Next step I'll bore the bearings.
I want to make sure the bearings are bored true, so I'll do them in place on the engine base.
The base is packed up on the lathe cross slide so the center line of the crank shaft holes in
the bearings are in line with the lathe spindle.
The hole position has been laid out on one of the bearing blocks, and center punched.
Then a prick punch is put in a collet in the lathe and the assembly is then packed up so
the prick punch goes into the punch mark. At this point, the screws that hold the base
haven't been tightened. Just snugged a little.
When I'm sure the piece is the right height it is squared to a face plate. Then the hold
down screws are tightened good 'n tight.
After adjusting the piece back and forth with the cross slide dial to make sure the
prick punch is dead center, the bearing block is spot drilled and checked for position.
If you drill a small center spot like this, you can pretty well see if you got the right
spot by eye. Your eye will naturally want to center up the "X" layout lines and the
spot. If it looks like it's off, it probably is. (If it were off, I could turn the
bearing block around and start over.) Thing is, you can pretty well tell when the
prick punch goes into the bottom of the punch mark when you are setting up, so it's a
fairly reliable method when working to layout lines. If you make your layout lines deep
enough, you don't even need to punch things like this. As long as the point on the
prick punch is sharp, you can actually feel it as it drops into one line, then the other.
With everything square, centered, and otherwise copacetic, the bearing blocks are drilled
right through, first with a small bit, then one just under the final bore, and then
reamed as in the picture above. This will make a nice straight bore for the crankshaft.
You can achieve an even better bore by align boring (some folks call it line boring),
but for this engine, reaming will do very well, especially in brass.
Now the crankshaft is tried to see if it's a good running fit, and to check for any
problems. The crankshaft hasn't yet been soldered, and I'm checking this first so if
there is a problem after soldering it up, I'll know it isn't the bearings that are causing
the trouble. Saves time if I have to trouble shoot things later.
Crankshaft soldering;
This is the result of the first soldering step. The large rings of solder that can
be seen on the top left surface and the bottom right one are what came through the joint
when soldering from the other side. Looks like the solder flowed fine. In the shot
above, the piece has been turned over and is ready for the second go-round, and you can
see that the second two bevels, (top right one and bottom left), haven't yet been done.
I didn't use hard solder for this fit up. The brand used here is Harris Stay Brite,
and though the container it came in says it's silver solder, it's not the type that can be
used for high pressure boilers. It says it contains no lead or cadmium, so I would guess
it's mostly zinc with a dab of silver put in to make it flow. Works fine for small fit ups
that aren't going into high stress places. Probably not what you want for soldering up a
crank for an I.C. engine, but for parts on small steamers that are not actually under steam
pressure, (i.e. boilers & fittings), it works well.
Harris also sells a good "real" silver solder in the USA. Google them if you need the good
45% silver stuff.
When the crank has cooled down, and after taking a toothbrush to it in some hot soapy water,
it's chucked up again and a live center put in the center hole in the end of the shaft. Then
the outside faces of the crank throw are cleaned up, along with the excess rings of solder
left from the soldering process. Same is done for the other side.
Last thing in the lathe is to make the radius on the crank throw off set. Forgot to take a
picture of that, but it just involved taking light cuts with the lathe turning fairly slow so
it didn't take the tip off the tool from the interrupted cut.
Then the crank is put into the milling machine and the center is cut out of the larger shaft.
This is the time to think twice and cut once, for sure! I vaguely remember cutting the
wrong shaft out from between the throws in the past. It was just as easy as cutting the
correct one...
So there it is. Close to being done. Obviously needs a little finish work, and there
are a few places on the crank pin that solder has built up that will have to be removed.
Progress so far, with a hint of a little more done in the back ground. That's for
another post.
Dean