Stratologger+RRC2 or Stratologger + GWIZLCX

I am looking to add redundancy to a large rocket I am constructing (40lbs). I have a strato-logger that I plan to use as the backup altimeter. I am trying to figure out whether I should purchase a Missile Works RRC-2 or a Gwiz LCX for the primary altimeter. I have had a g-wiz LCX before but only used it for 2 flights (crash, but not because of the computer). The reason I am considering the LCX again even though it is much more expensive than the RRC-2, is that I already have the 35$ data transfer set-up. In addition, I like the option to use accelerometer based apogee deployment. Any opinions?

RRC2s just work -- I don't think you can ever go wrong flying one.

-Kevin

And it seems like It would be much easier to set up too. I dont like using two batteries per launch for the LCX.

Aris said:

And it seems like It would be much easier to set up too. I dont like using two batteries per launch for the LCX.

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The LCX, like my HCX, can be run in single battery mode. Conversely an RRC2 can be set up for dual batteries (I run them both ways depending on mood I suppose). So this shouldn't be a consideration in the decision.

Would a big deciding factor be that the LCX has the accelerometer function enabling one altimeter to be barometric(StratoLogger) and the other accelerometer(LCX) based deployment.

Aris said:

I am looking to add redundancy to a large rocket I am constructing (40lbs). I have a strato-logger that I plan to use as the backup altimeter. I am trying to figure out whether I should purchase a Missile Works RRC-2 or a Gwiz LCX for the primary altimeter. I have had a g-wiz LCX before but only used it for 2 flights (crash, but not because of the computer). The reason I am considering the LCX again even though it is much more expensive than the RRC-2, is that I already have the 35$ data transfer set-up. In addition, I like the option to use accelerometer based apogee deployment. Any opinions?

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You may want to check out the Featherweight Raven for comparison, if you haven't already.

Adrian A said:

You may want to check out the Featherweight Raven for comparison, if you haven't already.

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Because it is more expensive I would like to know why this would better than the lcx other than size.

It looks like it has its own back-up system correct? because I see on the "featherweight interface program" webpage that you can do barometric and accelerometer based apogee deployment at the same time. Is this true?

Aris said:

Because it is more expensive I would like to know why this would better than the lcx other than size.

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• The Raven records all kinds of data that you can graph after the flight, so it's more comparable to the GWiz HCX that they sell for $235.
• It has 4 outputs instead of 3.
• It can handle 8 Amps through each output, rather than 4.
• It can provide full current in a 1-battery configuration.
• It can be used with single-cell lipo batteries, not just 9V batteries.
• Its accelerometer range is 70Gs, rather than 50 Gs.
• It works equally well with either end up.
• The Raven has a simulated flight feature, which lets you test out your av-bay and battery setup and deployment settings and review data from the results.
• The data connection is built-in.
• The Raven has more options and flexibility for the deployment settings.

Adrian A said:

• The Raven records all kinds of data that you can graph after the flight, so it's more comparable to the GWiz HCX that they sell for $235.
• It has 4 outputs instead of 3.
• It can handle 8 Amps through each output, rather than 4.
• It can provide full current in a 1-battery configuration.
• It can be used with single-cell lipo batteries, not just 9V batteries.
• Its accelerometer range is 70Gs, rather than 50 Gs.
• It works equally well with either end up.
• The Raven has a simulated flight feature, which lets you test out your av-bay and battery setup and deployment settings and review data from the results.
• The data connection is built-in.
• The Raven has more options and flexibility for the deployment settings.

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by deployment settings do you mean I can use the raven to ground test the charges?

Aris said:

Because it is more expensive I would like to know why this would better than the lcx other than size.

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The single most important thing, in my book -- if you have questions or problems with your Raven, you'll have no problems getting a response from Adrian. If you have problems with a G-Wiz product, good luck....

-Kevin

Aris said:

by deployment settings do you mean I can use the raven to ground test the charges?

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You can, either by connecting a USB cable to the altimeter and performing a simulated flight, or by moving the altimeter upward quickly to cause a launch detection. What I do for my rockets is use the simulated flight with my full av-bay setup and batteries, and bare ematches at my desktop. Then I check the deployment charge sizing separately in the back yard.

i see

Hi there! I had to post here. I think the Strattologger is a great idea, I have opne that has yet to fly. If it was up to me, I'd go with the RRC2 over the G-whiz. If you want to PM me about that, I can tell you of my G-whiz experiences, but I hesitate to do that on an open forum. I've also used Adept and Transolve altimeters, with no problems.

Aris, You just can't go wrong with either the Stratologger or the Missile Works unit for the price.....
My favorite airframe size is 4" dia. and, i like too REALLY thump them hard on M's and N's.....both have flown under this stress with never a failure.
Now, i can't say i've tried Adept but, alot of people i know have recommended them and spoke very highly of their performance over time.
If i can make a recommendation now....i would say if money was not a big concern, i would point you towards the MARSA54....Point out another accel. type altimeter that can be totally programmed in the field WITHOUT a laptop interface? Using a small joystick and LCD screen on the board, it becomes painless to set all functions on the go.......

Now, im going too be nice for once...over the last eight years of pushing these rockets hard i've learned something.
1. Nothing created by the hands of man will ever be perfect.
2. Sometimes electronics DO NOT live up to their reputation...spread by the many.
3. IF the customer service does not address the problem(s) encountered with said device.
4. The altimeter is JUNK.....period.

Ive also had serious issues with G-What-ca-ma-call-it AND another popular brand currently on the market.....you can also PM me and i will explain.

I said it before.....i'm being nice....in public.....

SS/EA 6BBL 71 Cuda said:

I said it before.....i'm being nice....in public.....

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And it's really tough for Gus to be nice, public or not :wink:

First off, Is there a real need for an accelerometer option on the altimeter? The marsa sounds like a nice flight computer but is too expensive for me now at $225. The missleworks RRC-2 is in my price range but I do not understand the mach delay function that needs to be set unlike the stratologger. How does it work and how do I know how long to set it for?

Good question about "Do i really need an accel option?".......I guess the answer for me is very simple....NO.....Using baro. only altimeters in flights up to 26k and/or speeds approaching Mach 2.5 i've had great luck with just the basic baro. type. Alot of it depends on what do you want too know after recovery?
I believe that the accel. type will give you a more accurate playback of the launch and flight......For me i just want too see everything work and, get the rocket back....i'm not going to over analyze the entire flight curve on a laptop latter....(I'm still a low-tech person living in a high-tech world.)
To give you an idea about mach delay lets go back to the previous version of the RRCX2 before the mini......There was a 25K version and a 40K version.....The 25K was able to set 4-8 or both for 12 seconds of mach delay.
The 40K unit had provisions for 5-10 or both in for 15 seconds of mach delay.
I've always felt that setting an adjustable delay between 12-14 seconds will cover 99.9% of the conditions you will experience in this sport no matter the diameter/size/weight/motor choice that you will fly.
No where in the Perfectflight Stratologger users manual will you see a definite listing of what the preset mach delay is but i would bet its around this number, most likely around 15 seconds......
Now for your question about setting the delay on the Missile Works.....if you go their site and click on the RRCX in the product description....page down to where you can download the users manual....The MW allows you to enter the setup menu by holding down the Select button during power up and, then releasing it to scroll along.....In a short time with a powered up unit and the directions in hand you begin to understand whats going rather quickly....just play with it!

Sorry, i missed that you asked about "What is mach delay and, how does it work?"
Think of this....there alot of "Unique" things going on with the air pressure inside you av. bay during a flight and, outside of the rocket itself...Mach delay just rules out variables that could cause early deployment of the apogee or main charges due to these extreme/unpredictable moments....Size/location/number of vent holes proximity to altimeters inside the bay and even overpressure of the bay due too the parachute/recovery system sliding down the upper tube into a poorly sealed bay cap can do very interesting things to the baro. sensor(s).
All were doing is eliminating some of these for the first or multiple seconds of the flight till things are "happy" and its time to "split or throw the laundry out".

SS/EA 6BBL 71 Cuda said:

Sorry, i missed that you asked about "What is mach delay and, how does it work?"
Think of this....there alot of "Unique" things going on with the air pressure inside you av. bay during a flight and, outside of the rocket itself...Mach delay just rules out variables that could cause early deployment of the apogee or main charges due to these extreme/unpredictable moments....Size/location/number of vent holes proximity to altimeters inside the bay and even overpressure of the bay due too the parachute/recovery system sliding down the upper tube into a poorly sealed bay cap can do very interesting things to the baro. sensor(s).
All were doing is eliminating some of these for the first or multiple seconds of the flight till things are "happy" and its time to "split or throw the laundry out".

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the mach delay function sort of puts the altimeter in a sleep mode where it doesnt take in measurements from the air correct? Btw, the perfectflite states that the stratologger is immune to the mach transition so there is no mach delay function. How did you come up with the 12-14 seconds of mach delay? Should I find a number more specific to my rocket by using rocksim?

Yes, your right about putting the altimeter into a "sleep mode". For myself with my current types of rockets and motor combinations i personally can't think of a situation where my 12-14 second "rule of thumb" would'nt fit in quite well.....using RockSim or even better yet RasAero to profile your expected flights will help determine baseline "windows" for you but, see if you notice a pattern.
The only time i've ever used RockSim in designing/profiling a rocket was for my L3 seven years ago......It's kind of a joke amongst many of my friends but, I still believe that the most powerfull computer you will ever use is the one between your ears.....and, a little experience behind it....NOT that i consider myself too be exceptionally smart in any way.

SS/EA 6BBL 71 Cuda said:

Yes, your right about putting the altimeter into a "sleep mode". For myself with my current types of rockets and motor combinations i personally can't think of a situation where my 12-14 second "rule of thumb" would'nt fit in quite well.....using RockSim or even better yet RasAero to profile your expected flights will help determine baseline "windows" for you but, see if you notice a pattern.
The only time i've ever used RockSim in designing/profiling a rocket was for my L3 seven years ago......It's kind of a joke amongst many of my friends but, I still believe that the most powerfull computer you will ever use is the one between your ears.....and, a little experience behind it....NOT that i consider myself too be exceptionally smart in any way.

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Is the baro altimeter affected by speeds past mach one or is it just at the mach transition. If it is just at the transition I would imagine the mach delay would be for like a M3700 in my 7.5" nike smoke like 6-8 seconds since the motor only burns for 1.8 seconds and decelerates from its max speed at mach 1.2 pretty quickly.

A second or two past burnout is usually good for mach delay.

On other large projects in this forum, the builder uses 2 of the same altimeter instead of 2 different ones. What would be the downsides to that technique? I love the simplicity of setting up the Stratologger and would enjoy using a second one for redundancy instead of another kind.

Aris said:

On other large projects in this forum, the builder uses 2 of the same altimeter instead of 2 different ones. What would be the downsides to that technique? I love the simplicity of setting up the Stratologger and would enjoy using a second one for redundancy instead of another kind.

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That would work. I know Gus does it. Just stagger your charges, i.e., add a half second or one second delay to one of the altimeters on the apogee and set the main charge at a different altitude. Should all be programmable settings. You are doing so so that you don't have two charges going off simultaneously (more likely to happen with same brand) and overpressurize your airframe.

dixontj93060 said:

A second or two past burnout is usually good for mach delay.

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It should be after the rocket becomes subsonic again, because not only the transition into supersonic flight, but also the transition out of supersonic flight can be critical.
Depending on the flight profile, the later transition can happen significantly later than burnout.

Reinhard

Reinhard said:

It should be after the rocket becomes subsonic again, because not only the transition into supersonic flight, but also the transition out of supersonic flight can be critical.
Depending on the flight profile, the later transition can happen significantly later than burnout.

Reinhard

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Yes, correct, sorry.

I think if I were to get 2 different kinds of altimeter instead of 2nd stratologger, I would purchase the LCX just because I am familiar with its setup and it was easy to use imo.

Aris, Now i'm back home maybe i can also answer some more questions.....Yes, like Reinhard says the transition out of mach can play havoc with mach delay. Thats where even with a 1.8 second burn, touching mach and then coming out proably at 2-2.2 seconds in the launch could be hazardous with a short delay.
Thats what i like about the Stratologger, it takes care of this for you and, if you are using a settable unit....set at say oh 10-12-14 seconds your still far from apogee and disturbing that event.
Good friend Daveyfire(Reese) and, i were talking supersonic shock and flow on fin shapes one day when he said something surprising too me....Airflow above mach and compounding can be predicted....airflow below mach is still a mystery.
Now don't anyone jump Dave for being "incorrect" but, that's how i understand it and i can see it. Whats going on to the atmosphere and venting inside the bay....well....alot i'm sure....in a short amount of time.
I have ALWAYS run the same altimeter next to the same altimeter in all my redundant flights and, never had any issues.....I've heard explanations such as..."Well what if theres a problem...design wise...manufacturing.. that might cause both too fail and you don't have anyway to save it?"
My answer is...i check every new altimeter out, power it up, run through the directions, and as a last resort shove them in a bay with little low current lights strung out to the bay ends... hooked to the firing ports.....stick a vacuum cleaner up to the bay vent holes and suck away.....release vacuum and watch for the light show.
Having two exact altimeters with a slight difference in apogee timing would be a good idea...one second variance is a good baseline.
The one thing i did to all my Stratologgers was to drool a little five minute epoxy into the void between the blue capacitor and the side terminal block...just a dab. Most likely NOT needed but, peace of mind to keep it put during some of the more "Evil" flights i had planned for them(N-10,000 thumps) so far, so good....no electronic "crushing".
Let me check in tomorrow as i've run out of time and, i will talk some other ideas....mostly bay setup. Take care.

Have you looked at the Adept22? Baro based, low cost, and Mach immune also like the Strato.

The odds for errors with dissimilar altimeters are affected in different ways. Some errors will become less likely, while other will become more likely. Generally speaking, the chance that no charge gets fired becomes less but the chance that a charge gets fired too early increases.

Two examples: Some altimeter or timers can be fooled by motors that burn very short (e.g. 38mm W9 or CATOs) or oscillate very strongly (some hybrids). If the system in use doesn't even realize that the rocket has been launched, it will not initiate recovery. This has happened in the past and is hard to test for on the ground.

On the other hand, recovery systems may trigger earlier than intended. For example the AltAcc will fire the main chute of continuity on the drogue is lost - possible in redundant setups where both systems use the same charge with different igniters. Another example are Ravens with older firmware versions that will fire prematurely at extreme altitudes (around 90k IIRC).

The average flier is usually unable to test its altimeter for these kinds of error without performing test flights.

Personally, I'm more than willing to accept the increased risk of an premature deployment compared to the risk of no deployment at all.

Reinhard