New double stroke design

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11/3/2017 10:00 AM

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11/3/2017 10:09 AM

Ah yes, the ol' double stroke...

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11/4/2017 5:03 PM

Looks like it would be a really tall engine.
I designed an engine for a college project that is single stroke that is 2 stroke. It could be 4 stroke but we kept it simple for the project.
We were able to double displacement without increase engine size.

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11/4/2017 5:59 PM

I don't get it... what's the point?

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11/4/2017 6:00 PM

So is that a 3 cyl or 6 cyl?

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11/4/2017 6:20 PM

FalseNeutral wrote:

I don't get it... what's the point?

They are claiming fuel efficency, so I'm guessing the idea is by sharing the cylinder they are pushing 2 cylinders with the fuel equivalent of 1.
Don't seeing this making good power.
1 because there are a lot of moving parts and no additional combustion force.
2. The combustion doesn't have anything solid to push against because of the cylinders pushing apart. doesnt seem like it would have tourqe.

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11/4/2017 6:24 PM

Melicar wrote:

So is that a 3 cyl or 6 cyl?

3 cylinder 6 piston

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11/4/2017 6:29 PM

FalseNeutral wrote:

I don't get it... what's the point?

Zesiger 112 wrote:

They are claiming fuel efficency, so I'm guessing the idea is by sharing the cylinder they are pushing 2 cylinders with the fuel equivalent of 1.
Don't seeing this making good power.
1 because there are a lot of moving parts and no additional combustion force.
2. The combustion doesn't have anything solid to push against because of the cylinders pushing apart. doesnt seem like it would have tourqe.

I think it's a stupid idea, combustion efficiency my be better in theory, but more moving parts will drop efficiency and make the engine sluggish. I'm not sold.

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11/4/2017 6:44 PM

A second crankshaft up high on the engine is great for the center of gravity.

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Tomac and/or Anderson for 2020.....

11/4/2017 6:54 PM

BobPA wrote:

A second crankshaft up high on the engine is great for the center of gravity.

Ha, next big thing in "centralization of mass" yamaha better build a backwards version

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11/4/2017 7:07 PM

Uhhh, yeah those cylinder ports will work out greaaaaat blink

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11/4/2017 7:38 PM

Watch it again. Less moving parts.

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11/4/2017 7:46 PM

It's a two stroke so depending on the volumetric efficiency curve it could make really good power. The cylinders never see vacuum (or at least not much) so they need the supercharger to provide a positive pressure differential all the time. That'll certainly help VE but it's difficult to compare to a NA engine. On the other hand the SC takes power to spin so . . . . .

I like the opposing pistons. The cylinder head on a typical engine is a huge heatsink, lowering thermal efficiency and increasing emissions. In addition, within reasonable compression ratios, the lack of valves/valve pockets means the pistons can be formed to provide a very tidy combustion chamber which is critical for high thermal efficiency. The ability to tailor the tumble and swirl of the incoming charge makes a huge difference in emissions and part throttle response. Good stuff.

Direct injection, good.

The lack of a valvetrain and all the parts is good. Again, depending on VE, overall friction and rod loads the engine should be able to rev pretty high. The extra crank adds relatively little to the overall friction (pistons/rings and valvetrain are the big hitters) but it does add quite a bit of inertial loading which hurts acceleration.

On the other hand, I see some of the same constraints that current two strokes must deal with. Without a dedicated stroke to expel exhaust gasses and fill the cylinder it's difficult to see how this design could make power (torque) over a wide range. The supercharger will definitely help on the intake side but there's just so little time at high rpms to completely evacuate the cylinder of spent gases, even though it seems this design has exhaust ports 360 degrees around the cylinder they are open for a relatively short time.

I don't see this coming to moto but I'll bet Mitch Payton would love to port and make pipes for those babies!

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Retired Mechanical Engineer, published technical writer, mscperformance.com, Bisimotoengineering.com,

11/4/2017 8:02 PM
Edited Date/Time: 11/4/2017 8:09 PM

In both 2 and 4 stroke engines, exhaust gasses are pushed out by the pistons, but in the demo, the are supposed to flow out? Or sucked through the injectors? I missed that part.

Also, what is going to suck the oil out of the top. I dont think it will work the same as a conventional 4 stroke in the way of top end oil flow

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11/4/2017 8:08 PM
Edited Date/Time: 11/4/2017 8:14 PM

FalseNeutral wrote:

I don't get it... what's the point?

Zesiger 112 wrote:

They are claiming fuel efficency, so I'm guessing the idea is by sharing the cylinder they are pushing 2 cylinders with the fuel equivalent of 1.
Don't seeing this making good power.
1 because there are a lot of moving parts and no additional combustion force.
2. The combustion doesn't have anything solid to push against because of the cylinders pushing apart. doesnt seem like it would have tourqe.

1.) Bore it out. You could use two 300cc (4 stroke) crankshafts for a 600cc displacement since the two crankshafts will share the 600cc worth of combustion.
2.) They are pushing against each other in the engine. It doesnt have to be solid non moving object. It just has to have an opposite reaction. It will still make torque. There is a cog joining the 2 crank shafts stop them from moving independently if that answers your question.
You should know the answers to both of those if you truly understand relative motion

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11/5/2017 1:32 AM

mingham97 wrote:

In both 2 and 4 stroke engines, exhaust gasses are pushed out by the pistons, but in the demo, the are supposed to flow out? Or sucked through the injectors? I missed that part.

Also, what is going to suck the oil out of the top. I dont think it will work the same as a conventional 4 stroke in the way of top end oil flow

Not quite correct. Once the exhaust port (2 stroke) or the exhaust valve (4 stroke) cracks open the high pressure cylinder gasses start rapidly propagating down the exhaust system. In both cases, the piston is actually moving down the cylinder on the power stroke, typically around 90 degrees ATDC on a 2T and about 140 degrees ATDC on a 4T. Most of the high pressure within the cylinder is dumped down the exhaust port before the piston reaches BDC. On a 2T, the opening of the transfer ports and entry of high velocity charge along with proper expansion chamber design helps scavenge and dispose of the remaining residual exhaust before the port closes on the compression stroke. On a 4T, all the remaining inert gasses are pushed out the cylinder on the exhaust stroke. It takes quite a bit of HP (negative work) to push even a small amount of residual pressure from BDC to TDC, so getting EVO timing right is pretty important.

Regarding the Double Stroke, I'm sure the exhaust ports (top of the cylinder) open quite a bit before the intakes (bottom on the cylinder). Therefore, the high pressure in the cylinder will naturally blowdown as the exhaust port is exposed by the piston. The rapid mass acceleration of all the exhaust gas towards the exhaust port tends to leave a low pressure area in its wake. This, along with the pressure generated by the supercharger creates a nice pressure differential for the intake charge to move into the cylinder, again, helping to scavenge and dispose of the remaining residual exhaust before the exhaust port closes.

Regarding the oil flow, all radial airplane engines have cylinders "upsidedown". They somehow manage to make them very reliable.

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Retired Mechanical Engineer, published technical writer, mscperformance.com, Bisimotoengineering.com,

11/5/2017 7:17 AM

So is it the 2 pistons hitting that create a spark? No spark plug?

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11/5/2017 8:14 AM

ga_pike wrote:

So is it the 2 pistons hitting that create a spark? No spark plug?

Maybe the injector goes on one side and the spark goes on the other.

I wonder if this would work with diesel applications where no spark is needed. Basically has a built in dual fueler. But where diesels have much more compression I don’t know if it would be super efficient since there is nothing super stable to push against.

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11/5/2017 8:16 AM

ga_pike wrote:

So is it the 2 pistons hitting that create a spark? No spark plug?

Maybe the injector goes on one side and the spark goes on the other.

I wonder if this would work with diesel applications where no spark is needed. Basically has a built in dual fueler. But where diesels have much more compression I don’t know if it would be super efficient since there is nothing super stable to push against.

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11/5/2017 8:22 AM

Just lay it down for lower weight. If one of the sides has a different friction, not good!

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11/5/2017 8:30 AM

Achates Power is contracted with Cummings to start producing opposed piston engines for the military in 2019.

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11/5/2017 8:51 AM

I don't think that engine can be vertical... oil lubing the top pistons would not get out, sideways pistons like VW and BMW motorcycles have been around forever.

I didn't notice how the exhaust was getting out. It looked like it flowed somehow through the center of the engine. Possibly with a turbo having a forced induction you can really pump as much air in as you want because of the direct injection, any extra air into the cylinder would just go out the exhaust and it would just be air, no fuel mixed with it yet. I don't know what affect that would have on emissions though.

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11/5/2017 8:53 AM
Edited Date/Time: 11/5/2017 9:00 AM

My dad tested this type of engine in the 60's for the British Army, It was a Commer TS3 and it was commercially available to power trucks back then, the test motors were also multi fuellers , designed to run on petrol , diesel, kerosene and i think parrafin. Its nothing new

https://en.wikipedia.org/wiki/Commer_TS3

I worked on the 5 stroke motor in this video from 3.14

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11/5/2017 9:12 AM

I feel my IQ dropping reading some of the reply's to this post. Although a few seem to know what they are talking about, geez at the dumb ideas flowing out. I have one... let's just make an opposing 4 piston engine? It would be twice as powerful as a 2 piston opposing. SMH...

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11/5/2017 9:48 AM

BobbyM wrote:

Watch it again. Less moving parts.

This.

The motor can lay sideways, too...making it an "opposed boxer" which would REALLY help with several design and engineering factors...from center of gravity to aerodynamics (lower hood and over-all dim's of the engine compartment, etc.) both of which have been factors when using a boxer engine as seen in new designs like Toyota's "86".

A short stroke version of this would take very little room and have minimal rotating mass. A longer stroke version would take more room and have more mass; but, typical design std's imply that it would make more torque.

Your cranks are out-board and opposing. This is an interesting design point when it comes to harmonics and balance. Those cranks are an engineers dream when it comes to utilizing opposing forces.

I like it.

No typical valve-train. Soooooo many fewer PARTS. Sooooooo easy to build. This design has the opportunity to utilize modern materials and can truly benefit from being a "clean sheet" design.

Nice!

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I ripped a start from Egypt and I was happy about that.

11/5/2017 10:31 AM
Edited Date/Time: 11/5/2017 6:46 PM

This is not the first time this design has been used. Fairbanks Morse built many engines in this configuration and were used in trains ships and other heavy applications.

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11/5/2017 2:07 PM

Blade Flanagan jr. wrote:

This is not the first time this design has been used. Fairbanks Morse built many engines in this configuration and were used in trains ships and other heavy applications.

i will be typing 'Fairbanks Morse' into you Tube again now. .. thanks LOL

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11/6/2017 4:30 AM
Edited Date/Time: 11/6/2017 4:33 AM

mingham97 wrote:

In both 2 and 4 stroke engines, exhaust gasses are pushed out by the pistons, but in the demo, the are supposed to flow out? Or sucked through the injectors? I missed that part.

Also, what is going to suck the oil out of the top. I dont think it will work the same as a conventional 4 stroke in the way of top end oil flow

mark911 wrote:

Not quite correct. Once the exhaust port (2 stroke) or the exhaust valve (4 stroke) cracks open the high pressure cylinder gasses start rapidly propagating down the exhaust system. In both cases, the piston is actually moving down the cylinder on the power stroke, typically around 90 degrees ATDC on a 2T and about 140 degrees ATDC on a 4T. Most of the high pressure within the cylinder is dumped down the exhaust port before the piston reaches BDC. On a 2T, the opening of the transfer ports and entry of high velocity charge along with proper expansion chamber design helps scavenge and dispose of the remaining residual exhaust before the port closes on the compression stroke. On a 4T, all the remaining inert gasses are pushed out the cylinder on the exhaust stroke. It takes quite a bit of HP (negative work) to push even a small amount of residual pressure from BDC to TDC, so getting EVO timing right is pretty important.

Regarding the Double Stroke, I'm sure the exhaust ports (top of the cylinder) open quite a bit before the intakes (bottom on the cylinder). Therefore, the high pressure in the cylinder will naturally blowdown as the exhaust port is exposed by the piston. The rapid mass acceleration of all the exhaust gas towards the exhaust port tends to leave a low pressure area in its wake. This, along with the pressure generated by the supercharger creates a nice pressure differential for the intake charge to move into the cylinder, again, helping to scavenge and dispose of the remaining residual exhaust before the exhaust port closes.

Regarding the oil flow, all radial airplane engines have cylinders "upsidedown". They somehow manage to make them very reliable.

Wow thanks for the explanation. To me, it makes sense for 99% of what youre saying except you said that "Most of the high pressure within the cylinder is dumped down the exhaust port before the piston reaches BDC". My understanding was that the valve does not open until BDC. Or does it open earlier? Is that what you mean by EVO timing? And by releasing the right amount of gas due to pressure difference, is the key to power? Rather then do negative work to push it out? I want to take one of your classes lol

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11/6/2017 5:57 AM

Nothing new about this design. Some of these responses are golden.

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11/6/2017 12:00 PM

It's all about efficiency. If you can follow the math, these guys really get into the logic behind the opposing piston theory.

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