Dual Rocking Engine

[Jeremy_BP]

Hi all,
My first engine build was a rocking engine. I'm not sure what it was about that thing, but the "blow over" piston really captivated me. I wanted more, and building another wouldn't satisfy that need. So I decided to build a dual rocking engine. And as though that wouldn't be enough of a challenge for a novice like me, I decided to make it at half scale. Fun, fun, fun!

Today I got a start on the main body and cylinders.

My plan was simple. Start with this block of aluminum and mill away anything that didn't look like an engine.

So I took it over to the mill for sizing. So far so good, all within ±0.0005"....

And then started to cut out the cylinder recesses.

Both of them cut out. Now I just need a slot for the flywheel to fit into...

Yeah, yeah, I know I need to clean up the finish on the inside of the slot.
I messed up a bit here, I accidentally moved an axis too far and cut that little step you can see on one of the walls. As such, that wall is now 0.0026" too thin. Fortunately, the wall thickness isn't very critical. Phew.

I then realized that I needed to go eat dinner. To be continued....

 

[Jeremy_BP]

Hello all,
I got some more time in the shop today. So Here's what I got done.

I drilled the air passage and then counter-drilled for an air fitting. I then drilled the air passages for the cylinders.

I can't remember where I read this trick (maybe here). By holding a laser up to the main air passage you can easily tell if your other passages intersect properly. Very handy.

I then began to drill out the cylinders.

After reaming out both. Two good cylinders. I couldn't fit my calipers in to measure depth while making these, so I just marked the depth on a piece of piano wire and measured that.

Now I just have to drill bearing holes and then I can get over to the lathe for the round bits.

 

[cfellows]

Movin' right along there, Jeremy. I'm kind of anxious to see how this turns out. I'm guessing it really ought to sing!

Chuck

 

[Jeremy_BP]

I really hope it works. :-\
The smaller they are, tthe faster they go!

 

[Jeremy_BP]

I was gone all last week, and so I couldn't get to work on this at all. But here's a fail.

I was making this bitty piston, and left a tad too much hanging out of the chuck. It seems that with diameters like this in brass, anything hanging out of the chuck is too much. Hrm.
When I began to remove the stub left over from parting, the shaft promptly bent. Oh well. Now I have to make two more.

 

[crab]

Hi Jeremy,have you done any more on this engine? I would like to see it run!
Crab

 

[Jeremy_BP]

Regrettably, school started and other projects. I haven't yet worked up the nerve to continue work on the engine, but I may someday.

 

[ronkh]

Jeremy_BP,

Get your nerve back asap.
Don't leave this thread hanging please.

Ron.

 

[Jeremy_BP]

The main issue I face is scale. The chuck I have can't hold any parts smaller than 1/16", and certainly not accurately. As many of the parts are smaller and I can't afford collets, I'm a bit stuck. Any suggestions?

 

[dalem9]

make an arbor for a drll chuck and see if that will work for you. I had an old battery drill that I took apart and the shaft for the chuck works great. Hope this helps. Dale