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Old 04-03-2018, 02:22 PM   #11 (permalink)
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Less than a percent of companies seeking to license tech they don’t already build succeed,
I doubt we will see these go anywhere

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Old 04-05-2018, 06:50 AM   #12 (permalink)
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Since the military are interested in this design, and Achates has partnered with Cummins and Fairbanks-Morse, it doesn't sound so unlikely to succeed. Well, even though Cummins has traditionally refrained from releasing any 2-stroke design after the failure of a prototype, the involvement of Fairbanks-Morse which is well experienced with this engine layout might be a sign of the viability of the project. Getting in touch with the right investors and persuade them to buy the license to make the engine is a whole different matter, but I'm sure the interest of the military is likely to attract some. I wouldn't doubt AM General to get involved...


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Originally Posted by acparker View Post
There is a patent, US2809614, assigned to Continental Motors (now owned by the Chinese government) that addressed stress issues with the rocker-arm (the term, rocker-lever, seemed a bit off, may have been a google translate thing) designs. They were looking at it for aviation use. Obviously, nothing came of it.
I'm aware of at least one opposed-piston Diesel aviation engine project, but it's not from Continental and resorts to a two-crankshaft design.


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I think the rocker-arm designs may have made a more compact engine than the two-crankshaft designs -- or not. It may have had less friction than gear towers.
I'm not so sure about the extent of an eventual compactness that could be inherent to the rocker-arm design with a single crankshaft, but maybe it would lead to an easier packaging for general aviation as a drop-in replacement to the old opposed-cylinder gassers that are still mainstream.
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Old 04-05-2018, 02:17 PM   #13 (permalink)
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I could not say that the single-crankshaft rocker-arm design is superior to other configurations, but I think it is significant that there were a cluster of patents in the mid to late '30's that resulted in two relatively successful designs being manufactured, Sulzer's ZG9 and MAP's 2H88 (Olds did manufacture some engines, but it is undetermined if they were a licensed Sulzer design, or based on his own patent), followed some twenty years later by the Rootes (Commer) TS3 which proved the most successful and most widely distributed.

Commer pursued this configuration because they wanted a low, compact engine that could be used in a cab-forward truck. The two-crankshaft opposed-piston designs are either very tall or very wide, and conventional diesels of the era were very large and very heavy.

OPOC, the other contemporary single-crankshaft opposed-piston design was based on the Gobron-Brille opposed piston engine, first appearing in 1898 and produced through 1922. With a single bank of cylinders, the height of the engine would be about the same as a conventional overhead cam engine.

Military involvement is no panacea. DARPA has left many good and proven ideas to rot, as the path through military procurement is anything but logical. The involvement of Cummins and Fairbanks-Morse is more significant.
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Old 04-06-2018, 02:24 PM   #14 (permalink)
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Quote:
Originally Posted by acparker View Post
I could not say that the single-crankshaft rocker-arm design is superior to other configurations, but I think it is significant that there were a cluster of patents in the mid to late '30's that resulted in two relatively successful designs being manufactured, Sulzer's ZG9 and MAP's 2H88 (Olds did manufacture some engines, but it is undetermined if they were a licensed Sulzer design, or based on his own patent), followed some twenty years later by the Rootes (Commer) TS3 which proved the most successful and most widely distributed.
The first single-crankshaft opposed-piston engine I heard of was the Rootes TS3 anyway...


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Commer pursued this configuration because they wanted a low, compact engine that could be used in a cab-forward truck. The two-crankshaft opposed-piston designs are either very tall or very wide, and conventional diesels of the era were very large and very heavy.
In the end it was a great engine, not just relatively compact but, apart from the particulate matter emission, it actually fares better than many electronically-governed Euro-3 engines fitted to vehicles with a comparable load capacity.


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Military involvement is no panacea. DARPA has left many good and proven ideas to rot, as the path through military procurement is anything but logical. The involvement of Cummins and Fairbanks-Morse is more significant.
Now comes another question: which company would be more likely to actually make the Achates-designed engine? Cummins has its 4-stroke tradition, while Fairbanks-Morse opposed-piston 2-stroke engines are still used not just for large-scale powerplants but also in military ships and even as backup power for submarines. So, even though Fairbanks-Morse engines tend to be more associated with off-highway applications, and in sizes not suitable to road-going vehicles, I'd still bet they could resort to the "battlefield-proven" marketing approach which had already been extremely successful with the Jeep CJ, the Hummer, the AR-15 and many other stuff.
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Old 04-06-2018, 04:39 PM   #15 (permalink)
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I am enjoying this thread. Thanks to acparker for the links to these wonderful engine side roads.

I remember seeing the Roots TS3 running around our neighborhood. I've always wanted to grab one and refit a more capable fuel system. I feel two strokes are dismissed as being too noisy and dirty without digging deeper into the design.

The only real problem is the oil that can slip by the fuel/exhaust ports. That can be minimized. An extended stroke TS3 can allow us to provide a head with an intake valve system reducing that source of oil bypass. Mapping of trapped exhaust allows us to provide natural EGR as well as additional EGR for reduced NOx. High pressure common rail injectors will reduce exhaust coking problems. Current clean diesel exhaust after treatments would make it viable for even the ultra strict California market.

Just dreaming out loud.
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Old 04-07-2018, 08:04 AM   #16 (permalink)
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Quote:
Originally Posted by RustyLugNut View Post
I remember seeing the Roots TS3 running around our neighborhood.
The only time I saw a TS3-powered truck, it was parked under a bridge in the Brazil-Uruguay border. Well, I wasn't even able to figure out if it still had the stock engine or if it had already been repowered with some Brazilian 4-stroke (the Mercedes-Benz OM352 had been a popular alternative for engine swaps in Brazil, Argentina and Uruguay).


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I've always wanted to grab one and refit a more capable fuel system.
Since I got to know about the TS3 I wanted to get one and fit into some Chevy full-size truck.


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I feel two strokes are dismissed as being too noisy and dirty without digging deeper into the design.
When it comes to 2-strokes, nowadays most people seem to forget the Diesel ones and only remind spark-ignited applications. Well, at least most 2-stroke Diesels resorted to an oil recirculation lube system, which makes it easier to implement some emission controls which became mainstream such as EGR.


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An extended stroke TS3 can allow us to provide a head with an intake valve system reducing that source of oil bypass.
The absence of a cylinder head is actually a desirable feature, since there is a smaller surface for heat losses through irradiation, thus the engine can convert more energy into motion instead of just waste it.
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Old 04-08-2018, 12:32 AM   #17 (permalink)
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Another aside, here is some information about MAP's 1950 Le Mans car (click on appropriate flag in upper right corner for English version):

Equipa 1/1950

Check out the aerodynamics on the mid-engine design. The engine was a 4 cylinder version of MAP's 2H88 used in tractors. It also set several records in another chassis at the Autodrome de Montlhéry. There is an old article about it here (please note that there may be some security issues with the site, or ads embedded in it, and url's in the text):

LES RECORDS DE LA MAP DIESEL - blog pour la mémoire de l'autodrome

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