Dr. Watson's Mechanical Arm

Steampunk Arm by Morrigun

Although Dr. Watson is normally depicted as having a bad leg, in the original story of Sherlock Holmes - "A Study in Scarlet" - he had a bad arm, which was injured in a military battle in Afghanistan. For Steampunk Holmes it's a lot more fun to keep the injury in his arm so that he can have this super cool mechanical arm.

The question I have is how is it powered? I don't like the idea that it's powered by steam because maintaining a miniature boiler on your arm and feeding it coal sounds pretty impractical. Instead, I've decided to borrow from the clockwork (aka clockpunk) genera and make it powered by a wind-up spring. The spring will self wind (like a self winding watch) from normal movement but if the arm is put to intense use there is a hand crank that can be deployed to wind up the spring that powers the arm. I also like the idea that the arm has different attachments including, of course, a huge gun.