Hi Pamela,
Sorry, I have not been online for a few days. Most of the knowledge I have on the Tipler Cylinder is from the book "Time Travel" by Brennan.
Unfortunately, that book is currently loaned to my sister so I will have to wing any explanation I give here. Nevertheless, to the best of my memmory the Tipler Cylinder requires a large accumulation of mass rotating at the speed mentioned in the previous entry. The result of this spinning mass would be a distortion in the space time continuim expanding in rings outward from the core. The first ring would destroy anything that enters it because of the high gravity. the next ring would enable someone to travel into the future. Then there is a third ring which is a null zone and then there is a fourth ring which would allow travel back into the past. If I remember correctly then this is a description of the cylinder. The main problem with the cylinder is the fact that the mass and gravity neccesary to create it would be equivalent to around a hundred white dwarves. Of course, in theory, if such a thing were to exist then it would break through the space time continuum, meaning that it would have always existed. (Theoretically.)
That is what I remember right off the top of my head. I am not sure that all the details are correct but I think that the general outline is accurate.
I hope that is what your looking for.
Eagle