From 1959 BR introduced the final 941 Grampus wagons as vacuum braked with a clasp brake arrangement. Most of them received a form of roller bearing - Hybox - perhaps used as being more resilient to ballast dust than conventional roller bearings. A drawing is in Bartlett, Paul W. & Mann, Trevor., (l985a) Non Hoppered Steel Ballast Wagons. part 3 The Grampus. Model Railway Constructor vol. 52 (part 610) pp 140 - 143 & 164 - 165.
