Circlip positioning 1

[gdodd]

The way a rectangular circlip is made they look like a loaf of bread in cross section, with one surface containing defined sharp edges and the other appearing convex.

Is there a rule of thumb that states the circlip surface forced against the circlip groove and subjected to the most load, must be the one that is flat or should it be the one which is convex?

My thinking is that if the convex surface forcibly contacts the groove shoulder it may work its way out of the groove through incorrect seating.

 

[WilliamH]

You are correct in your thinking. The sharp edge should be away from any force and in contact with the outer face of the groove. This is what we were taught at an OEM's race engine assembly school in reference to wrist pin circlips. Additionally (refering to wrist pins) they told us to position the open end of the circlip either up or down in reference to the cylinder bore. This positioning, in theory, reduced any vibratory effect that might cause the circlip to fall out.

This goes back to training I received in the early sixties. Hope it's helpful.

Will

 

[Metalguy]

If the engine will see "high RPM", the gap should be on the bottom (crank side). But it's better to use the full-circle Spiralox.

 

[gdodd]

The circlip is used to hold a starter motor pinion.

The pinion is lightly loaded against the circlip via a spring.

The concern is that if the convex face of the circlip is against the circlip groove shoulder and the flat face against the pinion that repeated starts could cause the circlip to ride over the groove and come off.

In this configuration the convex face of the circlip contacts the groove shoulder at the top of the groove reducing the load bearing capacity of the clip.

If it is mounted in the opposite direction there is more contact area therefore less likelyhood of circlip detachment.

Any comments please.

 

[franzh]

Two things come to mind:
(We are talking about flat circlips, not the round wire formed circlips, aren't we?)
1) If the circlip is internal (piston pin) then installing the circlip with the flat surface towards the pin is the recommended position.
2) If the circlip is external (pinion shaft) then the circlip should be installed with the flat surface away from the spring. This allows for the sharp edge of the circlip to engage the retaining groove. If the convex surface were in the groove, it could potentially ride out.

In the US, many clips are round wire, which fit in a circular groove around a starter shaft (GM) or a square cut clip in a square cut groove (Ford). The round clip also has a retaining ring around the clip to keep it from expanding during engagement.

Now, in reference to #1 above, I once heard a convincing argument about installing the circlips with the flat edge out as to allow for the clip to better engage the piston material with "grip". This was from an established race engine builder in the early 70's. To get the definitive answer, the circlip manufacturer should be the authority.
Franz

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[gdodd]

Franzh
Thanks for the useful tip
Yes it is an external flat cirlip though as I said above it is shaped like a loaf of bread in crossection.
Has anyone heard of circlips mounted with the convex surface out detaching themselves from an engine part while in service?