Altimeters and Cold

[talkin Monkey]

Has anybody done any bench testing?

I'm sure a refrigerator/freezer would simulate anything you would want to know about cold weather on the altimeter itself or your batteries.

Now, I've never actually "seen" a dual deploy altimeter, but I suspect they are triggered at apogee and set main altitudes via some type of membrane transducer.

Should a VERY controlled air pressure simulation/accent/decent be intoduced onto said transducer via some type of vacuum source(ultra controlled shop vac or valving?) You should be able to predict your "chilled" altimeter or batteries performance.

Don't even THINK ABOUT controlled shop vaccing your expensive altimeter until you hear some more experienced opinions than mine. I'd hate to see some one "Lawn Darting" their rocket because their altimeter was trashed by a vacuum cleaner or my far fetched ideas for an experiment.

 

[Adrian A]

My shop vac sucks the equivalent of about 3600 feet of air pressure. Nothing dangerous to altimeters about that, though of course you want to keep the static-generating hoses away from the electronics.

Can someone provide flight data from the MAWD, and which type of failure it was associated with? In fact, a list of which altimeter type had what sort of apparent failure might shed more light on this.

Too bad the RRC2 doesn't have a data logger so that we could get some insight into what it thought the altitude was at the time. A ground test at cold temperatures would be a good idea, though. To separate out altimeter issues from ondensation or battery theories, someone could leave their RRC2 out in the cold somewhere dry, and hook up warm, well-charged batteries shortly before the test.

 

[bobkrech]

I'd also like to see some data. Sandmantoy launched a MAWD and a MW RRC2, so his data, if he downloaded it, could be critical to getting to the root of the problem.

If the winds were high and gusty, it is possible that the gust pressure could have faked out the altimeter to give an early deployment if the static ports were too large or too few in number.

Al, perhaps you could compile and post a list of the failed flights with a more complete description of the hardware involved. Of interest would be the altimeters and the power supplies used including battery brands and types; the size and number of altimeter static ports on the rocket and the size of the altimeter bays; and the type or brand of e-matches used on each flight.

Speculation is fine, but it's going to take real data to get to the bottom of this.

Bob

 

[sandmantoy]

I will try to get the data downloaded from the rocket, I haven't done anything to the rocket since the flight. I have also not downloaded any data from a mawd yet so I have to figure out how to lol.

 

[falingtrea]

I wonder, if I just wrapped one of those chemical hand warmer pads in a Ziploc and tossed it in the AVBAY, would it help?

I wouldn't recommend using a ziploc bag. Those things require oxygen in order to work properly.

 

[talkin Monkey]

As an aspiring altimeter recovery enthusiast, here's some thought(s) rattling around in my....uuummmhhhh.......... alledged....mind.... ...............uuummm.............duhhhh.......Hey! What's that shiny thing over there?!?!?!.......................I'm Just Kidding...

Batteries?) It is my understanding that Lithium batteries are supposed to work pretty good in cold environments. Maybe I'm FOS, someone correct me.

Electronics?) Has anyone created or (does manufacture?) an isolated "Firing Board" with an isolated power supply that "Listens" to the altimer(S) and fires subsequentially via RLO? If not, I think I can Invent a good one....hey, there's that shiny thing again.

Alt/bay Environmental control?) Should contents of said self warming hand warmer concoction be thoroughly mixed and careully introduced to some type of type of sealed vessel in an insulated ALT BAY, it's benefits may be of a more positive outcome.

Has anybody electrically insulated with (Electronic varnish )their altimeters to prevent freaky "environmental" behavioral contaminations/malfuctions?

...Hey, there's that shiny thing again, it may result in some in some bananas for me after all this time...I must approach...WOW! Bananas for every one! ....MERRY CHRISTMAS! .....Hey? ...What's that shiny thing over there?.....

 

[sandmantoy]

Hey, Monkey- this listening board

"Firing Board" with an isolated power supply that "Listens" to the altimer(S) and fires subsequentially via RLO? If not, I think I can Invent a good one

If it where to be triggered with say 1/2 second can you make it fire for 1.5 seconds when triggered?

It's obvious monkeys are easily distracted by shiny things :lol:

 

[UhClem]

Has anybody electrically insulated with (Electronic varnish )their altimeters to prevent freaky "environmental" behavioral contaminations/malfuctions?

It is called a conformal coating and is very commonly used in industry. One of the reasons I purchased an AltAcc way back when was because it was the only altimeter (at the time) that was conformal coated.

I found a spray can of silicone conformal coating at the local Fry's and treated my other altimeters.

 

[ttabbal]

Has anyone created or (does manufacture?) an isolated "Firing Board" with an isolated power supply that "Listens" to the altimer(S) and fires subsequentially via RLO?

Sure. The NoMatch does this. It also includes the glowplug ignition stuff, but a board could be made to get the signal from the deployment channel and fire a charge from another battery. The simple version is just a transistor or optoisolator driven by the deployment signal from the alt. Getting more complex would include timer checking the inbound signal (has to be present for more than .5sec for example) and timed outputs (runs for 1.5sec or whatever). It all depends on what you want/need.

 

[sandmantoy]

I think the No-Match board has the glow plug attached to the board. I am in the process of machining a charge tubes with a glow plugs but will have to be wired to the board. I remember a thread where the where discussing the No-Match and was under the impression it had to be attached to there board. I check the No-Match site once in awhile but no more info has been put on it about how it is going with updates.

ttabbal
Sure. The NoMatch does this. It also includes the glowplug ignition stuff, but a board could be made to get the signal from the deployment channel and fire a charge from another battery. The simple version is just a transistor or optoisolator driven by the deployment signal from the alt. Getting more complex would include timer checking the inbound signal (has to be present for more than .5sec for example) and timed outputs (runs for 1.5sec or whatever). It all depends on what you want/need.

Remotely wired to a firing board that that you could count on getting the 1.5 seconds from an altimeter even with a short latch time. Able to hook up with multiple altimeters. Small foot print and stackable in case you need more than one, I want one!

 

[Hospital_Rocket]

No Match also makes a variant that has a separate charge holder from the circuit board.