The effective area of face gear is out side of PCD. ( 31.85 ) .
So the effective width of this gear is only 0.875mm . Its durability is not enough .
I try calculating to increase the effective width . ( = reduces the PCD. )
Inside of PCD is not effective . So I draw the picture as left .
P.C.D. is reduced by decreasing the teeth . If the ratio is 4.4 : 1 as `70's 308 .....
The teeth of pinion is 10 . So the teeth of main gear is 43 . ( If it is 44 each teeth cannot meet to each teeth . )
module = PCD / n
0.65 = PCD / 43
PCD = 0.65 * 43
=27.95
In this case the width of teeth is 2.825mm . It is 3 times of original .
It may be more smooth and more durable .
But its speed is too low in present .
Then , try to decrease the pinion teeth .
This picture is the pinion of 308PRO /408A . Its teeth is 9 . External diameter is 7.8mm . Modele is 0.65 . Dislocation is 0.5 .
module = PCD / n
0.65 = PCD / 44
PCD = 0.65 * 44
= 28.6
In this case the width of teeth is 2.5mm
PCD is reduced by reduction of module from 0.65 to 0.6 . Dislocation is 0.5 on pinion .
Teeth of main is 49 . Teeth of pinion is 10 .
module = PCD / n
0.6 = PCD /44
PCD = 0.6 * 44
= 29.4
Width of teeth is 2.1mm .
This case might be used on the last of `90's 308 / 310UL .
Too late ! MITCHELL !