Or even «full head of steam,» whichever you prefer. (sbnation.com)
The SNP want the vote to take place in autumn 2014, by which time they think they will have been able to build up a decent head of steam in support of independence. (politics.co.uk)
It's so hard to tell what changes in pricing do if you don't already have a good head of steam going. (indiesunlimited.com)