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OT: 6 stroke engine?

fmarino1976 said:
Have any of you guys heard of this engine? http://www.sixstroke.com/index.html
Can some of you knowledgeable engine tinkerers give your opinion? I know it is a motorcycle engine, but I find the fact that people are trying to innovate the internal combustion engine appealing. What do you think?

What about this 6 stroke engine: http://www.autoweek.com/apps/pbcs.dll/article?AID=/20060224/FREE/60222004/1024
Click to expand...

This is an interesting engine technique. Since most otto-cycle engines waste over 50% of their BTUs as exhaust, anything that can improve that figure is a good idea. Even if this system can be made reliable though it wouldn't be a good system for aircraft. The reason is that you would have to carry water to expend in the steam cycle. You might get cooling drag improvements but I don't think that would make up for the payload. Water is one of the heaviest things we carry besides ourselves! I think this would be an excellent stationary engine, running generators or pumps. For aircraft I think turbo-compounding would be a lighter, if somewhat complex way to improve efficiency.
Bill Jepson
 
6 stroke engine

Hello chaps fellow members,
I think there needs to be a differentiation between types of 6 stroke engine
The Crower cycle is indeed a six cycle utilising a second steam expansion stroke.
The Beare cycle completes its cycle in four strokes of the main crank and two strokes of the upper crank 4+2= 6. with no steam .
The Beare engine is an over expansion engine with some simmilarities to the Miller or atkinson cycles.
consiquently the exhaust temperatures are lower than the conventional 4 stroke as more energy is extracted from the expansion before the exhaust is opened. this reduces overheating problems with aircooled engines . The combustion chamber layout easily allows multiple spark plugs for ignition safety.
what follows is an explanation blerb. cheers Malbeare

SWEPT VOLUME

Imagine a four stroke engine single cylinder capacity one litre
Bore 115mm stroke 96.3mm swept volume of 1000cc.
Imagine a Beare Head with a bore of 75mm and a stroke of 56.5mm a swept volume of 250cc.
Imagine that the combustion chamber volume is 100cc. the trapped volume when both upper and lower main piston are at their closest proximity with the top piston down as far as possible and the main piston at TDC.
INTAKE.
The main large piston is at TDC, the upper smaller piston is at the top of its bore or BDC, so the cylinder volume is 250cc plus 100cc equals 350cc.
As the main piston descends it is increasing volume. At the same time the upper piston is descending reducing volume.
At main piston BDC the main piston has swept 1000cc and the upper piston has descended half its bore as it is synchronized at half the main piston rotational speed. It has swept 125cc and reduced the swept volume by 125cc
Therefore the cylinder volume at main piston BDC is 1000cc add the combustion chamber, add the volume left in the upper piston of 125cc so the total volume is 1225cc
So the swept volume of the intake stroke is 1225cc minus the volume at the start of the intake stroke of 350cc
875cc
COMPRESSION.
The cylinder volume is 1225cc
The main piston ascends while the upper piston continues to descend, both pistons are reducing volume.
At TDC main piston has swept 1000cc while the upper piston has swept a further 125cc
Cylinder volume is now 100cc
So the swept volume is 1225 minus 100cc
1125cc.

EXPANSION
Cylinder volume is 100cc
The main piston descends while the upper piston ascends.
Both pistons are increasing volume.
At BDC the cylinder volume is main piston 1000cc and upper piston is 125cc.
Total cylinder volume is 1225cc
So the swept volume is 1225 minus 100cc
1125cc

EXHAUST
The cylinder volume is 1225
From BDC the main piston ascends reducing volume while the upper piston continues to ascend increasing volume
At TDC the main piston has swept 1000cc, the upper piston has increased volume by 125cc
The total cylinder volume is combustion chamber 100cc and upper piston volume 250cc
350cc
So the swept volume is 1225 minus 350cc.
875cc


The total swept volume over the four strokes is 4000cc
Intake 875cc add compression 1125cc add expansion 1125cc add exhaust 875cc
Therefore the nominal average capacity of the Beare cycle engine is
1000cc
Similar arguments and dissertations could apply to the miller cycle.

The waters could be muddied somewhat more by considering only the trapped volumes after all the ports have been closed. The Japanese used to apply this principle to two-strokes with corrected compression ratios.
There is a further complication if the upper piston crank is delayed or advanced in its rotational relationship with the main crank, or if it is a conventional crank and con rod or a scotch yoke drive. All have effects on the swept volume in regards to crank angle position.
But the net results are that the Beare cycle has advantages in gaining efficiency, pumping losses are reduced as less energy is expended to suck intake and pump out exhaust. And more energy is extracted during the expansion stroke. The expansion stroke being the largest change in swept volume, because of port timings, means that the Beare head, dual opposed piston cylinder head has similarities to the Atkins cycle and Miller cycle but is subtly different and perhaps deserves the name of Beare cycle.
If the upper piston is delayed in its rotational relationship by about 20 degrees the maximum volume no longer occurs at BDC but is at173 main crank degrees on intake and maximum volume occurs at 548 for expansion and minimum volume occurs at 361 and the rate of change in volume during combustion is less than the conventional four stroke maintaining a closer relationship to the theoretical ideal of constant volume combustion.. and therefore higher maximum cylinder pressures are achieved even though the compression ratio and open throttle cranking cylinder pressure may be the same as the conventional four stroke.
 
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6-stroker

Hi Mal,

It has been some years since we spoke, and I saw your bike run. That was around the time Sir Alan Cathcart rode it, so wondering what has happened in the meantime. I gather you also have some aviation interest ?

Cheers

Martin Hone
ex-AMCN
 
Efficiency increase?

Thanks for taking the time to explain the Beare cycle engine. Now, assuming 2 similar engines, one with a conventional valve arrangement and the other one with a beare head, what kind of efficiency gain can be expected? Would fuel consumption be similar? Thanks again.
 
6 stroke engine

fmarino1976 said:
Thanks for taking the time to explain the Beare cycle engine. Now, assuming 2 similar engines, one with a conventional valve arrangement and the other one with a beare head, what kind of efficiency gain can be expected? Would fuel consumption be similar? Thanks again.
Click to expand...

This is what can be achieved in the fuel economy stakes on an early prototype a Yamaha TT 500 conversion. same port area same compression ratio, cranking pressure 135PSI for both engines.

FUEL CONSUMPTION TEST
ROAD SPEED MPH 4STROKE RUN TIME SECONDS 100cc FUEL 6STROKE RUN TIME SECONDS
100cc FUEL LOADED RPM
In 5th GEAR % LONGER RUN TIME
30 MPH 4ST 159 sec 6ST 216 sec 2000 RPM 35.8%
35 MPH 4ST 138 sec 6ST 184 sec 2500 RPM 33%
40 MPH 4ST 107 sec 6ST 134 sec 3000 RPM 25.2%
45 MPH 4ST 89 sec 6ST 101 sec 3500 RPM 13%


YAMAHA TT 500cc
Test by Malcolm Beare, Elliot Munro, Grant Guy, July 1995
The dyno used was an old motorbike dyno with the rear wheel driving a large fan with a speed readout dial. The throttle was opend enough to maintain the designated speed. So the power outputs were identicle
The sixstroke head was designed to as closely match the fourstroke as possible compression ratio , valve timing , port sizes. Not a fully optimised sixstroke much more port area is available.
and compression ratio could be higher.
The sixstroke would run happily at lower revs(1000) than the fourstroke in 5th gear. The fourstroke would pull 4000 RPM at full throttle the sixstroke 3500.
Same gearing same carburetor.
Fuel was gravity fed to the carb from a long clear tube with two level marks to indicate 100cc.
Harvey said:
Hi Mal,

It has been some years since we spoke, and I saw your bike run. That was around the time Sir Alan Cathcart rode it, so wondering what has happened in the meantime. I gather you also have some aviation interest ?

Cheers

Martin Hone
ex-AMCN
Click to expand...

http://www.sixstroke.com/truth.htm
this is my personal oppinion based on my experience
I resigned as a director of Jack Brabham Engines Ltd when it became obvious that the MD APC was utilising shareholders funds inappropriately.
 
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Crower 6 stroke

I spoke with Bruce not long after the article came out in Autoweek, so I may have forgotten some of his details, but basically I came away believing that his engine had some potential in aviation, although development would be more difficult than in land-based engines.

The advantages seem to be total elimination of cooling drag loses, lighter engines and lower BSFC. All cooling would be accomplished by the water injection, and exhaust loses would be lessened by the fact that the burning of fuel would reheat the combustion chamber, cooling the exhaust gases somewhat. He hinted at BSFC's in the .2 lb/hp/hr range instead of .35-.45, a considerable savings. This was from one test engine.

The engine would be simpler to manufacture in that cooling fins would be eliminated, and perhaps the oil cooler. It would be more complex in that it would require water injection into the cylinders, similar to the way a diesel injects fuel. Whether this would be in the form of Cummins style (cam driven injectors) or Bosch style (separate pump) didn't come up in our discussion. I do know Bruce at one time had some contact with Cummins Engine Company.

While starting with a clean sheet of paper would obviously yield the best engine, an existing engine could be modified by adding a Bosch style pump, injector, and new cam/drive gear. Freezing of the water at altitude seemed to me to be one of the bigger problems. I haven't tried to figure what the weight of the water would be and we didn't discuss it. I don't know exactly how much water needs to be injected per each volume of fuel. The writeup suggest about equal volumes. This would determine if the total weight of the system plus fuel would be a negative. I am sure sealing of the combustion chamber (rings) would be very important for engine life, and that could be another problem area.

I don't expect to see this system developed for aircraft in anything like the near future. Stationary engine and perhaps even automobile could really use the system. Indirectly, this could help aviation with lessened demand for petroleum-based fuels.

Again, these are my recollections/interpretations of Bruce's system. Give him a call if you are interested; he is most enjoyable to talk with.

Bob Kelly
 
not to hijack but

wow you fellas timing is impecable. a student asked a fellow instructor can a 4 stroke diesel run backwards? now were not talking for a second or two, but just sit there and run. say's he started one up it was running poorly and instructed to switch off and restart. it then runs perfect was told it was running backwards. is this possible. seems to me it could happen due to the short exaust pipe on the fork lift. the fact that you still have a compression stroke, an ignition event and and exhaust event. i know diesels are timed by fuel and this would be out of time but there would still be fuel. eventually it would pump the oil out of the lubricatin sys.
 
cytoxin said:
wow you fellas timing is impecable. a student asked a fellow instructor can a 4 stroke diesel run backwards? now were not talking for a second or two, but just sit there and run. say's he started one up it was running poorly and instructed to switch off and restart. it then runs perfect was told it was running backwards. is this possible. seems to me it could happen due to the short exaust pipe on the fork lift. the fact that you still have a compression stroke, an ignition event and and exhaust event. i know diesels are timed by fuel and this would be out of time but there would still be fuel. eventually it would pump the oil out of the lubricatin sys.
Click to expand...

No a conventional piston engine 4 cycle diesel won't run backward. The timing events are all wrong. Basicly the engine would be trying to inhale through the exhaust valve. Won't work.
Bill Jepson
 
a develpoment

http://www.freepatentsonline.com/4388900.html
guess that pretty much answer the question. it seemed to me not much changed when a diesel ran backward. the exhaust is open the intake is open oxy can be inducted either way. the glow plugs are hot, still a compression stroke. would be weak and eventually seize but i beleive it would run.
 
Efficient engine

Really the Baere engine is a gasoline version of an opposed piston Diesel 2 cycle. Slightly lower compression and gasoline instead of diesel. The valvel tract is novel, but not the only way to do this job. It is one of those "on the right track" ideas because the opposed piston diesels are some of the most efficient ICE's ever made. People have also tried the old single sleeve valve which is another old idea whose time has returned. Interesting technology, but not revolutionary. The fact that it can be fitted to an existing engine is it's biggest claim to fame. It is also misnamed, since it is a strict Otto cycle 4 stroke engine. The wankel rotary is also a 4 cycle engine that looks different. There are many ways to achieve the same purpose, I commend Baere in comming up with an idea that can be run, even if it hasn't , so far lived up to all claims. Good job,
Bill Jepson
 
efficient engine

Rotary10-RV,
thankyou for your comments
The dyno I used was meant to emulate a rolling road but I think it provided somewhat more load than a level road as top speed at full throttle was only 45 MPH but in practice on the road the conventional 4 stroke bike is capable of 85 MPH. I have converted the 30 MPH fuel consumption into MPG and Metric figures so that a clearer picture can be seen
the 4 stroke was achieving 50.15 MPG (US) , 60.23 MPG (UK), 4.6895 Lt/ 100K the 6stroke was achieving 68.13MPG(US), 81.8MPG(UK), 3.4529 LT/100K

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fmarino1976 Join Date: Jan 2007
Location: Tricities, TN
Posts: 55

OT: 6 stroke engine?

--------------------------------------------------------------------------------

Have any of you guys heard of this engine? http://www.sixstroke.com/index.html
Can some of you knowledgeable engine tinkerers give your opinion? I know it is a motorcycle engine, but I find the fact that people are trying to innovate the internal combustion engine appealing. What do you think?

What about this 6 stroke engine: http://www.autoweek.com/apps/pbcs.d...E/60222004/1024
__________________
A&P, IA, Avionics Tech, and finally: Pilot! (12/28/06)
Dying to build an RV10. Not quite ready yet

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I believe the Bruce Crower engine to be a credible engine
I think that we are in a similar position of needing SAE verified efficiency figures
 
malbeare said:
Rotary10-RV,
thankyou for your comments
The dyno I used was meant to emulate a rolling road but I think it provided somewhat more load than a level road as top speed at full throttle was only 45 MPH but in practice on the road the conventional 4 stroke bike is capable of 85 MPH. I have converted the 30 MPH fuel consumption into MPG and Metric figures so that a clearer picture can be seen
the 4 stroke was achieving 50.15 MPG (US) , 60.23 MPG (UK), 4.6895 Lt/ 100K the 6stroke was achieving 68.13MPG(US), 81.8MPG(UK), 3.4529 LT/100K

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fmarino1976 Join Date: Jan 2007
Location: Tricities, TN
Posts: 55

OT: 6 stroke engine?
<snip>
Click to expand...

Mal,
Nice to hear straight from the horses mouth so to speak. Your engine configuration is interesting. Novel thinking is rare. I'm sure you have seen some of the 2-cycle diesels I mentioned Fairbanks-Morse in the USA and I believe Napier and some others in the UK. These engines seem to work well because they can absorb power later into the expansion cycle (power stroke) than conventional single sided piston engines. Your layout does seem to have efficiency advantages. The hardest part is often how to drive from the "head" crank to "main" crank. Pardon my nomenclature but it easist for me to understand. I like what you have done because it doesn't REQUIRE a supercharger to run like the 2 cycle diesels. I would like to see how you plan to run and take drive from a multi-cylinder per bank engine. (I don't think it too difficult, I'd just like to see how the idea might expand) I spent considerable time researching the single sleeve valve engine, probably for the same reasons that you built your engine. I always like to look both backward and forward when designing. Often good ideas are abandoned when at some nexus of history. The sleeve-valve's demise was the gas turbine. Your design seems like it has shown good efficiency. Expected but needs updates to bring the power to where you want it to be. This can probably be done, you just need some time to get everything at its optimum. (Perhaps since the articles shown you already have.) Very few engines do as well as you already have. Keep at it and good luck! Keep us posted of progress.
Bill Jepson
 
Yes we are constructing a couple of prototypes to test a number of ideas. But I will not say much about that.
consider the limitations of the conventional 4 valve head. The valves dictate the shape of the combustion chamber and the shape of the piston top.There is only one place to put the spark plug and multiple plugs and direct injection is nearly impossible
The squish area is limited and the combustion chamber is flatish with a high percentage of combustion occuring in the valve cutouts in the top of the piston.
the best shape for the piston top is dead flat as this presents the minnimum surface area to the flame front thus absorbing less heat and keeping the heat in the gas for higher efficiency of the cycle and less engine heat.
The best shape for the combustion chamber is a sphere for similar reasons but the next best is a squat cylinder like the may fireball with plenty of swirl and squish. The best position for multiple spark plugs is in the sidewall of this squat cylinder.The 4 valve head breathes well but is not ideal for efficient combustion , the may fireball has a good efficient combustion chamber but does not breath well as it is only a 2 valve with maskesd valves. I am aiming with the Beare Head to have the best of both with the extra efficiency of the opposed piston design.
 
New twist on the same old

Some where deep down inside there has to be: Suck, Squeeze, Bang, Blow. That has not changed.

Even a jet engine is: suck-squeeze-(flame)expand-blow

The 6 stroke looks cool, but that rotary valve is more complication. Very cool but I always wounder, if a new engine is better, why does it not gain wide spread popularity? There are always trade-offs I guess. The claimed 35% better fuel burn over 4-stroke sounds pretty awesome if true. Love the burn out vid. Not sure what that proves but its fun.
 
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Suck, Squeeze, Bang, Blow

gmcjetpilot,
most major engine manufacturers have a huge investment inertia so it is hard to change production lines. so initially I expect it will be a small product run in a specialised field like unmanned survey reconosance or racing conversions.
Once totally proven then manufacturers will be willing to make the investment in new production lines. everybody is looking though.
The burnout is to display high torque at low revs just what you need for a direct drive propellor between 2000 rpm and 3000rpm for light aircraft. Just make it a biger prop when you do your lycoming continental rotax conversion with Beare Heads :p
 
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malbeare said:
gmcjetpilot,
most major engine manufacturers have a huge investment inertia so it is hard to change production lines. so initially I expect it will be a small product run in a specialised field like unmanned survey reconosance or racing conversions.
Once totally proven then manufacturers will be willing to make the investment in new production lines. everybody is looking though.
The burnout is to display high torque at low revs just what you need for a direct drive propellor between 2000 rpm and 3000rpm for light aircraft. Just make it a biger prop when you do your lycoming continental rotax conversion with Beare Heads :p
Click to expand...

Mal,
One thing that interests me is how much is optomised by combustion chamber shape? That is something that got me looking at the sleeve valve as well. Sir Henry Ricardo built some amazingly high output/cc sleeve valve test engines for Rolls Royce. He mentioned that they were resistant to detonation due to the combustion chamber lacking hot spots and being nearly perfectly hemispherical. If that is one of the trade secrets I'll understand.
Bill Jepson
 
chamber shape

Bill,
As a rule of thumb if you can eliminate the exhaust valve and have a good compact shape i.e. : closer to spherical , then it is worth about 2 compression ratio points using the same octane rated fuel. Say from 10 to 1 it allows 12 to 1.
cheers Mal
 
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