My son scored a great collection of Construx building toys when we visited my family's place last summer. This Fisher-Price toy from the 1980s was a hit with one of my younger brothers. Unfortunately, it was discontinued in 1988, briefly revived in the mid 1990s, then put to rest.
While we have a good collection my son is really into building houses and larger structures and soon ran out of the long beams. When I looked on eBay there were two options: spend a couple hundred dollars to get a huge lot of Construx or spend a little but not get the long beams.
A quick Thingiverse search revealed somebody had modeled the standard sized beam already. Using this model as well as a "real" long beam, I was able to remix this design into one exactly like the original long beam.
When I finish playing with the Construx my son will have lots of new pieces to use!
This exercise does raise an interesting point: what happens when a popular toy is abandoned by its manufacturer? Typically the supply dries up, costs go up for used sets, and another toy fades into obscurity. For most toys that is fine and an expected narrative arc in a consumer, throw-away culture. However, for toys that are worth keeping, like LEGO, Construx, or other open-ended building materials, this abandonment seems really unfair. The toys themselves are simple enough that with today's software and hardware they are capable of being reverse engineered, remixed, and fabricated. Construx have relatively tight tolerances but it is nothing a well-tuned FDM 3D printed cannot handle creating.
The legality of such remixes is uncertain: Fisher-Price and Mattel might not look too kindly on somebody selling ersatz Construx, but somebody producing his own pieces to extend his own collection of a defunct toy is an entirely different legally murky body of water.
This type of hacker approach to toys is entertaining and certainly not mainstream. I think it captures the original spirit of 3D printing hobbyists when they developed the first RepRap printers. They sought to create a machine capable of producing parts for other machines. The Construx is a machine of sorts for children to create other machines. I enjoy the money I saved not needing to buy eBay sets and I appreciate the new types of models my son will be able to create with a wider selection of building materials.