Category:Steam engines with Dabeg valvegear

English: Dabeg valvegear, a form of cam-actuated poppet valvegear. They used a desmodromic linkage to both open and close the valves, rather than relying on springs, weight or steam pressure. This gave precise timing over valve events, however it could also give rise to high forces against the valve seats owing to thermal expansion with superheated steam, and there being no free movement to absorb this. They also did not have the easy free-running of other gears when coasting, where the valve could fall away from the seat and allow free gas flow.