And the last major piece is now finished, the connecting rod.
I wanted to have a rod that was functionally simple, but looked like it had “marine style” bearing ends, with oil cups, gabs and keys. Turned into more work than I expected, I should have just split the bearings. If these ever wear out, I'll probably do just that. But, I do like how it looks.
First, I made the rod shaft out of a hunk of 1/2” square steel. I mounted an over-length piece between centers and tapered the round portion. I drilled/reamed two holes for the bearings. Then I milled the ends to size. When the end was milled to the proper height, the excess length (beyond the center point of the bearing holes) just fell off. This left a nice "half-round indentation" on each end. Then I milled to width.
The bearings are simple turnings, drilled and reamed to size.
The end caps were made from an over-length piece of stock. I drilled two holes a good distance apart, the length of both caps, plus about 1/2" allowance. I mounted an arbor in the lathe and manually rotated the piece 180 degrees to cut the ends round (that’s a lot of work…
) Back to the milling machine, and removed all the material between the two holes. Cut the piece in half, and mill each half to length
I then cheated, and assembled the ends using 5 minute epoxy. More on why in a sec…
The reason I glued things together is to do two things.
1) drill/tap holes thru the end caps and also the bearings for the oil cups. The oil cups are simple turnings. Not much to say there.
2) mill a 1/16” wide by 3/16” long slot in each end for the gibs/keys.
Seemed much easier to do this with the pieces all together solidly. Although milling a 1/16” slot thru a 1/2” thick piece of steel was an exercise in patience and light cuts. First, I drilled three holes with a .055” drill. I then took a “short” 1/16” end mill (cutting surface about 1/8” long) and milled out the slot until I couldn’t go any deeper, using .015” deep cuts and slow feed. I then switched to a longer end mill (about 5/16” long) and milled as deep as I could again. I then flipped the piece and repeated the milling process from the “bottom” until the slot was cut thru. Repeat on the other side.
Next up, gibs and keys out of 1/16” thick stock. These took deceptively long to make. I got the dimensions from the plans for the beam engine “Mary” (from Reeves), and adjusted them as needed for my size connecting rod. 5 degree taper.
And here’s a close up of one end. (still need to clean some of the red dykem off the key there
And the entire rod…
Now, just to make a few studs and do a little work on the display base, and I’ll be able to start assembly. Unless things go seriously wrong, it should be assembled and running (but not finished) for the NEMES show in a few weeks.