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## Main Question or Discussion Point

Im an intern at a manufacturing company looking at whether our end gaps are too small on piston rings. Can someone take a look at this and tell me if I'm doing it right?

We have a piston ring that goes into a 9 5/8" bore. The upper limit of the end gap is 0.136. Max temperature is 300°F. For the ring material the radial CTE is 4.4*10^-5 and axial CTE is 8.9*10^-5.

I said circumference c=∏*d=30.237 (assuming d=9.625)

length=circumference-max end gap=30.237-0.136=30.101

ΔT=300-70=230°F (assuming tolerances given at 70°F)

I assumed you use axial CTE α=8.9*10^-5

ΔL=α*ΔT*L=(8.9*10^-5 /°F)(230°F)(30.101")=0.616"

Since ΔL > max end gap, do I assume our piston rings close up?

That seems like a pretty drastic design error with the piston ring trying to close almost a half inch greater than the end gap, I wanted to see if I'm doing this right before I take it to my boss.

Thanks for any help.

We have a piston ring that goes into a 9 5/8" bore. The upper limit of the end gap is 0.136. Max temperature is 300°F. For the ring material the radial CTE is 4.4*10^-5 and axial CTE is 8.9*10^-5.

I said circumference c=∏*d=30.237 (assuming d=9.625)

length=circumference-max end gap=30.237-0.136=30.101

ΔT=300-70=230°F (assuming tolerances given at 70°F)

I assumed you use axial CTE α=8.9*10^-5

ΔL=α*ΔT*L=(8.9*10^-5 /°F)(230°F)(30.101")=0.616"

Since ΔL > max end gap, do I assume our piston rings close up?

That seems like a pretty drastic design error with the piston ring trying to close almost a half inch greater than the end gap, I wanted to see if I'm doing this right before I take it to my boss.

Thanks for any help.