Posted by Rick Denney on May 10, 2002 at 14:49:38:
In Reply to: Re: Re: Re: Re: Re: Re: Re: Re: Short action posted by John Swensen on May 10, 2002 at 14:36:00:
Yes, John, you are right. There is a turning moment between the finger and the spring, and between the finger and the intertia of the piston during acceleration. I judge that the force of my finger is perhaps two ounces, based on lifting items on my desk that seem to feel the same and then weighing them. If the offset is half an inch, then the moment is an ounce-inch. If the piston is five inches long, the countering moment over the length of the piston will be the same ounce-inch, and the force at the top and bottom edges of the valve to resist the moment will be .2 ounces.
On the other hand, if I put my finger on the edge of the button so that the force vector from my finger is at a 45-degree angle to the axis of the piston, and if I require the same two ounces to overcome the spring and intertia, then I'll also be putting a two-ounce lateral force at the button, which is a moment of 10 ounce-inches.
Bottom line for non-geeks: The force from an offset button might create a tenth of the lateral force of finger resting on the edge of a button that is out of reach.
That's why I am so happy with the adjutible offset finger button that John made for me to use on the York Master's fourth valve, which even with my gorilla hands is out of reach.
Rick "being precise but keeping things in perspective" Denney