Egg on face time. There is indeed an offset on the WOSP motor. Near enough
4mm - which would give the gear more clearance than the difference between
the two pinions which are 25mm and 29mm diameter, not radius.

Just as well I didn't go ahead and buy the later pinion for the old
PowerLite.

Thanks for bouncing things around chaps. Pushing me in the correct
direction. To understand it.

--
*If they arrest the Energizer Bunny, would they charge it with battery? *

Dave Plowman London SW
To e-mail, change noise into sound.

Dave Plowman wrote:

here is indeed an offset on the WOSP motor. Near enough
4mm - which would give the gear more clearance than the difference between
the two pinions which are 25mm and 29mm diameter, not radius.

sounds good then, also if your 25mm and 29mm were measured between gear
tips, the effective diameter would be less, since it should be measured
[more or less midway] between tip and root ... the "module" of the gears
should be compatible if the teeth/effective diameter of the two are the
same.

On 22/06/2020 14:03, Andy Burns wrote:
Dave Plowman wrote:

here is indeed an offset on the WOSP motor. Near enough
4mm - which would give the gear more clearance than the difference
between
the two pinions which are 25mm and 29mm diameter, not radius.

sounds good then, also if your 25mm and 29mm were measured between gear
tips, the effective diameter would be less, since it should be measured
[more or less midway] between tip and root ... the "module" of the gears
should be compatible if the teeth/effective diameter of the two are the
same.


Sounds to me like the gear has a module of 2. So, from the standard
calculations the 9 tooth gear would have pitch diameter of 18 mm and tip
diameter of 22. 11 tooth gear would have pitch diameter of 22 mm and tip
diameter of 26 mm. Your pinions are 21 and 25 mm OD, so perhaps there is
a little tip relief to help them cope with debris. The pitch radius only
differs by 2 mm so you would need an offset of 2 mm to change the pinion
safely. Your offset of 4 mm sounds like more than is needed. But,
involute gears are relatively insensitive to the centres distance. It's
only insufficient clearance that will destroy gears quickly, not excess.