My E01 fell 12 floors

I was on my balcony holding my daughter, who was in turn holding the E01. It probably doesn't need too much explanation, but she managed to unscrew the head and of course, drop it in the wrong direction. I was helpless as the head module fell hopelessly out of reach, in slow motion, seemingly taunting me before beginning its decent to the terrace 12 floors down. Anyway, a call to the security counter, a willing 2nd floor neighbor, and 2 days later, my headless E01 was re-united with its better half. It is now whole again and remarkably undamaged. There are small indentation marks, but I had to break out the macro lens to capture them. And yes, it is now back in the hands of my daughter. Enjoy!

Bruce

I suspect the fact that the head is so light meant that it has a low terminal velocity. Still, nice to know the head module can take a terminal velocity fall. Who wants to test the whole light?

There was a whole light test with the E01 and Arc.. can't find it but I know it's out there LOL

Bruce,

I'm just glad that no one got hurt.

I don't know what the terminal velocity that the flashlight head attained
during its fall but it probably could do some serious damage if it hit
someone in the head.

Also, I'm glad that you just let it fall instead of trying to rescue it and
end up falling over the railing with your daughter in your arms.

Inspgad said:

Bruce,

I'm just glad that no one got hurt.

I don't know what the terminal velocity that the flashlight head attained
during its fall but it probably could do some serious damage if it hit
someone in the head.

Click to expand...

Yes, that's all I remember thinking in that brief instant. Fortunately it fell onto a private terrace, and not onto the busy street.

Inspgad said:

Also, I'm glad that you just let it fall instead of trying to rescue it and
end up falling over the railing with your daughter in your arms.

Click to expand...

Yes, there are definitely some things more important than flashlights.

I suspect Jarl is correct but I reckon the entire light could have survived that drop too.

You were very lucky to get it back!

Inspgad said:

I don't know what the terminal velocity that the flashlight head attained
during its fall but it probably could do some serious damage if it hit
someone in the head.

Click to expand...

Doubtful. Watch Mythbusters where they test the terminal velocity of a penny.

Fenix FTW

NEW CPF RECORD!!!!!!!!!!!!!!:thumbsup:


13 floors next?

I suspect the low mass of the head had much to do with its survival. Had it been the whole light there would have been much more force generated, maybe enough to do some crushing. It probably came pretty close to terminal velocity.

Geoff

I bet the whole light could survive a fall like this. The light with Eneloop weighs 26g. Moving at 60m/s, that's 1.6N. That force gets exerted over a very small area, say 1mm^2. That's a pressure of 1.6MPa, and aluminum has a modulus of elasticity of 68GPa. There probably will be some cosmetic damage, but nothing catastrophic.

Those calculations should be right.

Extrapolating those calculations to an L2D give interesting results- technically it should structurally survive a terminal velocity fall. Anyone want to try??!

Link to the 5 story drop test.

https://www.candlepowerforums.com/threads/203409

Someone should contact Fenix, ask them for a light to throw off the highest thing you can (12 stories or higher), videotape it, and then send it to Fenix so they can use it.

If it doesn't break you got a light for free and Fenix will be selling a lot more E01s, and if it does, you got to throw something off a building.

Win, win. :laughing:

Jarl:

I don't believe it's weight had much to do with it's velocity over time. I believe the primary factor their is air resistance. Galileo I think, right? It's weight does have everything to do with the danger it represented on impact.

LukeA said:

I bet the whole light could survive a fall like this. The light with Eneloop weighs 26g. Moving at 60m/s, that's 1.6N. That force gets exerted over a very small area, say 1mm^2. That's a pressure of 1.6MPa, and aluminum has a modulus of elasticity of 68GPa. There probably will be some cosmetic damage, but nothing catastrophic.

Those calculations should be right.

Click to expand...

I don't doubt the flashlights would survive.

Anyway I'd hate to nickpick but a newton is kgm/s^2. It's a differential with respect to a time. Also, the 68gpa is young's modulus. But that has nothing to do with whether an object will fail or not, it's just the stress/strain curve's slope. What determines if it'll dent is your yield strength, at which point it will plastically deform and yield (hardening in the process, increasing your strength) until it hits your ultimate strength at which point it will start breaking apart. Now, while 68gpa is the young's modulus, aluminium will yield somewhere around 0.4gpa, work hardening till around .45gpa, a fraction of the modulus.

Anyway a 26g object falling 12 stories (im gonna average 50 meters) will achieve around 30 m/s, hitting with 13J of energy. Assuming it stops within 0.1mm, you're looking at an impact force of 127400 N. Assuming it hits within a .25mm x 1mm (if not smaller if it hits a high point in the ground) area, 127400N over 0.00025m^2 is actually around .51mpa. So it will crush, but over a very small surface area, meaning you'll get a couple of nicks.

dfischer said:

Jarl:

I don't believe it's weight had much to do with it's velocity over time. I believe the primary factor their is air resistance. Galileo I think, right? It's weight does have everything to do with the danger it represented on impact.

Click to expand...

My fluid dynamics text book is buried under a couple of boxes right now but all you would need is the cross sectional and size ratio of the fenix light (assuming it's falling head or *** first) to get the drag coefficient & surface area plus the density of air (depending on temperature and altitude) in order to get your terminal velocity.

LukeA said:

I bet the whole light could survive a fall like this. The light with Eneloop weighs 26g. Moving at 60m/s, that's 1.6N. That force gets exerted over a very small area, say 1mm^2. That's a pressure of 1.6MPa, and aluminum has a modulus of elasticity of 68GPa. There probably will be some cosmetic damage, but nothing catastrophic.

Those calculations should be right.

Click to expand...

:wow:

nerd




...er... um... I mean... what he said !

shomie911 said:

Someone should contact Fenix, ask them for a light to throw off the highest thing you can (12 stories or higher), videotape it, and then send it to Fenix so they can use it.

If it doesn't break you got a light for free and Fenix will be selling a lot more E01s, and if it does, you got to throw something off a building.

Win, win. :laughing:

Click to expand...

Actually, I'm currently on assignment in Taiwan. And, Taipei 101 is currently the tallest building in the world...:thinking:

If you take a close look at the E01 head, the dent goes from the threads to the head. I'm thinking that the o-ring could have taken some of the impact. Also, the threads could have also provided some cushioning. I think if it had fallen directly on the PCB, it would be game over.

slvoid said:

Anyway a 26g object falling 12 stories (im gonna average 50 meters) will achieve around 30 m/s, hitting with 13J of energy. Assuming it stops within 0.1mm, you're looking at an impact force of 127400 N. Assuming it hits within a .25mm x 1mm (if not smaller if it hits a high point in the ground) area, 127400N over 0.00025m^2 is actually around .51mpa. So it will crush, but over a very small surface area, meaning you'll get a couple of nicks.

Click to expand...

Nice! What would it do if it landed on my head with that amount of force?