PDA

View Full Version : Why are lightbulbs breaking?



Foehammer88
09-05-2005, 11:11 AM
Ok, i understand that the lightbulbs in the command center might pop because of vibration due to the depth charge attack or artillery shells exploding nearby... but they are popping when i dive really deep?? is that strange or what?

kimwh
09-05-2005, 11:48 AM
I suspect this maybe a Hollywood special effect with little fact http://forums.ubi.com/groupee_common/emoticons/icon_smile.gif

However - maybe the "flexing" of the sub under extreme pressure could be distorting the light bulb casing and attacment which would maybe explain the effect.

Alternatively I guess the internal air pressure in the sub would also increase if the sub is being compacted under intense pressure and could maybe crush a buld but I bet that would do a number on the crew's ears also.

Just a guess..

Sgt_Starbuck
09-05-2005, 12:12 PM
Same reason the Seaview always had sparks flying. Bad electricians.

Sarge

the_rydster
09-05-2005, 01:39 PM
This is because the DC's create a massive shock/pressure wave as the detonate.

Anton_Reinhold
09-05-2005, 03:22 PM
The inside of a bulb is a vacuum, 0 PSI. The air pressure at sea level is about 14.7 PSI. For every 33 feet or 10 meters that you dive beneath the surface, the pressure goes up by another 14.7 PSI. When you are down at say, 100 meters for instance, the outside pressure being exerted on the pressure hull is about 161.7 Pounds Per Square Inch. The hull does it's best to resist this, but steel is a little flexible and so as the sub goes deeper, it will actually shrink a tiny bit. When that happens the air pressure inside the hull, where you are, starts to rise. That means that the difference in pressure between the air outside the bulb and the vacuum inside increases. When it gets to be too much for the thin glass to handle, the bulb implodes in on itself.
Naturally, the shock waves caused by depth charges will easily shatter them as well as the glass guages.

Kaleun1961
09-05-2005, 09:55 PM
That has to be about the most scientific answer I have ever seen on this board. Excellent post, Reinhold.

noshens
09-05-2005, 10:01 PM
Originally posted by Kaleun1961:
That has to be about the most scientific answer I have ever seen on this board. Excellent post, Reinhold. Unfortunately he's wrong, light bulbs are filled with noble gases to prevent just that. and since light bulbs get really hot, the pressure inside of the bulb is higher than the pressure outside.

Kaleun1961
09-05-2005, 10:06 PM
Hmmmm. Guess I have to retract that one. Then it must be the torsional forces and shock from depth charges.

Skarphol
09-06-2005, 04:42 AM
Originally posted by noshens:
Unfortunately he's wrong, light bulbs are filled with noble gases to prevent just that.


I think the gas used in lightbulbs now is argon. Not sure if that was the solution in the 1940's. Lightbulbs had vacuum earlier, I don't know when they started using noble gases.

Skarphol

Anton_Reinhold
09-06-2005, 05:20 AM
Yeah I was talking about WWII era bulbs. I "think" they were still simple vacuumed out glass containers with a filament inside back then, instead of gas-filled like we use today. I am going on memory on this one, I haven't actually looked up any of that. Come to think of it, I wonder when neon bulbs came about...

bunkerratt
09-06-2005, 11:36 AM
it could be that they are not of good german quality..the french dock workers are sabotageing your boat http://forums.ubi.com/images/smilies/blink.gif

the_rydster
09-06-2005, 12:49 PM
Using a noble gas to increase the life of the bulb was discovered ages before WW2 but was presumably not taken advantage of by cheapskate U boat lightbulb manufacturers who it seem prefered a partial vaccume!

I suggest BdU 'sources' its lightbulbs from a more 'reputable' manufacturer from now on.

WilhelmSchulz.-
09-06-2005, 02:30 PM
Originally posted by Anton_Reinhold:
I wonder when neon bulbs came about... Neon. 1940's 50's???

The_Silent_O
09-06-2005, 02:38 PM
the answer here is easy of course...your computer is probably plugged into 120V/60hz american outlet...Those bulbs were designed for europes' 240V/50hz...forgot the transformer back at port...didn't you???? http://forums.ubi.com/images/smilies/88.gif

Skarphol
09-06-2005, 02:39 PM
One doesn't use neon in lightbulbs. That is two different technologies.

Lightbulbs make a string glow simply by pressing electrons through it. The resistans in the material heats it up to the point where it starts glowing. In order to avoid the material start burning it has to be in an oxygen-free environment, hence the vacuum, and later noble gases. Oxygen is such a overexagerated gas that mankind has built firestations every 5 miles in every city throughout the world. Noble gases are far more party-poopers and doesn't mingle with anyone.
Thomas Alva Edison experimented with lots of different materials, including human hair for the string. Most materials lasted much longer once the oxygen was removed.

In fluorecent lighting, neon is forced to glow on its own by means of an elecromagnetic field through the tubular shaped glass.

Skarphol

W.Irving
09-06-2005, 03:15 PM
Well, the only explanation for im/exploding bulbs must be a over/under pressure. Besides, it does not really matter if there's vacuum in the bulb or not.

Let's say there isn't any vacuum though, that it's filled with a noble gas (at a pressure of 1013 mbar). The bulb is switched on, and the temperature of the wire rises to 2000 centigrades. This will make the gas expand, the pressure will increase somewhat. When the boat dives, I can imagine the pressure exerted on the bulb from the outside will still be greater. Besides, glass isn't known to be the most flexible material. After a few dives and switching the lights off and on the glass will have fatigued.
Let's not forget the vibrations either! They're deadly not only to unflexible material, but also the fragile wire.

Praetorian27
09-06-2005, 04:23 PM
Ok...so why do the glass faces on the gauges break when diving deep? Is this the same difference in air pressure again? The air inside the gauge face stays the same, while the air outside it but inside the sub increases...so it breaks inward?

W.Irving
09-06-2005, 04:34 PM
I'd say the glass of gauges explode, rather than implode, due to the pressure of whatever the dial is measuring. The gaskets probably can't withstand the sudden pressure change caused by a DC, and so leaks a small amount of water or air within the airtight housing with the needle and the dial.
The housing has to be airtight and filled with dry air to prevent the glass from misting.
If they do/did break at all IRL.

Praetorian27
09-06-2005, 04:40 PM
Originally posted by W.Irving:
I'd say the glass of gauges explode, rather than implode, due to the pressure of whatever the dial is measuring. The gaskets probably can't withstand the sudden pressure change caused by a DC, and so leaks a small amount of water or air within the airtight housing with the needle and the dial.
The housing has to be airtight and filled with dry air to prevent the glass from misting.
If they do/did break at all IRL.

I don't mean from DC damage. With a brand new boat, you can go out into the ocean, dive deep...and the glass will break on the gauges just from the water pressure. I don't know why this is. Obviously I have never seen it in real life, but in movies and in this game it happens. Did it happen in real life? If so...why?

W.Irving
09-06-2005, 04:42 PM
Well, the same reason then. No shock, just prolonged exposure to a dense, highly pressurised medium that creeps through gaskets.

Or Hollywood.. http://forums.ubi.com/groupee_common/emoticons/icon_razz.gif

noshens
09-06-2005, 09:13 PM
My opinion is that when sub goes too deep bolts under high pressure start flying and hitting random things, including the light bulbs.

Kaleun1961
09-06-2005, 10:44 PM
Gee whiz. Haven't we done this one to death?

Chrystine
09-06-2005, 11:05 PM
*

Most enlightening €¦

I€m yet left now with more questions though €" chiefly:

1) I assume there was some reason they didn€t make the glass of bulbs €˜thicker€ or whatever might be €˜required€ to give them some additional longevity under those forces? I mean, it€s a submarine, it will dive, the glass will stress, etc €¦
So I€m wondering why not a €˜heavier-duty€ bulb?
Or is it more that €˜a light bulb is a light bulb is a light bulb€¦€..?

2) If this was a relatively routine experience for a sub diving to greater depths, did they also carry with them a store of replacement bulbs €" for just such eventuality?
I guess here I€m asking €" if so €" would replacement bulbs, and gauge glass, etc €" have been part of a U-boat€s standard €˜supply cargo?€

Best, & thanks if anyone who knows will kindly reply!
~ C.

rls669
09-06-2005, 11:21 PM
The thicker the glass, and the more pressure inside the bulb, the more conductive heat transfer from the filament. So a thick or high-pressure bulb is more likely to overheat and burst.

When installing a high-pressure sodium bulb,a single greasy fingerprint on the glass is enough to create a hot spot and make the bulb break when it heats up.

Maybe modern subs should use LED arrays -- cool, low power, and not very breakable http://forums.ubi.com/groupee_common/emoticons/icon_smile.gif

Chrystine
09-06-2005, 11:34 PM
*

..Ah-ha!
I figured there was probably some good reason €˜why-not.€

Thanks for that explanation, rls_ €¦ http://forums.ubi.com/groupee_common/emoticons/icon_smile.gif

~ C.

rls669
09-07-2005, 05:49 PM
There is also such a thing as a rough service lightbulb, but its toughness comes not from thicker glass but from extra filament supports to prevent the filament from breaking when the light is bumped or sujected to heavy vibration.