[TheForge] OT - Grease/oil seals for a gear box

[IowaHarry]

Paul wrote:
> Bruce Freeman wrote:
>   
>> Well, I am surprised!  I always thought of packing seals for plumbing
>> applications like valve stems, where the rotating rate is about once
>> per day!  I've looked up a little and find some of them are good for
>> "high speed" applications, but I don't have enough info yet to
>> determine what RPM that means.
>>
>> Does anyone know what considerations go into selecting design criteria
>> and packing material for an application with speeds upwards of 2000
>> RPM?  (I'm shooting for 10kRPM, but doubt I'll get there with this
>> prototype, for reasons other than the packing seals.)
>>     
>
> snip
>
> What I gotta say is wow. 10000 rpm is a lot for a seal. I tend to think 
> that the only type of seal that will withstand that speed is a ceramic seal
> see:
> http://www.pumpseals.net/Outboard_seals.htm
> for a look see.
> The ceramic seals operate well at high speeds but the majority of 
> installations that I have seen them in are for pumping water... they are 
> therefor cooled by the water.
>
> If you can restructure the shaft and housing to accommodate a sealed 
> high speed bearing such as those found in an automotive alternator you 
> would be well served. The poor alternator operates at high rpm ( its 
> usually 'geared' up at least 2:1 and some times 3:1, if the crank is 
> turning 4000 rpm you can see what that does to the alternator shaft 
> speed). Those bearings are pre lubricated and shielded.
> As a testament to their toughness the six bearings in my three cars, 
> 100050 miles, 150000 mi and 132000 miles are all original. if you can 
> adapt your shaft and housing sizes that's the way I'd go...
> Good luck
>
>   
10000 RPM, wow! That would require very precise installation of any type 
of seal. Packing will leak, it is supposed to, it uses whatever liquid 
is present for a lubricant. A mechanical seal would work but they are 
god awful expensive. I would suggest looking into lip seals. Most gear 
box, pumps and motors use lip seals. Bearing lube containment is usually 
lip seals. Cheap, simple installation. And you can buy a case of lip 
seals for the price of one mechanical seal. Try Chicago Rawhide or just 
go to your local bearing supplier and look at what is available. If you 
can machine a seat for your bearings you can machine a seat for the seal.

:Returning to lurker mode
Harry in Iowa
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