Revision to Tripoli Rule Regarding Wireless Remote Switches

Discussion in 'Rocketry Electronics and Software' started by Steve Shannon, Feb 4, 2020.

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  1. Feb 16, 2020 #841

    manixFan

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    How many Featherweight Power Perches and integrated A/V bays do you have, especially in 29mm and 38mm min diameter rockets?

    I would like to see your solution to adding a switch to those products in rockets that have already been built. I have a number of regular and carbon fiber rockets that use those products, and in spite of 20 years of experience flying rockets and being Level 3, I have not yet figured out how to easily do that in small rockets, especially those that were designed specifically for those products. As I'm sure you're aware, the battery plugs directly into either the Power Perch or the top of the integrated A/V bay.

    I look forward to see how you've solved this issue.

    And for what it's worth, it's interesting how solid state switches that have been used safely for years are now suddenly unsafe.


    Tony

    ps: your tone and suggestion to take up stamp collecting seems disrespectful and belittling to those of us who have made a large investment in time, money, and rockets that for years have been using what has been considered an acceptable solution, not to mention the vendors who have made significant contributions to our hobby. Just because it may not affect you personally, does not mean it is unreasonable for those of us who have labored under the impression that we were doing things correctly, and have now been told that we must modify years of effort, to try and understand why we were wrong. What changed that made solid state switches suddenly and immediately unsafe?
     
    Last edited: Feb 16, 2020
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  2. Feb 16, 2020 #842

    jderimig

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    The analogy in the industrial product world would ask the question
    "Does UL and TUV think all the product safety engineers on the globe are incompetent?"

    The RSO is not responsible for the FMEA of all rocket systems that are brought to his table. At best he is there to detect the BIG mistakes.
     
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  3. Feb 16, 2020 #843

    Steve Shannon

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    Just some clarifications:
    The people inspecting your rockets are not the RSO. Each launch is required to have one RSO who is responsible for the safety of the entire event.
    The people at the “RSO Table” help with that effort but with the exception of very small launches they are usually not the RSO.

    With that bit of pedantry off my chest, let’s talk about range safety:
    For years we have accepted the idea that accidents happen. At rocket launches the worst of those accidents (meaning the possibility of seriously injuring and possibly even killing multiple people per incident) are those which result in early deployments or unexpected ignition of rocket motors.
    This step the board has taken is intended to reduce the possibility that multiple people might be involved if an early deployment or unexpected ignition occurs by moving the location where power is connected to the field, rather than behind the flight line where families are walking around and looking at rockets, talking to flyers, etc. Having the power physically separated when approaching the sometimes crowded RSO table also protects the rocket inspectors and all the other people near that area.


    Ballistic recovery is another risk we must address, but one which good range management helps to mitigate. Also, a rocket falling ballistically is unlikely to strike and injure more than one person.
     
  4. Feb 16, 2020 #844

    mikec

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    Steve, I'd like to see a response to Adrian's messages about the Featherweight products, along with a timeline of when we can expect the TRA BOD to make a decision about them.
     
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  5. Feb 16, 2020 #845

    Adrian A

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    Here's how I see the range safety:

    1. Premature ground ignitions of high powered motors have seriously injured people, and have done the most damage, so far, of any type of rocket accidents while I have been in the hobby. They can, and have, injured bystanders, and this is a potentially fatal hazard. The accidents to date have been very preventable. We have a serious airstart safety problem in the hobby. More and better rules regarding airstarts are needed, IMO. Better education certainly is. I'm not generally a fan of adding certification requirements beyond what we have, but if we do it for anything it should be for high-powered airstarts.

    2. If a high powered rocket has a ballistic re-entry and squarely hits someone it WILL kill them. The sport has been lucky, so far, that this has not yet happened. Considering close calls I have seen, it's frankly just a matter of time before it does. When it does, we will all be asking the question about whether we have done enough to make sure that deployments happen. Deployment charges save lives. We have a ballistic re-entry safety problem in the hobby, though we may not really know it yet.

    3. Accidental deployment charge firings are relatively common. But despite their frequency, they have not caused any serious injuries as far as I know, let alone a fatality. The risk radius of a premature deployment is very small, in almost all cases affecting nobody except the person who is working directly with the rocket. And importantly, all of the events I have witnessed or caused were due to user error mis-wiring or a simple short combined with the error of not disconnecting charges before putting tools near the av-bay. Featherweight av-bays reduce the opportunity for user error because all user wiring is eliminated. If they are effectively prohibited, we might see the frequency of this problem go up slightly, rather than down.

    #1 and #3 are very different problems, with different consequences, different causes, and different solutions. I don't think it helps anyone to discuss them as if they are the same problem. The airstart safety problem is a good motivation to make changes to airstart policy to make the hobby safer. It's not a good reason for a sweeping rule change that affects everyone who does electronic deployments, particularly a rule change that effectively prohibits a class of products that have been used safely for over a decade.
     
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  6. Feb 16, 2020 #846

    Steve Shannon

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    The only thing to really respond to is the implied question whether the intent of the rule is to have an air gap at the RSO table. My answer is yes, there must be a physical separation of contacts somewhere between the battery and the charges. It’s possible that this will change as a result of the meetings.

    I asked a couple days ago and was told that the invitations will go out this week (today’s Sunday, the first day of the week).
     
  7. Feb 16, 2020 #847

    manixFan

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    I asked what I thought were relevant questions to your understanding of the issue, and this is how you respond. Thank you for making it clear you have no interest in a rational discussion of this topic, but would rather just insult those of us who feel the board has not considered all the issues at hand. It's always useful in a discussion when folks make their true feelings known.

    What does that say about your understanding that you have to resort to such tactics to try and make a point, rather than respond to the questions?


    Tony

    PS: I did not realize the site allowed for quoted posts to be modified after the fact. The original post that is now all xxxxx above was a link to a stamp collecting website. (Added only for clarity to those who read this post and wonder about my response.)
     
    Last edited: Feb 16, 2020
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  8. Feb 16, 2020 #848

    Adrian A

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    Yes, the invitations came out this morning, for a meeting sometime next weekend.
     
  9. Feb 16, 2020 #849

    Steve Shannon

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    Thanks, Adrian. I was just coming back to correct my post.
     
  10. Feb 16, 2020 #850

    manixFan

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    One thing that I would like to be considered is the physical environment that fireworks operate in vs. ours. Two of the commercial pilots that were part of the lunch discussion regarding this issue commented that the aerospace industry seems to be replacing mechanical switches with solid state to avoid the issues that come from working in an environment that induces a lot of mechanical stress on its components.

    As far as I know, fireworks controllers operate in a static physical environment. Are those switches rated for sensitivity to things like vibration and G-shock? It seems to me based on a simple experiment I did that a switch that may be perfectly suitable to create a safe environment on the ground may not do so when mounted in a rocket that is subject to handling and transport stress, or high g-loads while in flight. If the board has now decided that mechanical switches are the last line of defense, will the board consider actively managing what switches are allowed? Or will it be up to each flyer to research and make a decision as to the suitability of a particular mechanical switch?

    I ask in all sincerity that this issue be addressed seriously to avoid this current situation - a rule change that requires modification and obsolescence of already purchased and built components.


    Tony
     
    Last edited: Feb 16, 2020
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  11. Feb 16, 2020 #851

    cerving

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    I got my invitation this morning. Giving the Board and the manufacturers a chance to work together to develop common safety standards is a good thing for the hobby.
     
  12. Feb 16, 2020 #852

    Steve Shannon

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    Tony,
    Those are good points and I’m absolutely certain they will be reiterated during the phone call, but we’re not saying mechanical switches are superior to solid state switches. We are saying that leaving the batteries or charges physically disconnected until away from other people is a good precaution.
     
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  13. Feb 16, 2020 #853

    Pariah Zero

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    Gentle reminder: the requirement is an air gap. Mechanical switches are one option. Dozens more exist.

    But I swear, I’m going to have to hunt down the next person that says ‘twist and tape.’ Might as well smoke while measuring gunpowder. It’s not even funny as a joke.
     
    Last edited: Feb 16, 2020
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  14. Feb 16, 2020 #854

    cerving

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    I personally wouldn't use twist and tape for power, but it's OK for connecting deployment charges to the electronics. It's inside the airframe and not subject to the airstream, so there is virtually zero chance of it coming loose (unless you do a REALLY bad job of it).
     
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  15. Feb 16, 2020 #855

    Kelly

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    What am I missing? This is a common practice. A bit crude for my taste, but it can be done safely and successfully.
     
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  16. Feb 16, 2020 #856

    manixFan

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    For several of my rockets, short of a complete rebuild of the A/V bay and trashing the current electronics, that is my only option. It clearly satisfies the criteria and I have been assured that it meets the both the spirit and intent of the rule. However, I don't use tape, I use very small diameter heat shrink tubing over the join. I call it 'twist and tuck'.

    What about this method do you feel is unsafe? If I cut one leg of the e-match, there is no possible way for electrical energy to flow to the match. It's as big an 'air gap' as I'm likely to get. Admittedly, I will now have to strip wires, twist, apply heat, and then carefully insert the wires into the rocket out at the pad, greatly increasing the time it takes to get it on the rail (or in my case, tower).

    And saying you're going to hunt down the next person that says 'twist and tape' is not that gentle of a reminder! Other than a mechanical switch, what options do you suggest to create an 'air gap'?


    Tony

    here's an example of what I mean, the rocket uses a 38mm Featherweight A/V bay: Image 1 is what I present at the RSO table, images 2, 3, and 4 are what I do at the supposed prep area out by my tower:
    twist-tuck.jpg
    To be clear, I feel this is inferior to my current solution, but has been described by Steve as an acceptable way to meet the rule. And if the rules are revised to allow the Featherweight electronics, I haven't invested anymore time, money, and energy, on a rocket that already flies extremely well as is.
     
    Last edited: Feb 16, 2020
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  17. Feb 16, 2020 #857

    MGL

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    IMO, this is the best post in the entire conversation. Time to change the "air gap" rule and allow advanced methods to be implemented and furthered while addressing much more potentially dangerous aspects as Adrian stated.
    #solidstate
     
  18. Feb 16, 2020 #858

    John Kemker

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    So, my L3 cert flight in 2000 was following a Primary/Secondary/Tertiary system: Adept altimeter for apogee and mains deployment, BlackSky as secondary backup altimeter and a Johnson data transceiver with relay programmed for 70cm operation and controllable via 3 DTMF tones in a specified order for tertiary backup, in case both altimeters failed. Idea was, if it came in ballistic, I pull out an HT, hold down the transmit key, then key in the 3-digit code. POP! Vehicle separates, coming in fast, but not ballistic.
     
  19. Feb 17, 2020 #859

    Pariah Zero

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    Yeah... I’ve been on the bad end of rules changes at my local club making a bunch of my electronics unusable. (RC Helicopters, not rockets) my only option was to buy new gear. So I’m familiar with the feeling.

    Far better than tape. I do have an inexpensive improvement, provided it fits.

    Two questions:

    • what wire gauge?
    • how big is the hole?

    There are quick disconnects that are as narrow as 3mm. They’re about $0.15 for each end, and insulative boots cost about the same. So less than $1 per rocket. It gives you an excellent electrical connections, and are resistant to vibration, heat, etc.

    And it would let you avoid having to worry about stripping, twisting, and heat shrinking. Just plug & tuck.

    I totally understand if you want to wait to see if you would actually need to retrofit anything first, of course.
     
  20. Feb 17, 2020 #860

    Pariah Zero

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    Common, and yes. Safe... are you kidding? Most vinyl electrical tape adhesive lets go at 90°F.

    Stranded wire should neverbe twisted together; electrical codes in the US specify crimped splices, like a butt splice.

    If you have solid wire, you can use the lineman’s splice; or even better, a wire nut. (Neither of which are appropriate for stranded wire)

    I come from a professional environment where putting bare stranded wire ends in screw terminals is completely unacceptable.

    For example, terminating a normal 26 AWG stranded wire:

    The wire is cut to length and annular crimped inside of a wire ferrule, to prevent stray strands of wire from being “freed” over time (and vibration).


    Adjustments.jpg
    Adjustments.jpg
    Adjustments.jpg

    And then heat shrink on the back side of the wire to provide strain relief to the whole assembly.

    The annular crimp also makes it gas tight, greatly reducing corrosion (eliminated entirely if the appropriate grease is also used), and cold welds the wire+ ferrule, improving the electrical connection to be as good as soldering.

    At that point, the ferrule is inserted into the screw terminal, threadlock is applied to the terminal’s threads, and screwed down.
     
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  21. Feb 17, 2020 #861

    g.pitts

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    Nice system. Out of curiosity, what is the cost of the crimp tool? I've seen some priced reasonably, others (JST comes to mind...) are pretty spendy.
     
  22. Feb 17, 2020 #862

    manixFan

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    Those are the leads from the e-match, so they are whatever gauge the manufacturer uses. As I'm sure you're aware, all the e-match leads are solid wire, none of the wire I 'twist and tuck' is stranded wire. For a different project I recall looking those ferules, but IIRC, the crimp tool was like $100.

    The size of the hole varies, but I make it as small as possible to work with my current inventory of e-matches and the smallest heat shrink that will fit over the wire. That hole was originally drilled for a plastic rivet, so it's actually a bit bigger than necessary.

    So, what is it about 'twist and tape' that you find so bothersome? For many of the folks in my position, it's the only inexpensive, short term solution. We (weather permitting) have a launch this weekend, and if I want to fly any of my current rockets that will be the only solution I have time to implement between now and then.


    Tony
     
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  23. Feb 17, 2020 #863

    Speaknoevil

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    I was "air gapped" challenged with one rocket at a launch today and had to stand down. It was so much easier and faster before I had to add dangling wires and auxiliary switches :barf:.
     
  24. Feb 17, 2020 #864

    Steve Shannon

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    Do I understand that after participating in this discussion for the past 13 days you thought you’d ignore the rule and take a powered up switch to the RSO table anyway?
     
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  25. Feb 17, 2020 #865

    Speaknoevil

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    Oh, no, I did not. In fact, I may have been one of the few people that knew about the rule at the launch.

    Dangling wires off my magnetic switch worked OK, except had to reload and had to unwind the whole thing taking nosecone off, undoing twisted wires, back out past RSO, then the whole thing over again, verifying no power at RSO and twisting wires to my switch again at the pad.

    Air gapped challenged in the sense of a faulty mechanical switch on a second rocket.
     
    Last edited: Feb 17, 2020
  26. Feb 17, 2020 #866

    Steve Shannon

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    Ahh, I see. Sorry for the misunderstanding.
     
  27. Feb 17, 2020 #867

    Pariah Zero

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    Twist and tape just isn’t secure. I’ve seen it fail (outside rocketry) so often I’m kind of shocked to hear anybody uses it. I rank it up there with cracking an egg into your radiator to plug a leak.

    A good lineman’s splice will hold up, but they’re banned in electrical codes for good reason - it’s easy to do wrong, and better/faster alternatives exist.
     
  28. Feb 17, 2020 #868

    Speaknoevil

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    I get the whole regulations and code thing, but the fact is, twist and tape works. I believe it is because of the transient nature of our electrical connection need on any one rocket flight. Launch to main deploy is typically less than 8 seconds. Like riding a bull--let it fly!
     
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  29. Feb 17, 2020 #869

    Pariah Zero

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    “It works” is a poor excuse for bad craftsmanship, in my not humble enough opinion.

    I was answering why I don’t feel it’s good enough, and I’ve said my piece.

    While I’m fine with advocating what I think is the right way, I realize there’s no rule, nor do I have any sort of authority to enforce it... it is your rocket, after all.
     
    Last edited: Feb 17, 2020
  30. Feb 17, 2020 #870

    Pariah Zero

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    Depends on the tool... this is the one I bought... $64-ish.

    I have no idea if that’s spendy in a hobby where you have rockets named ”40 dollars a second.” (Love that name, by the way)

    Ironically, I have a hydraulic crimper for 0-awg wire that’s cheaper than the one for 26AWG in my pictures.
     
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