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30 DEC 2023
I've updated the OpenSCAD model to address two issues that have shown up in the previous revision. First, there have been a couple reports of the inside post cracking during normal use. The balls now have an extra collar around the post to address this:
And second, we had another incident where the ball rotation was jamming, just like on the initial recalled design. This was a real head-scratcher but by sheer luck I happened to be working on the 96-character type element at that time and had discovered that the Selectric III added a new part, a ribbon guide, to the front of the tilt ring and we needed to add more clearance to accommodate it. The typewriter with the binding problem was an IBM Personal (Selectric) Typewriter, which uses 88-character balls but shares a lot of parts with the S3. We took another look at the tilt ring and, sure enough, it's also got the ribbon guide.
I copied the clearance adjustments from the 96-character ball to the 88 and it's working correctly now! If you have a ball with a broken post or you want to use your type balls on a Personal please contact me for a free replacement.
(Oh, and no ETA yet on those 96-character balls.. Still have a lot of testing to do there.)