The Steamboating Forum

Engine on Ebay

Interesting engine on Ebay. I can't quite tell how its meant to work though.

It is a very interesting cross head design, would really like to see it in action.

Seems a lot of bother to keep from making a conventional crosshead, with no real advantage. The quadrants just roll on the ways ( I had to edit this, after rethinking it) The radial rack gear keeps it all together and in time. The two blocks at the apex on the pin are adjusters that keep it all tight. I doubt the engine is very old. The frame appears to be a weldment from hot roll steel.

I would imagine balance would be a real issue with all that mass going up and down.

-Ron

Good evening,

Quite a curious "crosshead", surely not useless but a little bit pointless.

Makes me think about this: http://bit.ly/bc7J0v... [Sorry, this is an IC engine, but it's worth taking a look at.]

Best regards,

Akitene

Dave Dearborn had one of these engines.

The crosshead is a gear segment with a rack on the crosshead guides.
It's very interesting to watch running!


Dave

There is plenty of room in that space for a straight line motion, with no gears. A novel crosshead, and pointless perhaps, but then I think we all like to watch things going up an down, rocking and rolling, especially if steam is making it go.

Looking at this for the umpteenth time and wondering why go to all that trouble. Perhaps the "welded up" frame is a reason. Welded materials like to "move about" as part of the welding process and so retaining good alignment of the crosshead guide might have been beyond the maker's skills? This doesn't really need it. Just a thought

The crosshead will wear much less than a conventional one because it rolls rather than slides

I think Tunneltug's got the aswer : it's to reduce wear .

Normally there isn't much wear on the croshead guides etc provided there is not too much angularity .
In other words if the con-rod is nice and long the sideways pressures will be slight and so will be the wear .
This engine appears to have a VERY short con-rod , presumably to reduce the overall height .

Regards Edward .

The wear has been transferred to the wrist pin. Normally the wrist pin is held by a set screw in the crosshead (eliminating one wear point), then rotates in the eyes of the rod. This must rotate in the eyes of the rod, and the apex of each quadrant. Two extra wear points. Now, comparing the pressure per square inch between the conventional crosshead guide and the surface heeled on the wrist pin from each quadrant on this engine, the conventional crosshead guide wins, as I see it.

-Ron