Thank you for the replies.

From the above: Eccentric Sheave to be in cast iron then. (Unless cast gunmetal is significantly better in this usage with black steel eccentric straps).

As regards eccentric straps and thus bearing surface of black mild steel:

Unfortunately the (original) eccentric strap design is very thin, an intricate shape, and highly visible. It was also left as polished steel in the original. My choice of black steel was dictated because of the difficulty in cutting this item out of bright steel as the stresses were removed and deformation resulted.. The thin eccentric strap means that there is not enough room for a bearing surface to be fitted on the inside wearing surface and for structural strength to be retained. A cast gunmetal eccentric strap would need joining to the eccentric rod with a bit of deft silver-soldering, and then tinning to look like steel – but could be achieved. Tho' I wonder whether the additional work would result in such a significantly better wearing surface and thus end result mechanically as to be worth-while.

Your reservations over the black steel as a bearing surface mean that an alternative that I might be able to sort out would be both eccentric sheave and eccentric strap in cast-iron.  Probably the best solution.

Thanks again for the 'food for thought',

Phil

Edited By Weary on 28/11/2016 13:46:39