It seems to me that you are fixing crankshaft spacing upon need for prop separation, then taking the rpm and piston speed that gives... Usually that sort of "design coupling" produces unwanted side effects. With a gear train, you can drive the prop(s) from which ever shaft suits, or make the prop spacing independant of engine configuration, and run the crankshafts in the direction and rpm that makes sense. Gear sets are widely used in the world and way lighter than e-machines.Counterrotating cancels torque reaction and make less prop noise.
A mean effective pressure of 4 to 5 bar will only need little turbo and cold inlet crankcase in series.
Exhaust piston can then be oil cooled if needed.
Achates can make more usefull engines using the twin AC generators method but it is a free country and not my money.
None as I still like my inverted V2 better .Prof. Neils,
What techniques do you have available & intend to use prototyping this OP twin? A successful engine needs skillfull machinists and post production tests performed.
All the Best,
CK LouPai
=======================There was never an OPOC (opposed piston opposed cylinder) snowmobile engine of the type being discussed here. Neither were VW's, Corvairs, or BMWs.
===============================You are confusing opposed cylinders with opposed PISTONS. OPOC engines have only one cylinder for each opposed pair of pistons with a crankshaft at each end. Being mostly 2 stroke cycle, there haven't been many around for emissions reasons for some time (the Commer TS3 being the last in a production road vehicle I can think of). While they have two crankshafts, they have no cylinder head nor valve gear and save a lot of weight, complexity, cost and efficiency by being such a simple design. They are also "uniflow" engines in that inlet is on one side and mass of combustion gasses keeps moving the same way to exhaust on the other side.
Here is a good video giving you a quick summary:
The OP opened this thread about a much larger engine with OPOC design. What he proposed would probably be far too heavy for aircraft use (with the M/G function and hardware). For aviation, they have a hundred+ year history of being relatively light, extremely efficient but due to 100-75 year old fuel injection tech, not very powerful. Also, they are ideally suited for 2 cycle uniflow construction using diesel and/or jet as fuel - so yet another big plus for aviation use. 2 cycle diesels are very different animals from 2 cycle SI counterflow or loop scavenged engines. As to cost and power: OPOC diesels have been built at very low HP (small outboard) but long ago but mostly have been fairly large engines. No reason (see Achates once again) they can't be made in 4-6 place genav sizes. There have also been some 80-100HP designs over last 30 years, but for any of these to really be affordable there needs to be some mass market application that turns out parts and/or whole engines that can be used or adapted for aviation. This is what is going on with most JetA engine designs - using automobile engines as source.===============================
I can see now what you're talking about, but like you said, "Being mostly 2 stroke cycle, there haven't been many around for emissions reasons for some time" and " While they have two crankshafts, they have no cylinder head nor valve gear and save a lot of Weight, Complexity, Cost, and Efficiency by being such a simple design." Maybe to you, but to not 99% of the people on here. First, you have (2) Crankshafts so more Weight, has more complexity than a standard 2 Stroke. You didn't say how much hp, Cost, Weight? Most people on here hate 2 Strokes, can't even rebuild a Standard 2 Stroke let alone a Hybrid. Rotax's biggest 2 Stroke they offered was the 618UL. Simonini 802cc, Hirth was I think 625cc. Sleds go up to 1000cc. Sled & Jet Ski Racers go up to about 2000cc today. The Part 103 Ultralight World needs a Single that is less than 65lbs, that make ideally 30-40hp, the Small Kitplane World needs a 40-60hp or 60-80hp depending on MTOW. Large Kitplanes need 100+hp. No Certified Airplane will use a 2 Stroke Engine no matter how good an engine it is. If you use the simple 7cc to make 1hp rule with a Tuned Pipe at 6500rpm.
While the title doesn't say opposed - In Posts #11, #12 and #16 Niels explained the type of engine he was discussing and asking input on - OPOC. Not opposed engines as used in Snowmobiles, VW.s, Corvairs, BMWs=======================
The Thread is "Vibration free powerplant." not OPOC Engines and the Engine was referred to as just Opposed. Rotary Engine were also mentioned, not an OPOC either.
The JET Engine killed the Piston Engine 70+ Years ago.
================================While the title doesn't say opposed - In Posts #11, #12 and #16 Niels explained the type of engine he was discussing and asking input on - OPOC. Not opposed engines as used in Snowmobiles, VW.s, Corvairs, BMWs
OPOC engines have been around since 1882
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Opposed-piston engine - Wikipedia
en.m.wikipedia.org
Per post #32 - Achates Power is actively working on a commercial OPOC design for modern applications.
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Where to Now for Diesels? - Achates Power
Where to Now for Diesels? September 28, 2021 • by Jim Park • Diesel internal combustions have come a long way since Rudolph Diesel fired up the first one running on peanut oil. Experts agree there’s lots of life left in internal combustion engines.Photo: Jim Park We can be pretty sure that...achatespower.com
As far as complexity -Two crankshafts are no more complicated/heavy than one parallel twin Rotax motor.
Rotax or OPOC 2 pistons, 2 rods, 4 crank webs, 4 bearings minimum.
Rotax 2 Heads OPOC - zero.
In post #12 the design goal of [email protected] ( [email protected] ) was given before M/G
Rotax 447 - [email protected]
Need is relative- Jet engines may not be the future powerplant of choice for Ultralight Craft
The OPOC engine has been around for 139 years and keeps reappearing.================================
Dude, if the OPOC Engines haven't caught on in 139 Years, your wasting your Time & Money!
People have been trying to use VW, 1/2 VW, Subaru, Mazda, Corvair, etc., Car Engines for 40+ Years on Airplanes, which most are too Heavy for Part 103
Show me a VW, 1/2 VW, Subaru, Mazda, Corvair, etc., making 400hrs, 500hrs, 600hrs?
===================================>The OP opened this thread about a much larger engine with OPOC design. What he proposed would probably be far too heavy for aircraft use (with the M/G function and hardware). For aviation, they have a hundred+ year history of being relatively light, extremely efficient but due to 100-75 year old fuel injection tech, not very powerful. Also, they are ideally suited for 2 cycle uniflow construction using diesel and/or jet as fuel - so yet another big plus for aviation use. 2 cycle diesels are very different animals from 2 cycle SI counterflow or loop scavenged engines. As to cost and power: OPOC diesels have been built at very low HP (small outboard) but long ago but mostly have been fairly large engines. No reason (see Achates once again) they can't be made in 4-6 place genav sizes. There have also been some 80-100HP designs over last 30 years, but for any of these to really be affordable there needs to be some mass market application that turns out parts and/or whole engines that can be used or adapted for aviation. This is what is going on with most JetA engine designs - using automobile engines as source.
I don't think they can scale down into the 40kW range mostly due to the size of injection components needed for CI, but actually could be built easily as an SI engine in that range. BUT, of course, it still gets back down to no sense trying to develop a whole engine for such a tiny market - ends up being very expensive.
On the two stroke thing: I have built literally hundreds of two cycle powered commercial airboats, mostly Rotax powered (503 days) and while I am not exactly 2 stroke SI crazy, they did an excellent job for us and let's face it, there is a massive component of sport aviation that simply wouldn't exist without them. Hard to beat the power/weight numbers.
None of the above will burn Jet A, diesel, bio-D, fryer grease, etc. CI engines are truly multi-fuel. The you list also all require separate re-drives. Finally: most of the engines you list would be considered extremely high polluters so probably have very short future.I could see an Opposed Piston Diesel Engine with a Turbo for Cars & Trucks, maybe Large Kitplanes, but not for Part 103 or even Small kitplanes. With the Global Climate changes and Politicians pushing for Electric Cars, Trucks, Bikes, even Semi Trucks, and Commerical Planes, and Snowmobiles. I don't follow ATV and Jet Ski much, but I wouldn't doubt their headed that way also.
I seriously doubt anyone will be Buying any Diesels in the near future, no matter how good they are.
Do we really need another Engine?
Just like Boing 737MaxClearly neither he nor you have been following development of the Otto Celera. Incorporates existing technology just more thoroughly interpreted and integrated. Already flying.
In fairness, the Boeing 737 up until the engine change that resulted in the "max" was a truly fantastic airplane. The issue was related to management trying to modify a design to allow use of same pilots without a new rating for a new design by calling it the old design. There have been few airplanes since the DC3 that were actually so very good at meeting their design and utility goals.Just like Boing 737Max
That is what I was thinking - Propellor loads - but a little different view.
What happens in a climbing turn?
Load is different on inside and outside props due to arc of the turn.
Granted not as bad as widely spaced twin engines mounted on different wings. But still there.
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