Ian,

I have built my variation on the Southworth and run it this season on my steam lorry at 160 psi. A few bits of experience I have gleaned:

• Include a bypass in the pump delivery line. That way you can get it warmed up on "no load". Makes life a lot easier.
• Mine is run on highly superheated steam (300 C+), so relies totally on the mechanical lubrictor. I had to adjust the Ewins element on this up to max delivery and put a fan tail spray on the oil delivery. Initially, the internals were dry after a run (too little oil), and what oil there was all seemed to disappear out of the valve rod gland – hence the need to "spray" the oil in.
• I have included 3 auto drain cocks (1 on a longish feed line, 1 on each end of cylinder). The free ball in a chamber type that are quite popular on smaller loco cylinders. I am not convinced they do much but they do no harm either. Incidentally, they don't really need drain cocks. They will run quite happily on pressurised water, which is what they do to get rid of condensate – they can only do this slowly though. The water will end up in your hot well, not the bilge.
• I always run the pump on air after a steam run, as my cylinder block is cast iron (as were Weir's). This blows out the condensate and gets plenty of oil in.
• Being cast iron, the shuttle valve still has a tendency to stick, so I have put two little plugs on the caps at each end. Remove the plugs, poke in two small screwdrivers and waggle the shuttle about a bit, replace plugs, open to steam and away you go.

The pump will run very evenly on air against no load (just like KA's example). On steam, even when warmed up it takes a few strokes to get into it's stride when you open the steam valve, but once properly warmed through is OK, but never as even as on air. I think this problem is likely to be more marked for you as a boat is unlikely to be running the superheat that I have.

An ex engineer on the Waverley tells me that they can be temperamental in full size. He recommends opening the steam supply valve when you light the fire and just let the pump warm up with the boiler, you will soon know when the pump is running from the "clonk – clonk". I have tried this approach and it certainly has some merit.

My modifications to the design were driven by two thoughts:

• As drawn it is a symphony of leaks conducted by 6BA bolts. It needs to be far more rugged to be a reliable boiler feed on boats (or steam lorries). If you think I am fishing for 6BA bolts in a filthy bilge or roadside verge – think again!
• As drawn it is not a Weir. The Weir was distingushed by the horizontal shuttle that incorporated a piston valve and distinct absence of extra ports and drillings.
• A bronze cylinder, piston and shuttle is not going to take kindly to highly superheated steam.

You can see more detail about the pump on my Flickr pages of the steam lorry build here:

**LINK**

The Weir pump album is 2 row 3rd from left.

Hope that helps, PM me to compare notes if you wish.

Martin

Where's the viaduct, Calstock?