[ARC5] BC-454-B Dymamotor Question

[J. Forster]

Two reasons, IMO.

First, even the smallest amount of grit or sand in a bearing will vastly
shorten its life. Anything with high speed bearings is built in high class
clean rooms today.

Even the best bearings fail because of this...  viz Hubble Inertia Wheels.

Second, the bearings have shims to adjust end play, etc. If not properly
shimmed, the bearing preload will not be correct, again shortening life.
They didn't make and use v0.005" +/- shims for fun.

YMMV,

-John

================


> From: Ken W7EKB
>
>
> *************************
>
> One thing I found very interesting in my "research" on the DM-34s I have
> here is that the manual states unequivocally that experience has proven
> that
> replacing bearings in the field resulted in very much reduced operating
> life
> and it was stated flatly that if a DM-34 needed bearing-work, it was to be
> sent
> back to the factory.
>
> I have been trying to figure out why this was the case.
>
> *************************
>
> From Richard kn7sfz:
>
> That's an easy one......."brinelling" (check Wiki)
>
> I just retired from a 45 year career in which changing ball bearings was a
> common part of my job.
>
> You can remove the  bearings any old way  (a puller is best, of course),
> but you must replace them without any stress applied to the outer race,
> that would then be transferred to the inner race by the poor balls and
> hence the 'denting' of them, which is then carried to both races and soon
> the bearings are screaming at you after running for a while.  If they must
> be pushed on, only the inner race must be used.
>
> Sometimes the bearing must be heated so it will slip nicely on the shaft
> without a press and hopefully into the end bell after it cools, and
> perhaps then heat the end bell for the final step.  Not an easy
> undertaking in one's garage.
>
> Just my .02.
>
> Richard kn7sfz
>
>
>
>
>
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