[TowerTalk] Which Thrust Bearing to Use

[jimlux]

On 12/9/16 6:14 AM, charlie at thegallos.com wrote:
>> Looks really well made.  I had the original Rohn counterpart for years and
>> it just kept on going.
>> I added a zerk fitting so I could grease it.  They last a very long time
>> dry without lube, but I am anal
>> about lubing everything hihi.
>>
>>
>> Bob
>> K6UJ
>
>
> Looks nice, but one thing I just have not been able to understand for years
>
> Tower thrust bearings are a LOW rotation speed, high load application,
> probably the WORST place to use ball bearings.  I would expect either
> tapered roller bearings, or today, do what most of industry does, and use
> an engineering plastic bearing.  I mean, we don't need a torlon bearing
> there (the loads are NOT that high)
>
> I mean, a glass reinforced nylon, or a PTFE (Teflon) (say a 25% glass
> filled or molly filled) isn't going to cold flow at ALL under loads a 2"
> mast could sustain, will NEVER need lubrication, will never corrode etc
>
> You either get them molded for you (for some materials would be the
> cheapest way - you do NOT want to know what torlon costs), or you slice it
> from tube, or you even just use end on rods set around the circumference
>
> I mean, today they run the pivot bearings and lower boom bearing on cranes
> in plastic bearings, because they hold up better than metals in those low
> rotation speed, intermittent rotation applications
>

For amateur use, you could probably buy a slab of the appropriate 
plastic from Cadillac or McMaster-Carr, use a hole saw to drill the 
hole, drill your mounting holes, and you're done.

Depending on your environment, a stack of HDPE cutting boards might work 
just fine, but I don't know about the UV resistance.

Torlon is a bit pricey... $1200 for a 12x12 sheet 1/2" thick

Moly filled Nylon is $37 for a 1" thick piece 6x6"  - Says it can be 
used outdoors, It's black, but that doesn't always mean it's UV resistant.

Black acetal (Delrin) is $26 for the same 1"x6"x6"