On Mon, 27 Jan 2003 04:00:00 -0500, TJ Sackville-West wrote:
> [email protected]
(Steve McDonald) wrote in message
> news:<[email protected]
>> There are no simple answers to your questions. It depends on the quality and intended pressure
>> capability of the pump and on the strength and endurance of the pumper. A general expectation
>> would be that 3 to 4 times the effort would be required to reach 80 psi,
Why? The "effort" involved, as far as it being a problem, is developing the force. Since pressure is
force/area, and the area, the pump plunger, is the same, the force goes up linearly with pressure.
So, twice the pressure, you have to force the handle twice as hard.
Inefficiency of the pump also does not come into play. Whatever inefficiency is there (what, your
pumping goes into heating the pump body??) is also going to at most increase with pressure.
You just don't like cheap pumps.
> as for
>> just 40 psi, considering that the pump and the pumper had the capacity to reach it at all. Most
>> cheap bicycle pumps in the sub-$10. range, in U.S. money, top out at about 60 psi.
Simply not true. I have had cheap pumps that I could use, with difficulty, to get pressures of
100psi. In fact, eventually, any pump could manage this.
> A $20. pump might hit 80 psi and
>> you could find one capable of 105 psi for $30. These are just rough estimates and apply mainly
>> to small, hand-held pumps. You may get more pressure capacity for your money from a large
>> floor pump.
My current "cheap, small" pump, a ToPeak Road Morph, can easily, and I mean easily, pump any tire to
120psi. It takse serveral strokes, but that is not the issue.
> Conclusion from Steve's statement seems to be that if you use the cheapest hand pumps there's
> virtually no (technical) way you COULD pump up your bicycle tire to 60 psi, even if you had the
> physical endurance to do it. So to achieve 'easy' road rolling pressures of 60-80+ psi in a tire
> you need both a more expensive hi-tech hand pump or use a floor pump.
Or you need the existence of a gas station pump. But really, if you accept his hypotheses at face
value I have a bridge to sell.
David L. Johnson
__o | And though I have the gift of prophecy, and understand all _`\(,_ | mysteries, and all
knowledge; and though I have all faith, so (_)/ (_) | that I could remove mountains, and have not
charity, I am nothing. [1 Corinth. 13:2]