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Old 01-03-2009, 01:59 PM
Don Moyer's Avatar
Don Moyer Don Moyer is offline
 
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Fred,

According to Oberdorfer, the snap ring is all about keeping the shaft from moving freely within its limits of travel which would be from where its shoulder contacts the hub of the impeller to the roll pin in the center of the accessory drive gear (I estimate this distance to be approximately 1/4"). The impeller itself is securely contained within the confines of the impeller chamber itself.

My understanding is that design engineers feel a bit clumsy over allowing a shaft to "float" freely within an assembly. As a practical matter, I don't think anything bad will happen if the snap ring is eliminated as long as the pump is installed. The designer's worst fear is probably over the small likelihood that upon removing the pump from the engine, the shaft could try to stay in the accessory drive and end up falling into the bilge.

In designing the MMI flange pump, we did eliminate the snap ring because the shaft is held securely within the two ball bearings.

Don
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