What are these DD parts?
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rharshberger
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Schurter rotary switches as noted in previous post, they are used to arm and dis-arm the altimeters. While fairly large they are a very good switch that has a positive click and are very common in our hobby. The static ports for the altimeter is the small hole just to the right of one of the switches, there should be more than one hole (like 3 or so).
markkoelsch
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I think so at least for TRA. I think the NAR has slightly different requirements- who are you certifying with?
Physical disconnection means that it directly interrupts the path to the ejection charge. Sometimes, the switches are just used to turn the altimeter on or off. Since there are two switches, it seems likely in this case that both might be achieved. To know for sure, you need to see the wiring or at least the schematics from the builder.
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To the OP-Looks like KenRico's setup. PM him he'll most likely send you other pics. Mounting them in the vent band prevents alignment problems like if they were mounted on the sled.
Kruegon
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And makes them ridiculously easy to access. On a StratologgerCF with the optional LED, you can mount the LED beside them. Allows you to visually see the "beeps". Great for redundant systems when you can't hear the beeps because the other one is also beeping.
That's a good reason to use 2 different altimeters.
Some altimeters allow you to adjust the frequency of the beeper so you can differentiate between them.
Kruegon
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The StratologgerCF allows such. But when two are beeping, the LCO is talking over the loud speaker, and the wind is whipping past your head, it can still be hard to hear everything. But then again, I'm the guy who overbuilds everything because my mind imagines ever bad thing that can happen.
I assume that the two switches are for redundant altimeters. But, if the path from the battery to the ejection charges passes through the altimeter, and the altimeter is deactivated, then that qualifies, no?
That is not enough for NAR or CAR. The path to the ejection charges must also be interrupted. That is why a lot of folks have wires sticking out of their rockets and they twist them together at the last minute and tuck them back in. Also, in some cases, people have switches like the ones shown to break the connection. Another alternative is to have a plug that must be inserted at the pad just before flight. Some folks use a switch with dual throw and multiple poles so all ejection charges are on in one position and broken in the other. I'm certain that there are even more creative solutions that I am not listing.
This is from the NAR L3 documentation so it may only apply to L3 certification and L3 flights. Similar documentation exists on the CAR site for CAR rules.
"2.4 The capability must exist to externally disarm all pyrotechnic devices on-board the rocket.
In this context, disarm means the ability to physically break the connection between a
pyrotechnic system and its power source. Simply turning off the device controlling the
pyrotechnic(s) may not be sufficient."
Likewise, redundancy is required for NAR L3 certification and flights.
"2.3 Each parachute event must be initiated by redundant control systems. Redundancy must
be present in the power sources, safe and arm provisions, control logic, and output devices
(e.g. bridgewires, electric matches). Redundancy is not required in the energetic materials
(e.g. black powder charges), parachutes, attach points, risers, and disconnects. Motor
ejection charges may be used as a redundant system, but rockets depending primarily on
motor ejection for any recovery event are specifically disallowed. ..."
This is from the NAR L3 documentation so it may only apply to L3 certification and L3 flights. Similar documentation exists on the CAR site for CAR rules.
"2.4 The capability must exist to externally disarm all pyrotechnic devices on-board the rocket.
In this context, disarm means the ability to physically break the connection between a
pyrotechnic system and its power source. Simply turning off the device controlling the
pyrotechnic(s) may not be sufficient."
Likewise, redundancy is required for NAR L3 certification and flights.
"2.3 Each parachute event must be initiated by redundant control systems. Redundancy must
be present in the power sources, safe and arm provisions, control logic, and output devices
(e.g. bridgewires, electric matches). Redundancy is not required in the energetic materials
(e.g. black powder charges), parachutes, attach points, risers, and disconnects. Motor
ejection charges may be used as a redundant system, but rockets depending primarily on
motor ejection for any recovery event are specifically disallowed. ..."
rharshberger
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So an altimeter arming switch and a battery disconnect switch for each altimeter is all thats required or at least thats the way it sounds as per NAR L3 req.?
... yet another reason to certify with Tripoli. Fewer points of failure.
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The use of a physical switch to break the circuit to the igniters matters in a L3 rocket because they tend to be large with a lot of BP, so if it went off accidentally there would be a much higher chance of injury than for a smaller rocket. Switch bounce due to vibration/G's is not going to be the same issue with an igniter circuit as it would be for the altimeter itself because the igniters are going to fire when the rocket is moving relatively slowly. A good practice would be to connect the igniter circuit on the pad then turn on the altimeters (two, it's a L3)... you'll have to do it this way regardless, because otherwise your altimeters will fail the continuity checks.
<plug>This is where the Eggtimer Remote Switch or the Eggtimer WiFi Switch shine... you can step away from the rocket before you power up the altimeters. If something blows, it ain't gonna be in your face.</plug>
<plug>This is where the Eggtimer Remote Switch or the Eggtimer WiFi Switch shine... you can step away from the rocket before you power up the altimeters. If something blows, it ain't gonna be in your face.</plug>
Titan II
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"The capability must exist to externally disarm all pyrotechnic devices on-board the rocket.
In this context, ‘disarm’ means the ability to physically break the connection between a
pyrotechnic system and its power source. Simply turning off the device controlling the
pyrotechnic(s) may not be sufficient."
The word "may" is important. Take a MW RRC3. If you hook up the battery to the battery connectors and the switch to the switch connectors, one may say the switch does not physically break the connection between the pyrotechnic system and the power source. However, I bridge the switch connectors and put the switch in line between the battery and altimeter. In this case, the switch does in fact physically break the connection between the pyrotechnic system and the power source.
In this context, ‘disarm’ means the ability to physically break the connection between a
pyrotechnic system and its power source. Simply turning off the device controlling the
pyrotechnic(s) may not be sufficient."
The word "may" is important. Take a MW RRC3. If you hook up the battery to the battery connectors and the switch to the switch connectors, one may say the switch does not physically break the connection between the pyrotechnic system and the power source. However, I bridge the switch connectors and put the switch in line between the battery and altimeter. In this case, the switch does in fact physically break the connection between the pyrotechnic system and the power source.
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rharshberger
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I like the idea a single switch can make the NAR requirements.
Yeah, that's what I was planning to do. I'm checking with my L3CC right now.
rharshberger
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Let me know how that turns out, I will be contacting mine as well.
rharshberger
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Please see my later post.
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rharshberger
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Okay just went and did a little more digging that Paragraph 2.4 is the new rule, E-match disconnects/safing devices are no longer required. Here the link and the notice is in the top of the page; https://www.nar.org/high-power-rocketry-info/high-power-resources/
rharshberger
Well-Known Member
Actually from the way its written you could do that or simply do as Titan II said, put a jumper wire in the switch block on the altimeter (if its set up for separate battery and switch attachments, like the RRC3 is) basically making the switch always on, then putting a switch into one leg of the battery so that when the switch is off there is no way for the altimeter to get power. I will go with a battery on switch and altimeter on switch, its not hard to wire and adds far fewer points to fail than the e-match disconnects.
Edit: Yep basically as you put it, one switch per altimeter, but it has to be to disconnect the battery, not to turn the altimeter on and off as normal.
watermelonman
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It is why I certified with Tripoli.
rharshberger
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Its not an issue with NAR any longer.
"Please note that some L3 reports mention required e-match disconnects, that may no longer be required.
Please see this document for the current L3 Requirements NAR L3 Certification requirements"
And, when you download by clicking on the link, you get what I quoted previously.
Anyway, that's good news.
Thanks for the update!
Yeah, it is confusing as all get out. The note on the web page says the rule has changed, then gives you a link to the rules, which takes you to the old rules.
Well, my L3CC won't be evaluating me on that basis, so I am covered.
I also had some e-mail with the certification committee about CAR reciprocity with NAR/TRA. They said, yes, we accept all CAR motors for certification flights; then in the same e-mail attached the combined list, which leaves out the CAR-certified motor that I plan to use (M1101).
Bottom line: if my L3CC signs my cert application, I'm good to go.
Well, my L3CC won't be evaluating me on that basis, so I am covered.
I also had some e-mail with the certification committee about CAR reciprocity with NAR/TRA. They said, yes, we accept all CAR motors for certification flights; then in the same e-mail attached the combined list, which leaves out the CAR-certified motor that I plan to use (M1101).
Bottom line: if my L3CC signs my cert application, I'm good to go.
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