Opposed Twin I.C.

[Brian Rupnow]

I woke up this morning, thinking about an opposed twin i.c. engine. something along the layout of Jason's flat twin Boxter, only a bit cruder perhaps, with an open crankcase and exposed camshafts and crankshaft. I really like the knife and fork style con rod layout, and the fact that it lets the opposed cylinders set in line with each other. I haven't really sorted this through in my head yet, but this would probably mean two camshafts, one above the crank to run the right hand cylinder and one below the crank to run the left hand cylinder.-----Or perhaps both camshafts above the crankshaft, offset to each side. A single centrally located carburetor with long intake runners to each side---maybe. I have to think on this a while.---It feels interesting----Brian

[Alyn Foundry]

I woke up this morning, thinking about an opposed twin i.c. engine. something along the layout of Jason's flat twin Boxter, only a bit cruder perhaps, with an open crankcase and exposed camshafts and crankshaft. I really like the knife and fork style con rod layout, and the fact that it lets the opposed cylinders set in line with each other. I haven't really sorted this through in my head yet, but this would probably mean two camshafts, one above the crank to run the right hand cylinder and one below the crank to run the left hand cylinder.-----Or perhaps both camshafts above the crankshaft, offset to each side. A single centrally located carburetor with long intake runners to each side---maybe. I have to think on this a while.---It feels interesting----Brian

Dear Brian.

Here's one that was prepared earlier, much earlier !!   

I really like them but very few have survived to the present.

Regards, Graham.

[Brian Rupnow]

Thank you Graham--That one certainly looks massive!!!----Brian

[Brian Rupnow]

This is a new arrangement of connecting rod caps that I have just seen recently. I don't think it holds any real benefit except in a really small sealed crankcase, but it is certainly unique. The "knife and fork" arrangement of the rods lets you run two opposing cylinders in line with each other instead of having to offset them.

[cfellows]

Brian, not to throw cold water on your design, but have you considered that most 4-stroke, twin opposed IC engines have a crankshaft with 2 connecting rod journals spaced 180 degrees apart?  This provides for much better balance of the engine and allows the cylinders to fire at equally spaced intervals.

Another of Find Hansen's engines has the arrangement I describe...

<a href="https://www.youtube.com/watch?v=tR-5ZtdXPrw" target="_blank">http://www.youtube.com/watch?v=tR-5ZtdXPrw</a>

Chuck

[Brian Rupnow]

So---Perhaps we'll rethink this. I am being told that it's very bad juju to  have opposed cylinders going to the same rod journal. I believe the folks who are telling me this. I wondered about it myself, but figured that if it wasn't a good idea somebody would speak up---and they did. I have enough problems with dynamic balance on my single cylinder engines without compounding it. So now--If the con rods go to seperate journals, 180 degrees apart, I can revert to the normal bolt on rod caps.

[Brian Rupnow]

Having been told that "Maytag engines run smooth as silk." I think I will take a page from Mr. Maytags book and start this over again. It appears that the Maytag was a 2 stroke, but having found that there is some serious Voodoo involved with 2 stroke engines, I will be going with 4 stroke, overhead valves.

[Alyn Foundry]

So---Perhaps we'll rethink this. I am being told that it's very bad juju to  have opposed cylinders going to the same rod journal. I believe the folks who are telling me this. I wondered about it myself, but figured that if it wasn't a good idea somebody would speak up---and they did. I have enough problems with dynamic balance on my single cylinder engines without compounding it. So now--If the con rods go to seperate journals, 180 degrees apart, I can revert to the normal bolt on rod caps.

Dear Brian.

" Not so fast " !!  Since my last post I spoke with Geoff at the Anson Engine museum. Virtually all  " Vis A Vis " engine manufacturers employed a single crankpin shaft. These engines, for the most part were of Horse powers in the 100's. So I wouldn't dismiss your venture too quickly.

The term " Vis A Vis " is from the French, " Face to Face " and was widely used by the various engine manufacturers of the time.

I have attached a photo of my attempt that was underway at the time our main Iron Foundry decided to close. I had not realised how badly things had got in the workshop since it flooded !! It's going to need some serious elbow grease to shift that rust !! The engine was based around the castings of our RLE model but " Tank cooled " instead of " Hopper cooled " 

Regards Graham.

[Jasonb]

Brian, I think Gade also made an opposed twin, basically two aircooled hit and miss cylinders much the same as my Recent Gade build but on opposite ends of the main bed casting. Just need to find the photo I saw of it (as a model)

The other option would be to say your engine is a 180degree Vee twin and then you can use a single crank pin

[Jasonb]

Found it, those M&M boys had hidden it away

http://www.morrisonandmarvin.com/gade_12hp.php

[Brian Rupnow]

Alright!! ---This is more like it. Thank you Malcolm Stride. Thank you Canadian Cub!!!---This is why we always save our 3D models. I have miles to go before I sleep, but I think I'm on the right track now.----Brian

[Jasonb]

Looks familiar, where have I seen something like that

[Brian Rupnow]

Size looks about right!!

[Brian Rupnow]

Jason--Your model is marvelous!! I am going to go for more of the "early industrial" look, with crankshaft and camshafts and gears exposed. I never did resolve the issue of coughing back vapour from the carburetor on my engine, so will probably design milder cams than were originally used.---Brian

[Jasonb]

There is room to get a single cam shaft in, just use longer tappets and guides.

Agree sometimes its a shame to cover up all the workings

[youtube1]https://www.youtube.com/watch?v=9yERrHgN_jI[/youtube1]