The USS Monitor was an ‘ironclad’ steam ship which famously saw service in the Civil War in the early 1860s. The ship's engine was designed by John Ericsson as a "vibrating side-lever engine." He had created similar engines before and decided to use the design again because of its advantage for a small, low-riding warship.

Most steam engines of the time had vertical pistons, which occupied a lot of space and made them vulnerable to enemy fire because they were partially above the waterline. In contrast, the Monitor's 30-ton, 400 horsepower engine had pistons that moved horizontally, which reduced the height of the engine and allowed it to be mounted below the waterline.

Although a successful fighting ship the Monitor was not stable in rough seas due to its formidable rotating turret and sank in the early hours of January 1, 1863.

The engine was recovered from the Monitor's wreck site in 2001. It is now resting upside-down in an alkaline solution to inhibit corrosion. Over the coming years, conservators will continue to clean and separate the many different pieces of the engine to preserve them properly.

The first model Monitor was shown at Harrogate in 2014 by Brian Stephenson to the design of Bob Middleton. It was built without castings, like Bob’s other designs. Julius de Waal has produced these CAD drawings for both metric and imperial (see here) versions. A double sized version can be found here. Drawings can be downloaded for personal use only.

This one is built to Julius’ metric drawings.

Next was the crankshaft main bearings (item 12) and the crankshaft main bearing locking rings (item 13).  Fortunately, I had a piece of phosphor bronze of the right length.  Can't remember why I had it.

First made the bearing blanks and another blank for the locking rings.

Finished off the locking rings first by drilling and boring to fit the bearing blanks.

This material is a real pig to drill.

After finishing the rings I replaced the 3 jaw chuck with a collet holder and drilled 9.8mm and then reamed 10mm.

Finally, the moment of truth.  Will the bores of the bearings align with each other?  Used a 10mm ground shaft from an old printer to check.  Managed to line them up but it was very stiff to turn.  Eventually, I managed to make the shaft turn freely with lots of playing around with the frames.

Items 7 and 9.  These are the front and rear rocker shaft bearing pillar bases.  I decided to do them in aluminium.  I needed an aluminium bar with a cross-section of 32 X 45mm.  Closest I could find was 50 X 50mm.  So with a combination of end mills, slitting saw and fly cutter I got it to the required dimension.

Drilled all the 3mm mounting holes at the bottom.

I decided to attempt doing them as a matched pair, so with a slitting saw cut it off.

This is what remained of the original bar.  Managed to save some pieces, so the excess did not all become swarf.

Continued on the front and rear pillars. Drilled and bored the 18mm hole for the bearing.

I then marked both pillars.  I found that there are a couple of dimensions missing on the metric plans.  They are not critical, so I used a best guess for them.  Removed some of the excess material with a hacksaw and started milling.

First one milled out.

Both sets of pillars were milled out.  Next operation was to separate them.  I only left 4mm between the front and rear pillar and I did not trust myself with the hacksaw, so the slitting saw was brought out again.

Next, some corners needed rounding off and was going to do it with a file, but then remembered I had a radius cutting tool which I haven't used in a long time.  So this was put to work.

Finished the pillars and did the brass bushes (items 8 & 10) for them.

Decided not to split the bearing housings. Using the carbide tip of the height gauge I engraved a line around the rear pillar to give the impression that it is split.  Not very visible in the photo.

The rocker shafts turn nicely between the pillars. I am using a 12mm shaft instead of 13mm as depicted on the plans.  The shaft is a bit tatty and will be replaced.

Part one here  Part two Part three  Part four Part five Part six Part seven Part eight Part nine Part 10 Part 11 Part 12 Part 13 Part 14 Part 15 Part 16 Part 17