Engine Recovery

For competition, it sounds like its ok to eject the engine, provided you provide a recovery device to return it to the ground safely, right?

That being the case, if you attached a streamer to a length of kevlar line, then attached the end of the line to the edge of the engine with a drop of superglue, would that be acceptable, or would that constitute an "engine modification"? The recovery device can easily be reused by simply scraping it back off with an razor knife to glue to the next engine.

kfox1111 said:

For competition, it sounds like its ok to eject the engine, provided you provide a recovery device to return it to the ground safely, right?

That being the case, if you attached a streamer to a length of kevlar line, then attached the end of the line to the edge of the engine with a drop of superglue, would that be acceptable, or would that constitute an "engine modification"? The recovery device can easily be reused by simply scraping it back off with an razor knife to glue to the next engine.

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While ejecting spent motor casings is permitted in some limited competition events with the addition of a streamer to the motor casing, it would NOT be allowed in PD or SD events as the model Must remain in one complete package durning the entry flight & recovery. Dropping the motor casing is not be allowed in ANY duration competition event period.

Not sure what particular competition event your thinking about but in the few where it would be allowed:
Why do you fell the need to use CA and Kevlar. Simply attaching the streamer with thin mylar tape to the outside casing is all that's needed.
Just make sure the streamer meets the Minimum Square inch size requirement listed in the PinkBook.
To allow room for these minimum size streamer wrapping the motor casing, we increase the motor tube size from T2+(.281"od) to either T2++ (.316"od), T3 (.375" OD) or roll a custom motor tube out of Tracing Vellum. Tracing vellum would be the Lightest way to go.

Micromeister said:

While ejecting spent motor casings is permitted in some limited competition events with the addition of a streamer to the motor casing, it would NOT be allowed in PD or SD events as the model Must remain in one complete package durning the entry flight & recovery. Dropping the motor casing is not be allowed in ANY duration competition event period.

Not sure what particular competition event your thinking about but in the few where it would be allowed:
Why to you fell the need to use CA and Kevlar. Simply attaching the streamer with thin mylar tape to the outside casing is all that's needed.
Just make sure the streamer meets the Minimum Square inch size requirement listed in the PinkBook.
To allow room for these minimum size streamer wrapping the motor casing, we increase the motor tube size from T2+(.281"od) to either T2++ (.316"od), T3 (.375" OD) or roll a custom motor tube out of Tracing Vellum. Tracing vellum would be the Lightest way to go.

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Hi Micromeister,

I'm still toying around with altitude competition ideas. Is motor ejection allowed there?

I was thinking kevlar might hold up ok with getting hit by an ejection charge blast without any wadding.

Mylar tape's an interesting idea. Would it melt if hit by ejection gas directly?

I was trying to think of a way to have a minimal t2+ tube while still having a streamer assisted engine ejection. I think the kevlar thing might work. Something like:
Bulkhead, coupler where rolled up streamer is, t2 sized cardboard disk (streamer end attached on one side, kevlar on the other. cardboard disk loose in the tube), kevlar string, with enough length that the cardboard disk can still be in place with the engine outside of the rocket, and the engine (glued to the kevlar line at one point on the end). The ejection charge would push on the cardboard disk, kicking the engine out of the rocket, and once the kevlar line is taught, it pulls out the disk and streamer. If packed loosely enough, the hope is this would allow the engine to kick out without affecting the rocket's continual upwards direction (and maybe even would help a bit), If the rocket continues to go up for a couple of seconds, it might get quite a bit more altitude. If its a non-payload altitude competition, it might be light enough for the rocket to tumble back safely? If not, then it would need some second deceleration mechanism for the rocket as we were discussing in the other post.

What do you think?

I think you should visit the NAR web site.
Download and READ(several times) the Model Rocket competition sporting Code (Pink Book). All the specific rule for each event are pretty clear.

All this extra stuff you are trying to add to an Altitude model adds unnecessary mass which effects the possible achieved altitude. KISMIF (Keep It Simple, Make it Fun) is ALWAYS the way to go with ALL competition models. The more complicated we try to make these models the more likely it will be DQ'ed for NO Deploy, Separation or some other recovery failure reason. Thinking outside the box is always a good way to learn but reducing the model to the absolute simplest, lightest configuration is the ONLY way to get close to placing in actual competition. To be honest the only events that can benefit from more complex designs are HD, RG, RCRG and all forms of SCALE. even with these reliability is more important then being complex. Hope that sort of makes sense.

I've said this before I'll say it again: Kevlar is NOT flame Proof, it is only heat resistant. it degrades every time it is exposed to temperatures above 900°f. our BP motors and ejection charges BEGINNING ignition temperature is 909°f and goes UP form there. Even our tiny Micro Maxx-II motors have a FLAMING "afterburn" that can last almost a full second.
All that to say putting a cardstock disc, Kevlar and the streamer material above and trying to be dragged out by the ejecting motor just has all kinds of negative aspects as opposed to keeping the motor ejection streamer wrapped around the motor casing itself, IF it were legal to eject the motor in altitude competitions.

Ok. I'll read through the Pink Book. Thanks.

I usually agree with the KISS rule. Its always going to be better to simply choose the right ejection delay and make the rocket as light as possible. Except (there is an exception to every rule), that there is no mmx engine with the proper ejection delay for these rockets. Not even close. Since it has been many years since they came out, with lots of requests since for better delays, I doubt it will come about any time soon. Therefore, to get around it some other way may pay dividends.

So, playing within the rules of not modifying or building your own rocket engine, (I really don't want to do either), what's the Simplest thing I can do to overcome the poor delay charge choices? (Rhetorical question).

Kicking out the motor safely while leaving the rocket to continue on, is one solution, assuming it will continue up, that its light enough to featherweight down, and that for competition they consider the highest point on the rocket, not the lowest point of the rocket. IE, the engine that was left behind. And that its not a disqualifier. Not sure. Figured I'd ask folks with more knowledge on the subject... I also didn't want to spend much time testing theories on something that wouldn't be legal anyway.

Thanks for the information about the kevlar. You saved me time/effort/money testing that theory. That's why I've been asking these sorts of questions. I know there are folks much more knowledgeable of some of these things then I.

Thanks for the help.

kfox1111 said:

Ok. I'll read through the Pink Book. Thanks.

I usually agree with the KISS rule. Its always going to be better to simply choose the right ejection delay and make the rocket as light as possible. Except (there is an exception to every rule), that there is no mmx engine with the proper ejection delay for these rockets. Not even close. Since it has been many years since they came out, with lots of requests since for better delays, I doubt it will come about any time soon. Therefore, to get around it some other way may pay dividends.

So, playing within the rules of not modifying or building your own rocket engine, (I really don't want to do either), what's the Simplest thing I can do to overcome the poor delay charge choices? (Rhetorical question).

Kicking out the motor safely while leaving the rocket to continue on, is one solution, assuming it will continue up, that its light enough to featherweight down, and that for competition they consider the highest point on the rocket, not the lowest point of the rocket. IE, the engine that was left behind. And that its not a disqualifier. Not sure. Figured I'd ask folks with more knowledge on the subject... I also didn't want to spend much time testing theories on something that wouldn't be legal anyway.

Thanks for the information about the kevlar. You saved me time/effort/money testing that theory. That's why I've been asking these sorts of questions. I know there are folks much more knowledgeable of some of these things then I.

Thanks for the help.

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One of the very first things you should know is just about ALL Altutude compeititons are tracked to EJECTION, not apogee. Tracking Micros is even more of a challange due to their tiny size and distance from the Tracking Theodolites. Most (not all) Micros are two small to use Altimeter altituded tracking so Visual is the only alternative.

This is why I suggested getting your hands on a copy of the pink book so you'll better understand the rules within which NAR comptetitions are flown. Becasue of the tracking to ejection (rule of thumb) ejecting the motor casing isn't going to help with achived "Tracked and Closed" altitude.

I can tell you first hand Tracking Micro Altitude models IS a REAL Challange even using a 300foot baseline (rather then the traditional 1000ft baseline).
Currently both 1/8A-Alt and 2x1/8A Cluster Alt, altitude National records are pinned at 83m (269') and YES these altitudes are directly tied to the Short average .854 second delay.

I have had Tracked and Closed flights of 92m (302') and 96m (315') in non-sanctioned launches back in 2000 and 2001 with the orignial MMX-1 plastic Casing 1/8A.2-1 motors that had the slightly longer average delay of 1.07s. So longer delays would really help. Unfortunately these older MMX-I motors are no longer certified for competition use and because Quest has a couple Million MMX-II motors on hand, having another run made with longer delay is simply out of the questions from a business standpoint.
Last time I spoke with Bill Stine directly about this question (we were acutally talking about having a true MMX-0 booster made) he mentioned that when the current stock is Greatly reduced a Booster would be coming for sure, but that extended the delay may be a problem due to lack of sufficent room in the casing as well as the added expense of additional certification testing. This conversation was more then 2 years ago.

Personally I believe higher flights are possible Only when we design a super light weight altimeter packaged on a PC board that will fit inside a T2 (.220" ID) tube and find or build a power source or Supercap to power it at 2.5volts or less. At this time that my friend is a pretty tall order.

The closest one i've found so far is the Czech Adrel Alt-Led with it's Lipoly battery but the smallest tube it can fit is T4(.448"od). I've thought of asking Pico if they could design such an altimeter but the power supply is really the biggest stumbling block, not to mention the custom price tag

Micromeister said:

One of the very first things you should know is just about ALL Altutude compeititons are tracked to EJECTION, not apogee. Tracking Micros is even more of a challange due to their tiny size and distance from the Tracking Theodolites. Most (not all) Micros are two small to use Altimeter altituded tracking so Visual is the only alternative.

This is why I suggested getting your hands on a copy of the pink book so you'll better understand the rules within which NAR comptetitions are flown. Becasue of the tracking to ejection (rule of thumb) ejecting the motor casing isn't going to help with achived "Tracked and Closed" altitude.

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Hmm... the pink book says that it should be tracked by altitude, and only by ejection by exception. So the choice to always do it by ejection a pragmatic one due to them being so hard to track? This is the reason I'm asking questions on the forum. The actual rules, and what happens on the field don't always match up.

Micromeister said:

I can tell you first hand Tracking Micro Altitude models IS a REAL Challange even using a 300foot baseline (rather then the traditional 1000ft baseline).
Currently both 1/8A-Alt and 2x1/8A Cluster Alt, altitude National records are pinned at 83m (269') and YES these altitudes are directly tied to the Short average .854 second delay.

I have had Tracked and Closed flights of 92m (302') and 96m (315') in non-sanctioned launches back in 2000 and 2001 with the orignial MMX-1 plastic Casing 1/8A.2-1 motors that had the slightly longer average delay of 1.07s. So longer delays would really help. Unfortunately these older MMX-I motors are no longer certified for competition use and because Quest has a couple Million MMX-II motors on hand, having another run made with longer delay is simply out of the questions from a business standpoint.
Last time I spoke with Bill Stine directly about this question (we were acutally talking about having a true MMX-0 booster made) he mentioned that when the current stock is Greatly reduced a Booster would be coming for sure, but that extended the delay may be a problem due to lack of sufficent room in the casing as well as the added expense of additional certification testing. This conversation was more then 2 years ago.

Personally I believe higher flights are possible Only when we design a super light weight altimeter packaged on a PC board that will fit inside a T2 (.220" ID) tube and find or build a power source or Supercap to power it at 2.5volts or less. At this time that my friend is a pretty tall order.

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Yeah, I've been keeping an eye out for batteries that might work. Closest I've found was the energizer 377 battery. Still not quite enough though. The weight limitation of only 1 additional gram makes it pretty much impossible to do anything electronic.

Micromeister said:

The closest one i've found so far is the Czech Adrel Alt-Led with it's Lipoly battery but the smallest tube it can fit is T4(.448"od). I've thought of asking Pico if they could design such an altimeter but the power supply is really the biggest stumbling block, not to mention the custom price tag

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One more question. Section 1.1 says that metal can't be used if it presents a hazard. That's somewhat ambiguous. Would a pen spring that exists inside the body tube and isn't exposed considered a hazard? If it is acceptable, I think I may have a solution that could be made to work. I'll give it a try if acceptable.

Thanks,
Kevin

kfox1111 said:

Hmm... the pink book says that it should be tracked by altitude, and only by ejection by exception. So the choice to always do it by ejection a pragmatic one due to them being so hard to track? This is the reason I'm asking questions on the forum. The actual rules, and what happens on the field don't always match up.

Wrong Again! the Pink book say tracking will be done to Apogee "WHERE PRACTICAL" in most cases it isn't. At the option of the CD "Contest Director" tracking can be done to Ejection. Which is almost always the PREFERRED method. This is especially ture with small fast moving tiny models.


Yeah, I've been keeping an eye out for batteries that might work. Closest I've found was the energizer 377 battery. Still not quite enough though. The weight limitation of only 1 additional gram makes it pretty much impossible to do anything electronic.




One more question. Section 1.1 says that metal can't be used if it presents a hazard. That's somewhat ambiguous. Would a pen spring that exists inside the body tube and isn't exposed considered a hazard? If it is acceptable, I think I may have a solution that could be made to work. I'll give it a try if acceptable.

Internal Pen springs are used all the time on the Old Mars Lander and other models, I've used them for years in and on various models. Minor parts like that are perfectly legal. metal "Structural Parts" and external airframes is where it become prohibitive and should be.

Thanks,
Kevin

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