I made a lubricator for my Mamod, it had been fitted with an in cab regulator but that left no provision for proper cylinder lubrication. So I built a simple displacement lubricator out of brass. I am surprised at the difference it has made, the loco is now much more controllable, uses less steam and water so runs for longer.
OK so it is not the prettiest of installations, bending the tube was a nightmare. But it works.
(Edited for speeling)