Part 11 by Vince Cutajar

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. Drawings can be downloaded for personal use only.

This one is built to Julius’ metric drawings.

The valve chest material was milled to size and the mounting holes drilled.  As the thickness of the material is 25mm and just to make sure that the drill does not wander, the drilling operation was first done from one side roughly half way through and then drilled from the other side.  I guess it was extra work but at least all the holes are exactly where I want them.

Then the faces were skimmed.

The face which will eventually be the valve chest cover was milled to give the middle a raised portion mostly for decorative reasons.
And finally the valve chest and the cover were sawed away from each other.

The thickness of the valve chest and the cover were milled to size.

I milled the pockets in the steam chests.  First it was chain drilled to remove some excess material.
Then using a long 6mm endmill the pocket was milled to size.
And the finished product. It took longer to think how to do it than actually doing it.
The steam valve chest mounting holes on the cylinders were drilled and tapped 3mm.  For this operation I marked the position of the first hole and then used co-ordinate drilling using the DRO.  Still, not trusting myself, I used the valve chest as a template and using a homemade transfer punch from an old 3mm drill, lightly marked the positions for the holes to check for gross errors.
Using 3mm threaded rod I made some studs for the valve chest.  That finishes all the work on the cylinders.
Finished the steam chest outriggers.  All holes drilled in the proper positions to match the steam chest and the front part rounded off.
Milled the bottom.  Started off with a 12mm endmill but I guess it was a bit blunt as the finish was not so great.  Then I remembered I had a 12mm ball nose mill so used that to do the side milling.
Cut the slot with a carbide 3mm slot drill.  Took it slowly with 0.5mm depth of cut for each pass and 2000 RPM which is the maximum for my X3.
And the finished products. They ring like a tuning fork.

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 -

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