Last weekend I drove up north a bit for some real cold weather testing of my Iris+ equiped with Pixhawk. I had to get up early in the morning to catch -30C temperatures which is about as cold as I'm interested in testing. At -30C, my gloved fingers froze after a few minutes. Not quite frostbite, but deep into pain territory.
Spurred on by Leonard's taunts, I also did some snow resistance testing. It passed. I'd say it can handle just about any amount of snow you could reasonably throw at it. :) I simply put electrical tape over the shell vents, and that's it. Throughout the weekend, I had absolutely zero problems related to the low temperatures. -30C is a non-issue for the Pixhawk and ESCs.
I actually haven't had this Iris for long, but so far I'm pretty impressed with it. The out-of-the-box tune was pretty much spot on. It flies extremely smoothly. The only changes I've made were to allow 45° lean angle, and enabling Stab and Acro modes. The camera I was using for on-board is a Sony AS100V on the semi-fixed front mount included with the Iris. The results are not great, heavy jello. I'm not sure if a real GoPro is much better? You can see the effect of the Sony's electronic image stabilization. If you peer through the jello, you can see that the video is actually quite smooth and watchable. I will probably make a damped undermount for the camera.
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That's a really good point David,
the large majority of damping mediums we currently use would be severely compromised (probably downright useless) at -30 degrees C.
The only thing I can think of that would work at all might be silicone and silicone fluid.
And even that stiffens quite a bit at really low temperatures.
Regular silicone actually retains normal flexibility till right at -30 degrees C and then becomes much stiffer.
Special low temperature silicone stiffens much more slowly from -30 down.
Other rubbers including nitrile - "Buna N" stiffen a lot at much higher temperatures.
There are probably some mil spec visco elastic dampers designed to work at these temperatures, but not anything we are currently using.
Even springs get stiffer.
Probably the best you could do would be silicone o-ring mount or silicone dampers if you can find them and then they will only work till -30 degrees C, becoming virtually rigid with even a further 5 degree drop.
Best Regards,
Gary
http://www.silicone.jp/e/catalog/pdf/rubber_e.pdf
I wonder if camera mount dampers that give a jello free image at 30C would be totally wrong at -30C.
Steve, yes, I always let them acclimatize for 5-15 minutes. It's important for the gyros.
For ESC's, the issue might have been ESC's without external oscillators. If they use internal oscillators, their timing isn't stable over temperature, and they won't pick up the Min Throttle setting properly, thus refuse to arm.
Side note: If you have to use your Android device in the cold, don't take you gloves off. Use a capacitive touch pen. Works for me.
@ Steve: I can't speak for Rob but I always let the Iris+ pre-freeze for a few minutes. I've also gone snow shoeing and skiing with the Iris+ in a pack for hours in 0 degree Fahrenheit temperatures and then flown with no issues. I think thats about -15 or -20 C, so thats in the range you are talking about. (I've also flown at extreme cold temperatures - 20 F to -38 F, but I wasn't dumb enough to be out skiing/snow shoeing in that - those were road side launches from a car).
Maybe having the Iris+ in the pack makes the difference, but I wonder if atmospheric humidity level is the real factor. Granted its always dry when its cold, but there are relative levels of dryness. My unscientific test of that is whether frost forms on my poles. If it doesn't, then its dry. Where I've been in northern Vermont and eastern Canada this winter its extremely dry. In the past, I've been out west and had my poles frost up. So I'm thinking frozen condensation (frost) on electronics and motors messed things up for you, whereas for me, everything just got cold, but no frost. Just a theory.
Hi Rob. Great job risking your fingers.
Did you allow the iris to "prefreeze" for an hour or so before flight? Minus the battery of course.
Just asking because I have had esc's that wouldn't arm after sitting outside at -12 C
Normally that wouldn't be done of course....I'm just curious.
Again, great job,
Steve
Hi Craig,
I just saw this on the local news the other night and thought that the self stabilizing spring loaded platform seemed to be quite effective.
A pretty unusual solution really.
It is mounting one of the Google street level cameras so they needed it seriously stabilized.
http://abc7news.com/science/google-working-to-map-san-francisco-bay...
The Baykeeper group out of San Francisco is using it in the SF Bay.
Best regards,
Gary
Yes, the joys of living in northern Canada!
Just before Christmas we had a week of -30C temps and one morning of -43C (same temp in F or C).
I drove to work in my wife's minivan ('cuz my work truck wouldn't start) and all the lights were lit up on the dash.
Most went away the next day, except for the ABS brake warning.
The GM dealer said we had to replace all 4 of the sensor cables in the brake hubs since they all broke.
He also said we shouldn't be driving when its that cold! WTF.
Things they don't tell you when they want to sell you a vehicle!
The normal precautions for flying in cold weather is to make sure the LiPo are kept above freezing temperature, since it may degrade the battery chemical reaction. Usually I just keep them close to my body before flying. Once you are up in the air, the internal current should generate enough heat to avoid freezing.
Great to See your experience with the Iris was so good Rob.
And a great video.
Did you have the internal stabilization turned on in your AS100V, because although I still get jello, it isn't that bad?
It's probably worth understanding that the Iris may be uniquely well adapted to that extreme cold due to its construction with Zytel Arms.
Zytel is a fancy enhanced Nylon by Dupont that is primarily made to work better at high temperatures but it coincidentally also works better at low temperatures.
Most Nylons and the majority of other thermoplastics tend to become very brittle at those temperatures and fracture and break easily.
In fact, Zytel was uniquely suited to that low a temperature, almost anything else would be likely to be more problematic.
Most of the resins used in used in composites and even aluminum tend to become brittle at those temperatures.
And aluminum does too good a job of conducting heat.
It just may be that the Iris is uniquely well suited to extreme cold.
(That's what they call a built up area in Canada?)
Best,
Gary
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