Martin Evans oil pump design

While looking for a mechanical lubricator design for my steamboat engine, I came across this by Martin Evans in ME3164. It seems to have the merit of simplicity but I am perplexed by the purpose of the gland on the ram. Any oil that leaks past the end of the ram will find its way out first through the four radial holes that are the ‘way in’ for the oil. Since the pressure at that point will be atmospheric, there will never be any pressure drop across the gland so it serves no purpose. It seems the design is entirely reliant on a very close fit between the ram and its bore at that bottom end. Any thoughts or experience?

I suppose it ensures that it will draw in oil from the four holes on the upstroke rather than have any air from the top of the tank drawn down through any gaps around the ram

It seems to be designed to be inefficient... if the ball seats properly and the ram is a good fit it will never lift at all. It can only work if the ram is a sloppy fit... hence the need for the gland as Jason describes.

Neil

I agree with you Andrew. The gland seems to serve no purpose. In fact the version of this pump shown in Martin Evans' book has the gland omitted.

Having said that, the great LBSC drew up pumps that included the gland.

They are no meant to be very efficient pumps, just delivering a small drop every thirty or forty revolutions of the wheels, so it probably doesn't matter one way or another.

Russell.

An old colleague of mine told me that the gland was to prevent air being admitted when the level got too low in the tank, but after having built a couple without the gland the steam oil provides a good enough seal.