Marine Compound Engine

March 2010.

John R. Bentley 2010.

Machining the
Disc Flywheel
-  for the Stuart Compound Launch Engine  -

(Part 3 of the crankshaft assembly page)

I followed the drawings as to diameter, thickness and the recesses

There is quite a bit of metal removal required and...oh, that stuff is dirty!

Grind up pencil lead all day then wallow around in it - same idea as working cast iron - I love it!

Boring the hole to exact size

The recesses are deep and a different size on each side

Flipped around in the 4-jaw chuck to turn the rest of the rim

Drilling for the grub screw

Bringing the wheel to final size while mounted on the crankshaft

When using a single grub screw or a keyed attachment to attach a cast iron wheel less than two inches in diameter to a small shaft, I know of no other easy way to get such a small wheel to turn perfectly. This is not a delicate gear wheel in a ladies' wrist watch - this flywheel may be used to transmit considerable power to a prop shaft and will require tightening the screw accordingly. There is a fairly good chance that this will lead to some eccentricity of the wheel which can be removed by turning the wheel surfaces down slightly in situ.

Another option is to make the fit extremely tight on the shaft - using an oversize shaft and/or an undersize hole. That sounds like using an undersize reamer then heating the wheel on and making it almost permanant. If anyone is going that far they might as well just turn the crankshaft, wheel and eccentrics from one solid bar and be done with it!

I may turn a shallow recessed area on the inner edge of the rim
to allow the paint to stop against a hard line.

If you have to know, it's gloss black enamel and green chalkboard paint mixed about fifty-fifty. The picture at the top of this page shows the color more accurately (at least on my monitor). It is a moot point because in the end I painted the engine Oxford blue.

That's all for now on the wheel, I may revisit it later.

Compound Launch main page


Castings, Materials and Fastenings


Cylinder Block

Top Cylinder Covers

Lower Cylinder Covers

Steam Chests

Crosshead Guides and Bracket



                 Flywheel (this page)

Connecting Rods and Crossheads

Main Bearings


Fittings: Oil Cups

Fittings: Drain Cocks

Fittings: Exchange Pipe, Flanges and Glands

Stephenson Link Reversing Gear (5 pages)

Completing and Erecting the Compound Launch Engine


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(c) John R. Bentley 2010.