Rotor binding at 270 degrees

[Brian Quick]

Good day all, I have a question for the gurus with my tower’s rotor.  I’m having a problem going through a full circle.  It seems to bind up at around 270 degrees. I did not have this problem earlier.  I’m assuming that the rotor/mast/thrust bearing needs to be realigned.  One other possible; should I not have screwed down the bolts on the Thrust Bearing?, possible a temperature issue?  Can someone else confirm that this would be the most likely issue, or please just give me your opinion.  IF it is needing alignment, then the best way to align it would be while it is vertical.  I’m trying to validate the issue before I go out and purchase the climbing hardware.  Below is a list of the components:

40’ Universal Aluminum Towers HD 35-40.  Can be folded over for antenna and rotor repairs.

Rotor is a BigRAK Rotor with a Green Heron Controller

700lbs vertical load, 24,000 braking torque.

Used a DX Engineering Thrust Bearing, DXE-TB300

17’ mast with the SteppIR DB18 antenna mounted about 6’ above the tower.  And an anemometer mounted on top.  Monday night had winds reaching 51.6mph.

Any volunteer’s to climb the tower to do this re-alignment? or anyone have climbing gear to loan out?  Otherwise I will go out and purchase.

[Fred Kemmerer]

Hi Brian,

Sorry to hear that you are having problems. You might want to check the following:

1. SteppIR’s are heavy antennas. Your thrust bearing should carry the weight of the antenna and mast; not the rotator itself. If the system is putting downward force on the rotator, this could cause binding and will, at a minimum, likely cause premature rotator failure. We adjust our rotators so that there is about a 1/4″ gap between the bottom of the mast and the rotator top plate or bottom stop when the rotator mast clamps are loose.
2. This step will help you to determine where the problem is. First, check to see if the bearing is the thing that is binding. This can happen in a number of different ways. Once you have #1 taken care of, loosen the rotator mast bolts that clamp your mast to the rotator and spin the antenna around to see if it turns smoothly for a full +/- 180 degrees from North. If it does, your problem is in the rotator. If it does not, then your problem is in the thrust bearing. You can also run your rotator lock to lock with the rotator mast clamp bolts loose and confirm that the rotator does not bind up.
3. The mast must be centered in the thrust bearing. If it’s not, Binding will occur. The best way to check for this problem is to loosen ONLY the bolts that fasten the thrust bearing to the tower top plate and see if the binding goes away. If this is the problem, first check that your rotator is centered on its mounting plate in the tower. Then check that your thrust bearing is properly centered relative to the rotator and top plate. With these steps done, you’ll need to check that the mast is centered in the thrust bearing. All three of these points must be concentrically aligned with the tower. Make sure that your thrust bearing, not the rotator carries the weight of the mast and antenna.

Good luck solving your problems. If you get a chance, let us know what the problem was here so that others can learn.

[Author]

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