six stroke engine

[Grael]

Found this link a while ago...

http://www.damninteresting.com/?p=467

So, who's gonna build one?

[Grael]

Hmmmm, I thought this engine would spark up more conversation than this...

[Doug]

What do you want us to say?

Its been done and out there for a while now and no one has seen a single mass produced machine of any kind using this 6 stroke system. So we must assume its not cost effective or completely developed.

I'd like to see a Uniflow crank case scavanged apposed twin low speed diesel myself

[Quinnf]

6 and 8 stroke cycle engines have been around for more than 100 years.  Nothing new there.  Mostly they seem to have been devised as a way of getting around the patents on the Otto 4 stroke cycle, the first of which was built in 1861.  Internal combustion engines were cutting edge technology in the late 1800s and early 1900s, and the best and brightest engineers were doing everything they could to out-innovate each other.  Hence, there is not much new to be learned today that hasn't already been thoroughly investigated.

One interesting 8-stroke cycle engine was built by Aeromotor that you can read about at:

http://www.lonestarengineworks.com/aeromotor_engine.html


Quinn

[Grael]

Point taken. I just never seen it discussed here before, (did a search) and I was just wondering what you all have to say about it because it seems that it would be quite a bit more efficient than a regular 4 stroke and worth building.

[Grael]

One interesting 8-stroke cycle engine was built by Aeromotor that you can read about at:

http://www.lonestarengineworks.com/aeromotor_engine.html


Quinn

Neato! Gives me am idea... I might just be crazy enough to order one...

[dpollo]

My father and his brother in law unearthed an Aeromotor while digging a basement in 1949.  Dad cleaned it up and got it to run. It made the most amazing sounds....  putt putt slurp bang!  I never got to run it myself as I was just an infant but enjoyed turning it over and watching the gears.  No one ever expected me to be a pianist so my fingers were expendable, I guess.

Then one day, the flywheel, crankshaft and con rod were gone !   Dad had made a  soil shaker for the greenhouses, and surprisingly we still use it despite 50 plus years of sand and soil over the working parts. The rest of the aeromotor eventually went for scrap but I did see another at an agricultural artifacts museum.

I may just have to get one of these models, but first will check to see if the machine work is simple enough for an amateur.

[sid]

the aeromotor is still around.a lot of them were dug out the ground and restored/it is supprising how many i see// never cared for them /of course that could be the price// the going rate is $2-$3000.00// the first one you see it would be hard to recognize it as a gas engine.. it look like a bunch of rusty gears moving  around..has no appeal at all.of course every openion will vary//sid

[Quinnf]

Yeah, they did some crazy things back in the day, but efficiency wasn't ever gained over the 4 stroke cycle and some of the variants.  When you factor in pumping losses and friction, you won't make up efficiency by allowing the engine to freewheel.  With good exhaust scavenging, a two-stroke cycle engine should be more efficient than a 4-stroke. 

I just bought one of those yuppie tree-hugger Toyota Priuses for the daily commute and lo and behold, the engine is an Atkinson cycle which is a variant of the 4-stroke cycle, but is more efficient at the expense of less power, which the battery storage makes up for to yield higher overall efficiency.

http://en.wikipedia.org/wiki/Atkinson_cycle

Quoth Wikipedia: "The Atkinson cycle may also refer to a four stroke piston engine in which the intake valve is held open longer than normal to allow a reverse flow of intake air into the intake manifold. Compression is reduced (for a time the air is escaping the cylinder freely rather than being compressed) but the expansion process is unchanged. This means the compression ratio is smaller than the expansion ratio. Heat gained from burning fuel increases the pressure, thereby forcing the piston to move, expanding the air volume beyond the volume when compression began. For any given portion of air, the greater expansion ratio allows more energy to be converted from heat to useful mechanical energy meaning the engine is more efficient.

The disadvantage of the four-stroke Atkinson-cycle engine versus the more common Otto-cycle engine is reduced power density. Because a smaller portion of the intake stroke is devoted to compressing the intake air, an Atkinson-cycle engine does not take in as much air as would a similarly designed and sized Otto-cycle engine.

Four stroke engines of this type with this same type of intake valve motion but with forced induction (supercharging) are known as Miller cycle engines."

So if it's efficiency you're looking for, it appears it can be achieved by just redoing the cam lobes.  Dunno if it would work in a slow speed engine, or not, but it's an interesting concept, and cam lobes aren't all that hard to grind and swap in one of these engines.  Might be a fun project.

Quinn

[Quinnf]

I know it's not a good sign when you're replying to your own posts, especially if you're over 50.  People start to talking, you know.

But I just ran across an animation that shows how the Atkinson Cycle works.  http://www.keveney.com/Atkinson.html 

And Dave Gingery documented the construction of one in

http://www.lindsaybks.com/dgjp/djgbk/diff/index.html

Quinn

[mike90045]

  Mostly they seem to have been devised as a way of getting around the patents on the Otto 4 stroke cycle, the first of which was built in 1861.

How long do patents end up hanging around ? 

[Quinnf]

I don't know what it was 100 years ago, but patents are now good for 20 years from date of filing or 17 years from date of issue.  Back at the turn of the last century this was cutting edge technology that was rapidly changing the world, and there was tremendous competition among engine manufacturers.  As the technology evolved new patents were filed on the innovation.  I suspect the Lister cold start valve was such an innovation because you didn't see the idea adopted by everybody else once the patent expired.

Quinn

[oliver90owner]

Quinn,

You are right, technology (the word hadn't been properly invented then?) had moved on and engines were now spinning at three times the lister CS.  Less metal, more power, cheaper.  New startomatic installations in the UK would have been much rarer by then as most places were on mains power by then.

Glow plugs were used on diesels in the 50s, so along with electric start things were easier to get going when very cold.  I remember the Landrover diesel engine (being a conversion of the petrol engine) being an early (for me) experience of dodgy heater plug starting systems.  If it wasn't glow plugs it was the 'ki' start like the Fergusons or the manifold heaters on Ford tractors.  Even ether, as a starting aid, was around in the late 50s.  I remember.  The top rings on our Landie were all shattered at 54 thousand miles, most likely due to starting it on ether and heater plugs!

Regards, RAB

Regards, RAB