[TowerTalk] Need the holes spacing on a Rohn TB-3 thrust bearing Oops...Transposed again

[Roger (K8RI)]

On 8/3/2010 11:21 PM, Roger (K8RI) wrote:
>
> On 8/3/2010 10:33 PM, Kevin Elliott wrote:
>    
>> I am trying to see if I can mount a TB-3 thrust bearing to a Rohn 25 rotor
>> platform, I realize I may need to re-drill the holes.
>>
>>      
> Not redrill, it's drill new holes as the ones in the TB-3 and TB-4 which
> are identical do not match any holes in the 25G accessory shelf
>    
>>    That is why I need the
>> center to center measurement for one set of holes.
>>
>>      
> I measure 3 13/16", but that was just with a ruler so give or take
> =/-1/16"?
>    
>>    Also if someone can
>> recommend another bearing to mount to a Rohn 25 rotor plate please let me know.
>>
>>
>>      
> Yaesu GS-605.
That is supposed to be GS-065, not 605

73

Roger (K8RI)

> It won't handle the load the TB-3 will, but it looks a lot
> nicer and is a lot smoother.    Does that mean anything? Probably not
> particularly if you are only putting up a tribander, even a large
> tribander. I'd not hesitate to use one with the Force 12 C-19 XR with
> the new WARC-7 stacked 6 feet above it.  ("They", meaning force 12" say
> you can stack the new WARC-7 as close as 4' to the C-19 XR. Ao I'm
> qualifying that statement.   No, those holes won't match either, but
> it's a smaller bolt circle with smaller bolts.  However due to the
> smaller bolt circle and the "cut-out" for mounting the "Ham series" of
> rotators so you can get at the terminal strips, positioning the bolt
> holes in the accessory shelf will take a bit of creativity.  IF you are
> careful in alignment, you end up with "half a bolt hole" on each side of
> that cut out.
>
> AS I am going to be installing a 25G with shelf, C-19 XR and possibly
> the WARC 7 on an Aluminum 6061-T6  2" X 3/16" (or 1/4") wall mast with
> the GS605 AND a Ham IV I am going to take a 1/4" thick aluminum plate,
> drill the matching holes (the box comes with the bolt circle template on
> the bottom) in the plate AND the accessory shelf with the bolts aligned
> to one of them lines up in the center of the cut-out. The plate will be
> bolted in place not only with the three thrust bearing bolts that go
> through the accessory shelf, but with 4 bolts (One near each corner of
> the Aluminum plate). Those 4 bolts will likely be 5/16" but 1/4" or 3/8"
> would also be fine.   Normally there is not a great deal of stress at
> this location so the size of the bolts is not critical, nor is the
> placement of the 4 bolts for the thrust bearing...that is as long as
> they line up with the holes in the bearing.
>
> The reason for going with 1/4" plate is two fold. The first is even
> support for the bearing due to the cut-out in the accessory shelf. The
> second is I have a dozen 6" X 8" pieces of 1/4" on hand<:-)) as they
> make good boom to mast clamp mounts for smaller antennas and are just
> plain all around handy pieces.
>
> 73
>
> Roger (K8RI)
>    
>> Thanks,
>> Kevin
>>
>>
>>
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>>      
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