and a radial 60 of the generally cylindrical body 12 the self expanding take up device 10 is shown at its maximum useful expansion 62 at this extent of expansion the moveable body 14 of the take up device has rotated through an angular increment of 180 degrees and extended axially within the sleeve 18 the two bodies 12 and 14 remain engaged along 180 degrees of their ramp surfaces as indicated by the shaded area 61 of the ramp surface shown in fig3 fig4 illustrates an extreme expansion 64 of the take up device 10 in which the moveable body 14 has rotated through an arc of 270 degrees the two bodies 12 and 14 are in contact along only 90 degrees of the ramp surface as indicated by the shaded area shown in fig5 while this may be useful in some applications it is preferred to limit the use of the single ramp design shown in fig1 5 to installations which will not require axial displacements greater than that shown in fig2 and 3 because there is a potential instability of the take up device 10 when the engagement surface of the bodies 12 and 14 is less than about 180 degrees fig6 10 illustrate the preferred embodiment of the expandable take up device 70 which has a.