There are currently two subparts/primitives for a common geometry of the tow pins:
4883s01.dat https://library.ldraw.org/parts/44458
and duplo_hook.dat https://library.ldraw.org/parts/47864
They differ only in the sharpness of the top lip overshoot.
The angle of the lip overshoot was larger (rounded to 1/16th above), but has now become smaller (very close to 0, i.e. half of the circumference of the pin, see e.g. fourth pic https://www.ebay.com/itm/125708641270). Some vehicles have an additional dent at the base of the pin (see e.g. sixth pic https://www.ebay.com/itm/364292486127). We should also keep in mind that one of the variants have a triangular plate instead of the top lip (perhaps plain cylinder would do). On the side, the attachment of the triangular "arm" occur at different angles, tending to be narrower for vehicles lacking the underside centre reinforcement. The pin top also has a few different shapes, ranging from fully flat to elevated centreline to circular dent.
I propose the following simplifications:
That would leave underside centre reinforcement and topside reinforcements as optional additions for the reusable subparts and allow a single primitive to be used with both older and newer tow pins.
4883s01.dat https://library.ldraw.org/parts/44458
and duplo_hook.dat https://library.ldraw.org/parts/47864
They differ only in the sharpness of the top lip overshoot.
The angle of the lip overshoot was larger (rounded to 1/16th above), but has now become smaller (very close to 0, i.e. half of the circumference of the pin, see e.g. fourth pic https://www.ebay.com/itm/125708641270). Some vehicles have an additional dent at the base of the pin (see e.g. sixth pic https://www.ebay.com/itm/364292486127). We should also keep in mind that one of the variants have a triangular plate instead of the top lip (perhaps plain cylinder would do). On the side, the attachment of the triangular "arm" occur at different angles, tending to be narrower for vehicles lacking the underside centre reinforcement. The pin top also has a few different shapes, ranging from fully flat to elevated centreline to circular dent.
I propose the following simplifications:
- Tops are modeled flat.
- The lip is reduced to half the circumference.
- Dent at base is ignored.
- Differing angles of "arm" attachment are ignored.
That would leave underside centre reinforcement and topside reinforcements as optional additions for the reusable subparts and allow a single primitive to be used with both older and newer tow pins.