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Has anyone noticed that swiping an original Atari Centipede trackball hard right or down can cause the ball to lift up and stall game motion, whereas swiping left and up it's pretty solid?

This has several causes, mainly due to geometry. When swiping the trackball towards the right (for example) the ball can slide up and horizontally along two rollers, reducing the effective angle of vertical constraint, making it easier to slide out of contact with the left roller with the sensor. Whereas when driving left the ball is forced to go directly up on onto a single roller without sliding between two, maintaining the full vertical constraint and keeping in contact with the sensor roller.

Atari_Centipede_Trackball_InsideRollers.jpg
[ Atari 2.25 inch trackball with the top cover and sensors removed, in game orientation ]

A contributing factor is clearance between the ball and the opening in the housing.

I measured a 0.5 mm (0.020 inch) gap using the original Atari housing but with replacement rollers and ball, with the ball seated. With the ball displaced (image below) the gap was about 2.0 mm.

Centipede trackball gap.png

If the gap was less I think it would jump less and settle faster.
But there's no way to shim the bearings/shafts/ball.

One variable is the roller diameter.

I'm looking for someone to measure the outer diameter of the roller shafts, away from the center wear-in area, of original Atari Centipede trackball rollers and current replacement roller sets.

MEASUREMENTS

Original Atari trackball roller diameters
<NEED MEASUREMENT>

Replacement roller diameters, bought from Arcade Parts & Repair in 2019 (no longer carried in 2025)
9.22 mm (0.363 inches)

Increasing the diameter from 9.22 mm to 10.10 mm (+0.88 mm) can raise the trackball 1.0 mm, which is enough to close most of the ball/housing gap in my Atari housing, illustrated by the following figure:

Trackball roller geometry.png

The trackball center above the roller centerline is given by:

Trackball vertical displacement formula.png

where x_d is 30 mm, the distance between the center of the trackball and roller center.
With this formula you can assess the impact of roller diameter on trackball vertical position.

I inquired at one current supplier about the roller diameter but they were unable to provide a measurement.

My trackball is exactly 2.25 inches diameter; the worn original one was only 2.19 inches diameter.

As noted by others, a heavier ball (cue ball) would help reduce the ball jumping up, but I want to test correctly sized rollers to minimize the gap.
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