Illustrating an Old Mystery

About two years ago, a mystery was solved for me by Colin Evans regarding the inclusion of a piece of wire in the barrels of Sentinel 7109's mechanical lubricator pumps.

On 22nd September 2013, I visited the Kew Bridge Steam Museum in London. On one of the big diesel engines, with a mechanical lubricator similar to 7109's, was an excellent example of what I'd been trying to describe two years ago - an oil droplet travelling up the wire.

Have a look at the third tube from the left:

Oil droplet on the wire in the third tube from left

So this simple idea clearly seems to work!