Marine Compound Engine

February 2011.

John R. Bentley 2011.

- Constructing the Fittings (page 1) -
Oil Cups, Drain Cocks, Glands and Pipe Flanges
-  for the Stuart Compound Launch Engine  -

Viewing a part-finished 3/16" stainless steel oil cup under the microscope

Machining some of the fittings at this time gives me a welcome break from the mainstream work. I started with the oil cups, which took me two hours each to complete. This is smaller work, but these diminutive components take as much time as larger size counterparts - they just use less material.

For a change, I chose to use etched stainless steel as the material for the oil cups instead of brass. There is plenty of gunmetal already in this lower area of the engine - the soleplate, bearing caps, eccentric straps, slider bracket and the connecting rods. I hope these silver-coloured cups, along with the crank webs will provide a welcome contrast.

Turning the same oil cup in the Taig lathe using the Lomo stereo microscope

Here is
my view of the same job taken through the microscope

Preparing the end of the rod for threading with a 5BA die

After threading, a 1/16" oil hole is drilled in from the bottom

The work from this end is now complete, leaving it ready for parting off

Parting off from the 3/16" stainless stock

Drilling the oil cup's reservoir in from the top (9/64" diameter)

Test fitting the cup in a bearing cap

Hanging from an iron wire - ready for a one-minute swim in ferric chloride

Here's how the etched cup looks after rinsing off in water

A completed oil cup back in the chuck to polish the top rim

(I just held a piece of 500-grit sandpaper against it while it was spinning)

Two cups in position...the third one is out of the view of the camera

Next: Drain Cocks

Back to

Compound Launch main page


Castings, Materials and Fastenings


Cylinder Block

Top Covers

Bottom Cylinder Covers

Steam Chests

Crosshead Guides and Bracket




Connecting Rods and Crossheads

Main Bearings


                 Fittings: Oil Cups (this page)

Fittings: Drain Cocks

Fittings: Exchange Pipe, Flanges and Glands

Stephenson Link Reversing Gear (5 pages)

Completing and Erecting the Compound Launch Engine


Return to main website home page

(c) John R. Bentley 2011.