1. An apparatus for wrapping prestressing steel wire around the outer surface of a concrete tank having a continuous vertical wall including the elements of: a. a plurality of vertical steel bracing beams attached to the upper part of the inside surface of said concrete wall and extending above said wall, said beams having an I beam guide rail attached to the outer faces thereof and positioned essentially parallel to the course of said wall; b. a steel scaffold comprised of frame members, movable along the top of said wall and including 1. steel rollers, attached to a said frame member, movable retained on the flanges of said I beam guide rail, 2. a rubber wheel, vertically mounted on an axle mounting in said scaffold, positioned to roll along the top of said wall and including a motor to drive said wheel and scaffold along the top of said wall, 3. a second wheel mounted horizontally in an axle mounting in said scaffold positioned to roll along the upper outer surface of said wall, and 4. a support platform having a winch thereupon for raising and lowering an apparatus for winding prestressing Wire, under tension, around said walls; and c. an apparatus for winding prestressing wire, under tension, around said wall, said apparatus being supported from said support platform by a cable associated with said winch.

2. a rubber wheel, vertically mounted on an axle mounting in said scaffold, positioned to roll along the top of said wall and including a motor to drive said wheel and scaffold along the top of said wall,

3. a second wheel mounted horizontally in an axle mounting in said scaffold positioned to roll along the upper outer surface of said wall, and

4. a support platform having a winch thereupon for raising and lowering an apparatus for winding prestressing Wire, under tension, around said walls; and c. an apparatus for winding prestressing wire, under tension, around said wall, said apparatus being supported from said support platform by a cable associated with said winch.