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Old April 7th 21, 04:23 PM posted to rec.bicycles.tech
Jeff Liebermann
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Posts: 4,018
Default tubeless or tubes

On Tue, 6 Apr 2021 12:46:44 -0400, Frank Krygowski
wrote:

I'd prefer a fire piston. https://en.wikipedia.org/wiki/Fire_piston


Good idea. I've built a few of those over the years for various
nefarious purposes. The problem for me was that the oxygen inside the
cylinder is rapidly depleted once the tinder starts burning. The hard
part is removing the piston and tinder from the cylinder before the
fire goes out. It can be done, but you have to be quick.

ISTM it would be a trivial modification of a frame pump or mini pump.


With a compression ratio of 25:1, the internal pressure would need to
be atmospheric pressure times the compression ratio minus one
atmosphere for gauge pressure or:
(24 * 14.7 psi) = 353 psi
The volume of a floor pump is sufficient to obtain a 25:1 volumetric
reduction if the piston goes all the way to the bottom of the tube.
However, it looks like length of the piston has been intentionally
shortened to prevent achieving such a high compression ratio. The
gauge on my floor pump also says that's not going happen (at least
until after the gauge explodes). I tried removing the hose and
pumping furiously to see if anything leaked. It seems that the rubber
piston seal and one-way valve leak rather badly. Without major
redesign and possibly some mechanical leverage, it's not going to
happen.

However, there are multistage bicycle pumps, designed to hand inflate
high pressure bicycle tires, which might work:
"High pressure, multiple-stage air pump with valve body inlet port
arrangement"
https://patents.google.com/patent/US8047818B2/en

If unsuitable for making a fire starter, it might be useful for
building a bicycle defense air gun giving new meaning to "taking the
lane".

Hmm. But then there would be no need for the butane. Yes, marketing can
be complicated!


Actually it's quite simple. The purpose of marketing is to convince
the potential buying public that they have a problem that is worth
solving. The purpose of sales is to then convince the buying public
that they have a solution for the newly created problem. Of course,
this creates yet another opportunity for marketing to identify a
problem with the solution and the cycle repeats itself ad infinitum.

Soon, everyone will be riding bicycles armed with a bicycle pump that
can double as a flame thrower, air gun, or in an emergency, tire
inflator.

--
Jeff Liebermann
PO Box 272
http://www.LearnByDestroying.com
Ben Lomond CA 95005-0272
Skype: JeffLiebermann AE6KS 831-336-2558
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