| Author | Message | ||
     Ulynut |
From Kneeslider magazine...  Two stroke engines are favorites of everyone who wants a really compact engine with lots of power, there are fewer parts and power delivery on every stroke. Of course, the blue haze from the exhaust didn't sit well with the enviro-police so they've pretty much disappeared from use in transportation, but, they are slipping back with new technology applied to the new designs. EcoMotors has a design called OPOC, Opposed Piston Opposed Cylinder. The design is just what it says, as you can see above, with 2 cylinders and 4 pistons. Peter Hofbauer came up with the idea when he was at Volkswagen, the outboard pistons take the place of the cylinder head and each piston only travels half the distance necessary for the full stroke, allowing higher engine speeds. An electrically controlled turbocharger can be used when necessary with adjustable boost, it can even spin up before the engine starts to give instant boost. The engine can be built in a modular fashion, allowing more cylinders to be added in pairs with a clutch between the modules so one pair can be used at start or light load with the clutch adding more cylinders when required. Emissions are said to be very low, meeting EPA standards for both gasoline and diesel configurations. They're looking for 100 mpg in an automotive application, so just think what you could do with something like this in a motorcycle. Very cool! | ||
| Xl1200r |
Not an entirely new concept, but a welcome addition me thinks: http://en.wikipedia.org/wiki/Napier_Deltic | ||
| Just_ziptab |
Needs to be built in a "V" configuration. Interesting..wonder how the short rods get along with the double long rods at high rpm? | ||
| Slaughter |
Junkers had similar concepts in the Jumo - opposed pistons, crankshafts on the "top end" of the engine - combustion chamber between 2 pistons. Cool idea. More moving parts but more tolerable piston speeds http://en.wikipedia.org/wiki/Junkers_Jumo_204 | ||
| Rick_a |
Baere had done something similar with a "six stroke" air-cooled Ducati v-2 engine years ago. It was essentially a 4 stroke Ducati bottom end with an opposed cylinder 2 stroke top end working as the valve train at half-speed. | ||
| Hughlysses |
Very interesting. I'll bet a two-cylinder set has perfect balance because of the way the pistons are arranged. Fairbanks-Morse also built similar diesels to the Jumo mentioned above with twin cranks and twin opposed pistons per cylinder. They were used in stationary applications, submarines (even nucs), and F-M made their own locomotives using these engines for a while in the 50's. | ||
| Ferris_von_bueller |
"There is nothing new under the sun" | ||
| Reepicheep |
Very clever, the valve is the piston, like a two stroke, but having two of them lets you get more control over port timing. Neat! | ||
| Natexlh1000 |
Remember that piaggio two stroke that had two pistons opposed like that? The carb had two throats, one larger than the other which only passed fresh air to the crank case. The other throat was smaller and sent a very rich mixture of fuel to the top end where a tiny piston would force it through a poppet valve into the combustion chamber. The article I read said that it didn't smoke like a normal 50cc. | ||
| Mr_grumpy |
I've actually driven a vehicle with a 2 stroke opposed piston engine. Commer, part of the Rootes group who were eventually taken over by Chrysler, used to produce trucks powered by the TS3 engine. 3 cylinders 6 pistons one crankshaft & 6 rocker arms, oh & one big supercharger. They were a beast to drive & extremely noisy, went well though. This one is down in DD's part of the world. | ||
| Mndwgz |
Rotax two strokes with the rotary valve are fairly efficient. Two plug heads are mandated on the aircraft models which probably also helps clean up emmisions, but they still needed oil in the mix. They can be tuned for max. RPM, torque and H.P. with pipe design and port timing with a little grinding on the rotary valve, run gas, alcohol, or even a mix of alcohol/nitro like this one did.  | ||
| Hughlysses |
Chrysler seriously researched two-strokes for auto power back in the 90's; this engine was originally going to power the Neon. It's not hard to build a two-stroke that doesn't require oil in the intake mixture, you just can't do it with crankcase scavenging like most small two-strokes have. With conventional two-strokes, the "back" side of the piston pressurizes the crankcase which forces fuel/air/oil through a transfer port into the cylinder where it's burned. This design necessitates mixing (or injecting) oil with the fuel so that the mixture swirling around in the crankcase can lubricate the bearings and cylinder. The Chrysler designs used an external Roots type supercharger instead of crankcase scavenging. This let them use a conventional oil sump and pressure lubrication system for their design just like 4-stroke auto engines. These engines used direct fuel injection (VERY new at the time) and two spark plugs per cylinder. Evidently the engine worked well but had high NO2 emissions. Chrysler got into squabbles with the EPA and the whole program was dropped. More info here: http://www.allpar.com/neon/stroke.html (Message edited by Hughlysses on December 22, 2009) | ||
| Prowler |
I still don't understand why nobody seems to be looking into the latest design DI 2-strokes (like a new Evinrude Outboard has). The performance/weight/simplicity advantages are huge, and it should have no huge issues meeting exhaust regulations. | ||
| Crackhead |
That wold be bad in a SM. with the motor tucked up high at knee level oriented front to back, the motor would be the frame and the fuel would be under the seat. The turbo and muffler under the motor. The trans output could be right at the pivot point for the swingarm. | ||
| Ft_bstrd |
Cool Deltic video: | ||
| Ft_bstrd |
Holy crap, this is a scary mofo: | ||
| Klcm54a |
The Germans made the first motorcycle. Then, they moved on to tanks for a few years. Looks like one cylinder to me. I'll bet it is still more dependable and leaks less than a fatboy.  |
