A question to carry into the reading
Which parts of a reconstruction are directly constrained by surviving evidence, and which remain proposals?
Read the original article with its Author Correction; compare the surviving fragments, reconstructed mechanism and stated uncertainties.
Reading and source
The inspected UCL original PDF retains erroneous Ψ lettering corrected to ϒ by the later notice, which also fixes displayed fractions. Keep both documents together. This is a proposed model, not an intact surviving machine or an independently reproduced archaeological result.