Pull Pins Outlawed!

[jadebox]

NFPA 1127 will adopt the new rules and it's just a matter of time before it becomes law. So you might as well get used to the Tripoli Rules. I personally don't think that the rules go far enough. Airstart motor electronics should have a shunt or kill switch and it should be accessible while the rocket is on the pad in the upright position. It is also a good idea to have electronics that don't arm the motor until they reach 300 feet AGL.

I agree with the first part, but the 300' limit would prevent you from using electronics to support clusters where you want to ensure that smaller motors in the cluster don't ignite until the main motor ignites.

-- Roger

 

[gldknght]

I agree with the first part, but the 300' limit would prevent you from using electronics to support clusters where you want to ensure that smaller motors in the cluster don't ignite until the main motor ignites.

-- Roger

I guess I don't understand what all the fuss is about in the first place. The timer I'm using for two stage has an on off switch to power the timer, and the timer has a g-switch the must be closed by launch forces for 1/2 second (I think) before the timer countdown will start. By the time the timer fires the second stage, the rocket should be WELL OVER 300'.

In the event of a hard chuff, the sustainer goes up without the booster since the rail buttons are on the sustainer.

And none of us should be flying anything that might not be stable in the first place.

 

[bobkrech]

I guess I don't understand what all the fuss is about in the first place. The timer I'm using for two stage has an on off switch to power the timer, and the timer has a g-switch the must be closed by launch forces for 1/2 second (I think) before the timer countdown will start. By the time the timer fires the second stage, the rocket should be WELL OVER 300'.

In the event of a hard chuff, the sustainer goes up without the booster since the rail buttons are on the sustainer.

And none of us should be flying anything that might not be stable in the first place.

AFAIK, NAR banned mercury switches years ago.

There are two kinds of G-switches: purely mechanical spring loaded momentary switches; and accelerometer based electronic switches. Which type you using? And how is it implemented?

If it is in a commercial product, the manner of use will be specified. Most mechanical spring loaded G-switches are activated at 2.1 G. The output from this switch is used to start an event timer. In smart timers, this switch also activates a reset timer which can be programmed to reset the delay timer if the acceleration switch is not held closed for a certain lenght of time. This prevents delay activation if the rocket is dropped or chuffing. If the qaltimeter has an accelerometer its data can be treated in many ways to determine liftoff so you really need to read the instruction for your electronics.

Bob

 

[gldknght]

AFAIK, NAR banned mercury switches years ago.


Bob

So far nobody has answered the only question I'm asking: Where is this in writing???? If it's not in writing, it doesn't exist, and can not be enforced. Besides in the tra rules, I mean.

 

[JStitz]

I'm surprised a lifer NAR member hasn't quoted some text, but the fact is that mercury switches really haven't been used since the late 1980's,
due to lack of interest.
Back in the 90's there was only ONE guy I knew of,Jeff Buss from Allentown Pa that was still using them in a 2 stage.
General consensus was that people were getting them from scrapped thermostats and they do in fact contain a small amount of a liquid metal that should not be planted in the soil in any flying field.

About this time in the early 90's, Adept had a mechanically tripped G-switch and High current timers that basically made mercury switching obsolete.
This is from an old flyer with a 1994 ALTS2 altimeter. (Yes Tommy..it still works fine) and yes $118 From the Vaughn Brothers was a bargain at the time.

Edit: I have to add a chuckle for the older flyers on here...
It was also this time that we saw how a high speed impact could cleanly "Shear" all the surface mounted wave soldered electronics completely off the board!

 

[gldknght]

This is the last I'm going to say on this. It's easy to say "This should not be done, because I don't think it's a good idea." Everybody is entitled to his own opinion. But it's just an opinion, not a fact.

If I say "you can't do that because it is illegal," it's no longer an opinion, but is presented as a fact. Facts need to be supported with evidence.

 

[JStitz]

Do you already have this Mercury switch built into your design?

I meant to be soft when I said there just wasn't anymore interest in Mercury Switching.

I'm an old Flyer and I have to admit that just the "ride along" altimeters like the Jolly logic sent me along the newer thinking path.
I always wanted MPH and G's included with my altitude, and Recharging from a USB port is just plain simple and cool.

 

[jadebox]

If I say "you can't do that because it is illegal," it's no longer an opinion, but is presented as a fact. Facts need to be supported with evidence.

The NAR Safety Officer Training Program includes a section specifically about mercury switches. It states "Although generally obsolete and unreliable, less sophisticated modelers may still attempt to use a mercury switch for staging."

Using a mercury switch in a rocket is a bad idea. Does it really need to be illegal to discourage the use of one?

-- Roger

 

[jadebox]

Just looked at the 2012 Tripoli Safety Code and saw this:
2-12.6 A rocket motor shall not be ignited by any of the following:
a. A switch that uses mercury.
b. “Pull wires” that disconnect or complete a circuit.
c. “Pressure roller” switches

BTW ... I just noticed that the section above was taken verbatim from the existing TRA Research Code. I'm not sure if that's been noted in this discussion (or what to make of it).

-- Roger

 

[gldknght]

BTW ... I just noticed that the section above was taken verbatim from the existing TRA Research Code. I'm not sure if that's been noted in this discussion (or what to make of it).

-- Roger

It's been noted several times that tra rules do not apply to non-tra members.

The NAR Safety Officer Training Program includes a section specifically about mercury switches.
Using a mercury switch in a rocket is a bad idea.

-- Roger

That is YOUR OPINION!!!!!!!

Now Here are the FACTS

This is what the article in the Nar Safety Officer training actually says about merc switches, note it DOES NOT say they can't be used or even that it's a bad idea:


"Does the model use mercury switches to initiate staging. Mercury switches rely on the deceleration after motor burnout to activate the upper stage. Some motors have a gradual thrust decay that will not provide a sufficiently "sharp" deceleration to activate the mercury switch. In this case the model will arc over in flight prior to upper stage ignition.
Verify that the modeler has chosen an motor with a "sharp" thrust decay. Verify that the modeler has some means by which to deactivate the system in the event of a flight failure or aborted launch.
Mercury is toxic. Most mercury switches use a relatively fragile glass envelope to contain the metal. The envelope can be made more rugged by shrinking a piece of heat shrink tubing over the switch and sealing the ends with epoxy."


Also, this is not the application I have in mind at all.

 

[jadebox]

It's been noted several times that tra rules do not apply to non-tra members.

That wasn't a reply to your posts.

-- Roger

 

[jadebox]

IAlso, this is not the application I have in mind at all.

You want to use a mercury switch to detect if the rocket is vertical before staging, right? Please let us know how well that works out.

-- Roger

 

[troj]

It's been noted several times that tra rules do not apply to non-tra members.

Provided it's not a TRA-sanctioned launch.

If you're a NAR member at a Tripoli launch, you have to follow the most restrictive of the rules. Just like if you're a Tripoli member at a NAR launch, you have to do the same. Otherwise the insurance coverage is void, for the launch and/or flier not following the Safety Code.

This is what the article in the Nar Safety Officer training actually says about merc switches, note it DOES NOT say they can't be used or even that it's a bad idea:

A lot of RSOs won't let you make it past RSO with a mercury switch. While you may not be able to find it in writing, the hobby as a whole frowns upon their use.

-Kevin

 

[rockets4kids]

It is interesting to note that they don't include magnetic reed switches in the list of prohibited launch-detection devices.

Their use would be allowed by the letter of the rules, but certainly not by the spirit with which they were written.

 

[cwbullet]

I can see why they changed the rules for mercury switches.

 

[degreaser]

I wasn't there for ldrs 29. You can learn a bit more in this thread:
https://www.rocketryforum.com/showthread.php?t=8324&page=5

Pad ignition of the charge and second stage.

One of the injured parties is suing TRA and the LDRS organizers.

https://www.courthousenews.com/2012/06/13/47397.htm

https://www.sandiegoreader.com/weblogs/news-ticker/2012/jun/14/lawsuit-filed-over-injuries-suffered-at-large-and-/

 

[o1d_dude]

Comments on pending liability cases have a way of showing up in the actual legal proceedings. Probably shouldn't be talking about what did or did not happen.

 

[troj]

Tripoli's leadership has asked that there be no discussion of this matter, until it is resolved. Therefore, any discussion of it, or comments about it, will be promptly deleted.

-Kevin

 

[Nerull]

I guess I don't understand what all the fuss is about in the first place. The timer I'm using for two stage has an on off switch to power the timer, and the timer has a g-switch the must be closed by launch forces for 1/2 second (I think) before the timer countdown will start. By the time the timer fires the second stage, the rocket should be WELL OVER 300'.

In the event of a hard chuff, the sustainer goes up without the booster since the rail buttons are on the sustainer.

And none of us should be flying anything that might not be stable in the first place.

The fuss is that your idea is completely unworkable. A mercury switch cannot reliably determine the orientation of a rocket in flight, under boost or not. It is the *most* likely to read wrong when your scenario would actually use it. It is completely and utterly useless for staging.

In an ideal world, people flying large, complex rockets would have a basic grasp of physics. Unfortunately we don't live in an ideal world.

 

[Nerull]

Also, this is not the application I have in mind at all.

It isn't, but if you try comprehending how it works, you might see why your method doesn't.

The reason a mercury switch can be used to detect burnout and initiate staging (but not reliably so) is that the forces on a rocket after burnout are completely dominated by drag. Your switch will not be able to detect if your rocket is going up, sideways, or down.

 

[gldknght]

It isn't, but if you try comprehending how it works, you might see why your method doesn't.

The reason a mercury switch can be used to detect burnout and initiate staging (but not reliably so) is that the forces on a rocket after burnout are completely dominated by drag. Your switch will not be able to detect if your rocket is going up, sideways, or down.

You guys Certainly can't read. I'm not asking for your OPINION on whether my idea will work or not. These OPINIONS have been duly noted. What I'm still looking for is actual DOCUMENTATION that applies to me that says I can't even try my idea without breaking a law or a safety rule OTHER than Tra's.

And for what it's worth, I studied physics in college, along with math, and electronics, so have a better then "basic" understanding of these subjects.

 

[G_T]

Ok, I'm NAR, so the TRA rules don't mean all that much to me, but I have a question anyway:

I was thinking of incorporating a mecury switch in between the timer and the ignitor for my two stage project. This would be used only as a cutoff in the event of a less than optimal attitude at sustainer motor firing. In other words, the mercury switch would not allow the ignitor to fire if the rocket is not fairly close to verticle when the timer fires. The mercury switch would in no way affect the timer opperation.

Is this not allowed? Is that in writing anywhere other than in the TRA rules?

This is not a direct answer to your question on whether or not it is allowed. It is in answer to the concept. You stated some background in physics; very well...

In the absense of an atmosphere, once first stage has burned out, then the rocket assumes an elliptic orbit trajectory with one of the foci of the ellipse being the center of the earth. Of course this ellipse intersects the ground in a couple of places but that is besides the point. The trajectory is elliptic.

The rocket itself is in free-fall in this scenario. In free-fall, the mercury switch cannot make any determination as to the orientation of the rocket. The closest it could do is if the switch is not located at the CG of the rocket, and the rocket obtains a pitch or yaw rate, then the switch experiences some G loading as a function of the distance from the CG and the pitch and yaw rate. At best, this G loading being detected could indicate that the pitch and/or yaw is changing. It cannot indicate orientation.

Now, add air resistance. The trajectory is no longer elliptic as the rocket is experiencing deceleration. In other words, it acquires a non-constant force vector in direction opposite to the flight direction vector.

Note that this force vector is opposite the flight direction, which is pretty much always down with respect to the rocket axis (for a stable rocket).

So, what can the mercury switch really tell you? Not much.

Gerald

 

[lawndartman]

If I am the RSO and you bring something like what you are talking about to my table.... You and your rocket are not flying. Period. There, it is in writing... Tim Thomas L3

 

[Nerull]

You guys Certainly can't read. I'm not asking for your OPINION on whether my idea will work or not. These OPINIONS have been duly noted. What I'm still looking for is actual DOCUMENTATION that applies to me that says I can't even try my idea without breaking a law or a safety rule OTHER than Tra's.

And for what it's worth, I studied physics in college, along with math, and electronics, so have a better then "basic" understanding of these subjects.

You have no grasp of the components you want to work with and how they function. You are a danger to yourself and others and should never be allowed past an RSO table. How's that for an opinion?

 

[sylvie369]

And for what it's worth, I studied physics in college, along with math, and electronics, so have a better then "basic" understanding of these subjects.

If you did, you would not have written this:

Don't need the mercury switch to detect anything.

A mercury switch will only allow current flow when the mercury is in contact with the wire leads. If the switch is oriented correctly, i.e. the mercury and the leads are at the bottom, then if the rocket tilts of verticle so the leads lose contact with the mercury the switch opens, no current flow.

The key point in this discussion is that you are wrong about the facts. It's time for you to accept that fact.
Then having acknowledged your mistake, you could separately ask nicely for a reference to a law that prohibits the use of mercury switches. I'm sure in response someone would point out that while there is no such law (AFAIK), RSOs in general would not let you fly with one because of the environmental concern. Then the discussion would be over, and you would have learned something important.

Wouldn't that be a nice, civil resolution? Then if you were really set on staging high power rockets, you could ask some nice, civil questions about how to most safely do so, and you'd get some really great answers, because there are people here who know a lot about the topic.

 

[cerving]

Just looked at the 2012 Tripoli Safety Code and saw this:
2-12.6 A rocket motor shall not be ignited by any of the following:
a. A switch that uses mercury.
b. “Pull wires” that disconnect or complete a circuit.
c. “Pressure roller” switches

I don't know if I've been getting away with this for long-is this new? I'm bummed because I have a Xavien 'Fist' and a bunch of pull pin sets from Programmin' Pete. Looks like g-switches and timers from now on. I support the Mercury switch elimination but I do like microswitches for some uses. Does this mean burn wires too?

I think the intent is that they don't want somebody using some kind of switch/breakwire that completes a circuit and fires the engine of the upper stage DIRECTLY, i.e. without some other intervention of the electronics (such as a minimum altitude detect or a timer). This is a conceivable configuration if you had the first stage with a very short ejection delay (1-2 secs) that pops the booster from the upper stage and thus trips a switch or breakwire. It's easy to see how this could be dangerous on the pad. Airstarts definitely require a minimum of two events, at least one of which should be altitude based so that it prevents anything from happening on the ground. Ground-based breakwires or a G-switch timer make a good second event indicator.

You'd think that Tripoli would have addressed airstarts specifically by now instead of using vague legalese.. NAR doesn't either, though.

 

[gldknght]

If you did, you would not have written this:



The key point in this discussion is that you are wrong about the facts. It's time for you to accept that fact.
Then having acknowledged your mistake, you could separately ask nicely for a reference to a law that prohibits the use of mercury switches. I'm sure in response someone would point out that while there is no such law (AFAIK), RSOs in general would not let you fly with one because of the environmental concern. Then the discussion would be over, and you would have learned something important.

Wouldn't that be a nice, civil resolution? Then if you were really set on staging high power rockets, you could ask some nice, civil questions about how to most safely do so, and you'd get some really great answers, because there are people here who know a lot about the topic.

I don't need to ask questions on things I already know how to do. I don't need to ask questions that I already know the answers to. I've been flying rockets, single stage, clusters and multistage rockets since before the were electronics for things like staging. Re-read all of the posts in this thread, I only asked one question (nicely, civilly)from the beginning with regard to mercury switches.. Where is it written? Everything else is just opinion. I don't have a rocket, multistage or otherwise, with any mercury switches in it. I don't own any mercury switches.

I am a danger to no one. Anyone who has ever flown with me can tell you that safe launch and recovery is my only priority. This is why I want a reference to a rule, law or regulation that talks about mercury switches in rockets that applies to me. Because I won't even think about doing anything that violates a law. I'm not interested it TRA rules because they don't apply to me.

Your opinions are not law.

 

[G_T]

https://www.epa.gov/hg/

Perhaps you should start here. Rockets may not always be recovered. They may not always be recovered intact. Consider never putting anything into them which (1) you are not willing to put into the ground (2) the landowner is not willing to have you put into his/her ground (3) there are regulations disallowing putting it into ground or air.

If you have legal questions, dive into the regulations, or hire a lawyer. Neither NAR nor TRA rules are law but are requirements you will have to meet to get a non cat 3 rocket to fly at an organization affiliated field and probably at all the independent fields.

I expect you know all this anyway. But perhaps others do not, and may follow your proposal in ignorance. That is my biggest reason for contributing to this discussion. And, FWIW, one of my degrees is in physics but I do not have a degree in law. So any legal advice you may derive from this post has no value.

Gerald

 

[JPVegh]

https://www.epa.gov/hg/

Perhaps you should start here. Rockets may not always be recovered. They may not always be recovered intact. Consider never putting anything into them which (1) you are not willing to put into the ground (2) the landowner is not willing to have you put into his/her ground (3) there are regulations disallowing putting it into ground or air.

If you have legal questions, dive into the regulations, or hire a lawyer. Neither NAR nor TRA rules are law but are requirements you will have to meet to get a non cat 3 rocket to fly at an organization affiliated field and probably at all the independent fields.

I expect you know all this anyway. But perhaps others do not, and may follow your proposal in ignorance. That is my biggest reason for contributing to this discussion. And, FWIW, one of my degrees is in physics but I do not have a degree in law. So any legal advice you may derive from this post has no value.

Gerald

No doubt using mercury switches in a rocketry application is pretty dumb but by the standards you have listed above you should not use NiCad, Lithium or LIon batteries either. For that matter using lead for nose weight would be out of the question as well.

 

[G_T]

Worth considering, actually, as there are substitutes for most of what you list. Certainly so, for NiCd, and lead. As for lithium... https://www.hkmacme.org/course/2009BW11-01-00/SP CS_Nov.pdf (just a quick link I found for you - probably a lot of other stuff out there).

My point is to consider this sort of thing. Not to react. Not to assume.

I am trying to be of assistance to you and to others. But I will drop out of this thread as there is no reason for it to become something personal. I apologize if I have contributed to making it so.

Gerald