This infernal train set!!!

This comes down to the living room every time the grandkids arrive, and I am bullied into building it up.
Its not easy for me as kneeling down for any length of time causes my blood pressure to go haywire.
Every time I finish the construction of this major engineering operation, they all disappear.
Is some sort of penance or does Granny put them up to it.
We will never know, but all is not lost, I have dismantled it and hidden it.
He He He.