The proper term is stress? Since there is also compression. My 3yo son usually ends up with really "tense" tracks if he manages to build a circle. The lever to

The proper term is stress? Since there is also compression. My 3yo son usually ends up with really "tense" tracks if he manages to build a circle. The lever torque of the track length makes them bend a tiny bit, so there should be tension in the outer rail. The fittings are quite close fits.