A thimble assembly for a cyclone separator comprising a plurality of mounting brackets separately mountable on a shelf of the separator along the perimeter of an exhaust opening, a plurality of segments vertically successively suspended from the brackets, the segments of an upper row being joined to the brackets, the segments of each successive lower row being joined to the segments of a row immediately above, each bracket exclusively serving a chord of an arc concentric with the preferably circular opening that is substantially the same in length as the chord of an arc that a segment spans, a center-to-center chordal spacing of adjacent brackets being the same as a center-to-center distance of an adjacent pair of segments.