Office of Steam Forum for Model & Toy Steam Gas & Hot Air Engines

I had some fun today making these fiddly little fellows - oil cups. I ground a 45 degree chamfer tool which made short work of these. Not much to them really, although drilling the little through hole takes some care. Otherwise pretty simple - but being so small I am rather pleased with the result.





The inside finish isn't the best - maybe the drill wasn't in the best shape.





Still not too shabby and they look the part well enough.



Not many parts left now. I need to form up the eccentric connecting rod, then it's time for the flywheel, then assembly and test.

time for the flywheel. I spent a good half hour first filing off some of the sharp parting lines on the spokes and rim ID, and just generally smoothing it out and cleaning it up. My chosen approach for machining sequence  was to mount it on a faceplate, but stood off from the faceplate on some aluminum spacers - 3 of them - around the rim. I set that all up on the bench, and measured the clearance between the backside of the hub and the faceplate, and machined an aluminum support block to fit snugly in there, so as to not spring the hub when making the bore. As you can see, the spokes are quite spindly.

During set up I also measured the flywheel and the gap behind the rim in multiple places, to make sure the casting was sitting fairly parallel to the faceplate. Although there is plenty of stock I don't want it mounted at an angle, resulting in a thin rim in places or something weird. Then I transferred the set up to the lathe, where I tried to center the ID of the rim and the OD of the hub by eye, using a pointer.





The idea is to try and keep cast features concentric so that things don't look completely out of whack when operating. In the end, it turns out that the opposite sides of the casting were mis matched, and there was a flat spot on the rim, so I could only do so much to keep the as cast features running true - but I at least balanced it as best as I could.

Then I took my time to make sure that I could actually get tools in where they needed to go.



I wasn't planning to turn the OD of the hub - but made sure I had the option available.



Setting up to make sure I could run the tool completely off the rim:



It all worked like a charm, and went without drama. I ran the lathe in back gear at 50 rpm, so as not to risk my set up, but it was completely solid. No singing, ringing or squealing from the part during machining - it went very well indeed.

I did find a couple of casting voids in the rim. I elected not to remove them all the way.



The bore was made by drilling with 4 different sizes of drill to remove most of the material. Then I changed over to a boring tool to take out about 25 thou. My thinking here is that this gives a better chance of making the hole concentric and parallel to the axis of the rim - a drill might have wandered a bit. When there was only 0.008" left to go, I changed over to a chucking reamer to finish the hole.



Checking the bore along the way with gauge pins. Exceptionally versatile tools - I am so glad I purchased a set.



Final check after reaming - a 375 minus pin slips in, a 376 does not. Perfect!



I did not take pictures of the second side - but all that happened there was in essence the same as the first side, the only difference being that I clamped the machined surface of the rim directly to the face plate, and then trued the part up by clocking on the machined outer diameter of the rim.

Once that was complete I transferred to the mill for the locking screw feature - which is a tapped hole through the hub at 15°. For that I set up and angle plate at 15°, which was established using an angle slip gauge to the milling table.

Here I have the flywheel clamped to the angle plate at the hub. Set up is not yet complete, but I ran out of energy somewhat, and besides it's time to get supper going.



So tomorrow I hope to finish clamping the flywheel, then get the upright spoke as close to upright as possible. Then I'll find the center of the wheel, mill a flat in the hub, and drill and tap the screw hole. And that will be that.