By 1741 John Harrison had commenced H.3, working to entirely new design to begin with, in his quest for perfectly uniform running. It was a slow process and in the end H.3 was fairly similar to H.2 anyway. It was slightly shorter and lighter, and had circular balances in place of dumb-bell shapes. A bi-metallic curb (which allowed for variations in temperature) replaced the gridirons. But H.3 had the serious drawback of being impossible to adjust without dismantling and re-assembling which were long procedures (Quill, 1966:65).
