At 08:51 AM 12/12/2006, Bill Turner wrote:
>I've had towers for years but never used a thrust bearing. Now I want
>to. In comparing the Rohn TB-3 and the Yaesu GS-065 I see the Rohn
>sells for about three times the price. Is it three times better?
>This may sound odd, but the reason I want a thrust bearing is to
>provide a lightning path directly from mast to tower rather than
>having the strike go through the rotator to the tower. In other words,
>I want to use the thrust bearing to ground the mast as opposed to
>having the mast free-floating. Does that make sense?
If you use a ball or roller bearing, the lightning might destroy the
bearing, because the contact area is very small. (actually it might
just flashover the entire bearing)
If your only concern is lightning, why not mount a wide low
inductance electrode close to the mast. A clearance of 0.1" will be
jumped at a few kV, and will have very low impedance once the arc is
lit. Any pitting or erosion will occur on the electrode and the
mast, as opposed to inside a bearing.
I'm thinking about something like a piece of 1"x1/8" copper bar stock
with the 1" direction parallel to the axis of the mast. The end of
the bar stock is spaced a small distance from the mast. You can bolt
it to the tower, or, use the ever popular exothermic welding to
connect it to a down conductor.
>All comments welcome.
>TowerTalk mailing list
TowerTalk mailing list