Hello all;
Today, a little finish up work on two of the shafts made last time, and on to bigger things.
Two of the smallish shafts are supposed to have a tiny hole drilled at one end for hairpin cotter keys.
They are to hold on the free running rod that goes from the crankshaft to one of the displacer arms.
That's what the print wants, and what are shown in the assembly drawing, but I really don't think they
look so good. Instead, I'll use E clips.
I have some in 1.9mm size, which works out to about .075". They will go just fine on a 1/8" shaft.
The clips are .020" thick, so I ground up a grooving tool .022" wide.
Then grooved one end of each of the two little shafts.
Here they are with their clips. Much cleaner than having a pin sticking out of the end of the shafts, IMO.
Someone might like to note the blue M&M...
Before I go on, I got an order in from PMR today. I don't remember using their flywheels in the past,
except one that came with a casting kit long ago. I ordered up two pairs a few days ago to see if they
looked like they would go well with this engine. The top pair are 3.5" dia. part no. FWC-S4, and the
bottom set are 3" dia, part no. FWC-S13.
They're both quite nice. The larger pair look to be injection molded, as the parting lines are quite fine.
These run only $6 apiece. Very reasonable. They're aluminum.
Now, on to something fun. (Lathe work is still fun, for me.)
This piece will be the shell of the displacer can. It's drilled to depth, then bored for the proper ID and
a nice flat bottom hole.
The piece needs to be very light, like the weight of a baby's breath. To get it light, the walls are very
thin at only .012". The piece is also fairly long, at 1.375", and if I were to try to cut the wall thickness
along it's full length, it would most likely collapse out on the open end.
The pic above shows how it was done, using the un-cut thick walls as their own work holding device.
By cutting down to the thinnest thickness in short runs of about .3", the piece can support itself. Once
one section is cut down, it's not messed with further.
The infeed on the cross slide dial is noted, and each time another section is cut, the final pass is set at
that mark.
This goes on until the whole thing is cut down to the .012" wall thickness for the 1.375" length.
With the thing done, it's parted off. I cut the last bit by hand with a jewelers saw so the piece wouldn't
be damaged as it came off the parent stock.
The next piece is the cap that goes into the displacer can shell just completed. This cap incorporates
the mounting for the displacer rod, too. All the operations on this piece are done in one setup to make
sure the different diameters and reamed hole run on the same centerline.
In the shot above, I've put the displacer rod in the reamed bore in the end of the piece so I can check
it with a DI. It can't have any appreciable runout.
Once I'm happy with the runout, the piece is parted off.
And that's another day's work for me. Not much, but I'm happy with the parts.
Here is the complete displacer can/cap/rod assembly. The cap is a very snug push fit, and has been
sealed with Loctite. Same for the rod. When the Loctite is cured, the piston is checked for leaks. It
needs to be air tight. If it's not, air will come out of it when the engine gets warm, and that's not
wanted in an engine that is supposed to run as a closed system.
To check it, I put some water in the kettle and got it to about 200F. Then poured the water in a bowl
and submersed the assembly. The hot water will heat the air inside the can, and if there were leaks,
there would be bubbles. No bubbles, here.
Here's the progress shot.
Thanks for checking in, folks.
Dean
