The Steamboating Forum

Final rod

Flywheel

And a quick mock-up to get a visual of how a twin could look.

Still much left to do on this engine, expecially the frame.

And an early 2D drawing of a twin marine to use the same cylinder and 3" bore.

And the boat that I dream of building some day.

I would build the engine more like a marine version of this engine, without the ugly flywheel.

Thats about all the boat-type stuff I got.

Oh, I forgot, maybe a porcpine boiler like this, or a water tube type with three drums as shown in the engraving.

Hi PatJ,

How have you got on machining the steam ports in the valve chest? Getting a long enough cutter, to get that deep without flexing, must have been a problem. It's usually easier to have a removable valve chest.

Mike-

I have tried to adhere to the original construction/assembly techniques of the 1800's in all respects, so having a separate steam chest is out of the question.

So then that leaves the task of figuring out how to mill the ports in the valve seat.

I would plan on the cores for the ports protruding through the valve seat, and would use undersized port cores in order to make a hole slightly smaller than the ports.
Then I would mill to final size using light cuts.

The valve seat is not too far down in the steam chest, and so one of the larger bits should easily mill that.
The good part about the valve seat is that it will wear in, so I am not too worried about a super precision valve/valve seat interface, and I can scrape the valve seat if necessary.

For ports this large, and with a cast-in port opening, and using gray cast iron, I am pretty sure I can mill the ports with a long bit and light cuts, but if I just can't get the reach, then I would scribe lines and use a dremel to final size the ports.

Before I got into castings, I use to try and mill 0.125" ports through solid brass plate, and that always resulted in bit failures. Brass seems to be very bad about snagging a bit, so I try to avoid it, and use gray cast iron when I can.