Part 4 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. A double sized version can be found here. Drawings can be downloaded for personal use only.

This one is built to Julius’ metric drawings.

Hacksawed a piece of 12mm thick BMS for the crank.  Milled it to size and drilled and reamed two 6mm holes.

I then milled of some of the waste material.
I machined the required shafts to length and bought material for the inner flywheel (item 30) which is also part of the crankshaft.
The plans call for this item to have a diameter of 80mm and 15mm thick.  Instead of BMS I am going to use 316 stainless to avoid rust.  The slice I have is 100mm diameter.  I intend to make the flywheel larger to give it more mass. Started facing one side in the 4 jaw chuck.
Flipped it around in the 4-jaw chuck to face it and remove the excess material.  In fact, I had to remove about 5mm to get to the required thickness of 15mm.  I used carbide inserts for this operation.  For the roughing out stage I used some chipped inserts that I had kept and then changed to a new one for the last 0.5mm.  Before I took it out of the chuck I marked the centre of the flywheel.
Off to the mill, where I drilled and reamed the centre hole 8mm.
Offset the table by 26mm for the crank pin and stepped drilled 14mm and then using a 15mm slot drill opened it out to 15mm.
I made the Flywheel insert (item 31) from stainless.
This goes into the the 15mm hole of the flywheel.  I made this for a slip fit.

Finished off the shafts to create a shoulder for the press fit.  And these are all the pieces of the crankshaft.

Next I pushed in the various shafts.  Finished off the edge of the flywheel with a Dremel grinder.
I ended up with a flywheel of 99mm.  A family shot of the crankshaft/flywheel.
The plan was to spend a whole day fitting the crankshaft to the frame to get the crankshaft running smoothly.

So you can imagine my surprise when the crankshaft ran perfectly when installed for the first time.  In fact, I did not believe it and thought I was doing something wrong.  So I removed it and had a coffee to wake up.  Thirty minutes later I was back at it.  Re-installed it again and it turned smoothly again with no stiff spots anywhere.  Guess it was beginners luck giving me a hand.

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