get up a head of steam

get up a (full) head of steam

 
1. Lit. [for a steam engine] to build steam pressure in order to start operating. It took nearly thirty minutes to get up a full head of steam so that the locomotive could start moving.
2. Fig. to develop sufficient energy, enthusiasm, commitment, or determination to undertake something. It's nearly noon before I can get up a full head of steam and accomplish something.
See also: get, head, of, steam, up