Originally I had one I bought at 6 bucks with a dented ball. It worked for a while, but I always had trouble with the scroll wheel. It was sticky at some position and free at others. Once I bought another good one, I opened the bad one up. To my dismay these guys have taken a pretty nice design but screwed it up by copying not the original die, rather one that is completely out of tolerance. That is why you hear the early EM guys saying the scroll was smooth while the newer users all are complaining of scratchy-ness.
I dont have a good camera right now, so cant take hi-res photos, so linking from google. To my horror now a days people give importance on form over functions, found only ONE exploded view. This will suffice till I post photos.
https://www.google.com/search?q=expert+mouse+scroll+ring&source=lnms&tbm=isch&sa=X&ei=FAndUdXtCaWEiwLutIG4Cw&sqi=2&ved=0CAcQ_AUoAQ&biw=1440&bih=760#facrc=_&imgdii=_&imgrc=txHuhRoS9OK2ZM%3A%3Bw***_BLhyskfhM%3Bhttp%253A%252F%252Fsoftsolder.files.wordpress.com%252F2009%252F08%252Fdsc00061-trackball-scroll-ring.jpg%3Bhttp%253A%252F%252Fsoftsolder.com%252F2009%252F08%252F09%252Fkensington-expert-mouse-trackball-scroll-ring-troubles%252F%3B750%3B563Now the fun part:
there are 3 parts, the scroll ringy thing, the inner bowl and the metal ring. Of course the 5 white balls. The inner bowl is fixed to the bottom by screw while the plastic-rubber scroll ring as well as the metal roller sandwich this and the roller is joined to this with melted plastic tabs.
Dont open this as once you open, there is not much space to glue it back. You may have to resort to drilling holes nad screw mounting the roller plate. I have not done so, but will have to do that way.
My balls actually did not look like round, rather some roundish shape, but dont know how they became off-found rubbing between two plastic surfaces. So surely there is some spotty play there. Kensington might have saved some costs over the roundness. Would try some bearings in future.
My next bright idea was may be the metal scroller is rubbing against the back of the bowl. So I ground the metal on a flat surface hoping some miracle. It feels slightly better. Will try mirror polishing both the inside and the outside of the metal roller/disk by grinding/polishing over a flat mirror.
I also removed few microns from the lip and it has made it pretty free, but still assymetric pressure binds. I also could not remove the metallic seize bearing scratchyness noise which I think comes from inside.
I think I found the issue with all these. The outside scroller has a groove and the static bowl has a lip that stays inside the groove over a round star like carrier that has about 7 thin rubber rollers. Also I guess since friction between same surfaces are more than dissimilar surfaces, having both the bowl as well as the scroller is creating the most friction. Add to that both these rubbing surfaces are not precision ground/cast, so there is some more/less gaps between these. To my understanding they have cheep-fied a bad design which would have worked nice if the engineers followed the original mold etc. The reason is there is no horizontal side-to-side stabilization mechanism as well as a vertical stabilizer that is uneven and loose.
What more we can get from such a thing. This might be a reason some users have good ones and are not even talking about disposing this.
What I plan to do? Since the outer ring is of simpler design with no assymetric shape, I plan to take it to a CNC shop and cut few copies on a T6061 aluminum. I hope the aluminum will pose the minimum friction and will be a reasonable lighter substitute. It would also self polish and lubricate the plastic. I could even anodize it with different color. Ideally this lip in groove design feels like they copied a metal version to plastic but could not handle the tight tolerances and differing materials that would have made it possible.
