An engine design they think is new 3

[enginesrus]

https://www.youtube.com/watch?v=Ov73-okhkG0

I wonder if Fairbanks Morse knows about this? They still make the OP engines, and have been using this architecture for I don't know how many years. And why would they say the idea was abandoned in the 40's? The hype for some of these supposed great IC engine ideas is just getting old.

 

[SuperSalad]

The static nature of the cylinder and the fact they use a common crankshaft keeps the timing and power transfer near perfectly steady in traditional inline, boxer, V, etc. engines.

Since the surfaces of the cylinders or the pistons can never truly be perfect, wouldn't each piston have different frictional characteristics exerted on it? Since the opposing force on each piston is another piston (a dynamic element)and the two crankshafts aren't connected, wouldn't one side receive more power than the other from combustion outside of theoretical models?

Or am I totally wrong about this? I also didn't delve too much into their design though; do they have a way to overcome this aspect?



Andrew H.

http://www.mototribology.com

 

[SwinnyGG]

The two crankshafts are connected.

 

[tbuelna]

Achates is just one of many recent efforts to revive the opposed piston two-cycle CI engine concept. However, based on publicly available information it does appear they have made some headway at resolving the many fundamental issues with this configuration.

Here is an OP diesel engine effort I worked on almost a decade prior to the start of Achates' project:

https://docs.google.com/viewer?url=patentimages.storage.googleapis.com/pdfs/US6182619.pdf

The patent drawings are taken from my layout model of a single cylinder test rig. I left the company after finishing preliminary design of the test rig in late '96, so they didn't list me as an inventor on the patent filed in '98. The test rig was built and run on the dyno, but I don't know how much more work was done before the project was terminated.

 

[SuperSalad]

The two crankshafts are connected.

Then there's two crankshafts with one under more stress than the other in that situation, no?

Andrew H.

http://www.mototribology.com

 

[CWB1]

Achates Power is reviving the century-old opposed piston layout to make gas-powered cars more efficient.

Not sure anyone is under the impression that design is new, its definitely a turd regardless.

 

[berkshire]

Here is a direct link to Achates,

http://achatespower.com/cafe-2025-regulations-achievable-improved-gasoline-engines/

Since they are using transfer ports I want to see how they prevent oil leakage into the exhaust pipe.
B.E.

You are judged not by what you know, but by what you can do.

 

[RodRico]

Achates doesn't claim it's new. They reference the key prior works in their core patent. They claim they can fix what plagued the earlier attempts using modern design tools, and I think that's fair. Looking into their emissions, I found documents referencing urea injection on their site, and that tells me their native emissions aren't stellar. I'll take them at their word regarding some small gains, but it doesn't seem better *enough* to warrant all the money and attention IMHO.

 

[SwinnyGG]

Then there's two crankshafts with one under more stress than the other in that situation, no?

No. The pistons sharing a cylinder are exposed to the same conditions at the same time- there is no difference in force applied to them.

 

[enginesrus]

Its in production now. Fairbanks Morse has been using this for I'm guessing 80 years plus.

 

[SomptingGuy]

I'm not convinced that the mission is to deliver a viable product here. It's government funded research.

Steve

 

[RodRico]

Here's another opposed piston diesel that's in production:

http://morozov.com.ua/eng/body/addmotor.php

It's not an auto engine, it's a multi-fuel *tank* engine! The 6TD variant is the latest in a long series of tank engines dating back to the 5TDF engine used in the T-64 tank (deployed in 1967). Of course most of these opposed piston engines trace their heritage to the Junkers Jumo 205 which entered service in 1932 (

https://en.wikipedia.org/wiki/Junkers_Jumo_205).

Over 900 of the Jumo engines in one configuration or another were used in German warbirds. The Wikipedia article linked above also mentions a few other notable opposed piston engines: The Commer TS3, Leyland Motors L60 tank engine, Rolls-Royce K60 engine, and the Fairbanks Morse 38 8 1/8 (in addition to the 5TDF and 6TD already discussed). That's an awful lot of engine designers who view this architecture as more than a research exercise.

 

[BrianPetersen]

There's also no reason to suspect it will be any more successful this time around than it has been over the last 50 years. If it were that much more efficient and without any downsides then why can't you buy a car with such an engine in the showroom today? Why couldn't you do so 50 years ago? Why did the Commer TS3 (a.k.a. Commer Knocker) cease production after several years in production?

Reason: hidden downsides that the advocates never tell you about.

In a diesel engine, squirting fuel in from the edge of the cylinder probably doesn't give as good in-cylinder fuel and air distribution as squirting fuel in from the middle into a central bowl in the piston, and in this day and age, if you can't get the emissions right, the whole deal is a non-starter. Opposed piston means you can't use a central injector with a bowl in the piston.

All piston-ported engines have issues with lube oil escaping via the ports. That's bad for emissions. Again, in this day and age, if you can't get the emissions right, the whole deal is a non-starter. Detroit Diesel built piston-ported two-strokes for on-road applications for 50 years, and they gave up and went four-stroke when faced with 1990s-era emission standards, and those standards are a lot tougher today.

 

[RodRico]

Brian,

All good points. In my engine, I have no spark plug or fuel injector, so I've sidestepped that problem. I have provisions for lubricating around the ports and preventing oil from entering the exhaust, but they are unproven and still worry me.

Rod

 

[gruntguru]

Brian you missed the obvious downside that has nothing to do with efficiency - architecture and packaging. The classic Jumo design using two crankshafts is very tall and requires a cumbersome geartrain to link the crankshafts. Alternatives like the Commer "knocker" reduce the height but introduce clumsy/heavy reciprocating rockers.

I don't believe injection from the side(s) is the dealbreaker - there are many efficiency advantages to OP architecture that compensate to varying extents.

je suis charlie

 

[BrianPetersen]

An engine of an awkward shape should be a self-revealing flaw when someone tries to design something that uses it. A Fairbanks-Morse-style engine is not going to fit transversely in a Honda Civic using its existing packaging and drivetrain layout, no way no how, but it might have a chance oriented longitudinally lying flat in a Subaru. The old VW flat-four was an awkwardly-shaped engine by modern standards, but it fit in well with what VW did with it.

A DOHC 4-valve cylinder head is not particularly compact, in any case ...

The Wankel rotary made its name for being compact, and Mazda designed cars around it, and yet, you can buy kits to stuff a Chevrolet small block V8 under the hood of those cars and still be able to close the stock hood on it, which is great for when the Wankel kicks the bucket, which it will ...

 

[RodRico]

Speaking of boxer engines, here's a picture of Ecomotors' Opposed-Piston Opposed-Cylinder (OPOC) engine. This configuration eliminates one of the crankshafts and has a nice and low center of gravity. Note the stroke of each piston in an opposed piston engine is about half that of a single piston engine having the same displacement, and this helps offset the height (width in the case of the OPOC) penalty of the architecture.

 

[RodRico]

Here's a web-page dedicated to the opposed-piston engine. It lists most of them according to configuration and provides a bit of information about each. The OPOC engine shown in my prior comment is of the Wittig type.

http://www.opposedpistonengines.com/

 

[Marquis]

Achates makes some heady claims. The fact - they have been twisting the truth using selective data and massaged simulation data for so long. When they finally had hardware they found the bsfc achieved was no where near what they claimed. The issue was- their cult like atmosphere - where anyone who was a critical thinker or a pragmatist, was pretty much fired until you were left with the koolaid drinkers.
The best point bsfc figure they achieved on their 4.9 litre 3 cylinder engine was around 194 g/kwh. They were predicting and touting in the 180s before that. Neither are remarkable. Also- consider that- a 4.9 litre 3 cyl is a massive cylinder and they were continually comparing it to the Ford Scorpion 6.7 litre engine and making ludicrous assumptions for after treatment efficiency. Similarly touting the benefits of a longer stroke engine while ignoring the associated knock on effects to friction isn't prudent. When you put it in this context its not remarkable at all. A good quality 4 cylinder 4 liter diesel will achieve about the same best point bsfc with similar common rail hardware. SOme of the bigger cylinder HD applications may get in the low 180s.

I also find it amusing when they tout the use of no valvetrain - hence claiming less friction- totally ignoring the fact that the valvetrain has been replaced by a whole crankshaft and set of pistons. Folks are seeing through these lies now. Don't get me wrong, I do see the potential of a two stroke diesel, but not one run by a cult. The other inherent hurdle for a uniflow scavenged 2 stroke is getting the after treatment lit off quickly- it will tend to fun a lot cooler than a conventional 4 stroke. You see this on the old Detroit diesels also. This is due to the bypassed air.

To the original poster- Achates bought the General Atomic OP engine and hardware. They also did consultancy work for Fairbanks Morse but ended up causing a lot of carnage there. TARDEC hasn't been impressed with them either. Lets see how long they last....

http://www.auto-scape.com

Sideways To Victory!

 

[Lou Scannon]

Marquis!, haven't seen you here in a while.
This breakthrough technology merry go round is predictable and monotonous. It is invariably a case of a crackpot or a sly, albeit sane, person or group pulling the wool over the eyes of the greedy and gullible.
My prediction is, the next big breakthrough (not evolutionary step) in IC engines, if it ever comes, will NOT be presaged by a drawn out venture capital campaign, but will appear suddenly from a world class OEM, or possibly from a brilliant, capable, well-rounded, and internally funded not to mention secretive private party or consortium.

"Schiefgehen wird, was schiefgehen kann" - das Murphygesetz