[GreenKeys] MITE question

[Bruce Gentry]

They are noisy. The motor bearings are sealed, so there is no user lube 
for them. The 60 cycle motor runs at 3600 RPM, and the cooling fan adds 
inertia to that, so it does coast a bit. A great deal of the noise comes 
from the motor itself and the reduction gears. The motor is small for 
it's horsepower rating, so it has windings and magnetic structure that 
produce a very intense magnetic field. This causes the motor to run hot 
and produce a lot of noise. In mine, the bearings were  bad and 
replacing them helped reduce the noise. I used a bearing that was 
factory lubricated with high temperature synthetic grease.  Another 
issue is the gearing and the nature of this kind of synchronous motor. 
Although the motor turns 3600 rotations a minute, the instantaneous 
speed during each rotation is not uniform. When there is a gear train 
that has inertia of it's own, the reduction gears are subjected to 
torque in both directions during each rotation of the motor which puts a 
lot of strain on the bearings in the first reduction gear set. They were 
loose in mine and replacing them helped reduce or more precisely change 
the tambre of the noise to something a bit more tolerable. Another  
factor is the use of noisy straight spur gears in the train, especially 
the motor pinion and first reduction gear. Other machines tend to use 
much quieter helical or worm gears for the first reduction.  The Mite is 
interesting and small, but I think noise was either ignored in the 
design or accepted as a necessary byproduct.

       Bruce Gentry, KA2IVY



On 4/30/15 1:03 PM, Nick England wrote:
> I hauled my MITE KSR (AN/UGC-41) off the shelf recently and spent a 
> little time getting it running OK - mainly cleaning, lubing, and 
> making up some cables.
>
> But having never seen or heard one of these things before I'm 
> wondering if the motor operation is normal or not. It just takes a few 
> seconds to spin down after power off - recognizing it has none of the 
> mass like a M28 motor/gear set, is this typical or not? I couldn't 
> find any motor lube info in the manual. Gears seem OK, etc.
>
> It has some gear noise but I have no idea if these things are supposed 
> to be dead quiet or wail like a 747 ready for takeoff. Actually I 
> don't think it sounds much different from the one on this YouTube video.
> https://www.youtube.com/watch?v=dMAklaw4pdk
>
> Thanks,
> Nick England K4NYW
> www.navy-radio.com <http://www.navy-radio.com>
>
>
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