Kudos to you guys for trying to solve the VVS problem! For your second experiment, may I recommend attaching the iphone to the disc of a variable-speed angle grinder? You'll get a much larger range of speeds, as well as the ability to aim the camera freely. You'll be able to test how your accelerometer algos handle pitch and yaw IN ADDITION to centrifugal force!
I hope you're joking. If you do plan on doing this then please do it in a suitably strong wire cage, power it on remotely, make sure it is tied down very solidly and make sure nothing you care about (including you, significant others, co-workers, children, pets, possessions etc) is in the plane of rotation because this will fail spectacularly. Keep in mind that if the grinder becomes dislodged or unbalanced that the plane of rotation may vary rapidly. Too rapid to get out of the way. The iphone will desintegrate due to the forces involved and the shrapnel will cause serious injury.
Please do not do this unless you really know what you're messing with (and if you do then you won't).
On second thought, simply please do not do this. Spinning an iPhone up to 10K rpm or higher is a very bad idea, the label reads 11K rpm max, 850W, those things don't usually have soft-start so it'll just fire up and start throwing things.
Appeal to authority fallacy comes free of charge: I've had a pretty serious metal workshop and have seen several interesting interactions between angle-grinders and various objects in otherwise controlled circumstances, it is astounding how fast things can go wrong. Just having a grinder disc shatter on you can take you completely by surprise even if you know the danger, this is far more dangerous, it is Darwin award material.
Really great points. I think that when working around power tools it is sometimes forgotten how careful you have to be.
Everyone innately knows certain things like "don't stick fingers in light socket" but other things aren't immediately obvious. Perhaps because you are juxtaposing something like an iphone and maybe are focused on the worse case scenario as being a destroyed iphone (in other words the money issue) instead of the iphone flying off into someones face.
I was watching an episode of "Property Brothers" (a typical renovate a house HGTV type show) and was amazed that they were having the owners participate in demolition without using practically any protective gear (while using crowbars and sledgehammers etc.)
Wait until you get a nice long steel nail that jumps away on you from the crowbar just as it exits the wood and embeds itself 2" deep in another piece of wood. if you're lucky.
Or when a sledge hits a really hard pebble just off the side of a solid wall and it gets catapulted out.
Sledges, crowbars and pickaxes are really dangerous tools and especially if you should wear goggles at a minimum, and probably a helmet too.
And, no, I'm not from the cradle to the grave coddling department.
Yeah I really don't understand the parent making that comment either. As if it's so much work to have some safety gear on.
From busting apart shipping crates as a kid I also realized that in addition to the goggles and helmet you also need boots that can take stepping on a stray nail as well. Not sneakers, definitely not sneakers.
I absolutely buy they are dangerous, but are they as dangerous as a chainsaw or big angle grinder? I'd take a nail 2" deep in my leg over a chainsaw in my leg any day of the week.
(Personally I'd wear PPE with either type of equipment)
Really, I can't stress this enough, the kind of energy you can imbue a 4" nail with using a crowbar is something fierce.
Or maybe the crowbar would just fly up and split your head open. 4' of nice steel makes one hell of a spring.
Big angle grinders are actually safer than small ones... until the disks shatter, then you have a real surprise. Circular saws will do fun stuff as well every now and then, they just love it when they get pinched in the cut. So you have to plan how the material will warp before you start cutting otherwise it might cause the dangling part to squeeze shut the cut (when you want the opposite).
Chainsaw in your leg? Not good. Wear ballistic protective covering and you should be fine. The clutch in your saw won't like it one bit but should you ever need it you'll be very happy you spent that money, and a clutch is so much easier to replace than a leg.
With a grinder you want to wear safety classes, no gloves (so you can't get caught). For chainsaws there are as many opinions on safety as there are chainsaw wielders. Even the pros are surprised every now and then, usually not by the saw but by the tree.
The best advice I can give you for saws is don't use one with too little power and keep it sharp at all times (and that goes for all edged tools). Wear a helmet with a screen and ballistic gear (pants, jacket).
If you're super experienced then you can make up your own mind and you'll likely disagree with all of this :)
My dad is a builder, and I've worked for him as a labourer many many times. It really gives you a better perspective on how dangerous all this is...
Anyway, circular saws: dad was cutting some pretty nice wood for a fence. Circular saw hit something in the wood, bounced up, then straight down onto his left hand thumb, severing it entirely.
He then drove to hospital. They reattached it, he was lucky enough to have Australia's best nerve surgeon on call at that hospital that day, and now he's got near 100% movement in it. Very very lucky.
Angler grinders blowing, now that's something that will put the fear of god into you...
I agree your dad is very lucky. That's about as good an ending to that story as you could possibly have. One day I was cutting staircase support (all those triangles you have to cut out) from a 2" x 12" board, the same thing happened and the saw just jumped right out of the cut. I slammed it down before it could get out of control and it still managed to cut a really nasty gash into the wood before it finally stopped moving. Incredible how fast that went from everything fine to literally fighting the saw. Nobody got hurt that time so all is well but still it gave me even more respect for rapidly rotating disks of steel.
I had an angle grinder disc blow on me last fall when cutting through a rooftile, that too was quite an interesting experience. It would have been less of a problem if it had shattered completely but of course one segment on one side decided to hang on. If not for eye protection that would have ended in the hospital for sure.
The one thing I've noticed is that if you rarely work with tools you are really at risk. Then as you work more more with powertools you get more experience, you become a bit more confident and more aware of the risks. That's good.
Then when you're working with them for a really long time two things will converge in a bad way: all that experience and confidence will lull you into a false sense of safety an then the law of large numbers catches up with you, very rare occurrences will happen to you because you are doing it so often.
If you're not paying attention right at that moment you could very well end up in hospital or worse.
"all that experience and confidence will lull you into a false sense of safety"
I've noticed that that happens with many different things in a similar way.
You get confident, you slip up, you work faster, you make mistakes.
When you start out boating (with a new boat) you are oh so very careful.
Then you gain confidence and you start to take more chances. All the sudden things that you could never imagine yourself doing when you start you do. An example might be getting caught in an inlet with a boat during a period when larger boats are all trying to go in or out at the same time and you are tossed left and right.
Programming as well. Say doing a rm -fr foo * in stead of rm -fr foo* and not catching it because you hit return to fast instead of making sure the statement was correct. [1]
[1] I got into the habit of doing for i in foo* ; echo $i ; done and then inserting the rm -fr statement (by using uparrow) just as a precaution to slow me down.
> I got into the habit of doing for i in foo* ; echo $i ; done and then inserting the rm -fr statement (by using uparrow) just as a precaution to slow me down.
I do the exact same thing only I use 'ls foo*' first, and when doing bulk updates / deletes with sql servers I again first do a select and then modify the select once I'm sure it will hit the right rows.
11k RPM is not as fast as you might think. That 660,000 RPH * ~8 inch diamiter circle. So outer edge is 3.14*8inch/12/5280 ~= .0004 miles per revolution or 260MPH. But the center is stationary so actual force is a little less than you can throw it.
Edit: Camera is not centered on the iPhone. So if you center the camera it's worse than that. I would personally not stand anywhere near it.
The very fastest fastballs are ~100 MPH. So 260 is not 'a little less than you can throw it', what will happen is that it will get dislodged on one corner, do a partial spin and then come flying at you (if it doesn't break up before that).
I'd really hate to be hit with anything at 260 MPH, especially not with a phone. Those things are hard!
That's why you want something that functions as a Shear pin. Basically, you don't want to have it attached in such a fashion that it could gain those kinds of speeds.
Have you never used a small 11k angle grinder? Those things try to jump out of your hand even worse than the big 6k RPM ones (without soft-start, of course).
Happened to me 20 years ago while sanding wood flooring (the edges). The angle grinder got stopped by a brick and flew out of my hand. I'm not a strong person but seriously doubt anybody could have held to it. Moved totally erratically through the air and scraped my knee just so, but I still can feel the shock. Taught me to respect even small power tools.
I have used a 11k RPM grinder, not that I would have called it small the thing was like 10 pounds. So, I can can see how they might be harder control with newer motors and swapping steal for plastic.
Backing up, being safe with power tools is IMO more a mindset than a set of safety equipment. As such you need some understanding of the forces involved. Not, just to be safe right then but so you don't get lulled into a false concept of safety because the overblown worst case you picture did not happen.
You have absolutely no idea what an unbalance of even a few grams will do at those rotational speeds. The thing will escape your grip even if you're quite strong if you're not holding it very tightly.
I don't think anyone was seriously considering trying to hold it. My comment was more in line with "The iphone will desintegrate due to the forces involved and the shrapnel will cause serious injur". Granted, those disks can shatter and I assume an iPhone may also shatter, but saying it will is a different.
PS: I am going to leave this alone. It's dangerous, but I do hope someone posts a video of this at some point.
I have a hard time envisioning the kind of hold-down that would be required to hold a smooth iphone onto an angle grinder. That's going to be a really neat bit of engineering. And then of course the guts of the iphone will die anyway, I seriously doubt that it was designed with that kind of abuse in mind. But we can place bets on how many seconds it will last.
Jesus Christ man I was kidding.. don't actually do it. Whatever you attach the phone with probably won't hold, and the phone will turn into a projectile traveling at high speed in a random direction. And if the phone does NOT come off, then you've got your hands on an unbalanced angle grinder going full tilt. Bad news bears all around.
I want the next "Will It Blend?" to be these people attaching iPhones to a variety of terribly dangerois machinery at high speed. Grinders, chainsaws, motorbike wheels.
Or maybe some safer things too - place it on a record on a turntable and film the face of the DJ doing some mixing?
I want the next "Will It Blend?" to actually answer the stated question — "can this iPhone be used to make a smoothie?" — rather than "can it be blendED?".
Seems like strapping an iPhone to an angle grinder is getting close to answering the stated question...
No, I mean "can this iPhone be used to make a smoothie", not "can a blender turn this iPhone into an iPhone smoothie".
Take a blender, remove the blades, put iPhones on the spindle where the blades were. Now fire up the blender and throw in some fruits. Will iPhones spinning at $whatever RPMs be able to turn your fruits and wheat grass into a delicious smoothie?
The original is actually "Will It Be Blended [by this blender]". I want to know "Will It Make a Suitable Replacement for a Blender".
Safety issues aside (as has been well-discussed by others already), the accelerometer won't report more than ~8G. Going any higher than that (which is not hard to do even with a moderately slow rotation) won't be very useful for testing out your app.
