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#22
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Vaseline
On Oct 3, 2:31*pm, Zog The Undeniable wrote:
KC wrote: Zog The Undeniable wrote: Don't use it on pump washers. *This can lead to an explosion, which usually wrecks the pump or its hose. Wow. *Seriously? *This sounds like urban legend/myth to me. *Someone with just (not) enough science knowledge thinks, "hmmm... petroleum based jelly... high pressures in a bike pump... friction... PV = RT .... all "petroleum" products are combustable... ergo, petroleum jelly as a pump lube will EXPLODE!!! Danger Will Robinson, DANGER!!!" I know the guy who wrote this in Real Life (TM), and he's a reliable source (he's also a career scientist): http://yacf.co.uk/forum/index.php?to...8249#msg128249 As a chemist, I think that it's fairly unlikely that the pressures involved are enough to cause combustion. I do not think that the link supports the contention. E.P. |
#23
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Vaseline
Ed Pirrero wrote:
On Oct 3, 2:31�pm, Zog The Undeniable wrote: KC wrote: Zog The Undeniable wrote: Don't use it on pump washers. �This can lead to an explosion, which usually wrecks the pump or its hose. Wow. �Seriously? �This sounds like urban legend/myth to me. �Someone with just (not) enough science knowledge thinks, "hmmm... petroleum based jelly... high pressures in a bike pump... friction... PV = RT ... all "petroleum" products are combustable... ergo, petroleum jelly as a pump lube will EXPLODE!!! Danger Will Robinson, DANGER!!!" I know the guy who wrote this in Real Life (TM), and he's a reliable source (he's also a career scientist): http://yacf.co.uk/forum/index.php?to...8249#msg128249 As a chemist, I think that it's fairly unlikely that the pressures involved are enough to cause combustion. "T" is in that equation too dude. I do not think that the link supports the contention. E.P. |
#24
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Vaseline
wrote:
Karl Clutz wrote: Don't use it on pump washers. This can lead to an explosion, which usually wrecks the pump or its hose. Wow. Seriously? This sounds like urban legend/myth to me. Someone with just (not) enough science knowledge thinks, "hmmm... petroleum based jelly... high pressures in a bike pump... friction... PV = RT ... all "petroleum" products are combustable... ergo, petroleum jelly as a pump lube will EXPLODE!!! Danger Will Robinson, DANGER!!!" I know the guy who wrote this in Real Life (TM), and he's a reliable source (he's also a career scientist): http://yacf.co.uk/forum/index.php?to...8249#msg128249 I'm not saying your friend didn't witness a pump explode. But I do not believe his explanation. Even if he used gasoline for a lubricant, I doubt that combustion of the vapors could be caused simply by pumping. Keep in mind that he claims the pump cylinder is what exploded. The pump cylinder gets new fresh, cool, and free of vapor air every stroke. So vapor concentration in the pump cylinder is very low (mixing of air in the tube & hose with pump cylinder air against a pressure gradient would be minimal, I think). Combustion is, IMO, highly unlikely. I call BS. But I'm interested in the idea... if I'm wrong and it is possible, someone explain it. Don't dodge and weave like that. It is BS solid and complete, and don't pump with Nitroglycerin in the pump. I just assumed that was humor. An engine, whose piston is sealed more thoroughly in the cylinder, with a high compression ratio of 10:1 (more than a hand pump can muster) will not 'explode' even with properly vaporized gasoline, not vasoline. That was a hyperbolic attempt at humor. -- Andrew Muzi www.yellowjersey.org/ Open every day since 1 April, 1971 ** Posted from http://www.teranews.com ** |
#25
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Vaseline
wrote:
On Fri, 03 Oct 2008 22:31:25 +0100, Zog The Undeniable wrote: KC wrote: Zog The Undeniable wrote: Don't use it on pump washers. This can lead to an explosion, which usually wrecks the pump or its hose. Wow. Seriously? This sounds like urban legend/myth to me. Someone with just (not) enough science knowledge thinks, "hmmm... petroleum based jelly... high pressures in a bike pump... friction... PV = RT ... all "petroleum" products are combustable... ergo, petroleum jelly as a pump lube will EXPLODE!!! Danger Will Robinson, DANGER!!!" I know the guy who wrote this in Real Life (TM), and he's a reliable source (he's also a career scientist): http://yacf.co.uk/forum/index.php?to...8249#msg128249 Dear Zog, "On LEJOG some years ago one of our party had done just this, and blowing up his tyre outside Ironbridge the pump exploded, leaving about 6" of the barrel behind." I'm puzzled, but willing to learn more. I'd expect that an explosion would break the fellow's arm. The pump piston would be blown back upward much more easily than the sides of the pump housing would be blown apart. I'd expect any explosion to burst the pump at the bottom, not six inches up, where compression has fallen off dramatically. I'd expect that an awfully high pressure would be needed to cause combustion, higher than a roadside bicycle pump produces. Maybe vaseline vapor is more easily ignited? Even if the vapor ignited, it's hard to imagine enough vapor to match the power of an ordinary firecracker, which is not likely to burst a pump six inches up or leave the fellow's arm undamaged. A different explanation is that there was no explosion, just a defective or damaged pump housing that burst. When a defective housing bursts, the piston isn't blow back, so no one's arm is broken. The housing can fail six inches up the barrel, where the defect or damage is. And there's no need to produce enough temperature by sheer compression to ignite whatever faint vapor is available from a little vaseline. Maybe you could look into whether they considered such things? Cheers, Carl Fogel If such an event actually occurred, it's my guess that the pump must have been a plastic-barreled high pressure pump like a Zefal I have. To achieve high gas temperatures from compression, the pump surfaces should have low thermal conductivity -- plastic does, that's why it feels "warmer" in your hand. My Zefal has bore diameter of ~0.75", so (theoretically) it can produce 225 psi with 100lb of force. My calculations show that ~165 psi would achieve the self-ignition temperature of Vaseline (vapor). As for the failure "six inches up the barrel", the end of the Zefal is reinforced with a grip/sleeve for about the first 5.5". I'd guess that there isn't a whole lot of excess burst strength in the un-sleeved upper section of the barrel, so I'd expect it to fail at about 6" from the end. I'd test it with a firecracker, but hey those are illegal here and besides, I spent $12 for this pump. The pressure seal of the Zefal is of the plastic cup type, so there's plastic-to-plastic contact that probably achieves high frictional loads as the cup skirt spreads under high gas pressure. Plastic pump? Hot day? Muscular guy pumping very fast & hard? Sticking presta valve? I wouldn't say this myth is busted yet. Of historical interest: http://blog.modernmechanix.com/2008/...or-the-smoker/ |
#26
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Vaseline
On Sat, 04 Oct 2008 10:15:46 +0100, Zog The Undeniable
wrote: My track pump will manage 160psi, as will a decent hand pump like a Truflo hpX. The last time I compression-tested a car, the compression was about 140psi at cranking speed, so it's in the same range. Admittedly that was a petrol car, but old carburetted cars used to suffer from run-on (dieselling) after switching off (hence "gulp valves", fuel cut-off solenoids and other measures). What was called "dieselling" was not true compression ignition, but rather ignition brought about by red-hot carbon deposits in the cylinder heads. |
#27
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Vaseline
Peter Cole wrote:
Plastic pump? Hot day? Muscular guy pumping very fast & hard? Sticking presta valve? I wouldn't say this myth is busted yet. Of historical interest: http://blog.modernmechanix.com/2008/...or-the-smoker/ If you search Youtube for "fire piston" you'll see many examples of more modern versions. |
#28
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Vaseline
Joel Mayes wrote:
Don't use it on pump washers. This can lead to an explosion, which usually wrecks the pump or its hose. Wow. Seriously? This sounds like urban legend/myth to me. Someone with just (not) enough science knowledge thinks, "hmmm... petroleum based jelly... high pressures in a bike pump... friction... PV = RT ... all "petroleum" products are combustable... ergo, petroleum jelly as a pump lube will EXPLODE!!! Danger Will Robinson, DANGER!!!" But, it's the first I've heard of it, so I dunno, could be true. But seems somewhat implausible to me. -KC Seems perfectly sound to me - the engine in my car works on the same compression-ignition principle, and that will run on a variety of fuels. In fact, the bicycle pump is remarkably similar to the apparatus used to demonstrate the process for educational purposes - the only major difference is that the demonstration equipment is transparent. The flash point of Vaseline is around 204 Celsius, I've never seen a pump get hot enough to be uncomfortable to the touch, let alone boil camphor. Flash point has nothing to do with it. It's the auto-ignition temp that matters, which for petrolatum is about 290C, or 554F. Pretty hot. BTW, everyone is saying that the compression ratio of a bike pump is too low. If a pump can handle P150psi, then isn't the compression ratio greater than 10:1? The pump draws in air at 1atm, and pumps it up to 10atm (150psi). That sounds like 10:1 to me. -KC |
#29
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Vaseline
Peter Cole wrote:
Plastic pump? Hot day? Muscular guy pumping very fast & hard? Sticking Presta valve? I wouldn't say this myth is busted yet. Of historical interest: http://blog.modernmechanix.com/2008/...or-the-smoker/ If you search YouTube for "fire piston" you'll see many examples of more modern versions. BS just the same. I have had several pressure gauges broken on my double acting floor pump by riders trying to inflate a tire trough a Presta valve that was still screwed shut. That makes pressure exceed the 200 psi range on the gauge. The HP leather piston is lubricated with 30W motor oil and caused no combustion... only a gauge that would no longer register zero nor the correct pressure. Jobst Brandt |
#30
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Vaseline
wrote in message ... BS just the same. I have had several pressure gauges broken on my double acting floor pump by riders trying to inflate a tire trough a Presta valve that was still screwed shut. That makes pressure exceed the 200 psi range on the gauge. The HP leather piston is lubricated with 30W motor oil and caused no combustion... only a gauge that would no longer register zero nor the correct pressure. Jobst Brandt I find it hard to believe that you would allow riders that don't know enough to unscrew the Presta valve to use your pump. Especially more than once. |
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