[AZ-Observing] ATM meeting reminder - AND a Dob question
- From: Paul Lind <pulind@xxxxx>
- To: az-observing@xxxxxxxxxxxxx, sac-forum@xxxxxxxxxxxxx
- Date: Thu, 26 Feb 2015 19:34:00 -0500 (EST)
The monthly ATM/Astro-imaging meeting will be at my place on Tuesday, March
3rd, at about 6:30. Bring a project.
Here's a Dob question: The literature states that Teflon Dob bearings should be
sized for 15 psi. However, Coulomb's model states the frictional resistance is
only related to the total normal force N and the coefficient of friction u
(whether static or sliding), and is not related to area of contact. The
Frictional resistive force is simply u*N. So, what's with 15 psi? I tried
quadrupling the area of my altitude bearing pads and can't see much difference.
Maybe the ripples in Ebony-Star Formica have something to do with the choice of
15 psi.
http://mech.subwiki.org/wiki/Coulomb_model_of_friction
Paul Lind
210 W. Tierra Buena Land
Phoenix, AZ 85023
602-350-6190
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