I’m a huge fan of both Lego and Meccano, for use in demonstrating engineering mechanisms to clients (as well as understanding complex mechanisms myself).
Meccano is based on the Imperial system and therefore the two are incompatible (I’m 100% metric by choice and now use only Eitech components).
Today’s invention is a bridging piece which allows me to connect Lego to Eitech consistently. I tried buying such parts, but these days it’s just easier to 3D print them.
The grey bits are Lego, the blue bits Eitech (metal) and the yellow is the piece in question.
(If I find I need a stronger connection, I have ways to achieve that, but it usually means I’m trying to build an actual system, not a demo/prototype 😉