Nah, it just goes out the nozzle.
Well, I had one that did not a few decades ago;
Last edited:
Nah, it just goes out the nozzle.
I’ve wondered about this, but I haven’t tried plugging motors and I have never read of such things happening. your follow up post says you’ve seen it at least once. Anybody else have this happen?Putting an epoxy plug over an ejection charge rather than a -0 motor well, could blow your epoxy plug out like a shot gun shell wad.
TVM from Apogee concurs with @Art Upton:I’ve wondered about this, but I haven’t tried plugging motors and I have never read of such things happening. your follow up post says you’ve seen it at least once. Anybody else have this happen?
Fair enough. It worked fine for me before it was made clear that is wasn't an acceptable modification, but that's just a small set of anecdotes. Tape/wadding has worked fine too, even on motors with ejection charges, to direct that out the nozzle.Well, I had one that did not a few decades ago;
It seems to me that 1) plugging a booster this way is safe, 2) plugging an ejection charge this way is unsafe, and 3) there are people out there who wouldn't understand the (importance of the) difference.Not permitting an epoxy plug for this purpose is nonsense. It in no way impacts the structural integrity of the motor. Calling this a modification and prohibiting it seems like an over reach.
If I can plug a motor with an ejection charge with wadding and tape with no discernable disturbance of the tape after firing, I'm not sure why epoxy would be worse. It would make it easier to use to normal rockets vs oddrocs.It seems to me that 1) plugging a booster this way is safe, 2) plugging an ejection charge this way is unsafe, and 3) there are people out there who wouldn't understand the (importance of the) difference.
Allowing it for boosters would lead to people doing it for motors with ejection charges.
I would very much like to learn how to do this. Would you mind posting the details of how you pack and tape these? Being able to do this with the C5-3 would be hugely useful to me.Tape/wadding has worked fine too, even on motors with ejection charges, to direct that out the nozzle.
I don't remember that. I do remember reading about using safety fuse to effect the delay, ignited by an ordinary booster motor. This may have been in the NAR Tech Review. Back then I think motor caps were paper and would occasionally work loose in the packaging. Also, a clay capped delay motor with ejection charge can ignite an upper stage motor unmodified, but reliability is not high.Back in the mid 70s the NAR Model Rocketeer ran an article on delayed staging to get higher altitude in competition. If I recall Correctly it was written by a top competitor.
You removed the clay cap , emptied the charge on like a B6-2 and used it as a booster motor.
Some complained about that and called the motor maker and after that it became a motor modification that made it a no no, per safety reasons.
Nar leaves it to the motor mfg to define what is and what is not a mfg approved motor modification, and Estes was asked specifically about epoxy plugging or removing caps and ejection charges and they said these were not approved modifications so Nar does not allow them. Aerotech on the other hand says that shortening a delay or removing ejection charges are mfg approved modifications.Not permitting an epoxy plug for this purpose is nonsense. It in no way impacts the structural integrity of the motor. Calling this a modification and prohibiting it seems like an over reach.
Actually it is pretty strong.Dang! When you mentioned that approach it seemed like such a clever idea!
A -0 engine has no ejection charge or smoke charge. We are just talking about the little “pfft” when the flame burns through the top of the black powder. That can’t be that strong, can it?
I don't remember that. I do remember reading about using safety fuse to effect the delay, ignited by an ordinary booster motor. This may have been in the NAR Tech Review. Back then I think motor caps were paper and would occasionally work loose in the packaging. Also, a clay capped delay motor with ejection charge can ignite an upper stage motor unmodified, but reliability is not high.
100% affects neither the structural integrity, the burn profile, or the safety of the motor. NAR and/or Estes are choosing CYA over actual safety.Not permitting an epoxy plug for this purpose is nonsense. It in no way impacts the structural integrity of the motor. Calling this a modification and prohibiting it seems like an over reach.
You can see how this would create a slippery slope type of problem...
Speculation about other things that people *might* do is not a valid argument. Those same people *might* use a -0 motor in a single stage rocket thereby creating a lawn dart. That is unsafe, so plugged motors are no longer permissible at NAR events. With speculation, anything is possible.It seems to me that 1) plugging a booster this way is safe, 2) plugging an ejection charge this way is unsafe, and 3) there are people out there who wouldn't understand the (importance of the) difference.
Allowing it for boosters would lead to people doing it for motors with ejection charges.
If you were to plug a motor that way and something was to happen and property or a person got damaged/hurt and that was discovered as part of the investigation it could void the liability coverage for you or the property owner and could result in the risk of a loss of a field and or worse so you'd have to weigh if that's a risk worth taking.
That is not entirely true. TRA has an entire experimental classification where you can mod until your heart's content.Note Tripoli does not allow non mfg approved motor mods
You can talk about how stupid it is or isn't but that's beside the point, it really just comes down to insurance coverage. If you were to plug a motor that way and something was to happen and property or a person got damaged/hurt and that was discovered as part of the investigation it could void the liability coverage for you or the property owner and could result in the risk of a loss of a field and or worse so you'd have to weigh if that's a risk worth taking.
I built a big glider with swing wings and rear ejection back in the 70's when active in NAR competitions. The vertical stabilizer wast attached to the basswood spar comprising the fuselage, upside down from a conventional empenage. It flew very well and won several competitions. Never had an issue with the ejected motor mount (small streamer wound on it) damaging the empenage. Opened, it's wingspan was about 40", so it came down softly.Thinking outside the box, what are your field rules And conditions?
outside of competition, there is nothing in NAR rules nor the safety code that says you can’t eject a motor, and there are number of kits including the Semroc Hawk glider (which I believe is a repro of an Estes and/or Centuri kit), and the Sprite and of course the Mosquito which are motor eject.
so skip the vent holes, make sure the pod nose cone is glued in firmly or add a bulkhead, throw some JB weld or other heat protectant on the base of the cone or rear of bulkehead. Usually don’t need anything to hold the motor in place, if really “falling out” loose on pad put a loose friction fit, and let her rip.
I’ve been doing this for years with 13-24 mm motors (D12s, E motors might be pushing it) without any issues.
I look For and when found I pick up the casings if I can find them, I don’t sweat it if I can’t as they are biodegradable.
some fields have rules that disallow free falling casings, and Miiiight want to skip it if high fire danger due to dry field conditions.
there are ways to add streamers if you feel the need, even on minimum diameter. See post 20
https://www.rocketryforum.com/threads/glider-front-motor-eject-feasible.181457/#post-2476414
I agree that "shortening" motors is a modification. I would also agree that removing the delay grain on a motor to make it a booster would also be a modification (I've personally never done that and probably wouldn't.) But removing the clay cap and dumping the BP to make a plugged motor and calling this a "modification" seems like a stretch. I've done this more times than I can count. I hear everyone one on here who says they asked NAR/Estes and that is what they said, I just don't agree with what they consider to be a modification.Maybe, maybe not. But to keep things simple, the rules/guidelines may just use a "belt and suspenders" blanket approach as to what's allowed and not allowed with motor modification.
If they allowed certain types of plugging, what about shortening rocket engines? For example, cutting an A8-3 in half as much of the motor casing is just empty space. Or how about removing some or all of the clay cap covering the ejection charge to make it less powerful (or for some other objective). You can see how this would create a slippery slope type of problem...
True but not for BP motors, a modified composite motor is considered research but there is no research black powder as they don't support that.That is not entirely true. TRA has an entire experimental classification where you can mod until your heart's content.
Speculation isn't a valid argument? Tell that to the decades of product liability case law. What a reasonable consumer may or may not do in a hypothetical situation is 100% relevant to a company's rules, policies and warnings concerning their services/products.100% affects neither the structural integrity, the burn profile, or the safety of the motor. NAR and/or Estes are choosing CYA over actual safety.
You can stick wood in there. You can stick dog barf in there. You can fill it with sand. But you can't put glue in there. Nonsense.
Speculation about other things that people *might* do is not a valid argument. Those same people *might* use a -0 motor in a single stage rocket thereby creating a lawn dart. That is unsafe, so plugged motors are no longer permissible at NAR events. With speculation, anything is possible.
I think you (and a few other(s)) are missing the point. The point isn't what's ok and what's not ok from a practical or engineering perspective. The point is what's ok and what's not ok from a legal/insurance coverage perspective.I agree that "shortening" motors is a modification. I would also agree that removing the delay grain on a motor to make it a booster would also be a modification (I've personally never done that and probably wouldn't.) But removing the clay cap and dumping the BP to make a plugged motor and calling this a "modification" seems like a stretch. I've done this more times than I can count. I hear everyone one on here who says they asked NAR/Estes and that is what they said, I just don't agree with what they consider to be a modification.
Rocketry is about experimentation, that is part of the reason most of us got into it. I have and fly many rockets that are clusters. I suppose I could just buy a single motor and stick in there, but what is the fun in that? Sometimes sticking 7 or 8 BP motors into a rocket requires some changes to make it work. Much like how folks on this forum calculate how much BP to put into an ejection charge and adjust/tailor the qty to their rocket or specific application.
The attached picture is a great current example. I have an Estes E12-6. While prepping a rocket, I dropped it on the floor...a laminate floor. So not a hard impact, but enough to break the clay cap and spill my ejection charge everywhere. Personally, I have no qualms about flying this motor. Could it cato because I dropped it? Perhaps. It also might cato even if I didn't. Maybe Hobby Lobby dropped it on their floor while stocking shelves? Who knows and I don't really care.
So per this discussion thread, my options are:
1) Destroy the motor (very unlikely).
2) Static fire it? (more likely than #1, but also not likely)
3) Remove the rest of the BP and pour epoxy in the top and stuff it in one of my cluster rockets since I don't really need/want 8 ejection charges going off.
4) Remove the rest of the BP and measure out 0.7 grams of 4fg, install on top of delay grain and secure with a piece of tape and fly it.
Probably either 3 or 4 is going to happen. It all depends. If something was to happen with the flight, would it be caused by me restoring the ejection charge or plugging the motor with epoxy? I really can't imagine that scenario. That is kind of like the car dealership voiding your warranty because you installed a K&N air filter--they can try to make that argument, but it doesn't hold much water. If the rocket in this case crashes, it would be because the other XX motors didn't eject my chute. Or I didn't get them all lit. Or I packed my chute wrong and the other motors ejected, but it wasn't successful. Lot's of reasons for failures.
This is just debate on the topic...we can have different opinions. When you look at why and how TRA and NAR tests motors and the criteria for approving them, option 3 and 4 above don't change the basis of the motor certification at all (burn time, delay time and tolerance, casing temperature, casing integrity, etc.) AT G77-79 motors are assembled at home with 5-min epoxy and require that epoxy to secure the primary pressure bulkhead. This is much less consequential than that.
I am not missing that at all, in fact I addressed it.I think you (and a few other(s)) are missing the point. The point isn't what's ok and what's not ok from a practical or engineering perspective. The point is what's ok and what's not ok from a legal/insurance coverage perspective.
the company could take basic steps to prevent the situation (like telling a consumer not to do something).
Don't add epoxy to the back end of certain Estes BP rocket engines or you could risk losing insurance coverage.I am not missing that at all, in fact I addressed it.
But let's discuss it. What does the law, and the relevant insurance policy, say about this matter?
As has been hit above, I would bet my motor stash that that deference is to satisfy insurers.What is covered is determined by what NAR considers permissible within the NAR Safety Code. NAR *chooses* to defer to the manufacturer without exception, and that choice is the point. The same is also true for Estes.
@mh9162013 beat me to it.I am not missing that at all, in fact I addressed it.
But let's discuss it. What does the law, and the relevant insurance policy, say about this matter?
Thank you for clarifying that we are discussing your opinion and not actually "what's ok and what's not ok from a legal/insurance coverage perspective." Now that we have dispensed with that facade...Don't add epoxy to the back end of certain Estes BP rocket engines or you could risk losing insurance coverage.
As for case law, that would depend on each state, but I think it's safe to assume that if your rocket harms another and the proximate cause for the harm was your decision to violate a warning or guideline from the manufacturer, you will be deemed to be at least partially at fault for the person's damage. How much you have to pay will depend on the applicable state law concerning negligence (comparative, pure comparative, contributory, etc.).
TRA doesn't allow BP motors, modified or unmodified. But they do support modification of all motors they allow.True but not for BP motors, a modified composite motor is considered research but there is no research black powder as they don't support that.
I think the universally relevant "law" would be the model rocket safety code.
I am confident that plugging a motor puts your insurance at risk.
The answer to that question is self-evident, given the presumed (and likely) requirements and advice from the insurance companies and attorneys, ie "do it my way if you want legal and insurance protection."The question on the table? Should the NAR allow...?
Enter your email address to join: