Oscillator Cylinder Pattern

[vtsteam]

Thanks Jason, what I was planning on doing was chipping out the space to rectangular in both the trunnion standard and the cylinder ports with chisel. I have some small ones, and can grind even smaller to fit. I could also try fitting another hole in -- there is space for it towards the center.

I'm trying to think how the vertical channel from the port face meets the horizontal one from the end of the cylinder. If they are both rectangular (ish) they seem like they would be oriented different ways if there needs to be a narrow entry into the bore.

I'm also a little worried also about breaking thin drills chain drilling holes to meet crosswise holes.

My other design concerns are about the narrowness of the outer circular band leaking badly, and the overall spring pressure needed to keep this engine together at 50 PSI steam being excessive.

But it's a live and learn project.... guess I'll find out.

I do appreciate assistance.

[Jasonb]

I'll put some air of known pressure into a couple of my engines tomorrow and then see if I can measure how much weight is needed to compress the springs to a similar length.

My thought on the passages for the cylinder would be two holes from either end that come down each sided  rge port holes but overlap the holes from the port face

[vtsteam]

Thanks greatly Jason.

More thoughts (random type) while working on this problem:

1.) You could get more throw in an oscillator by reducing the size of the flywheel and bringing it closer to the cylinder. More throw means bigger ports. My present imaginary flywheel is 8" diameter.

2.) You could get more space for bigger ports by widening the port face even further -- in fact all the way out to the flanges. But that would require a different shaped casting. Still that would make a lot of sense. If doing #2, I would also relieve the center area somewhat, and open that to atmosphere to reduce friction and the force of steam pressure where it isn't needed.

3.) You could consider doing a uniflow exhaust, but that would require a longer piston, reducing stroke and displacement. I was imagining a 0.688" long piston in this engine. But I think inlet port size could then be enlarged beyond the restrictions imposed by trying to fit in an exhaust port on the valve face. Is that right?

Just thinking about #3 further, the remaining free length of the bore is presently 2.74" with end caps on. I think that would mean for a double acting uniflow version, that the piston might need to be about 1.23" long vs. the 0.688" I had imagined.

Edit...later... : Yeahbut.... a uniflow exhaust also would reduce the stroke (because of the longer piston) which would mean that the rocking angle is reduced, which reduces the size of the ports again.

The best way to handle this oscillator cylinder (if starting from scratch) would be #2 to make that round port face go all the way out over the end flanges. This would give you max space for the ports. Another benefit -- you wouldn't have to drill from two directions for the L shaped port passages. Just drill straight down through the flange area. Maybe needing a slight angle from vertical.

Even More Later Thoughts:

I could braze some pieces onto the cylinder to extend the port face out over the flanges, if I wanted to try the above. We're getting into Frankenstein mode if I try that....

Continuing to Blather:

Maybe I have enough meat there already for #2 if I turn the present face down far enough to put a flat on the flanges.........

[vtsteam]

If I moved the ports off of the main circle, I could no longer use the channel type manifold. It would have to be external.

[vtsteam]

Jason, I turned the face down flush with the outer flanges, and found I'd gained some diameter on the port circle if I went to the as--cast edge, rather then my earlier machined edge. This allowed me to fit 4 holes in, starting with .125" and gave me a port area of 0.0442" as shown below on left. Older version on right. I think that's going to be the final port plan.

[Jasonb]

I had thought of another option which would have been to add a separate circular disk to the port face to increase it's diameter, plenty of space for some CSK screws and JB Weld to seal. The teardrop shape would be easier to form in a thin plate allowing a big simple passage behind like a 1/4" wide slot

[vtsteam]

I thought about that also Jason, though I could braze it in. But I think maybe I'll just do the best I can as above.

If I were ever to do this again, I'd cast the back of the cylinder rectangular instead of circular, sort of like this:

[vtsteam]

It was down to 5F last night, but was scheduled to reach 35F today, with rain and then cold weather tomorrow. So I took the small weather window today to cast the end covers from the patterns made earlier.

Below are:

1.) Patterns separated from loose pieces, and laid out in an inverted drag, dusted.
2.) Drag filled and rammed, then rolled over.
3.) Loose pieces added back
4.) Sprue and riser positioned, and cope set on top
5.) Cope filled and rammed, then lifted off showing loose pieces stay with it
6.) Gates cut in drag
7.) Patterns pulled leaving mold cavities (minor breakout in left hand cover)
8.) Iron melted and poured. 8-1/2 lbs Iron. Mostly left over sprues, risers, small ingots from disk rotor melts. 14 grams ferrosilicon. Total time from furnace start to pour -- 30 minutes 

[vtsteam]

And here are the castings after breaking out. I took a file to the thin parting line flash on one of the covers, and it filed well, so I'm pretty sure the rest, being much thicker, will be good to machine.

[CI]

Artwork with a purpose.
 

[Sanjay F]

Looking great, I can't wait to see an engine built from the bottom up; the design of the patterns, the casting of the parts followed by the machining and final assembly ...... fantastic! 

[vtsteam]

Thanks CI, Sanjay! 

Major ice storm today here. Just got back from shovel sanding our 600 foot long drive into the woods. But I still did manage to get some time in on the engine. I guess that's the right term by now, since it has more than one part!

Well here are the two cover plate castings turned down get rid of the rough surface. Nothing is finish sized yet. I need to final bore the cylinder yet, and take a touch off of one of the flanges. Then I can finish the two covers to fit, and drill for fasteners.

[vtsteam]

Yesterday, I built a simple 5" dia. rotary table for my drill press. A couple years ago I built much heavier one for my milling machine, but that's located in a completely unheated shed 300 feet away from my somewhat heated tiny workshop nearer the house. This should work well for drilling sets of radial spaced holes in the workshop, though not for milling.

Today I set up a boring table fixture I made awhile back, in order to bore the oscillating engine cylinder. I haven't used it much, so spent awhile to setting up accurately. But I was able to get a pass in at the end of the day. Slow going on my small benchtop lathe with only manual feed, but we'll get there in the end!

[CI]

Nice boring rig !
.

[Jasonb]

Progressing Well but never too late to go with a vertical, this popped up last night and I thought of your cylinder. I think it mast have a form or rocking or rotary valve on the trunion but a nice looking engine.