Technical innovation continued. Unlike railway locomotives where equipment is mounted on a frame, traction engines use the boiler as the frame. This cuts down on weight but introduces stresses and holes for the rivets which could be a source of leaks or failures. In 1870 Aveling introduced horn plates which were extensions of the outer firebox and which carried all the motion, cranks and gearing. Preston regards this as one of Aveling's most important inventions. Also in 1870 he took out a patent on a simplified reversing gear. Eight years later he managed to move the gears between the bearings, not overhanging. The resultant motion was stronger and narrower allowing a more compact engine.