Hi Tom,
The reason the Belleville discs improve PE is that they force the bearings to rotate in a predictable way with the motion of the worm. Left to their own devices the ball bearings tend to stall then start again in unpredictable ways likely when the clearances are taken up by misalignment in the worm and bearings. Placing a light load on bearings is a well documented mechanical engineering practice for precision mechanisms and many bearing manufacturers have engineering notes on the practice. That is how I found out about this many years ago when I applied the idea to my HEQ5-Pro/Sirius and EQ6/Atlas mounts 6-7 years ago back in my EQMOD says.?
Another good idea I had but didn't try due to updating to OPWs was to fix the worm blocks to the worm cover to in essence make the cover a rigid bridge between the blocks to make backlash easier to do. The way to do this would be to use a pin on the top and cut a slight recess under the existing grub screws on the cover to set the blocks in the cover well aligned with the outer bearing which is being preloaded by the Bellevue disc. By bridging the blocks they would move as one making backlash easier to set well. The other thing to try to achieve is to locate the gearbox output shaft as closely on axis as possible with the worm shaft.??
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Chip Louie - Chief Daydreamer Imagination Hardware
Chip Louie