E.P. Allis 3000hp Quadruple Expansion Corliss Engine, 1893 in 1/12 scale

[Dave Otto]

Nice results!

Dave

[bananarchy]

Flywheel Spoke Machining - End Faces

After a few more pours, I've got fourteen (potentially) good parts and two setup parts ready to go on the mill. A couple will end up having more shrinkage porosity than I thought, so I'll have to cast a couple more, but I'm proceeding with this set for now, since it's going to be a bit before the next pour.

The mating ends of the raw castings are about 1.400" thick, and the objective is to finish the hub end at 1.000" and the rim end at .750", with the cast shaft of the spoke located symmetrically between the machined end faces. To achieve this, each spoke ended up going on the mill table 7 times and the surface grinder 4 times. There was probably a way to reduce that count slightly, but results matter more than efficiency in this case. Both sides of both ends were roughed down leaving .050" per side, and then measurements were taken on the surface plate to see how asymmetrical the shaft was to the rough faces. The shafts are rounded and tapered, so a consistent location was marked from each end, and the measurements in this spot were compared when the part was flipped over. Each part was marked with the necessary adjustments, and material was removed as needed from each end, with shims placed as needed under one end on the second cut to ensure everything is properly parallel. Some parts required no adjustment at all, and the worst was about .035" out. Not bad.

Following centralization, the ends are brought down to the final (mill) dimension, leaving 5 thou per side for grinding. Clamping these on the table was a little tricky - I've got the aluminum bars running across the spoke shafts, but any real force on these bends the shafts and distorts the geometry of the ends, so the main constraint is with toe clamps from the sides. Not my favorite, but nothing moved.

Both sides (and both ends) are then ground to 1.001" for a nice snug fit with the hub (the width of the mating groove ended up a grand or two above nominal). Four parts fit nicely on the 8x18" mag chuck.

[bananarchy]

Flywheel Spokes - End Faces Cont

Now with both ends at 1.0", only four steps left - mill, grind, mill, grind on the rim ends of the spokes to get them to .750". The first side repeats the previous milling setup, with 5 thou left for grinding (to a total thickness of .875"). For the second side, a spacer is required between the spoke end and the table, so an old parallel was sacrificed to the gods of precision and ground to .1255" (the extra half thou is there because the hub ends are actually 1.001"). After one last trip to the mill, the final side is ground in batches of 3. This is the first real job I've done with this grinder and I'm still learning a bit, but having the right wheel definitely makes a big difference (Norton 32A46-IVBE). I was able to hit the thickness +/-.0002" no problem, with most of the parts within .0001". Grinding really helps with getting everything nicely flat and parallel, since there's basically zero distortion due to workholding forces.

Next up, drilling a bunch of holes!

[CI]

The castings look very good.
A few thoughts about risers, runners, gates, sprues, etc.:
I can only speculate; I don't know exactly what would or would not work in your exact situation, so take all this as what if's.

1. I normally use a rectangular gate at the top of the runner, so the runner would be in the drag, and the gate in the cope.
The idea is that when you pour, the runner fills first, and sweeps slag, inclusions, loose sand, entrained air, etc. into the spin trap before the metal completely fills the runner.
Once the runner is full of hot clean metal, then the gate starts filling the mold cavity.
If the runner and gate are at the same level, some trash will get swept into the gate as the initial metal flows past the gate.

2.  You could use a sprue at one side where one of the spin traps is located, and let the runner feed a single spin trap on the opposite end of the runner.
This would allow you to use one spin trap only, and stil get the sweeping/cleaning action.

3. The abrupt 90 degree transition at the bottom of the sprue where it meets the runner will cause a splash back when the sprue is filling, entraining air, slag, etc.
The bottom of the sprue could have a smooth radius transition into the runner to maintain laminar flow.
The spin trap will take care of the initial turbulence and entrained air/sand/slag, but the turbulence during due to a 90 degree bend may break off some sand.

4. Risers are always a bit of an art.
If I were doing it, I would have a 2.5" diameter, 4" tall riser above each end of each spoke, with a neck at the base of the riser into the casting about 1" diameter.
Risers tend to push the crucible size up quite a bit.
Having large sections on either end of a smaller section would be prone to hot tears without risers.

I have seen some use a runner down the center of two long castings, with gates branching off to the mold cavities in two or more places, with the sprue in the center of the length of the runner.
Again, I would put the runner in the drag, and the gates in the cope at the top of the runner.

Your castings are so good that one can only speculate on possible ways that may or may not help to improve them.
Looking great !
Following along.