Maximum size acceptable engine eject at NARAM and NSL?

[BABAR]

I haven’t been to one of these events but they sound like a lot of fun.

I have some designs that use engine eject (non competition, just sport rockets.). I figure mini ATs thru Cs would be okay. Will Ds pass muster?

Thanks

Tom

 

[shreadvector]

I haven’t been to one of these events but they sound like a lot of fun.

I have some designs that use engine eject (non competition, just sport rockets.). I figure mini ATs thru Cs would be okay. Will Ds pass muster?

Thanks

Tom

All Model Rocket Motors and High Power Rocket Motors with ejection charges are designed and certified to use those ejection charges to eject recovery systems.

If you build a large or complex high Power Rocket, then you may need to use an alternate or redundant recovery system deployment, such as an extra ejection charge fired by electronics.

 

[rharshberger]

I haven’t been to one of these events but they sound like a lot of fun.

I have some designs that use engine eject (non competition, just sport rockets.). I figure mini ATs thru Cs would be okay. Will Ds pass muster?

Thanks

Tom

Are you asking what size motor is okay to eject the casing out like featherweight recovery?

 

[BABAR]

Fred,

Thanks,

I should have been more specific. When I refer to engine eject, I mean engine free falls by tumble recovery.

Example would be Estes Falcon Boost Glider. In my cases the rocket itself recovers with helicopter or air brake recovery.

Clearly a free falling engine casing would not be an option for high power rocket.

Will RSOs at NARAM or NSL have any issues with an ejected free falling D motor casing?

Thanks again.

Tom

 

[samb]

Yes, they will have an issue with any size free falling motor in competition. DQ. At local contests that I’ve participated in a small piece of mylar taped to the motor met the letter and the spirit of the law. It’s stated on the nar.org competition page “Basics of the Rules”. Sorry I can’t get a link right now.

 

[Amsterdam]

BABAR, I don’t think they like any, even tiny mmx motors to free fall, regardless of it being a contest or not.

A solution would be to tape a streamer and wrap it around the engine itself. But you’d have a heck of time getting that in off the shelf tube sizes.

 

[dhbarr]

I would think it would be reasonable to ask someone to run sims on falling spent casings to see how much energy they're packing.

At a guess, 13/18's and short 24's in paper would be slow and tumbly; long 24's and all 29's would be stable enough to pick up speed; and nobody should be dropping phenolic or aluminum in any size.

I think this would also allow for d12 rackers, which is a nice feature.

To reiterate: these are just my musings, I don't know whether anyone's looked into studying it.

 

[rharshberger]

The nozzles tend to make the paper casings heavy at one end....

 

[samb]

For me, it’s not about slowing it down as much as it gives me a small visual aid to point to while yelling “HEADS UP !” I just put a little two inch strip of Mylar on any motor spitter I fly now. If it’s a tight fit I’ll hit the inside of the motor tube with dollar store CA, sand, check the fit and repeat until I get the fit just right.

 

[Rocketjunkie]

I've had no issues, either with falling motor cases or RSOs with rack rockets up through 29mm F15s. I've even flown a 5 stage 38mm G160 Silver Streak version.

 

[snrkl]

The issue (at our club anyway) is the risk of a fallen casing being hot or still active and starting a fire. Especially as the case can fall unseen and start a fire that isn’t immediately obvious or close to get to.

Also, I can imagine a hot motor hitting your head or ending up down a shirt could be nasty.

To the best of my knowledge the safety code (can never remember if it’s NAR or TRA) strictly specifies no intentional ejecting of motor casings.

 

[samb]

I'll assume that the flights Rocketjunkie posted were not part of a NAR contest. I'll also assume that the RSO at that launch gave those flights the due diligence they deserved IMO.

The NAR Model Rocket safety code doesn't mention the subject of ejected motors.

The NAR high power safety code says that the rocket must have a recovery device so that all parts of the rocket are recovered safely. I could see that wording interpreted as including the motor casing.

 

[BigDuphis]

Didn't the mosquito rely on motor eject and then tumble recovery?

 

[samb]

Didn't the mosquito rely on motor eject and then tumble recovery?

Absolutely. Motor spitting kits and designs have been around almost from the beginning.

 

[BEC]

In an NAR contest ejecting a motor is generally a disqualification. In sport flying, as others have noted, there is nothing specifically in the Safety Code which prohibits it. Any RSO should consider where such an ejected casing is likely to land (NOT on people) in deciding whether to OK it or not (and in the dry season whether a hot motor casing falling without the benefit of a rocket is a fire hazard when it hits the ground).

For models like the little Mosquito which are designed to kick the spent motor out, the model itself is as much a hazard - it does NOT tumble (never mind what it says on the package), it generally comes in ballistically and falls faster than the spent motor itself (which generally does tumble some).

At club launches that I run we fly Mosquitos and 220 Swifts and other mini-motor models that intentionally eject their spent motors all the time (with the aforementioned awareness of where the casing might go). The ejection charges in some Estes 13mm motors are so strong that predicting where the motor might go is sometimes not easy as they get kicked quite a distance and rather strongly. This also sometimes accelerates the already streamlining-in Mosquito towards the ground....

I would probably be OK with a model that intentionally ejects an 18mm motor (such as the Falcon boost glider mentioned in the fourth post - or a Gyroc). I'm not sure what I'd do if someone came with a 24mm-powered model that was designed to spit the motor.

Speaking of Gyrocs - the revised version Semroc is now selling uses a 13mm motor and ejects the motor in a pod with a streamer on it.

 

[Steve Shannon]

Neither NFPA 1122 nor 1127 specifically prohibit ejecting a motor, but as others have said, all parts must be safely recovered. That’s reflected in the Tripoli High Power Safety Code:
Recovery
6-9.1 A rocket shall be launched only if it contains a recovery system that is designed to return all parts of the rocket to the ground safely.

A model rocket motor kicked out over the range at apogee is unlikely to cause injuries or even start a fire, but neither is impossible and that’s a sufficient reason for a club to ban the practice locally.
Another very important reason I would discourage motor ejection of small model rocket motors would be landowner relations.

 

[Micromeister]

In non-contest Sport flying 1/8A through G motor single use casings...are perfectly legal to eject and fall free without any attached recovery system.
Personally I like to add a small streamer (about one round around the casing) to motor over D12's.

The Mosquito has NEVER been a tumble recovery rocket! It is Feather Weight Recovery, but they all come in ballistic after kicking out the motor casing...regardless of what the catalog says! The only true Tumble recovery rocket Estes has ever produced is the Scout and Scout-II.

 

[samb]

In non-contest Sport flying 1/8A through G motor single use casings...are perfectly legal to eject and fall free without any attached recovery system.
...

Yes, legal, certainly. Would you agree that sometimes, when conditions exist on launch day like those described by Steve and Bernard, the prudent RSO might have to make the tough call : “Ladies and gentleman we will have no motor spitting today. As always, your kind cooperation is appreciated by your hard working range crew. “

 

[tHoagland]

The only true Tumble recovery rocket Estes has ever produced is the Scout and Scout-II.

The Wacky Wiggler?

 

[Micromeister]

The Wacky Wiggler is a "Break Apart Feather Weight" recovery rocket NOT Tumble.

 

[BABAR]

Appreciate all the replies.

I think I can do a small streamer on my Air Brake Recovery designs and most of my Heli's. The Gyskelion model would be tough, since the motor casing itself is what is holding the rotors closed. I think if I bring one, I will just have it sized for a C casing, if I can't fly it, no big deal. It's a fun design, it's my only Tri-Rotor, everything else is Quad.

Reasonable at some launches where fire danger is high to restrict engine eject, just like they restrict Sparky motors.

Wow, John, people have flown engine eject with a "G"? Yikes! And I thought I was pushing it with a "D"!

In any case, I understand that free engine eject is not allowed in competition, and I am NOT considering using it for anything High Power (although I AM toying with making High Power helicopter, I may try that for my Level 1 Cert if I ever get that ambitious! It would definitely have positive motor retention!)

Thanks again,

Hope I see some of you guys at either NARAM or NSL next year.

Tom

 

[BEC]

The only true Tumble recovery rocket Estes has ever produced is the Scout and Scout-II.

...and the Sprite (K-15)

 

[DaveW6DPS]

If I were the RSO, I would have some concerns with safety, and also in making sure the casings are picked up off the launch site.

(And I could be pulling RSO duty at NSL2019...)

 

[rharshberger]

If I were the RSO, I would have some concerns with safety, and also in making sure the casings are picked up off the launch site.

(And I could be pulling RSO duty at NSL2019...)

Our clubs method is simply to ensure that motor spitting models dont eject over the spectator areas which they shouldn't if the rods and rails are tilted away from the spectator areas. Most motors spit usually haven't been planned, they seem to be mostly inexperienced fliers either incorrectly friction fitting or not getting the motor hook properly engaged ( usually the newer type with the finger tab).

 

[Micromeister]

...and the Sprite (K-15)

Like the Mosquito, My original Sprite never tumbled either. always came in ballistic but gently enough it was always flyable again.
According to the instructions kicking the motor was to move the CG far enough to have the rocket tumble...alas mine never did...it was a feather weight ballistic recovery.

I'll repeat my earlier statement! the ONLY TRUE Tumble recovery rocket Estes ever sold was the Scout and Scout-II

 

[BEC]

When the Sprite doesn't spit its engine entirely (it's not supposed to - the shorty engine slides back to stop on the full length EH-2 exactly the same way the Scout works) it tumbles just fine, just like a Scout.

 

[Andrew_ASC]

Haven’t flown this extreme 12 yet, but as designed it spits the entire booster Fincan downward without a streamer. It flies on D-E Estes motors, I guess the energy of the booster is so low nobody cares.

 

[rharshberger]

View attachment 362931
Haven’t flown this extreme 12 yet, but as designed it spits the entire booster Fincan downward without a streamer. It flies on D-E Estes motors, I guess the energy of the booster is so low nobody cares.

The Extreme 12 like many Estes stagers uses tumble recovery, as soon as the booster separates it becomes unstable and starts to tumble.