Oscillator Cylinder Pattern

[vtsteam]

Thanks guys! 

CI: I've used both. I don't like to generalize, different methods for different requirements and materials.

For Portland cement bound sand cores (per luckygen1001), of >= 1" dia, and using flexible plastic PVC pipe, a single slit usually works. Some thicker PVC pipe samples I've found don't separate well with a single slit, but can be split and hose clamped. Other samples have worked okay with a single slit, I've found.

For baked sand cores <1" dia I use steel tubing or pipe and splitting and reassembling those with hose clamps is the way to go because I can bake the core in the box that way. Plastic pipe would require transferring the cores to a bed before baking.

Portland bound cores, tend to be too fragile in sizes below 3/4" during a pour in iron, even with wire reinforcement in my experience, so I use baked sand cores for that.

I'll be using Portland bound cores for this one, btw.

Paul R: Thanks -- hope this will be helpful!

Jason:

Fabulous pics! Very appreciative!  I like the side blocks for the valve base a lot. My valve base is a lot closer to the end cheeks, and by the time I fillet both, I think it will probably fill in that area.

I was thinking about possibly making the valve face block a loose piece, pinned in place by the trunnion axle. That way I could remove it and substitute a conventional steam chest block to make a multi-purpose pattern. Sort of a Tinker-Toy approach. Yup to a boss on the other side -- just planned a through dowel. I don't know if I can pull a loose piece off, we'll see. (Hmm, unintentional pun...)

I'll be doing that all today as soon as my wife leaves the house for lunch with a friend. She hates the smell of Bondo, and the shop is too cold to cure that stuff out there. (5F this morning and breezy)

She said it was okay to do while she's gone. 

[Jasonb]

Round valve chests and covers are not unknown so you could just use the one pattern.

[vtsteam]

Jason, wow, what does the valve inside look like?

[crueby]

Just looked up the patent for it - instead of a rectangular valve and straight ports like we are used to, the Church one has a round (disc) valve and the ports are arched as well. The valve can rotate, and was intended to reduce wear on one side or the other. It operates just like a typical rectangular one, sliding back and forth over the ports.

[vtsteam]

Thanks Chris, does it rock around a pivot or does it reciprocate back and forth? If back and forth it must be smaller than the case? So does it have any kind of guide?

[Jasonb]

For ease of making the model just uses straight slots and a rectangular valve.

[crueby]

Thanks Chris, does it rock around a pivot or does it reciprocate back and forth? If back and forth it must be smaller than the case? So does it have any kind of guide?

It goes back and forth just like a rectangular one. The disc is a smaller diameter than the case. Attached is the patent for it - interesting that in its original form the chest was rectangular, they must have optimised it later for a round chest like his picture showed.

[vtsteam]

Interesting stuff Jason and Chris. I think I will probably make a rectangular chest for the time I make a horizontal mill engine. Something I've always wanted to do.

But for now, the oscillating cylinder pattern, flanges successfully Bondoed, and sanded a bit. Aired out the place as best I could with the front door open to the "fresh" breeze for about 5 minutes. Woodstove attempting to counter...

Before the Bondo party, I'd dimpled the spots opposite where I hope to add the valve block and the trunnion boss opposite. I marked these out by laying a strip of paper around the cylinder and slicing across with a knife where they met. This made a strip the exact circumference long. I marked the pattern where the strip ends met, Removing the strip, I measured and marked the halfway point along its length. Then replaced it in its original position, and transferred the halfway mark to the cylinder. This gave me two exactly opposite points.

Next, using dividers I found the half way crosswise dimension between cheeks at each of those points and marked the intersections. That's where I drilled for the pegs.

[vtsteam]

I did a little sanding with some 320 paper -- the scrap spruce 2by stuff I used for this pattern isn't ideal due to easily raised grain, but we'll get it smooth when I hit it with sanding sealer later on.

I added some thin blue packaging tape to serve as a release, and then Bondoed the valve block in place out in the shop, which had reached 50F after a full morning's heater run.

The 1/4" dowel keyed the block in position, but was then removed so it wouldn't lock it down when the filler cured.

[crueby]

When the engine is done the patterns will make a nice display next to it!

[vtsteam]

Thanks Chris! I'll do that for sure -- if it ever is an engine. 

You know, you mentioned the warm weather coming our way this week. If I can get this pattern done in time, and if I can get my greensand thawed and conditioned, and if I can get the furnace going -- been under wraps for a year.....uhhhhh maybe.....
well.... I'm not going to say.

Anyway, got the valve block free, and it shaped up well. Looks like the loose piece idea will work with this one. Happy with that!

Jason, looks like I'll need to add those blocks you were talking about.

[vtsteam]

Hmm, if I do try to cast on Wednesday, that's not enough time to cure a Portland cement core. It's going to have to be baked sand. And for that I need at least a core plate if I'm going to use a PVC waterpipe as corebox.

Might have some metal pipe or tubing the right size to make a dual purpose version, I'll need to check on that tomorrow.

[crueby]

Currently  thursday is looking even warmer but windy here in western  ny state, how bout up your way?

[Jasonb]

If the cylinder walls are thick enough you may just be able to drill vertically down to the ports from either end. Blocks are really there to allow the cylinder wall to be thinner, I think in that photo they were 2mm (0.080") so too thin to drill, at least for that size of engine.

[vtsteam]

Chris, you're right, Thursday does look good! But portland cores need 3 days to cure and dry. I'm shooting for baked sand cores, presently looking for the right size ID metal tubing or pipe. Friday is also warm but rain, followed by a night of 16F. My least favorite winter combo. 

Jason, just checked and the barrel is 2" OD, and the core will be 1-1/4". Of course it depends on what it will need to be bored to if there are flaws, but I had imagined a 1-1/2" bore. So if all went well, maybe .25" thick walls?

But just looking at it now -- blocking that area would make it easier to mold anyway. Very thin section there to no real purpose.