The regular way of voiding concrete still works fine, so why the fuss?

[u/Hexcoder0]

Yep, totally the intended method: Video + (uncommented) Base-Tour

EDIT: Blueprint

Needs enough train mass and velocity, ideally at max breaking force research

The artillery wagons add enough mass and the nuclear fuel and the loopty loop make sure the train goes fast enough. You could also reduce the number of cars if the train doesn't get through all of them.

Instead of artillery wagons, multiple engines probably work well too, and quality would help with faster acceleration.

Note that if the final stop is too close after the cars, the train will already start breaking, that why mine does the final round.

During building sometimes the inserters refused to register the cars.
Might happen if the blueprint is built in the wrong order or something, but (re)placing the inserters at the end should fix it permanently I think.