A different opposed piston engine

[Brian Rupnow]

I have been fascinated with Gail's post about his opposed piston engine. I do not want to plagiarize someone else's post, so I have been surfing around the internet looking at "other" types of opposed piston engines. I found one today, and spent some time doing some preliminary modelling in Solidworks to see what would be involved. I'm not totally sure that this is "do-able" as a model engine, but I thought it was well worth having a look at. This is what I come up with---a 3/4" bore x approximately 1" stroke air cooled single crankshaft engine. I'm not sure if I will go farther with this or not, but it IS interesting.---Brian

[chuck foster]

brian what you have modeled is an atkinson differential engine

<a href="https://www.youtube.com/watch?v=vFvRwdKgGNU" target="_blank">http://www.youtube.com/watch?v=vFvRwdKgGNU</a>

chuck

[b.lindsey]

Chuck, the one in the video seems to be an alternating piston arrangement rather than both pistons going in and out at the same time as Brian shows. There are similarities in the action of course but that would seem to be a major difference. I am certainly no expert on Atkinson's though and will follow the discussion here.

Bill

[Brian Rupnow]

Mr. Lindsey is correct. The Atkinson is a far different engine, action wise.

[chuck foster]

you guys are correct

chuck

[GailinNM]

Brian,
I would love to see you go ahead with this concept.  There were several commercial engines that used this configuration.  All that I know of were two stroke and compression ignition.
Here are a two links that you might find interesting:

http://www.mekanizmalar.com/one_crank_opposed_piston_engine.html
http://www.oldengine.org/members/diesel/rootes-listerts3/ts3.htm

Also search on   Commer TS3
And a TS3 video:
<a href="https://www.youtube.com/watch?v=G-OqYFB4ofY" target="_blank">http://www.youtube.com/watch?v=G-OqYFB4ofY</a>

Most of the commercial engines used a Roots blower to provide pressure for the two stroke intake air.  As you know I went with a 4 stroke spark ignition system and that required that I extend a combustion chamber to house the valves and plug.

I have attached an image of one of the earliest known opposed piston engines that uses a third cylinder to provide scavenge air and used hot tube ignition.  I had thought it might be interesting to build. It could be built as a 2 stroke glow ignition with a side mounted glow plug in the center.  But I have another design for a more conventional engine underway. 
Gail in NM

[wagnmkr]

Brian, good to see you back at it again.

A very interesting concept there for sure.

Cheers,

Tom

[BronxFigs]

Chuck Foster....please check your PM.

Frank

[BronxFigs]

Elmer Verburg has an opposed-piston engine design that's similar in concept. 

It may be easier, and less complicated to build this type of configuration for use with compressed-air.  Maybe .... a Fellow's Slave-Valve in the common head .... admitting compressed-air to both pistons at TDC .... rotary valve on the crank....etc.

Thanks for the engine designs, and renderings.  All very interesting.


Frank

[Brian Rupnow]

My plan for this engine is that it will be a 4 stroke, internal combustion engine.-I am glad to see the interest it is generating.--Brian

[Brian Rupnow]

Okay--I wasn't 100% sure that this would work with a conventional crankshaft, but it will. My 3D models are not correct in all cosmetic aspects, but the parts which count, i.e. widths and center distances, etcetera are spot on. I can animate this in Solidworks and everything goes round and round without crashing, just as it should. The big ugly looking part, grey in color, has an offset in it which means that the blue "connecting links" are far enough apart not to hit each other and to allow a bit of space between them for a center crankshaft bearing if I decide that I need it.

[Brian Rupnow]

Interestingly enough, everything seems to go together amazingly well. That being said, as you can see I haven't modelled in the valves, cams, nor timing gears yet, nor the flywheels. I think I may make the intake valve an "atmospheric" type, same as I have used on many hit and miss engines, so it won't need a cam.--And yes, you are correct, the sparkplug and both valves fit in the center between the two cylinders. I couldn't see any good way to mount everything with one long double ended cylinder, so that has morphed into two cylinders and a center plate which will have the sparkplug and valves mounted in it, and also give me a way to support the cylinders. I may go with only one flywheel, out on the back side of the main vertical support plate. I will probably spend another $100 and buy a complete ignition package with batteries, etc. from Roy Sholl to provide my spark. Of course, if I do go ahead with this engine, I will provide the blueprints to anyone who is interested. I will probably post drawings as I go along, but its much safer to wait until I have a running engine and have made any required updates or changes to the drawings. Then I will post a download link to all of the drawings as pdf files so you won't need any specialized software to open them.

[Brian Rupnow]

Here we have a couple of cross sections through the center of the cylinders. One shows the pistons almost at "Top Dead Center"--they will actually be flush with the inner ends of the cylinders when they are at top dead center. The other shows the pistons at "Bottom Dead Center".--And yes, there is a slot in the outer ends of the cylinders to provide clearance for the linkages. The slot is less than 3/4" wide, so the piston will be fully supported even in this extreme position. The piston rings (which I have not modelled yet, nor grooved the cylinders for) will not go back far enough to catch the rings on this slot. Each piston will have one Viton o-ring.

[BronxFigs]

Brian-

Very nice concept.  Can't wait for your further developments to be posted.  With all the components out in the open, in full view....will make for a real interesting-to-watch, model engine.

Waiting in New York City...... Frank

[Roger B]

Adolf Saurer in Switzerland produced a rocker arm opposed piston engine for their first car in 1898.

The details I have are limited.
Bore 135 mm
Stroke 2 x 110 mm
Speed 600rpm
Power 5 HP
Fuel (in German Petroleum) which I think is Paraffin or Kerosene
Ignition by hot tube with a separate Petroleum burner and fuel supply
Four stroke cycle apparently as an inlet valve is mentioned.
Water cooled.
Fuel injection, the fuel pump is operated by the inlet valve rocker.
Flyweight governor.
Two drip feed lubricators

There is a picture in the book Saurer by Kurt Sahli published by Stämpfli in 2002.

I don't know if I can scan it and post it without the publishers permission.

The rockers and I assume the crankshaft are open.

The fuel is injected into the inlet pipe before the valve ( it looks like the pipe is heated by the hot tube burner to ensure vaporisation.

There is a small pump which I assume is for the cooling water driven off one of the rockers.


If anyone is interested in more details there may be some available at the Saurer Museum in Arbon