early in the burn, with a G125 - it looked almost like an ignition failure, except I saw a small flash of blue flame, and when I went to look at the rocket itself, then nose was ejected about 1 cm or so...
Thinking that this was a bit odd, I removed the motor for inspection... the case had cracked right at the delay assembly, which had fallen off... about 2cm of the motor was loose inside the rocket; the ejection powder and delay grain were unburned (and the powder was loose in the airframe, since the rupture had carried away a flake of the casing and opened the side of the powder chamber behind the paper seal)... the forward end of the propelllant was visible, unburned (except that the core was a little enlarged on one side where the igniter was). It looked like the failure had occured in the immediate pressure spike of ignition, and extinguished everything before there was really enough heat in the propellant surface to keep things burning after that.
-dave w
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says...

Sounds about right, particularly with the smaller motors. The majority I have seen, though, have been of the Alien CATO variety. And when you are talking about K and up motors, it gets real ugly real fast. SssssSSS..BOOOM! Seen stainless blast deflectors twisted up by whatever comes out of the bottom of the self destructing motor hitting them.
Drawback of the system, as the forward motion of the motor is checked by the rear closure. If it comes off, there is nothing to prevent the motor from going forward (unlike, say, brand K motors that have an external thrust ring separate from the rear closure).
--
Tweak

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On Mon, 01 Nov 2004 09:25:07 -0800, David Weinshenker

I think the ends popping would be safer because the stuff would just go straight up & down. This yeilds a much smaller splash pattern. I test my ex stuff in a hole dug with a post hole digger. If something over pressurizes, I only have to look for the stuff that went straight up. Since it only went straight up, it's much easier to find.
For those that don't know, the aluminum casings have almost no fragmentation. Many other substances can't make this claim.
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That is not the point in regulatory matters. Literal words are.
Sadly.

In any case there have been manufacturer claims over the years that the ends are designed to fail to prevent either unroll or fragment.
Jerry
--
Jerry Irvine, Box 1242, Claremont, California 91711 USA
Opinion, the whole thing. <mail to: snipped-for-privacy@gte.net>
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On Mon, 1 Nov 2004 11:45:40 -0500, Tweak

Yep - best one yet.
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