[TowerTalk] US Tower Crank-Up Tower Thrust Bearing

[Mac]

That was not enough answer,  ok so you know the thrust bearing ID  now 
you need your mast to closely match this size 2-1/16" size.  A 2" od 
mast is not really acceptable, if you still have the eccentric collar 
presuming this bearing is eccentric, the collar can be hand fitted to 
the bearing and then locked with the set screw. For ham applications 
this works, due to the limited rotation speed, but in the real 
mechanical world using eccentric bearings and collars are most often 
intended for one direction only.

Another list member has offered he shimmed his mast to make up the 
difference, that is not how i was taught or shown the 1/16" difference 
is to be accommodated, the difference should be made up for by the 
bearing proper being eccentric whereby using a perfectly round collar 
will find the small misalignment point and most often rest in that 
position, but at our rotation speeds it is a small point of 
significance, but to shim the difference is not normally the preferred 
or acceptable technique, using a bigger OD mast is. Or of course a 
smaller ID bearing

Its a crap shoot, all 2" pipe is not equal, but presumed you have a non 
2" galvanized mast then have it galvanized, your 2" od mast just grew in 
OD size by some thickness of the galvanizing process and how many times 
it might or might not have been dipped.

I am sure a better answer will be proffered by someone here and it will 
make perfect sense to you.

mac/mc  w5mc

On 7/28/2019 4:02 PM, Mac wrote:
> This measurement is near insignificant, it needs or should comport 
> with the mast size O.D. not all mast are equal in size by a long shot.
>
> By its self is not enuff answer.  The mast and thrust bearing are near 
> symbiotic in their relationship.
>
> best:  mac/mc  w5mc
>
> On 7/28/2019 1:06 PM, W3OA wrote:
>> A buddy and I are doing some work on a US Tower crank-up with an 
>> unknown history.  He measured the inside diameter of the thrust 
>> bearing as 2 1/16 inches.  Does this sound right or is it possible 
>> the bearing has been replaced with one that is not the same size as 
>> the original?
>>
>> 73 - Dick, W3OA
>>
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