Opposed Piston Engines

[Charles LamontParticipant @charleslamont71117]

The red engine in Jason’s post #812827. This ingenious and remarkably compact arrangement was devised by John Ericsson. An example of the type was used in the famous Monitor.

There are two separate cylinders back to back.

Looking at the top photo, the first clue is if there is a single piston, why on earth would you connect it to the crankshaft twice? Next, the connecting rods are at about 90° to one another. The starboard side is fully in, and the port side at about mid-stroke. If both sides were connected to a single piston the mechanism linkage could not move. In fact, that 90° angle determines the phasing of the two pistons. So (another clue) no flywheel is needed, because there are no dead centres.

A small disadvantage is that a large diameter gland is required to accomodate the rocking link to the bell crank arm. This will cause quite bit of friction and makes the areas on each side of the piston rather unequal.

[JasonBModerator @jasonb]

That would explain the two eccentrics and presumably two valves. It would be quite a nice one to model which is why I have kept the images, I like it’s simplicity a lot more than the Monitor.

Interestingly the Patent model seems to have “normal” size piston rods. It makes use of a crosshead and guide at each end and I assume there is a vertical slot to allow for the up/down movement of the lever as it describes an arc. No valve detail.

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