Mike wrote:
> Pin the Mast, ask my friend K6MCL across town about not following the
> instructions :-)
>
> Actually I was the guy that really suffered as I had to climb up the tower
> and hang of the side and use a transfer punch to mark the holes and then
> drill in a hole from each side, not fun. Better to do the job on the
> ground, those Aluminum Clam Shells cannot be tightened enough to hold the
> mast reliably.
>
> I don't understand really understand the rest of questions, I have a thrust
> bearing and do not see how it relates to the mast turning in the Clam
> Shells.
>
Using a thrust bearing to support the load when the mast is rigidly
installed in the rotator isn't just a poor idea it's a bad idea. The
farther apart the thrust bearing and rotator the worse it gets.
There are two problems. The first is some rotators are designed to work
with a load applied. The second it the difference in the expansion
coefficient between the mast and the tower. On a long mast it's
possible to pull the top up on the rotator causing damage from mild to
catastrophic. I've seen rotators completely trashed by having a thrust
bearing used to support the system weight.
Actually, thrust bearings should be used to eliminate the side thrust
to the rotator.
My system completely destroyed a TB-3 thrust bearing. I'm replacing it
with an 8" piece of 2 1/2" DOM to serve as a thrust bearing.
73
Roger (K8RI)
>
> Mike, K6BR
>
> -----Original Message-----
>
>
> Hi all,
>
> My Yaesu rotator (DXA1000) specifies that the mast be pinned 50mm
> above the base. I am also using a yaesu GS-65 thrust bearing. The
> retaining plates that they have with this rotor are very nice, by the way.
>
> If I pin the mast using the supplied bolt per instructions, there is
> precious little slack in the 9mm hole which allows the weight of the
> mast to be taken off the rotator-none that I can tell in fact. Does
> the use of the pin bolt mean that the antenna/mast weight has to be
> carried by the rotator and not by the thrust bearing?
>
> Do you think it would be a good idea to drill a larger hole in the
> mast so that there is noticeable room to pull the mast up off the pin
> as I tighten the thrust bearing bolts? Or should I follow the
> rotator installation instructions, figuring that is how it is
> engineered? My understanding is that having the weight of the mast
> and antenna (TA53M with 40M add-on 65lbs) would be better for the rotator.
>
> Tom
> K8TOM
>
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