Redo for my horizontal 2 cylinder compressed air engine

[cfellows]

Chuck
I am interested in your comment about difficulties with two cylinders operating out of phase including balancing the air supply. I am attempting a two clyinder beam engine (my second project, my first departure from plans) and I intend to have them 180 deg. out of phase.
Dave

Hi Dave, 180 degrees phase difference only presents balancing problems when the compressed air is being admitted to the two cylinders with different elapsed time between them. I assume your engine will have two power pulses per revolution, alternately 180 degrees apart, so the spacing between power pulses is equal.

I had difficulty balancing the air on my engine because I'm running the engine in 4 stroke mode where there were alternately 2 power pulses for one revolution then no power pulses for the second revolution. That's what causes the syncopated or loping sound. That meant there was always more time for pressure to build up in the line for the first power pulse than the second.

Again, there's never a problem balancing on any multi-cylinder engine as long as the power pulses are evenly spaced apart.

(For some reason this seemed really difficult to explain :-\)

Chuck

 

[MarioM]

Earlier this year, while setting up my engines for display, I dropped this engine on the concrete floor, rather severely bending the crankshaft. I tried straightening it, without much enthusiasm, but couldn't really get it straight. I've never really cared much for this engine anyway. It seems kind of misshapen and I could never get the air supply balanced properly between the two cylinders.

So, I've decided to make some changes to it and see if I can make it more to my liking.

The first thing I've decided to do is make a new crankshaft. This time, I will have the two pistons in phase instead of 180 degrees apart. Since the engine is 4 stroke in operation, each piston will fire on alternate revolutions. So, here is the pictoral of making the crankshaft.

I started with a piece of 1" x 3/8" cold rolled steel 5" long. After marking it out, I used my bandsaw to cut too axial slits along side the future main journal. This will relieve the stresses before I finish marking and center drilling the ends. I also center drilled the spaces between the webs that will need to be cleaned out.

Next I drilled holes where I had center drilled

Then used my bandsaw to cut out the waste metal from between the webs

With all the stresses relieved, I marked out the centers on the ends

And center drilled them so I could mount the crank between centers in my lathe

After putting a 3/16" screw between the center webs to keep the gap from collapsing, I mounted the crankshaft between centers in my lathe

To turn the connecting rod journals, I use 3 different cut off blades. The first two, a left and a right, are sharpened at a slight angle so I can have clearance when turning the sides of the webs.

Here you can see the right face cutting blade mounted at a slight angle so only the point contacts the side of the web. I've turned both journals down to a little bit over size using the angled cutoff blades.

Here I'm using a squared ended cutoff blade to turn the journals down to finished size.

And here you can see my progress so far, along with the old crankshaft that it will replace.

Next, I'll cut out the other waste and turn the main journals.

Chuck

Chuck, while searching for information regarding the Topsy Turvy that Harold built you mentioned this post, but I can not see any of the pictures........you know why??

Thank you
Mario