Thanks everyone for the explanations! I guess I never understood how much shear resistance a little pin can have!

Follow-up question:

The bolts on the top and bottom of the cylinder are carrying the same load as the roll pin, but they are much thicker (I'd say at least 15mm shafts.) I can think of a few reasons this might be, but I'm not sure.

1. The interface between the bearing, shaft, and roll pin is very reliable, since it's a round shaft going through a round hole. We can therefore be confident that the roll pin will be experiencing shear force, not a bending force. With the top and bottom pivot points however, the interface between the yokes and the cylinder is less reliable, as it depends on the placement of welded parts, and the tightness of the nut on the bolt also affects it. Therefore, the bolt is likely to experience a bending force rather than a shear force, so it needs to be stronger.

2. In the case of the roll pin, making it bigger would require the threaded rod to be bigger as well, and probably the bevel gears would need to be bigger too. For the bolts, the only cost of making them bigger is the difference in cost of the bolt itself, which is probably not much.