Posted by Joe Baker on August 17, 2001 at 18:04:48:
In Reply to: Re: Re: Re: Re: valve extensions or other remedies posted by Klaus on August 17, 2001 at 17:18:52:
Klaus,
Intuition would tend to indicate that your statement is correct; however, I think I can persuade you that this is one case where forces do not work in the way you think they will.
Given the described mechanism (most importantly, 0 deflection of the extension), if you place your finger on the extension and push down-and-away, common sense tells you that you will introduce additional friction on the far side of the valve/casing. In this case, your common sense is correct. Now, consider perfoming the opposite, namely pushing down and pulling toward you at the same time. It should be intuitively obvious that you will now have additional friction on the near side of the valve/casing. So, obviously, there must be SOME angle where those two balance out and the friction is evenly distributed.
If you do a little vector arithmetic, it can be proven that this point is, in fact, reached by pushing down parallel to the piston's motion. This is true regardless of the length of offset or the angle of the extension as it departs the valve stem (although one that is perpendicular makes it much easier to approximate straight travel without having to add the friction vector for keeping you finger in contact with the extension).
The real trick will be the same as without an extension: making a motion that describes an arc exert a linear force. Tough problem, that one!
Joe Baker, who knows that sometimes math is stanger than fiction.