Vaseline

Kenneth wrote:
On Sat, 11 Oct 2008 09:31:37 +0200, Tosspot
wrote:

Kenneth wrote:

snip

Might this be of interest:

http://www.grannysstore.com/Wilderne...re_pistons.htm

All the best,
Fascinating, I might have to get one of those just to try it. Wikipedia
as always has a bit more on them

http://en.wikipedia.org/wiki/Fire_piston

25:1 apparently.

Howdy,

When I posted the link, I had not seen that others had
mentioned fire pistons.

You might want to check youtube. Seeing these things work is
quite interesting.

All the best,

"interesting" indeed. wood is porous. it is astonishing to see a
porous material sustain pressures sufficient to achieve this.

Peter Cole wrote:
Kenneth wrote:
On Sat, 11 Oct 2008 09:31:37 +0200, Tosspot
wrote:

Kenneth wrote:

snip

Might this be of interest:

http://www.grannysstore.com/Wilderne...re_pistons.htm

All the best,
Fascinating, I might have to get one of those just to try it.
Wikipedia as always has a bit more on them

http://en.wikipedia.org/wiki/Fire_piston

25:1 apparently.

Howdy,

When I posted the link, I had not seen that others had
mentioned fire pistons.

You might want to check youtube. Seeing these things work is
quite interesting.

All the best,

I mentioned them 2 or 3 times on this thread already, the last time on
10/8.

I also used some online calculators to estimate the "adiabatic"
temperatures of the gas under likely bike pump compressions.

The questions a whether the gas in this scenario can actually reach
adiabatic (no thermal loss) levels and autoignite, whether sufficient
vapor could be present (and in the right mix) to shatter a pump body,
and lastly if such an explosion would shatter a pump at the position and
manner described.

While I first was as skeptical as anyone here, looking at a plastic
Zefal (HPX) pump I have, I found I couldn't completely rule out the
possibility. I still think it's a really long shot, but I can't say it's
impossible. I do think that for it to have any chance the pump would
have to be a high pressure plastic bodied pump like I have. Perhaps the
reason that other reports of this haven't been made is that this kind of
pump is rare, or perhaps the exact conditions are exceedingly rare, or
perhaps the report was bogus -- I really don't know.

the probability of a polymeric pump barrel rupturing through material
flaw failure /far/ exceeds that of combustion pressure exceeding its
unflawed strength. and when you account for the rupture occurring half
way up the barrel where compression is minimal, probability of failure
being due to ignition drops to zero.

Peter Cole wrote:

While I first was as skeptical as anyone here, looking at a plastic
Zefal (HPX) pump I have, I found I couldn't completely rule out the
possibility. I still think it's a really long shot, but I can't say
it's impossible. I do think that for it to have any chance the pump
would have to be a high pressure plastic bodied pump like I have. Perhaps
the reason that other reports of this haven't been made is that this
kind of pump is rare, or perhaps the exact conditions are exceedingly
rare, or perhaps the report was bogus -- I really don't know.

The HPX is aluminium.

~PB

Pete Biggs wrote:
Peter Cole wrote:

While I first was as skeptical as anyone here, looking at a plastic
Zefal (HPX) pump I have, I found I couldn't completely rule out the
possibility. I still think it's a really long shot, but I can't say
it's impossible. I do think that for it to have any chance the pump
would have to be a high pressure plastic bodied pump like I have. Perhaps
the reason that other reports of this haven't been made is that this
kind of pump is rare, or perhaps the exact conditions are exceedingly
rare, or perhaps the report was bogus -- I really don't know.

The HPX is aluminium.

~PB


I have an aluminum one and a plastic one.