[Milsurplus] DM-28-Q Part Needed

[Mike Hanz]

  John's observation is useful.  The end play is specified for most (but 
not all) dynamotors, and is a clearance that is normally checked when 
bearings are replaced, along with inspecting the aluminum bore that 
holds each the bearing in place.  Bearings from the 1940s didn't adhere 
to the incredibly close tolerances available today, and the check was a 
good idea anyway because of bore conditions.  I have seen as much as an 
1/8" of play in some, and watching the movement of the armature back and 
forth in worn bores during operation is fascinating, if not very 
elucidating. :-)   Normally the end play runs less than .010", and in a 
well fitted end cage, that is more than adequate. The intent is to avoid 
placing the bearing in a preloaded position - those bearings are *not* 
intended to have a preload.  They need a small amount of room for 
armature expansion during heating/cooling cycles - the bearings are a 
light press fit on the armature shaft but slightly looser in the bore.  
See http://aafradio.org/docs/Dynamotors.html  for more if you're 
interested.

Very 73,
Mike  KC4TOS

On 9/7/2010 6:56 PM, J. Forster wrote:
> If the seals were intact, I'd assume the thing was assembled correctly.
>
> -John
>
> =============
>
>>>> I assume you regreased them?
>> Not yet,  but I have some Mobil Mobilith SHC100 on hand for that purpose.
>>
>>>> Did you see any evidence the thing had been taken appart before?
>> No.   There's a white seal that says "SAAMA Seal" on it though.  Don't
>> know
>> if it's original or from an overhaul.
>>
>> Mark K3MSB
>
> ______________________________________________________________
> Milsurplus mailing list
> Home: http://mailman.qth.net/mailman/listinfo/milsurplus
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:Milsurplus at mailman.qth.net
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
>
>