[Milsurplus] Sealed ball bearings in military gear

[Clarence M. Owens]

Hi All,

I have two questions about the military's use of sealed ball bearings in
rotating equipment like dynamotors and inverters.  I've started going
through all of my dynamotors cleaning and regreasing the open ball
bearings.  I'm using a Valvoline synthetic grease rated for very high
temperatures.  Looks like good stuff and it did not separate at all in the
tub, unlike the Mobil synthetic grease I have.

First, when did they switch from open to sealed bearings?  I'm suspecting
it was late in or some time after WW II since the only two units I've found
with sealed bearings are a T-195 dynamotor and a PU-7/AP 400Hz inverter.  I
have the T-195 dynamotor but the PU-7 was something I played with when I
was in college.

Second, what's the general thought about how well the sealed bearings hold
up in use after these many years?  The T-195 dyno seems to run OK but I've
only run it for a few minutes so far.  When I had the PU-7 back in 1960 or
so it ran for a few minutes and ate its bearings.  I won't be changing the
T-195 dyno bearings on the if come but am curious about experiences with
using these old high speed sealed bearings after long storage.

Thanks,

Clare Owens  N2RJB