Forum Discussion
wmoses
Jul 18, 2014Explorer
dugggg wrote:
Why such concern over a tiny fraction of an ounce? Because at 65mph the centripetal force is nearly 3 pounds! That's quite a load on a rubber valve stem.
First of all I liked your technical response to this - nice to see some engineering in these here forums from time to time. :)
I have not done any calculations myself but I doubt that the centrifugal force on the sensor (centripetal at the rim) will be 3# at 65 mph on a 0.42 oz sensor. For one thing the centriXXXal forces are in an axis perpendicular to the axis of rotation while the valve stem is at some acute angle to that vertical axis. So the centrifugal force acting on the sensor needs to be resolved into stem-axial and stem-transverse components. It is the latter one that causes the relative outward deflection at the tip of the valve stem that could cause the sensor to contact the rim.
Naturally the deflection is a function of several things, length of the valve stem being one. That would explain why W.E.BGood has the problem shown in his pictures while other don't. :)
In other words rubber may be good for some and not so good for others.
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