2.6 and 3" birds, do you always run dual altimeters?

[firemanup]

With recovery being controlled by an altimeter, and smaller birds like 2.6" and 3" birds do you always use dual systems, or are you comfortable with a single proven altimeter?

 

[o1d_dude]

At this point, no.

I use motor eject as a back up. Coming down under a drogue is much better than coming in ballistic but admittedly not as good as coming down under the main.

I have not yet experienced an alt failure with my Missileworks RRC2+’s.

...Knocks on wood...

 

[heada]

I don't consider redundant electronics until I get to the 5.5" and bigger.

 

[Cameron Anderson]

Generally speaking, I will run a single 4-event altimeter with redundant charges - drogue @ apogee then apogee +1.5 seconds and main at 1,000 and a backup @ 850. I've found it more likely that a charge event will underperform than an altimeter will fail.
With that said, if I have room, I will more often than not throw a second altimeter in there and wire it up as a back up, not because I feel like I need the redundancy, but if it is in there to log a specific flight parameter I might as well use it. 3" is way easier to run two altimeters that 2.6...that slight extra room goes a long way.

 

[Antares JS]

I've always run only a single altimeter in up to 4" with no issues. I am only considering a redundant one in a bigger rocket because it's (understandably) a requirement for level 3 cert.

 

[Titan II]

Yes

 

[djs]

I've run dual altimeters in 54mm (2.1") rockets. Normally i don't, but that's more due to lack of altimeters than anything else. It takes a bit of careful engineering to get it all to fit, but it can be done. Honestly I'd probably do it in all of my rockets if I had enough altimeters

 

[Speaknoevil]

Once I figured out how to implement dual alts front/back on the Additive Aerospace sleds, I now do dual deploy down to 54mm airframes.

 

[Paradox_2112]

I run dual deploy, single altimeter in any rocket I can fit it in from my 1.5" to 4" rockets. I usually will run missile works rrc2 in smaller rockets and rrc3 in 3 & 4" . Hope this helps.

 

[Jmhepworth]

If I can make two altimeters fit, I use two. If I can’t I make sure I have motor backup.

 

[cwbullet]

I rarely do 2 altimeters below 5-inch rockets.

 

[Kelly]

It depends more on the value of the rocket than the size.

 

[Nytrunner]

Only dual-alt rocket is my 5.5" L2 vv

 

[Tim51]

I lost a 3" (pictured below courtesy SARA) that only had one altimeter. Although I never found the rocket (it came in ballistic from around 7.5K' into soft peat moorland) I doubt that it was the altimeter itself that failed - it was an SLCF (a superbly reliable little gadget in my view), and that actual same altimeter had flown before with no problems. However, since it was that rocket's first transonic flight, my theory is that something was shaken loose, either by acceleration vibration or yaw-roll coupled oscillation, and I've come to suspect that something was a particular type of cheap metal key switch I'd chosen to install, which was ok on slower flights but failed on this. For the next 3", 4" and 5.5" AV bays I built I had a rethink on everything and it has space for 2 altimeters, better secured wires and screw switches, but that's just become my preference: any system, with redundancy or not, is only as good as the connection points.

 

[mrwalsh85]

I have flown my 2.6" Fiberglass Madcow Screech on motors ranging from an Aerotech J350 up to a Loki L1400. I only fly with one altimeter, and that is an RRC3. It flies just fine. I plan to stuff a Loki L1040 in it someday. That will be exquisite!

 

[Steve Shannon]

With recovery being controlled by an altimeter, and smaller birds like 2.6" and 3" birds do you always use dual systems, or are you comfortable with a single proven altimeter?

Only if I’m launching to higher altitudes where I might lose sight of it. I use redundancy to ensure safety for the people on the ground and to protect the value of my rocket. For small rockets on small motors that I can see the entire flight I use single altimeters or even motor deployment.

 

[Mugs914]

Stretched 3" LOC Forte, RRC3 primary with RRC2+ backup. Belt and suspenders... I like to use two alts if they'll fit. Smaller/lower stuff is fine with just one, like Steve said.

A bit of paranoia perhaps...

 

[cerving]

I'll put two in the AV bay if they can fit... not hard with 4"+, harder with 3" and 2.6", difficult with 54mm. Eggtimer Quarks are a good backup altimeter... they're very small, and cheap.

 

[blackjack2564]

For sport fliers usually under 5-6000 ft I use 1 altimeter with TWO e-match per charge. This almost eliminates the chance of failure. [99.9%]

For Xtreme or high altitude flying over 10,000 which usually means L and M motor cases. I use 2 altimeters...I want all my expensive gear back in one piece.

By the way I used to fly at Walcott back in the glory years and remember your Thor collection. I rode with Wildman to the launches for years, what a nice crowd we had there. AND all the great stories that happened there.
Years later Scoop bought your 6in. and we did a 3 way crazy jim drag race in Argonia on M-2200 skids!

 

[mbeels]

For sport fliers usually under 5-6000 ft I use 1 altimeter with TWO e-match per charge. This almost eliminates the chance of failure. [99.9%]

Do you put your two e-matches in series or parallel? Do they tend to fail open, or short?

 

[mrwalsh85]

For sport fliers usually under 5-6000 ft I use 1 altimeter with TWO e-match per charge. This almost eliminates the chance of failure. [99.9%]

How do you get 99.9%? If your altimeter browns out, fails, battery wires just "give up"...? So many more chances to fail, other than wiring two ematches.

 

[ghostfather]

Sort of depends on the altitude more than the size of the rocket. I routinely fly a 4" rocket on I motors that was originally built for motor ejection, as it rarely goes above 3K. I've recently converted it to dual deployment with PerfectFlite CF that's fairly trustworthy because I got tired of walking out to retreive it on windy days.

I've also flown some minimum diameter rockets with single board AltusMetrum altimeter/GPS. The idea is to save space and weight, and it's a calculated risk using a single point of failure when flying to 20K. AltusMetrum makes good reliable stuff, though.

My level 3 project (which I may get to fly when the Corona restrictions allow me to travel) is a 6" straightforward fiberglass rocket, using double altimeters and a GPS unit. All fairly conservative. It can fly anywhere between 5K and 20K, depending on the motor, but the point is to demonstrate that I know how do do this safely and reliably.

 

[Cameron Anderson]

How do you get 99.9%? If your altimeter browns out, fails, battery wires just "give up"...? So many more chances to fail, other than wiring two ematches.

Purely anecdotal, but I have never seen a commercial altimeter fail.
I've been failures that are all user induced or could have been eliminated with just a little ground testing...cheap battery, underpowered battery, cheap battery connectors, incorrect programming, poorly secured battery, undersized ejection charges. The list goes on, but the common trend is user error.

 

[firemanup]

For sport fliers usually under 5-6000 ft I use 1 altimeter with TWO e-match per charge. This almost eliminates the chance of failure. [99.9%]

For Xtreme or high altitude flying over 10,000 which usually means L and M motor cases. I use 2 altimeters...I want all my expensive gear back in one piece.

By the way I used to fly at Walcott back in the glory years and remember your Thor collection. I rode with Wildman to the launches for years, what a nice crowd we had there. AND all the great stories that happened there.
Years later Scoop bought your 6in. and we did a 3 way crazy jim drag race in Argonia on M-2200 skids!

Damn would like to see pics of that, is it still flying??

Yeh i liked Walcott for sure, been to princeton twice this year so far, seems like its pretty nice group as well.

Will be redoing my L3 at midwest power this fall.

 

[firemanup]

Ive run dual alts in anything 4" or bigger that im sending to real altitude.

I have a 3" im about to start that is going to be a little tighter space wise, so i was wondering, it will be going hi so i will likely figure out a way to get 2 on board.

 

[Tim51]

My level 3 project (which I may get to fly when the Corona restrictions allow me to travel) is a 6" straightforward fiberglass rocket, using double altimeters and a GPS unit. All fairly conservative. It can fly anywhere between 5K and 20K, depending on the motor, but the point is to demonstrate that I know how do do this safely and reliably.

Very much hoping I get chance to see that in action

 

[blackjack2564]

Do you put your two e-matches in series or parallel? Do they tend to fail open, or short?

Parallel, always twist insulated and bare wire for strain relief & good connection.

Match head has 1 wrap of tape around exposed metal on head, then 2nd match wrap to hold in place with no chance of short.
They are always burned from BP after flight, never had failure, so never bothered to check.

When only using 1 match: over the years had 6 failures. they all showed continuity before hand so I assume those were shorted. 2 of them burned the nichrome wire but did not ignite pyrogen. This is over 10yr period. included daveyfire....oraxel...MjG and chinese orange.. Over 2,000 matches fired. I was prepping other projects along with mine for years. When use 2 altimeters with 2 match per change ...8 per flight. They add up quick. Look at chart below, my odds of failure using 8 matches is less than 1 in 2 million.

How do you get 99.9%? If your altimeter browns out, fails, battery wires just "give up"...? So many more chances to fail, other than wiring two ematches.

99.9 is for match failure rate when using 2. I obtained it through research, which is what one does to eliminate failure.

I personally have talked to every designer of every altimeter I use, to get BEST info on battery, match, failure points etc. I have approx 25-27 altimeters/timers... including Strato's, Missleworks which I did testing on for 3yrs and wrote the quick start manual covering common failure points and how to avoid. Telemeg'a. Past use Featherweight, R'das and many more.

Brown out is virtually impossible with models incorporating caps to avoid that. Unless you have a horrific event, then dump alt. and use another. Using a "possibly" damaged in flight altimeter, happens way to often, because fliers being "cheap".

Proper testing of new units and 1st flight "buddy" flights with a proven altimeter are a must.
All wires are replaced after every flight, since matches are direct wired to altimeter, so no issue there.I use twist and tape switch wire for flying, those get replaced after flight.
My rare Xtreme flights use proven combat robotic screw switches with military grade neoprene coated wire rated 65amp.

Battery either new or used, volt tested EVERY flight. Proper mounting for high G flight and check list eliminated all other issues.

Most likely cause for failures are user error, not doing "pull" test on every connection every flight. that alone will eliminate a very common error. The list is to long for here, but rest assured. I'm batting 99.9% non failure rate and you can to if you invest the time and effort to do so. good luck & have fun.

PS forgetting to arm electronics does not count in failure rate.......lol
That just makes U/me a Dumazz member.

 

[Flyfalcons]

If it fits, it ships. I was originally planning on a single altimeter for my Punisher 3, but because I'm planning on flying loads with no ejection charge, the decision for redundancy was made and it's getting my usual RRC3 & RRC2+ treatment. Using 2S 180mah Lipo packs instead of 9V saves tons of room.

 

[mrwalsh85]

Parallel, always twist insulated and bare wire for strain relief & good connection.

Match head has 1 wrap of tape around exposed metal on head, then 2nd match wrap to hold in place with no chance of short.
They are always burned from BP after flight, never had failure, so never bothered to check.

When only using 1 match: over the years had 6 failures. they all showed continuity before hand so I assume those were shorted. 2 of them burned the nichrome wire but did not ignite pyrogen. This is over 10yr period. included daveyfire....oraxel...MjG and chinese orange.. Over 2,000 matches fired. I was prepping other projects along with mine for years. When use 2 altimeters with 2 match per change ...8 per flight. They add up quick. Look at chart below, my odds of failure using 8 matches is less than 1 in 2 million.
View attachment 421845
View attachment 421846



99.9 is for match failure rate when using 2. I obtained it through research, which is what one does to eliminate failure.
View attachment 421848
I personally have talked to every designer of every altimeter I use, to get BEST info on battery, match, failure points etc. I have approx 25-27 altimeters/timers... including Strato's, Missleworks which I did testing on for 3yrs and wrote the quick start manual covering common failure points and how to avoid. Telemeg'a. Past use Featherweight, R'das and many more.

Brown out is virtually impossible with models incorporating caps to avoid that. Unless you have a horrific event, then dump alt. and use another. Using a "possibly" damaged in flight altimeter, happens way to often, because fliers being "cheap".

Proper testing of new units and 1st flight "buddy" flights with a proven altimeter are a must.
All wires are replaced after every flight, since matches are direct wired to altimeter, so no issue there.I use twist and tape switch wire for flying, those get replaced after flight.
My rare Xtreme flights use proven combat robotic screw switches with military grade neoprene coated wire rated 65amp.

Battery either new or used, volt tested EVERY flight. Proper mounting for high G flight and check list eliminated all other issues.

Most likely cause for failures are user error, not doing "pull" test on every connection every flight. that alone will eliminate a very common error. The list is to long for here, but rest assured. I'm batting 99.9% non failure rate and you can to if you invest the time and effort to do so. good luck & have fun.

PS forgetting to arm electronics does not count in failure rate.......lol
That just makes U a Dumazz member.

Ah, I understand now. Your 99.99% rate is actually for e-matches alone. Altimeters are not factored into your calculated success rate.

For what it's worth, at LDRS38, the RRC3 that was on Marvin the Martian failed on us. We had a proper beep-out at the pad, but the charges never fired. Upon downloading data, there was none to be downloaded. I initially had problems programming, too, but I finally got a successful program upload. I've been in touch with Jim Amos, and just need to send in that altimeter for diagnosis. Probably a good time as any, with no launches around here that necessitate any RRC3's. Thankfully we had three altimeters onboard for this project, so the charges did go off.

....strangely enough, the charges were never needed on that flight....... LOL

 

[Buckeye]

Do you put your two e-matches in series or parallel? Do they tend to fail open, or short?

It seems strange, but series is the best. Professional fireworks do it this way. Also, if using LiPos, which have low internal resistance, the added resistance of matches in series will prevent overloading the current to the output channels (Most altimeters are not properly designed to use LiPos). There are many threads on this topic, and some guy learned the hard way and fried his altimeter with a bad combo of Lipos and parallel matches.