Opposed Piston Engine

[GailinNM]

This engine was inspired by some drawings by Hugo Junkers in the late 1880's. It is in no was a model of any of his (or any one's) engines. Junkers' engines were 2 stroke Diesel engines and this is a 4 stroke spark ignition engine.

I put this in "CNC assisted" section because I plan to use CNC for some of the parts.  None of the parts require CNC but because of my failing vision and limited motor skills it sure makes it a lot easier.  I plan this to be a photo essay with no drawings included in the thread to begin with.  After the engine is running I will release a drawing package as part of the thread if there is any interest, but I don't think that it is fair to release drawings on and engine that not been run. It's been many years since I had an engine that did not run but with increased physical limitations it would be unwise to make to many assumptions.

Gail in NM
 

[GailinNM]

Here is one of the drawings that started it all.

Looking at the drawing you cn see the exhaust and intake ports on the sides of the cylinders. The only thing I really copied from this drawing is the general arrangement of the crankhaft and pistons.
Gail in NM

[GailinNM]

And a couple of general arrangement drawings to get started with. 




The side connecting rods are not shown on the side view.  Many other details are not shown.  Some of them have not been designed.

Basic specifications are:
Bore 0.375 inch
Stroke 0.500 inch
Base 6 inches long

Gail in NM

[ProdEng]

Gail, that's an interesting looking engine, look forward to seeing it develop.

[steamer]

That's really cool Gail....I'm watchin!

Dave

[ths]

A very investing project, and I look forward to seeing more of it.

Cheers, Hugh.

[AussieJimG]

Interesting project. Some of the large marine diesels had this configuration. I think they were two stroke. This could also be two stroke spark ignition.

I will be interested to see how the valves are placed and operated.

I will be following and will doubtless learn lots as I do from all your projects.

Jim

[Bearcar1]

What an interesting looking engine Gail, I have a chair pulled up and popcorn on the stove. Am looking forward to see how this develops.


BC1
Jim

[GailinNM]

Thanks for the interest. 
A few more comments before the construction part of this thread starts.

You may have noticed that along with the imbedded image that I have attached the same image to each post.  This is because I like the freedom to flow text around the imbedded images describing each operation, but it puts the thread content under the control of the photo hosting web site.  This way if Photobucket (or I) go belly up and the embedded photos are lost the thread will not become completely worthless.
 

Why were opposed piston engines developed?  In this configuration there were two primary reasons. 
 1. As a two stroke the cylinder could become one piece for both pistons thus getting rid of the weight and bulk of a cylinder head.  In this model that reason goes away as a cylinder head was necessary to house the valves necessary for 4 stroke. There are ways around this but as I drew them I did not fand one that I liked.
2. With the long side rod configuration, the crankshaft had less bending loads on it.  On the power stroke as the near piston was pushing on the crankshaft the far piston was pulling on it. so So more f a torque reaction was generated and less bending.  Many more modern opposed piston engines used 2 crankshafts that are coupled  by chains, gears or some other mechanical means.  The Deltic design engines use 3 crankshafts in a triangular arrangement with each crankshaft driving 1/2 of each of 2 wo banks of cylinders. I thought about 2 crankshafts but this arrangement has more visible "monkey motion" which should make it more fun to watch. 

While the advantages of two stroke operation are evident, some means of primary compression to get fresh air into the cylinder is needed.  Some of Junkers' designs used
air pump cylinders on each side of the power cylinder.  The pumps had seals on both ends of the cylinder with a piston rod extending from each from each end. They served as a cross head  to drive a yoke connected to the far piston. Later multi cylinders ones used a variety of blowers for primary compression, just as some modern non-opposed two stroke diesels do.

Gail in NM

[Jo]

Thanks for the interest. 
You may have noticed that along with the imbedded image that I have attached the same image to each post.  This is because I like the freedom to flow text around the imbedded images describing each operation, but it puts the thread content under the control of the photo hosting web site.  This way if Photobucket (or I) go belly up and the embedded photos are lost the thread will not become completely worthless.
 
.... Gail in NM

Gail... Watch this space the Admins, actually a very very nice man who goes by the name Arnold    , is trying to sort that little problem 

Jo

[NickG]

Likewise, really looking forward to this Gail, never seen an arrangement like that before. Thanks for sharing.

[GailinNM]

Jo: I will watch for another solution.  I know Arnold from another life.  He is not only very nice but also very talented.

Nick: Engine wise, it is hard to come up with anything that has not been tried before. Many ideas were never developes as there were other ways of doing things that were better. Still the make for interesting models.  I once thought I had invented a new steam engine valve gear.  My name will go down in history.  Turned out to have been invented in the 19th century.  Twice, under two different names that I had never heard of and I have several books on nothing but valve gear developments. 

But enough of me getting side tracked.  Here is a sort of cut away view so the relation ship of some of the working parts can be seen.  The bottom end is like that of a side valve utility engine.  15 tooth Crankshaft gear drives an idler gear, also 15 tooth, which drives the 30 tooth gear on the camshaft. The gears are 48 DP with 14.5 degree pressure angle. Nothing magic about this. I just happen to have a full set of cutters for this combination. The cams drive tappets that have an adjustment to take up backlash in the valves.  Not shown on the drawing are the valve springs that close the valves.  The valves operate on directly on seats cut into the aluminum combustion chamber pocket between the cylinders.   The tip of the spark plug is in the other side of the pocket. The auxiliary view shows how the long connecting rod operates the opposing piston through a rod operating in a crosshead with a short connecting rod.  The crosshead is two 3/16 inch wide slots in the frame sides with3/32 x 3/16 ball bearings in the slot.
Gail in NM

[Alan Haisley]

Gail,
This will be interesting to watch. Do you expect less overall vibration with the mass of two opposed pistons?
Alan
 

[AussieJimG]

I lay in bed last night trying to figure out why someone would use this configuration in a full sized engine. I didn't come to any conclusion.

And this morning, all was revealed. And with the valve arrangement too. Thank you Gail, now I can concentrate on following.

Jim

[tvoght]

An interesting subject, Gail. And it does look like it will be fun to watch run.

I'm Looking forward to watching the build.

--Tim