Steam engine (Tiny horizontal double acting, maybe with reverse)

[gbritnell]

Now comes the fun part. I made a layout of my stop points to create the recessed area leaving the drain cock and exhaust port bosses. I then went in with a .094 diameter ball end mill and started stepping the metal away. The cuts were stepped over at .012 until I reached the inside edge of the bosses. From there I started stepping around the bosses until I got to the stop dimension leaving the flange for the heads.

[steamer]

Wow George!   How do you organize a job like that?
Do you have the dimensions laid out on a reference table and you step it off?
Can you show us how you work that magic?
 

Dave

[gbritnell]

I then remounted the stock in the lathe and cut the cylinder free from the bar. I always leave a couple of thousands on the face in case the cutoff operation raises a burr and needs to be cleaned up. This one went smoothly and all that was needed was a little filing to get it to size. The ports were drilled and then I used a sharp hobby knife to clean up the small radii left from drilling. It looks ragged in these pictures but you have to realize the intake port is only .03 high so the photo exaggerates what you see. Likewise for the bore, it will be polished when all the final porting is drilled. A little more work with a polishing stone to remove the tool marks and it will look just like a casting.
gbritnell

[gbritnell]

Hi Dave,
Like I mentioned earlier, I have a drawing program on my computer so I draw the cylinder and develop all my tangent points for a particular sized cutter. In this case it was an .094 ball mill. I marked my dividing head for the radial stop points on each side of the bosses and at the extreme ends around the exhaust ports. It's a lot of work but it sure makes it look more interesting than just a smooth surface like the previous engines.
gbritnell

[steamer]

Thanks George!

I'm going to go for that ....I want to learn to do that.

I think that is a skill I want to learn...even if it's only half as good as you!

 

Dave

[Don1966]

Wow! George you and Jason make it look so easy, and I know it is not as easy as it looks. You really need to write a book on your techniques. That is some awesome bit of work on a small scale. I like! Just keep those photos coming.

Don

[ProdEng]

Very helpful to see how it is done, thanks.  Despite understanding that machining is the relentless application of logic, at times it still appears to be magic

[gbritnell]

With the previous engines being the vertical type the crankshaft is semi hidden inside the column. With this engine the crankshaft is out in the open so it needed a little detailing. To remove the extra stock to make the counterweights I needed a fixture, a small fixture. I took a small block of aluminum, drilled it through .089 diameter, drilled and tapped 2-56 for retaining screws and removed the unwanted material. I then used a .010 slitting saw to cut the retaining caps free. I left a small island of stock to support the crank pin. This would also keep the crank perfectly horizontal for nice square cuts. The pictures are deceiving in that the cutter I'm using to cut the counterweights is only .062 diameter.
gbritnell

[gbritnell]

In the first picture it's hard to tell how small the 2 parts are so I took another shot on a penny to give the relative size. They're small!
gbritnell

[tvoght]

I think this is going to be my favorite of the tiny series. But who's to know what comes next? Thanks, George.

--Tim

[zeeprogrammer]

Gee whiz George. Talk about a nano-engine.
What's the size of the bolts on the control rod?

[Don1966]

Gee! I never realized how small they were looking at the penny. I know this is going to be my favorite tiny.
You are a master George.

Don

[gbritnell]

All the bolts are M1x.25. To scale they could be a little smaller but this size tap is my bottom limit.
gbritnell

[Jo]

In the first picture it's hard to tell how small the 2 parts are so I took another shot on a penny to give the relative size. They're small!

Small  does not really describe it. 

It is just amazing. 1mm is plenty small enough to go with threads.

Jo

[ProdEng]

I love the fixture for machining the crank, sometimes you just have to make some tooling to get a job done.