Opposed Piston Engines

[Richard SimpsonParticipant @richardsimpson88330]

Just a Sunday morning musing as I have a browse through some of the beautiful projects there are on display here.  Having had experience in my sea going career of what are referred to as opposed piston internal combustion engines, I have frequently thought of such an engine configuration to be at the pinnacle of reciprocating engine design as regards power to weight ratio.  This is, of course, precisely why they were developed into the ‘Deltic’ configuration, which went on to power diesel locomotives and fast navy craft of the post war period.

Obviously the downside of the configuration is that it can only be used in a 2 stroke cycle engine, as there is nowhere to put the normally required valves for a 4 stroke engine, rendering them not popular with the drive towards fuel efficiency, but I’ve often wondered whether an opposed piston arrangement could have ever been used as a steam engine.  So my question is whether anyone has ever come across a model of such an engine, either as a design or a finished item?  I cannot see any reason why it would not work with steam as steam inlet and outlet is simply controlled by ports, pretty much in the same way as a 2 stroke internal combustion engine works.

[Robert Atkinson 2Participant @robertatkinson2]

How about using a sleeve valve with opposed pistons?

Robert.

[Richard SimpsonParticipant @richardsimpson88330]

I don’t see why that couldn’t be done with opposed pistons.  I’m really just wondering if there has ever been a model of an opposed piston engine.

For anyone not familiar with the arrangement look up ‘Doxford Marine Engines’ and have a look at this display piece in the Science Museum.  Double click to enlarge, well worth it:

 

[cogdobblerParticipant @cogdobbler]

I have seen pictures of an opposed piston Stirling  engine model. The displacer pistons were opposed, with the flame in the middle of the horizontal displacer cylinder and the two finned “cold ends” at each end of the one cylinder. I can’t for the life of me remember it’s name or find it online. I rather think it was perhaps a commercial kit a the cylinder fins looked cast, from what I remember.

Never seen an opposed steamer though. Could be an interesting project , especially if you used rocking beams to connect two conrods to the same crankshaft as some early engines did. Might be a very wide engine with the crossheads at each end.

[Richard SimpsonParticipant @richardsimpson88330]

Ah, found a couple of combustion engines, so they exist:

 

 

Can’t find a steam engine though.

[cogdobblerParticipant @cogdobbler]

<p style=”text-align: left;”>Some lovely workmanship there. And two very unusual engines.</p>

[Colin BishopModerator @colinbishop34627]

Is this the sort of thing you mean Richard?

DIY Assembly Steam Engine Kit Model Science Experiment with Electric Generator

Some other interesting engines on the website.

Colin

[cogdobbler]

On cogdobbler Said:

I have seen pictures of an opposed piston Stirling  engine model. …

Ericsson I think, circa 1860, but I can’t find the book!

Opposed cylinder steam very likely explored by the Victorian’s but I doubt many were made because complex engines are less reliable than simple ones.   That I’ve never come across one may not mean much because dozens of long forgotten firms made steam engines during the Victorian era, often in small quantities.    Might be worth researching the engines fitted to Torpedo Boat Destroyers in the 1890s.

Opposed diesels were developed to meet a 20th century requirement: things needing high-power efficiency within tight space and weight limits.  Submarines, long range patrol boats, and then railway engines.  Not easy! Took a lot of effort to develop the Deltic.

Dave

[Richard SimpsonParticipant @richardsimpson88330]

Hi Colin, Many thanks for that, however that is an opposed cylinder engine and not an opposed piston engine.  An opposed cylinder engine, such as a lot of Porsche engines, Volkswagen Beetles and BMW motorcycles have cylinders, each with its own piston, on either side of a common crankshaft.  Frequently referred to as a ‘Flat Four’, ‘Flat Six’ or ‘Flat Twin’ etc.  An opposed piston engine has two pistons in one cylinder, which move in opposing directions.  Both pistons are connected to a single crankshaft, either by gearing or by different con rods.

[Richard SimpsonParticipant @richardsimpson88330]

Dave, What an interesting read Ericsson proved to be.  Quite a few innovative ideas that become accepted throughout the 19th Century.  And by the look of it possibly the first ever sea going Marine Engineer.

The Deltic engine was an absolutely stunning piece of engineering design, just studying a cross sectional drawing can only make anyone marvel at how the concept was even created.

[JasonBModerator @jasonb]

One of our members is currently building an opposed piston IC engine.

I can’t see why it would not work for steam. Really it just needs to be two Uniflow or single acting cylinders sharing a common “head”. As they would be single acting you could get away with just conrods and no need for crosheads and their associated guides

One of Elmers many enginedesigns is a simple opposed piston engine, I’ve got the drawings knocking about

Variations on the theme are IC engines like the popular Mery casting kit which has a central piston and combustion chambers at either end

[Richard SimpsonParticipant @richardsimpson88330]

I guess that would effectively be considered a ‘Double Acting’ internal combustion engine.

[Robert Atkinson 2Participant @robertatkinson2]

The USS Monitor engine was opposed pistons but in two cylinders. I’s been modelled:
https://modelengineeringwebsite.com/USS_Monitor_engine.html
That might make a starting point.

[Colin BishopModerator @colinbishop34627]

Thanks for the correction Richard, I’ll never make an engineer but I do find watching these devices in action and their ingenuity fascinating. A few years back there was a chap at the Brighton show with a collection of Stirling engines in different variations which he was demonstrating.

Colin

[David JuppParticipant @davidjupp51506]

A ‘closer to prototype’ model of the USS Monitor engine can be seen at

http://www.stationarysteam.com/stationarysteam_003.htm

Unfortunately the full set of drawings mentioned on the site no longer seems to be available for download.

[cogdobblerParticipant @cogdobbler]

<p style=”text-align: left;”>I found the model opposed Stirling engine I mentioned earlier. It’s called the Essex. Castings by Myfordboy apparently.</p>

[Richard SimpsonParticipant @richardsimpson88330]

Some beautiful engines there gents.  Thanks for the links.

[JasonBModerator @jasonb]

This is quite a nice model, I think it is one piston but with opposing rods. been a while since I saw it in the flesh.

[Roger BParticipant @rogerb61624]

I am building a 20mm bore 2 stroke diesel based on the Junkers CLM engines that were used in transport as well as stationary applications. There are some pictures on my Flickr and You Tube accounts:

Junkers Inlet Piston | Roger Bryant | Flickr

youtube.com/shorts/sL9x0OvkPTY?feature=share

The full build log is on MEM.

[Richard SimpsonParticipant @richardsimpson88330]

Jason,  Trying to put the bits and pieces together from the pictures.  Obviously two throws on the crankshaft connected via the shaft to two piston rods in either end of the cylinder.

It does look like though the large arms on the shaft connected to the crankshaft via the con rods are both angled inwards.  It does look however that the two piston rods are both in different positions, one being all the way in and the other being all the way out.  This would tend to indicate that, if there are two pistons they are not working in opposition.  Maybe the rods are both connected to either side of the same piston.  Or maybe one piston is the working piston and there could be another opening and closing ports.  Although there does appear to be a valve chest so I can’t say.

[Wade BeattyParticipant @wadebeatty78296]

I was engineer on a tugboat many years ago that had 2 Fairbanks Morse 38 8-1/8 opposed piston engines. They were used on diesel locomotives and submarines also. The upper and lower crankshaft were connected by a vertical angle gear drive on the front of the engine. To change a top piston you could either disconnect all the top connecting rods and pull the top crankshaft or remove the lower piston and pull the top piston down into the crankcase. A painfull process as I remember. You might look at drawings for inspiration.

[Richard Simpson]

On Richard Simpson Said:

I don’t see why that couldn’t be done with opposed pistons.  I’m really just wondering if there has ever been a model of an opposed piston engine.

For anyone not familiar with the arrangement look up ‘Doxford Marine Engines’ and have a look at this display piece in the Science Museum.  Double click to enlarge, well worth it:

 

What a fabulous model!

Not been to the science museum for a few years and I never spotted this model, but there again the museum is huge.

I wonder who built the model? Love to get some drawings and make a copy of that engine in the science museum. Anyone any idea of where drawings might exist?

I have seen YouTube videos of “dancing Doxfords”, I never had any experience with them when I did my apprenticeship in a shipyard it was large Blackstone diesel engines and similar.

All the best

Derek

[JasonBModerator @jasonb]

I remembered that Elmer has another opposed piston steam engine, his #34.

This is actually a twin cylinder horozontal with each cylinder having a pair of pistons and a rotary valve feeding and exhausting at the middle of the cylinder. One piston is on a solid rod and the other a hollow one so all the linkages are at one end of the engine. I’ve seen a few builds of this one but not the best layout for marine use unless it’s a paddle steamer..

[derek hall 1]

On derek hall 1 Said:

On Richard Simpson Said:

I don’t see why that couldn’t be done with opposed pistons.  I’m really just wondering if there has ever been a model of an opposed piston engine.

For anyone not familiar with the arrangement look up ‘Doxford Marine Engines’ and have a look at this display piece in the Science Museum.  Double click to enlarge, well worth it:

 

What a fabulous model!

Not been to the science museum for a few years and I never spotted this model, but there again the museum is huge.

I wonder who built the model? Love to get some drawings and make a copy of that engine in the science museum. Anyone any idea of where drawings might exist?

I have seen YouTube videos of “dancing Doxfords”, I never had any experience with them when I did my apprenticeship in a shipyard it was large Blackstone diesel engines and similar.

All the best

Derek

Probably the best place to start would be the Science Museum themselves.  I sailed on a ship that had one of the last Doxfords ever made.  Usually Doxfords were large slow speed engines but, in a last ditched attempt to compete with the likes of Sulzer and Wartsila they came up with a three cylinder, much more compact medium speed version.  During our last walk around at night, the ship ran unmanned, it was totally hypnotic to lean over the handrails and watch the top three pistons and their beams bouncing up and down at somewhere in the region of 500 rpm.

The trouble was that, being a 3 cylinder 120 deg engine, there was a possibility that the engine could stop in a ‘dead band’, with all three cylinders symmetrically positioned.  If this was to happen then there would not be any starting torque when compressed air was applied and the engine would not start.  To get around this they fitted a hydraulic device to the front of the engine incorporating a ram with a pin on the end that, when operated located on one of three large curved teeth on a flywheel.  If the engine was stopped in one of the three dead bands and a start command was received this device automatically jumped into action to physically engage, pull the engine out of the dead band, disengage and allow a start.  We nicknamed this device “The Praying Mantis Gear” When I was on this ship there was a story going around that, during trials the Praying Mantis decided to engage itself while the engine was running.  It was apparently ripped out of its mounting and thrown across the engine room.

We used to test the Praying Mantis as part of our starting up procedure by deliberately turning the engine into a dead band and then trying to start it.  This thing in action was something Heath Robinson would have been proud of.

This is a picture of the development engine, now housed in a museum.  It is, by a long way the smallest marine engine I ever worked with but it certainly has the most stories attached to it:

[JasonBModerator @jasonb]

Seems worth posting the link to some photos of the Doxford works again.

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