Thanks all for your contributions.
daveboling wrote: you could develop a formula to work out the bits you don't know.
Yes but what is that formula and could it be used if you wanted to change just one of the dimensions .
Take the example given by Andy Skiff 12.83 x 1.4 slip, 90mm block 24mm tube. Say you wanted increase the inside curvature by decreasing the diameter of the block but keeping the same slip measurements ,what would be the diameter of the tube.
For the formula to work you should be able to substitute and one of the dimensions and arrive at four valid working measurements.
RORY
I'm Spartacus .