Hello Roger
The scrap aluminium tube I used has a wall thickness of about 0.75 inches,
the object being try and find bearings/materials that I could fairly
easily fit together in order to fabricate the housing with minimal machine
shop access. Having done the bench metal cutting etc. I did get the edges
etc. cleaned up by asking for help from a local machine shop, otherwise,
the original 1979 bearing assembly was a true amateur radio "kitchen
table" product.
73, John. G3JVC/GM3JVC.
> On 2/28/2013 3:17 PM, John E. Cleeve wrote:
>> Gentlemen,
>>
>> I have read the thread with interest, and here is my solution. Back in
>> 1978, and in order to cope with the likely forces applied to a tower top
>> thrust race, I looked at the commercial products available but chose to
>> "engineer" my own, making use of roller bearings to provide a more
>> effective solution.
>>
>> I looked for taper roller bearings with a centre bore of 2 inches or
>> more,
>> and by using a commercially available two part metal collar, clamped
>> around the antenna support shaft, with the lower edge of the collar
>> resting on the edge of the inner ring of the taper roller bearing, as
>> the
>> antenna shaft passed down through the bearing, the weight of the antenna
>> is transferred to the inner ring of the bearing. The taper aspect of the
>> roller bearing performance will cope with any radial forces applied to
>> the
>> bearing.
>>
>> New, taper roller bearings are quite expensive,
>
> I agree but, I've found wheel bearings to be relatively inexpensive new.
>
>
> but a metal scrap/vehicle
>> breakers yard will provide a very cheap source, especially if you are
>> prepared and able to remove them yourself. The taper roller bearings I
>> used, came from the rear wheel hubs of scrapped heavy goods vehicles,
>> and
>> they are more than capable of handling the largest antenna related
>> stress,
>> and better still, cheap, they cost about $1 each!
>>
>> Of course, the bearing unit requires a "housing" in order to be fitted
>> to
>> the tower top plate, but again, the same scrap source provided short
>> lengths of suitably sized, thick walled aluminium tube,
>
> Depends on what you mean by thick walled. I prefer a substantial
> retainer with the bearing pressed in. I also prefer an over sixe ID
> with an adapter that has a shoulder, that is a slip fit on the shaft,
> but pressed into the bearing. If the shoulder is large enough I can
> drill and tap it, allowing me to lock to the mast to support it for
> rotator removal.
>
> My rotator, a PST-61 has wheel bearings top and bottom so it can
> tolerate long masts through thrust bearings that might pull o the
> rotator due to unequal expansion and contraction with temperature.
>
> 73
>
> Roger (K8RI)
>
> in the form of
>> scrap "offcuts" sold by weight. I was able to fabricate a very
>> acceptable
>> "product", and fitted with a suitable weather protection "hat", i.e a
>> scrap aluminium container lid, and the bearing well packed with grease,
>> one such unit has been in position since 1979.
>>
>>
>> Sincerely, John. G3JVC/GM3JVC.
>>
>>
>>
>>
>>
>>
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