Raven 3 Info

[FondyKevin]

I currently use the raven altimeter because of it's functionality and size. For the most part it has worked flawlessly. I went to Mile High Mayhem in Colorado this year. (Editorial Comment: Colorado and The Pawnee National Grasslands is one of the finest places to do rocketry.) I launched an upscale Sprint using the Raven 3. Long story short there was no deployment. I never found the rocket (or what would be left of it) so I don't know what was the cause. I am thinking it was more power supply related than anything else. However looking at some forum posts there was some mentioning of accelerometer based apogee deployment and off vertical flights. The Sprint's flight path was not perfectly vertical. There was weathercocking although I am not sure of the degree from vertical. My guess is that it could have been 10-15 degrees off vertical. Just wondering if that could have been a cause since I used accelerometer based flight events. Also the Raven can be switched from accelerometr base to baro base for flight events. Most baro based flight controllers require specifically sized port holes. In the raven's user manual there is no mention of port holes at all. If switching to baro how should the port holes, if any, be sized.

Also wondering if anyone has used the Raven for staging and if so could you pass on your knowledge and experience concerning set-up.

If anyone has any specific setup hints or guidelines for the raven concerning deployment events, would be great if you could include on this thread


KevinB

 

[cerving]

If you have the apogee detection set to baro, it doesn't matter what the flight profile is... the highest point WILL be your apogee, regardless of the flight angle. I'm guessing this wasn't a near-mach flight, so the port size doesn't really come into play either. I think your first instinct is most likely correct... most deployment failures that I see are battery disconnection issues. Unless you forget to put powder in the charge wells because you prepped the night before and taped over the well. (Guilty as charged... once, and only once.)

 

[Buckeye]

How did you confirm no deployment, and what are the circumstances as to why the rocket was not found? Sorry to open the wound, but more info may help us root cause the problem.

I just started playing with accelerometer altimeters and ran into deployment issues. I am quickly coming to the opinion that for 99% of flights, baro should be used for deployment. Accel is just along for the ride to collect more data. Once you exceed the baro sensor, say 40k feet, then you need to rely on the accel for deployment. Or maybe GPS. I don't know, I'm nowhere near 40K feet with my rockets!

I am surprised the Raven makes no mention of vent holes. Vent hole size is really not a big deal, however - many configurations can work. There is a calculator on the Vern K website for 3 or 4 holes. My rockets are 4" diameter or less, and all pretty much use some combination of 3/16" holes, simply because that is the size of my screwdriver to turn the power switch!

 

[WoShuGui]

I have had a Raven 3 shut down when the rocket slipped off a standoff on the pad after being armed. It bumped on the blast deflector hard enough for the accelerometer to detect a launch. If that happens and there is no actual lift-off, the Raven 3 shuts down recovery events after about 5 seconds. I did not notice the continuity beeps had stopped and the rocket was launched with the Raven 3 unarmed. Fortunately I had a backup baro only altimeter and recovered the rocket, but that was a lesson learned.

 

[FondyKevin]

I had individuals witness the rocket come in ballistic. I spent the rest of the day searching but could not find
anything. I am thinking that it was a power issue but thought I would entertain the idea of an issue with the Raven. Thought it would be a good way to discover more info concerning the unit and also to find out how others are setting the events. I am also surprised that there is no mention of vent holes. Based upon the instruction manual one could assume that none are needed.

 

[FondyKevin]

Wow! First time I heard that happening. Thanks for mentioning it.

 

[mikec]

I am also surprised that there is no mention of vent holes. Based upon the instruction manual one could assume that none are needed.

It's true that the Raven manual makes certain assumptions, like vent holes being needed if you're relying on the barometric sensing.

It also doesn't mention that later Ravens had issues with accelerometer calibration that could cause slightly early or late accelerometer-based apogee events. This is why the FIP defaults to barometric apogee. But it wouldn't cause the apogee event to not happen, only to be early or late by a few seconds.

All that said, I've used the Raven for a lot of complex flights (including accel-apogee for flights where I didn't trust my venting) and I like it, but there is unquestionably a learning curve for how to set it in anything but the simplest cases, and some subtleties in how the settings work.