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My mom's birthday was recent. We had some people over, brought a few presents, and got a helium happy birthday balloon which I thought was ridiculously expensive for what it was (why? inflation! Heh). It turns out helium itself is quite expensive even in such small quantities. Plus it's a limited and somewhat scarce resource, yada yada.
Hydrogen went out of fashion as a lifting gas after the 1932 Hindenberg explosion, but that was an airship. A 1 foot diameter party balloon would have roughly 1 gram of H2 inside if my math is right. If that gets ignited, is it more of a danger than, say, dropping a lit match by accident? I can imagine a rather loud pop, but would it be enough to damage hearing, blow out windows, or anything like that? There is a standard chemistry class experiment where you have H2 bubbling up from a liquid and put a lit wooden splinter into it and there's a pop, but I guess that would be more like milligram amounts. Thanks. 2601:644:8501:AAF0:4043:7961:893C:EC1 ( talk) 02:03, 12 March 2024 (UTC)
I have been reading the Lac-MĂ©gantic rail disaster article, and what happened with the air brakes doesn't seem to be consistent with what is stated in the railway air brake article.
The Lac-MĂ©gantic rail disaster article says that the air brakes failed because the locomotive was shut down:
As described above, the air brakes are thus fail-deadly: if power is not available to supply air, the brakes fail. This seems to me to be an atrocious, terrible design which makes no sense, so I started reading the railway air brake article. That article instead says:
This seems to contradict the other article by claiming that Westinghouse air brakes are "nearly universally adopted" and fail-safe. So, what is going on here? Did the train in the Lac-MĂ©gantic rail disaster use a fail-deadly straight air system instead of the fail-safe Westinghouse system? If so, that puts into question the claim that the Westinghouse system is nearly universally adopted and raises the question of why that train did not use the Westinghouse system. If the train did use the Westinghouse system, and that system really is fail-safe, then the loss of power and air should have applied the brakes and held the train in place, unless the Westinghouse system is not really fail-safe.
â SeekingAnswers ( reply) 04:29, 12 March 2024 (UTC)
There were three braking systems on the train: the automatic Westinghouse-type train brake, the independent direct air brakes on the locomotives and handbrakes on all vehicles. The Westinghouse brake relies on stored compressed air to actuate the brakes and the pressure in the continuous pipe (the "train line") to keep them off. The stored air will eventually leak, but in normal operation this is topped up from the train line via a valve. A slow leak in the train pipe will cause an ineffective operation of the brakes until the stored pressure has reduced to that of the train pipe; as the report has it: "Due to the slow decrease in brake pipe pressure, no automatic brake application occurred". The direct brakes use compressed air from the locomotive to apply and hold on the brakes; this is independent of the Westinghouse system. Finally the hand brakes are applied by (typically) turning a wheel which screws the brakes on.
The engineer brought the train to a stand using the automatic brakes. He then applied the direct brakes. He applied the hand brakes on the locomotive "consist". The four trailing locomotives were shut down. He then performed a hand brake effectiveness test which should involve releasing all air brakes and gently nudging the loco to ensure that the hand brakes are holding. However he forgot to release the direct brakes, and so the test merely confirmed that direct brakes and hand brakes held the train. The train was then left with the lead loco running, the direct brakes applied and some handbrakes, and the train pipe energised so that the Westinghouse automatic brakes were held off. Following the fire and subsequent shutdown of the lead locomotive the air started to leak out from the direct brakes until eventually the train started to roll downhill. The train did not part until the derailment, so there was no full application of the Westinghouse system, the slow release mentioned above ensured that the Westinghouse brakes remained off.
The full report can be read at Railway Investigation Report R13D0054, but be aware that it is a technical report running to 191 pages! Martin of Sheffield ( talk) 11:00, 12 March 2024 (UTC)
Will it ever become possible to penetrate the time-space continuum? I frequently fantasize about having some national government send a drone back in time to 1916 in order to kill Lenin in the hope that doing this would have prevented the 1917 Bolshevik Revolution and thus secured much better 20th and 21st centuries for Russia in a parallel universe (our real universe would remain unchanged due to the grandfather paradox).
Lenin was quite literally the worst thing to happen to Russia, with his creation of a totalitarian one-party making Stalin's subsequent rise to power much easier (does one think that Stalin would have won any free and fair multiparty elections in Russia in the 1920s?) and with the Soviet Union making Tsarist Russia seem like an extraordinarily mild pussycat in comparison. Tsarist Russia at least nominally allowed opposition parties, even though it tried to weaken them and spy on them, and certainly allowed for free emigration, unlike the Bolshevik regime. And it executed a couple of orders of magnitude less people than the Bolsheviks did. The Bolshevik takeover of Russia wasn't even a good thing for most Bolsheviks themselves, who subsequently got purged and killed by Stalin. How ironic! Creating a monster-state and then personally being devoured by that very same monster-state! 172.56.186.104 ( talk) 05:06, 12 March 2024 (UTC)
Science desk | ||
---|---|---|
< March 11 | << Feb | March | Apr >> | March 13 > |
Welcome to the Wikipedia Science Reference Desk Archives |
---|
The page you are currently viewing is a transcluded archive page. While you can leave answers for any questions shown below, please ask new questions on one of the current reference desk pages. |
My mom's birthday was recent. We had some people over, brought a few presents, and got a helium happy birthday balloon which I thought was ridiculously expensive for what it was (why? inflation! Heh). It turns out helium itself is quite expensive even in such small quantities. Plus it's a limited and somewhat scarce resource, yada yada.
Hydrogen went out of fashion as a lifting gas after the 1932 Hindenberg explosion, but that was an airship. A 1 foot diameter party balloon would have roughly 1 gram of H2 inside if my math is right. If that gets ignited, is it more of a danger than, say, dropping a lit match by accident? I can imagine a rather loud pop, but would it be enough to damage hearing, blow out windows, or anything like that? There is a standard chemistry class experiment where you have H2 bubbling up from a liquid and put a lit wooden splinter into it and there's a pop, but I guess that would be more like milligram amounts. Thanks. 2601:644:8501:AAF0:4043:7961:893C:EC1 ( talk) 02:03, 12 March 2024 (UTC)
I have been reading the Lac-MĂ©gantic rail disaster article, and what happened with the air brakes doesn't seem to be consistent with what is stated in the railway air brake article.
The Lac-MĂ©gantic rail disaster article says that the air brakes failed because the locomotive was shut down:
As described above, the air brakes are thus fail-deadly: if power is not available to supply air, the brakes fail. This seems to me to be an atrocious, terrible design which makes no sense, so I started reading the railway air brake article. That article instead says:
This seems to contradict the other article by claiming that Westinghouse air brakes are "nearly universally adopted" and fail-safe. So, what is going on here? Did the train in the Lac-MĂ©gantic rail disaster use a fail-deadly straight air system instead of the fail-safe Westinghouse system? If so, that puts into question the claim that the Westinghouse system is nearly universally adopted and raises the question of why that train did not use the Westinghouse system. If the train did use the Westinghouse system, and that system really is fail-safe, then the loss of power and air should have applied the brakes and held the train in place, unless the Westinghouse system is not really fail-safe.
â SeekingAnswers ( reply) 04:29, 12 March 2024 (UTC)
There were three braking systems on the train: the automatic Westinghouse-type train brake, the independent direct air brakes on the locomotives and handbrakes on all vehicles. The Westinghouse brake relies on stored compressed air to actuate the brakes and the pressure in the continuous pipe (the "train line") to keep them off. The stored air will eventually leak, but in normal operation this is topped up from the train line via a valve. A slow leak in the train pipe will cause an ineffective operation of the brakes until the stored pressure has reduced to that of the train pipe; as the report has it: "Due to the slow decrease in brake pipe pressure, no automatic brake application occurred". The direct brakes use compressed air from the locomotive to apply and hold on the brakes; this is independent of the Westinghouse system. Finally the hand brakes are applied by (typically) turning a wheel which screws the brakes on.
The engineer brought the train to a stand using the automatic brakes. He then applied the direct brakes. He applied the hand brakes on the locomotive "consist". The four trailing locomotives were shut down. He then performed a hand brake effectiveness test which should involve releasing all air brakes and gently nudging the loco to ensure that the hand brakes are holding. However he forgot to release the direct brakes, and so the test merely confirmed that direct brakes and hand brakes held the train. The train was then left with the lead loco running, the direct brakes applied and some handbrakes, and the train pipe energised so that the Westinghouse automatic brakes were held off. Following the fire and subsequent shutdown of the lead locomotive the air started to leak out from the direct brakes until eventually the train started to roll downhill. The train did not part until the derailment, so there was no full application of the Westinghouse system, the slow release mentioned above ensured that the Westinghouse brakes remained off.
The full report can be read at Railway Investigation Report R13D0054, but be aware that it is a technical report running to 191 pages! Martin of Sheffield ( talk) 11:00, 12 March 2024 (UTC)
Will it ever become possible to penetrate the time-space continuum? I frequently fantasize about having some national government send a drone back in time to 1916 in order to kill Lenin in the hope that doing this would have prevented the 1917 Bolshevik Revolution and thus secured much better 20th and 21st centuries for Russia in a parallel universe (our real universe would remain unchanged due to the grandfather paradox).
Lenin was quite literally the worst thing to happen to Russia, with his creation of a totalitarian one-party making Stalin's subsequent rise to power much easier (does one think that Stalin would have won any free and fair multiparty elections in Russia in the 1920s?) and with the Soviet Union making Tsarist Russia seem like an extraordinarily mild pussycat in comparison. Tsarist Russia at least nominally allowed opposition parties, even though it tried to weaken them and spy on them, and certainly allowed for free emigration, unlike the Bolshevik regime. And it executed a couple of orders of magnitude less people than the Bolsheviks did. The Bolshevik takeover of Russia wasn't even a good thing for most Bolsheviks themselves, who subsequently got purged and killed by Stalin. How ironic! Creating a monster-state and then personally being devoured by that very same monster-state! 172.56.186.104 ( talk) 05:06, 12 March 2024 (UTC)