3001old with Split Tubes – Inner Wall Variations on Mold Numbers 77 to 96

The molds for the bricks with split tubes and mold numbers 77 to 97 were revised a few times. I think this was done to improve the mold release of the bricks during production.

Each of these steps makes the brick stick a bit more to the inside half of the mold when the mold halves separate.

Version A

The first bricks (with pat. pend and pat. pend erased) had smooth inner walls.

Version B

Small, triangular cuts are made into the corners of the mold.

Version C

A thin inner “rib” is added inside the long walls.

Version D

The inner rib is now present on all inner walls.

Later bricks used a design similar to version D with inner ribs on all inner walls. On those molds the cut introduced in version B is not used.

(This is a new image of something I described earlier so I can refer to it more easily.)

[Original post and comments on Flickr.]

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