O3400 Min Diameter L3

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airforcetp1991

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Correct. The ones I got were 130mAh but it appears they've been superseded by those 150mAh models.
If you're worried you can bench test them with some grain of wheat bulbs and see how many times you can do a simulated flight (with dual deploy) before the bulbs stop lighting up. I've never done it to exhaustion myself but I have done it three times in a row off a single battery and the bulbs lit every time.
Makes sense, I will do that when I proof the size of CO2 required.

-Tony
 

airforcetp1991

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I think they are underrated. Once you get use to their operation they are pretty solid. I have had multiple Mach flights up to 2.2, high G flights up to 137G, and a few violent deployments and they have never failed me (my poor wiring almost has). But yes, they are not as easy as a screw switch, they require more wires, they are more expensive, and you should make the outside where the switch is so you can easily arm/disarm. They excel at not needing an arming hole and not being affected by CF parts. But all switches have there place and I used rotary, screw, mag, and wifi in different situations.
137G, dang, what type of build was that?
 

rocketace

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137G, dang, what type of build was that?
It was a 38mm minimum diameter just long enough for the H999 called POOF!

 

airforcetp1991

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It was a 38mm minimum diameter just long enough for the H999 called POOF!

That was crazy, I love those fast liftoffs! Most I’ve hit is like 40G though, I’ll try to stop bringing it weak haha

-Tony
 

CalebJ

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I read over the chart and expected an impressive liftoff.

I was not prepared for THAT.
 

rocketace

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That was crazy, I love those fast liftoffs! Most I’ve hit is like 40G though, I’ll try to stop bringing it weak haha
Time to step it up! Ok, I think your project it the definition of stepping it up. Keep up the amazing work, I am enjoying following along!
 

shootthemoon

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"On a similar note I am going back and forth with regard to screw vs. rotary switches. I have used both before and I like the smaller size of the crew switches but I feel there is a limited amount of torque you can put on them. I like that the rotary switches have a positive detent and they can be mounted such that Z axis acceleration of launch/coast is inline with the armed position."
Does anybody use the twist and tuck any more?
 

airforcetp1991

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So long as you covered the exposed part of the connected wires so they didn’t touch anything metal in the AvBay I guess that would work. A small screw switch seems like it is easier but just my opinion.
 

dhbarr

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I've never tried twist-n-tuck, fishing wires out of a hole next to an armed altimeter after a misfire doesn't seem like my idea of a good time. Twist-n-tape, maybe.
 

airforcetp1991

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Preparing for a CO2 deployment test this weekend. This has been my typical method. I use a PVC pipe of the same diameter with at least a 10% increase volume for a margin of safety. You can see in the pictures that there is an even larger margin of safety given how much of the volume will be occupied by the 2 chutes and the shock cord later. I will use a 35 gram CO2 in the Tinder Eagle system. The top cap will have a slightly snug fit (more margin of safety) and be held with 3x #6 nylon shear pins (same setup as planned design). The bottom cap is held with 4 steel screws and is not intended to move. I will actuate it using my low power rocket launch box and be behind a wall for safety. I'll have some iPhone highspeed footage though. I also have a few acres of land in the desert here so no I won't be making a CO2 bomb in a neighborhood....

My thinking behind this method is 2 fold.

1) Proof of concept for charge/CO2 size and shear pin size

2) Minimize risk to expensive CF airframe and electronics (especially with a NC AvBay...

Spears welcome..

-Tony
 

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3stoogesrocketry

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I've never tried twist-n-tuck, fishing wires out of a hole next to an armed altimeter after a misfire doesn't seem like my idea of a good time. Twist-n-tape, maybe.

I never push the wires back into the rocket . twist and tape with electrical tape then tape the twisted part to the outside of the rocket. I have flown mach 1.8 with twist and tape only.
 

tfish

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A lot of folks use twist and tuck and it seems to work for them. I never have, and continue to use screw switches. Works for me.....
some where around mach 2.2 and above.. twist and tape stops being a good choice
1st mishap...tape came off and wires 'untwisted'.
2nd mishap..one set of wires severed at the hole.

I fly mostly dual electronics..

I now use screw switches.

Tony
 

TonyL

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I can say that the fit of the coupler, the axial location of the pins, and any vents all play a significant role in how the CO2 system performs.
What I take that to mean is that a mock-up is a good place to develop, but a ground test of the flight system is still important.

br/

Tony
 

airforcetp1991

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I can say that the fit of the coupler, the axial location of the pins, and any vents all play a significant role in how the CO2 system performs.
What I take that to mean is that a mock-up is a good place to develop, but a ground test of the flight system is still important.

br/

Tony
Very good points. I used the same axial pin location for my mock-up and I plan to use the same size vent hole in the mock up as well. I don’t say that to imply a ground test isn’t important but trying to get it as close as I can.

What CO2 system have you used in the past? Any big lessons learned?

-Tony
 

TonyL

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We are working with Cameron's products. They work well, and we have started characterization tests, but still have more data to collect before we can draw conclusions.
 

airforcetp1991

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Cameron Tinder 🙃
Well sounds like he sure does work there haha I can say I am extremely impressed with the Eagle system! Very easy to assemble and clean and it worked exactly as advertised. Given the test was with a totally empty AvBay I think the 35 gram Co2 size is overkill but my thinking is I would likely need to add the weight saved by selecting a smaller cartridge as ballast anyway... I've had nothing but great experiences as far as customer service goes with them as well.

-Tony
 

airforcetp1991

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Mako test was a success today. I used a 0.2" wide by 0.05" thick zip tie that was very tightly secured around an old DMS shipping tube that is approximately the size of the chute bundle. Cutter worked as advertised and the noise was very low. Impressed again by Tinder Rocketry.

-Tony

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pbahorich

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I am designing a L3 build for this summer, for a BALLS launch or locally if the waiver is approved. The overall concept is a 60" carbon airframe from Wildman with a 2" switch band and a 24" VK nosecone. Redundant Raven4 altimeters and Raptors for the drogue deployment. It is a head-end dual deployment concept with a Sim max altitude of ~85,000 according to RASAero II (rounded fin edge for a conservative estimate) with a max Mach of ~3.6. Planning on 3 or 4 #6 shear pins for each section.

One of the biggest things I am struggling with is the fin attachment method. I am not planning on a tip to tip, mainly due to lack of the equipment to make this happen to be completely honest. The fin design right now is 0.1875" G10 with a 1" bevel (made by PML). The question I would like some help with is will a solid fillet be sufficient using hysol loctite ea e-120hp epoxy? The other option I am looking into is drilling and tapping holes in the fin and using steel screws through the tube wall to help reduce the chance that the peel strength of the tube wall will be the limfac. I am not set on the number of screws but from an engineering point of view I like the concept. I can't help but feel like this would be more common if it was really necessary though...

Any additional BS flags would be greatly appreciated. Thanks!

-Tony
My apologies for being 3 weeks late to the party.

As an aerospace systems engineer who works with system level reliability analysis, we use a tool called Fault Tree Analysis (FTA) which analyzes both the probability and severity of faults. On an airplane with certified software, tested and inspected wiring, and no technician level configuration prior to flight, dual identical systems are usually a good approach. But I will explain below why dual identical altimeters are not a best practice for an amateur rocketry application.

A few months ago at FAR, I watched a 54mm minimum diameter M motor University project lawn dart. They used expensive and identical altimeters. Telemetry showed that neither altimeter commanded chute deployment at apogee. They will never know if it was due to a setup error or a software issue. I would suspect a setup error but can't eliminate a software issue. This anecdote is backed by sound reliability and safety practice however.

Identical altimeters protect against wiring problems (very likely) and hardware failures (very unlikely). They don't protect against user setup errors (very likely) or software issues (somewhat likely, particularly when pushing the flight envelope).

Dissimilar altimeters protect against setup errors (very likely) and software issues (somewhat likely), in addition to the protection that redundant identical altimeters would buy you. Yes, the chance of a single setup error doubles when two different setups are used, but since it only happens on one altimeter, the failure is inconsequential.

But If a setup error occurs on one identical altimeter it will likely be repeated on the other identical altimeter, and thus a single failure leads to catastrophe. This is what we call a common cause failure in the industry and these are designed out of any certified aircraft system. I personally don't believe common cause failures belong in a high performance rocket configuration either.

P.S. Ditto on what others wrote regarding the Fingertech switches. These are robust switches and I used them on my L3. Typical screw switches may vibrate into the closed position in the trunk of a car after a four hour drive (don't ask me how I know).
 

airforcetp1991

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My apologies for being 3 weeks late to the party.

As an aerospace systems engineer who works with system level reliability analysis, we use a tool called Fault Tree Analysis (FTA) which analyzes both the probability and severity of faults. On an airplane with certified software, tested and inspected wiring, and no technician level configuration prior to flight, dual identical systems are usually a good approach. But I will explain below why dual identical altimeters are not a best practice for an amateur rocketry application.

A few months ago at FAR, I watched a 54mm minimum diameter M motor University project lawn dart. They used expensive and identical altimeters. Telemetry showed that neither altimeter commanded chute deployment at apogee. They will never know if it was due to a setup error or a software issue. I would suspect a setup error but can't eliminate a software issue. This anecdote is backed by sound reliability and safety practice however.

Identical altimeters protect against wiring problems (very likely) and hardware failures (very unlikely). They don't protect against user setup errors (very likely) or software issues (somewhat likely, particularly when pushing the flight envelope).

Dissimilar altimeters protect against setup errors (very likely) and software issues (somewhat likely), in addition to the protection that redundant identical altimeters would buy you. Yes, the chance of a single setup error doubles when two different setups are used, but since it only happens on one altimeter, the failure is inconsequential.

But If a setup error occurs on one identical altimeter it will likely be repeated on the other identical altimeter, and thus a single failure leads to catastrophe. This is what we call a common cause failure in the industry and these are designed out of any certified aircraft system. I personally don't believe common cause failures belong in a high performance rocket configuration either.

P.S. Ditto on what others wrote regarding the Fingertech switches. These are robust switches and I used them on my L3. Typical screw switches may vibrate into the closed position in the trunk of a car after a four hour drive (don't ask me how I know).
You make some excellent points. Funny enough I am virtual TDY to Air Force safety training right now and we are talking about these same processes in class.

While I certainly agree with you that having two different altimeter types can be beneficial, I have a Raven4 and RRC3 in my 54mm MD redundant dual deploy, my thinking on using dual Raven4s for this project was based on the predicted apogee altitude. Looking at previous similar builds I saw many people using Ravens for two reasons. The first was the small size which I would argue is the least important with my internal volume, and my decision to use the expansion terminals. The second is the accelerometer feature of the Raven. This is important to me first for "Mach Proofing" the altimeter during the ascent but also for ensuring a reliable apogee detection. I know that other manufactures offer these features so they are not exclusive to the Raven. Subjectively I also have confidence in the Raven having flown it to Mach 2 and yesterday to about Mach 1.2. By the time of the L3 I hope to have at least a few more supersonic flights on it. Yes, these are anecdotes.

My thinking is that the likelihood of a simultaneous component/software failure of 2 Ravens is extremely low and certainly lower than the likelihood of a setup error on my part. With the Raven expansion terminals that I plan to use the wiring is as simple as I've seen on flight computers. I don't mean to dismiss your 54mm core sample story by any means and I would really like to know what others that have flown to these altitudes think about altimeter choice. The TeleMEGA v4.0 system looks awesome, especially with the integrated tracker although IDK if that is putting too many eggs in one basket. If I didn't already have the Featherweight tracker I would be very inclined to go with that product and buy their ground station.

It's good to hear another positive review of the Fingertech switches!

-Tony
 

airforcetp1991

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After my Eagle testing this weekend I thought about something I hadn't before. When the Eagle goes off (or possible both near simultaneously), there will be a LOT of force on the base of that sled as the AvBay over pressurizes. I am slightly concerned about putting that load (>250# based on ~210 min needed to shear the pins and how far the cap went) on a 3D printed edge of the sled base. This should be for only a fraction of a second before the shear pins shear but I don't want to overlook this. I have an Aluminum av bay lid and I am thinking of attaching that to the bottom side of the sled base so that the aluminum edge sits against the NC wall. I'll sand the aluminum edge to better match the NC wall taper. I don't have the final dimensions of the prototype sled I plan to use yet so there's that, I also may want the aluminum there for ballast but I'd be interested to hear people's thoughts on this. Thanks.

-Tony

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