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Guest_PAULIE_D_*
post Apr 28 2005, 09:35 PM
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Six-Stroke Engine
The capacity for original thought is a mark of genius. In the past century, it has delivered us countless advances. Often, they have been achieved against the odds, in the face of reactions ranging from disinterest to scorn: almost every engineer has to deal with dismissive responses to new ideas, usually on the basis that something so different obviously can’t be good. On that basis, we should all be riding single-cylinder side-valve motorcycles. Daring to be different is obviously essential.
Malcolm Beare, a 53-year-old Australian wheat farmer is indeed an original thinker. Designing a better motorcycle engine has been his mission since 1981, when he built his first prototype. Beare has created an innovative hybrid design of the internal combustion engine, combining a two-stroke top with a four-stroke middle section of sorts. An exciting V-twin Ducati-based BEARS/Sound of Thunder racer incorporating Malcolm’s self-built frame, fitted with a 90deg V-twin version of the Beare six-stroke engine was the first multi-cylinder application of six-stroke technology.
Beare began working 23 years ago on a stratified charge opposed-piston two-stroke, he recalls, “but after building a couple of prototypes I realised flow control was a problem, with too many ports going everywhere.” He thus simplified it into a six-stroke, with the objective of improved efficiency by overcoming the drawbacks of poppet valves, with rotary valve application (commonly used in two-stroke engines). This overcomes the problems of poppet valve inertia that inhibits flow, especially the exhaust valve hotspot within the combustion chamber.
While various rotary valve designs made in the past were advantageous because they didn’t restrict flow or absorb as much energy as poppet valves, they had significant overheating problems, with associated drawbacks in sealing, lubrication and oil consumption. So Beare decided to produce the best of both worlds, taking the basic components of a rotary disc-induction two-stroke engine, and mating it with a four-stroke motor.
“After a great deal of work and experimentation since building my first six-stroke prototype in 1990, I truly believe we’ve refined the concept, proved its reliability and established its worth, so now we have it fully patented — even in the USA — and ready for commercial use in the variety of applications it obviously lends itself to —including motorcycles, stationary engines and propeller aircraft engines.
Below the cylinder head, everything is conventional. So one advantage is that the Beare concept can be transplanted on existing engines without redesigning. But above there, he’s thrown away the cylinder head, complete with poppet valves. To replace the camshaft and associated valves, Beare has retained the cam drivebelt and fitted an ultra short-stroke upper crankshaft complete with its inverted piston, the belt driven at exactly half engine speed.
This piston slides up and down in a sleeve, past inlet and exhaust port cavities set into the cylinder wall, very much like on a two-stroke. Continuing the two-stroke analogy, the Ducati-based V-twin is fed fuel-air mixture via a reed valve, thus preventing exhaust gas exit through the inlet port. Beare technology recently has been paired with a new form of fuel injection known as the Pulse Fuel Injection system, which has been tested by the US Naval Air Warfare Centre, among other international authorities. Unlike conventional fuel injectors, compressed air is used to atomise liquid fuel and pre-mix it with air, increasing efficiency and reducing emissions. Interestingly, this nozzle technology is being developed for emission control systems in diesel exhausts for Ford Motor Company.
At the other end of the upper crankshaft is a two-stroke type rotary disc valve that regulates exhaust timing, cutting off the exhaust flow at the appropriate time to stop gas returning into the cylinder, and thereby creating the inlet cycle suction. This being its only function, the valve bears a light load, reducing lubrication and sealing problems. The Ducati I rode uses hardened, anodised aluminium rotary disc valves, which work well. Then, during the compression and expansion strokes, the upper piston seals both ports, leaving pressure between the two pistons. The lower piston is a conventional flat-top three-ring design, while the conical upper one (so shaped to aid gas flow during both inlet and exhaust cycles, by guiding it towards the ports) has two rings — one compression, one oil.
In the combustion phase, twin sparkplugs provide ignition. Not only does the engine run on pure petrol (no need to add oil, because it is positively lubricated, in spite of the application of two-stroke technology), it’s very happy on low octane unleaded fuel — a boon for the Indian market. OK, so the Beare six-stroke has impeccable credentials but that just gives a hint at the commercial and technical advantages Malcolm seems justified in claiming. This new technology has some strong backing — Sir Jack Brabham, the renowned three-time World F1 Champion, keenly supports the Beare idealogy and his eponymous firm has gone to the world market along with CEO Alan Casey.
The obvious benefit in eliminating poppet valves on a four-stroke is that it removes any chance of valve float, which in turn implies a far higher safe rev limit for the six-stroke — an eye-popping 28,000rpm in theory, given the half engine-speed operation of the upper crankshaft, and the fact that GP reed-valve two-strokes peak at 14,000rpm. But Malcolm Beare says the rev limit, primarily depends on what the crankshaft can bear and so he’s arbitrarily limited the Ducati-based 6S-V2 to 9000rpm, at which point he says 86bhp is delivered at the rear wheel. Instead of absorbing about 10 percent of engine power in driving the camshafts, the cambelts now deliver about nine percent net power back to the main crankshaft, via the upper, conical porting piston. If you factor in a 1997 model Ducati 900SS delivered 73bhp at the rear wheel in stock form, that’s quite an impressive claimed power increase.
But there are other, much more significant apparent spin-off benefits from the Beare design. It is these that make it seem so very viable for a demanding Indian market, the most important being the ubiquitous fuel economy. Beare claims his engine is 35 percent more economical at low revs/throttle openings than the equivalent conventional engine, and 13 percent less thirsty at high rpm/full throttle. Therefore, there are reduced hydrocarbon emissions, because you use less fuel to achieve the same performance.
Next, there’s improved torque at lower revs proven on all prototypes, which will surely help in the stop-and-go nature of congested Indian traffic. Beare discovered the six-stroke version produced the same torque as the four-stroke conventional motor 1000rpm lower down the rev scale, as well as making exponentially more torque as revs rose. But in a commercial application, perhaps the most attractive benefit is the significantly reduced number of moving parts, compared to a four-stroke — not as few as a two-stroke, but what you appear to get is improved performance and torque, coupled with four-stroke inherent advantages. Fewer moving parts also mean reduced manufacturing costs.
My riding impression of the 6S-V2 revealed that while the Beare V-twin may appear a little rough at the edges, it’s obviously built to a budget as well as acting as a rolling testbed for continuous modification. So let’s ignore the looks and worry about the sizzle.
For starters, it has an absolutely unique engine sound, like nothing else I’ve ever heard in my life. You clearly hear the ring-ding two-stroke signature above the trademark four-stroke V-twin boom from the twin megaphone exhausts. An uncanny two engines in one. Malcolm claims there’s much reduced mechanical noise from the engine, because of fewer moving parts. Without any tappet noise, it’s remarkably silent — and that’s in spite of being air-cooled. Heat dissipation is not a problem, so while it’d be easy to water-cool the engine, there’s honestly no need for the extra complication on grounds of noise or thermal efficiency. Riding the bike for a dozen laps showed up three significant assets for the six-stroke engine and one negative. The question mark hung over the power curve: while there’s no doubt it revs reasonably high by four-stroke standards, there seemed to be no direct benefit in doing so — there was no more power up high at, say, 8000rpm than there seemed to be 2000 revs lower.
One thing Beare certainly doesn’t need to worry about is torque, a vital ingredient for the Indian rider, which together with the crisp, responsive throttle pickup and the reduced vibration are the three strong points of the six-stroke motor. The Beare engine is unbelievably muscular in terms of torque, and importantly from very low revs. Ironically, you appreciate this because Malcolm’s evident talents as a bush engineer are not matched by those of a tube-bender: the square-tube chassis was pretty awful in terms of handling. But the fact that the bike jumps around over bumps and doesn’t steer very well actually helps you appreciate the engine’s responsiveness,because you need to back off the throttle in, say, the middle of a chicane to allow the chassis to recover. But when you get on the gas again — get ready for a surprise. Not only is there instant response when you twist the wrist, there’s tractor-pulling torque at seemingly whatever revs the engine’s turning over at — even as low as what felt like 2000-3000rpm or so.
There’s also no transmission snatch at very low revs, indicating a responsive, torquey motor, while the manner in which it pulls hard from way down low bears all the hallmarks of a long-stroke engine design, whereas the opposite is in fact the case: the lower ‘four-stroke’ crankshaft assembly has 86 x 57mm dimensions, while the upper ‘two-stroke’ measures 60 x 25mm.
Yet the inherent nature of the Beare motor is one of a torquey slugger, belying these measurements. And allied with the so-responsive pickup and a wide spread of usable power, makes this bike ridiculously easy to ride. You hardly need to use the gearbox, just park it in top gear and ride. Even backing off the throttle in the middle of a turn doesn’t require hooking down a gear — just crack it open when you’re ready and feel the front wheel start to aviate on you. My hands-on assessment of the Beare six-stroke leads to some inescapable conclusions. What we have here is a hybrid engine design with the advantages already recounted above, allied with good squish, the ability to run radical bore/stroke ratios, quiet mechanical operation, and no exotic materials such as ceramic coatings or costly alloys required, nor complicated machining operations.
As such, the Beare design surely seems worthy of serious consideration for powering low-cost transportation in developing countries like India, where expense of manufacture, fuel economy and torque (delivering carrying capacity for people and/or goods) are all paramount factors, yet where emissions matter too.
The industry trend away from cheaper two-stroke power in favour of costlier but cleaner four-stroke engines in both Europe, Japan and South EastAsia makes a concept like the Beare six-stroke, which offers the best of both worlds, project a strong case towards volume manufacture. At the time of going to print, Autocar India had learnt of a six-stroke small capacity single-cylinder protoype being in the pipeline for production by a leading motorcycle manufacturer in China, but few details are available. What is known is that a 150cc six-stroke Taiwanese single-cylinder bike from Yingang is ready to roll. The questions of how the technology will work in actual practice, whether it does make it into production reality at all in India, and how reliable it proves under harsh and demanding use remain to be answered. Watch this space.


Links:
http://www.sixstroke.com/
http://www.jack-brabham-engines.com/sitemap.htm
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Halflifehavock13
post Apr 29 2005, 07:28 AM
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Its gonna be interesting if automakers pick up on this.
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z0ne
post Apr 29 2005, 08:58 AM
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QUOTE(Halflifehavock13 @ Apr 29 2005, 11:28 AM)
Its gonna be interesting if automakers pick up on this.

it is an interesting idea. but, i highly doubt that automakers, especially US automakers will pick this up.. too much shit going on and too much that could possibly break would be something along the lines of their excuse.. also, they would need to re-train like 200,000 mexican mechanics on how to fix our cars when they break down
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fiber optic
post Apr 29 2005, 09:42 AM
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QUOTE(z0ne @ Apr 29 2005, 10:58 AM)
they would need to re-train like 200,000 mexican mechanics on how to fix our cars when they break down

I'm so relieved to see that there's no ignorance on these forums.
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Phix
post Apr 29 2005, 12:12 PM
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QUOTE(fiber optic @ Apr 29 2005, 01:42 PM)
I'm so relieved to see that there's no ignorance on these forums.

Heh. I never tire of your sarcasm. thumbs_up.gif
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malbeare
post Apr 29 2005, 01:12 PM
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Hi folks here is some more info not appearing on the website cool.gif

(1)The 6-stroke engine is fundamentally superior to the 4- stroke because the head is a net contributor to, and an integral part of the power generation within the engine, unlike a cam only absorbing power.
(2) The 6stroke is thermodynamically more efficient because the change in volume of the power stroke is greater than the intake, compression, & exhaust strokes.
(3) The compression ratio can be increased because of the absence of hot spots in the combustion chamber.
(4) The rate of change in volume during the critical combustion period is less than in a 4stroke.
(5) The absence of valves within the combustion chamber allows design freedom 50% squish compact shape .
(6) A one-piece engine from crankshaft to upper shaft becomes feasible. No head gasket.
(7) Fewer components, 15 per cylinder compared to 40 for a 4-stroke. Therefore the cost of manufacture is much less.
(8)Can be fitted to standard engine blocks so the market is much larger than the OEM sector, also includes the retrofit aftermarket sector.
The engine has proven to be robust on the racetrack, & have significant advantages over 4-strokes
(1) The valving is desmodromic
(2) There are no valves to drop or bounce.
(3) The rev limit is only what the bottom end can stand.
(4) Gas flow on intake increase of 20%.
(5) No possibility of engine damage if the timing belt slips or snaps
(6) the reed valves are so close to the intake ports that their tips become the virtual port opening. This achieves variable port area & variable engine demand valve timing. The tips open late & small amounts with low throttle settings & open early & fully at full throttle

Malbeare
http://www.sixstroke.com/

The valving is really piston porting augmented by disks and or reed valves. First the upper piston opens the exhaust ports. No other ports are exposed for 20 to 30 degrees to allow for a blowdown period. When the intake ports are exposed the reed valves prevent backflow and the intake disk is blocking its port. The exhaust stroke continues and towards TDC the exhaust disk begins to close its port and the intake disk begins to open its port. The intake reeds open whenever pressure differentials between intake manifold and cylinder allow. The disks are set in timing for the desired overlap. The exhaust system design plays a large part in evacuating the cylinder and starting the intake, as the ports are fully open at this stage.
The exhaust disk closes and intake continues.
The upper piston closes all the ports at aprox 60ATDC and compression begins. I have found it to be most advantageous to retard the upper piston in its relationship with the main piston by between 10 and 20 degrees to have peak cylinder pressure at the upper pistons TDC or aprox 15degs ATDC ignition timing advance seems to be best at aprox 25 degs advance.
The cycle has some similarities to the Miller and Atkins cycle in that the intake volume is less than the expansion volume.
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ZonDa
post Apr 29 2005, 01:22 PM
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cliff-notes anyone?
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Dylan
post Apr 29 2005, 03:04 PM
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The name's ディラン ^_^
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QUOTE(ZonDa @ Apr 29 2005, 05:22 PM)
cliff-notes anyone?

Haha, yeah. The thread title sounds interesting though!
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moe89
post Apr 29 2005, 04:29 PM
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I'm not exactly sure what this is exactly about, but advancement in technologies is good either way thumbs_up.gif laugh.gif
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z0ne
post Apr 29 2005, 07:11 PM
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QUOTE(fiber optic @ Apr 29 2005, 01:42 PM)
I'm so relieved to see that there's no ignorance on these forums.

its just harmless fun. cyclone says shit all the time and i dont take it to heart.
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goota
post Apr 29 2005, 07:50 PM
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QUOTE(malbeare @ Apr 29 2005, 02:12 PM)
Hi folks here is some more info not appearing on the website cool.gif

(1)The 6-stroke engine is fundamentally superior to the 4- stroke because the head is a net contributor to, and an integral part of the power generation within the engine, unlike a cam only absorbing power.
(2) The 6stroke is thermodynamically more efficient because the change in volume of the power stroke is greater than the intake, compression, & exhaust strokes.
(3) The compression ratio can be increased because of the absence of hot spots in the combustion chamber.
(4) The rate of change in volume during the critical combustion period is less than in a 4stroke.
(5) The absence of valves within the combustion chamber allows design freedom 50% squish compact shape .
(6) A one-piece engine from crankshaft to upper shaft becomes feasible. No head gasket.
(7) Fewer components, 15 per cylinder compared to 40 for a 4-stroke. Therefore the cost of manufacture is much less.
(8)Can be fitted to standard engine blocks so the market is much larger than the OEM sector, also includes the retrofit aftermarket sector.
The engine has proven to be robust on the racetrack, & have significant advantages over 4-strokes
(1) The valving is desmodromic
(2) There are no valves to drop or bounce.
(3) The rev limit is only what the bottom end can stand.
(4) Gas flow on intake increase of 20%.
(5) No possibility of engine damage if the timing belt slips or snaps
(6) the reed valves are so close to the intake ports that their tips become the virtual port opening. This achieves variable port area & variable engine demand valve timing. The tips open late & small amounts with low throttle settings & open early & fully at full throttle
(7) air assisted fuel injection has unsurpassed (5 micron with 20% air premix) fuel mixture preparation directly into the cylinder without the inhibiting poppett valve in the way, just a lovely big port. And the injector is protected from combustion.
Malbeare
http://www.jack-brabham-engines.com/

The valving is really piston porting augmented by disks and or reed valves. First the upper piston opens the exhaust ports. No other ports are exposed for 20 to 30 degrees to allow for a blowdown period. When the intake ports are exposed the reed valves prevent backflow and the intake disk is blocking its port. The exhaust stroke continues and towards TDC the exhaust disk begins to close its port and the intake disk begins to open its port. The intake reeds open whenever pressure differentials between intake manifold and cylinder allow. The disks are set in timing for the desired overlap. The exhaust system design plays a large part in evacuating the cylinder and starting the intake, as the ports are fully open at this stage.
The exhaust disk closes and intake continues.
The upper piston closes all the ports at aprox 60ATDC and compression begins. I have found it to be most advantageous to retard the upper piston in its relationship with the main piston by between 10 and 20 degrees to have peak cylinder pressure at the upper pistons TDC or aprox 15degs ATDC ignition timing advance seems to be best at aprox 25 degs advance.
The cycle has some similarities to the Miller and Atkins cycle in that the intake volume is less than the expansion volume.

is this the real guy?

cuz does anyone else notice his name???


anyways, thanks for the info ^__^
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Guest_PAULIE_D_*
post Apr 29 2005, 09:49 PM
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QUOTE(goota @ Apr 29 2005, 11:50 PM)
is this the real guy?

cuz does anyone else notice his name???


anyways, thanks for the info ^__^

I would imagine it is him.

Thanks for the info! Please stick around and contribute to the forum. thumbs_up.gif
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Guest_PAULIE_D_*
post Apr 29 2005, 09:55 PM
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I would like to see an animated gif / flash movie or a series of diagrams which clearly show the 6 different strokes.
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The Milky Man
post Apr 30 2005, 01:07 AM
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QUOTE(PAULIE_D @ Apr 29 2005, 09:55 PM)
I would like to see an animated gif / flash movie or a series of diagrams which clearly show the 6 different strokes.

Yea, I was looking around to find one of those... huh.gif
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fallon
post Apr 30 2005, 07:32 PM
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Very interesting. Basically it sounds like more power with increased efficiency in a more compact simple package. it gets my vote.
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malbeare
post Apr 30 2005, 07:56 PM
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Thankyou for your comments. We would like to go seriously racing but lack the readies at the moment.
To help keep a cap on power and, hence, speed, the MSMA has decided to propose a reduction in engine capacity from 990cc to 900cc. "The intention is not to reduce performance but to prevent a continuous improvement in speed and lap times," according to the press release.

2004 2007 weight changes
2 Cylinders 135 Kg 133Kg - -2Kg
3 Cylinders 135Kg 140.5 Kg +5.5Kg
4 cylinders 145 Kg 148Kg + 3Kg
5 cylinders 145Kg 155.5 Kg +10.5 Kg
6 cylinders 155Kg 163 Kg +8Kg


The proposed changes to the rules also affect the minimum weight standards, adding more weight to engines with more than two cylinders from 2007.


The proposed changes above may indicate the technical direction that some manufacturers are pursuing for the future. As Honda is the most powerful voice among the companies, it is interesting that the proposed minimum weight for five-cylinder machines, such as the Honda RC211V (and Proton KRV5), has been increased the greatest amount. This may indicate that Big Red is already working on new engine configurations and is looking to abandon the V-5.

And, as two-cylinder bikes are the only ones to get a minimum weight decrease, might we see the introduction of a 900cc MotoGP V-Twin? If so, it wouldn't be as powerful, no doubt, but it would enjoy nearly a 50-pound weight advantage over a V-5-powered machine. And, as a Twin would have a 66-pound advantage over a six-cylinder-powered bike, it looks like the rumors of a Honda V-6 will not be fulfilled.

The MSMA is also looking at perhaps reducing the 2005 rule for a 22-liter fuel tank capacity (down 2 liters from current rules) for the 2007 season.

The introduction of 4-stroke machines to MotoGP has resulted in a huge amount of newfound interest in the class. Now, with revised regulations again on the table, the series might get even more interesting.


The Testastretta engine fitted to the Ducati 998R 2002 version, the bore is 104 mm.
Unfortunately, such a large bore currently causes combustion problems with dramatically decreased efficiency.
This stems fundamentally from the need to augment the injection advance and from the worsening of the "shape factor" of the combustion chamber which, with the reduction of the bore/stroke ratio, becomes ever broader and flatter. The "shape factor" is a critical synthetic value to check a combustion chamber's good operation, and a good indicator of its compactness and "thermal efficiency".
It should be borne in mind that aspirated racing engines require rather extreme valve lift and overlap angles, therefore, cavities are made in the piston crowns to prevent contact with the half-open valves. The combustion chamber is therefore practically contained in the piston cavities, such cavities becoming bigger as the stroke/bore ratio decreases, which makes it hard to obtain the high compression ratios required by high specific power engines.

The Beare sixstroke does not have these limitations because the main lower piston does not have valve cutouts and the combustion chamber is a compact design with squish contribution from both upper and lower pistons. The shape is much more like a fist than a flat hand hence thermal efficiency is high .
Combustion chamber diameter oprox 75mm
The main piston is lighter and stronger than the 4-stroke, because the lack of cutouts allow a thinner slightly domed top
Malcolm does believe that the sixstroke 15kg weight advantage will be a major benefit for the Beare Sixstroke, much more so than the 30kg handicap enjoyed by Twins in 500cc twostroke racing. "Working on the assumption that all these four-strokes are going to make enough horsepower, 15 kilos is a lot," he says. It’s straightforward enough, the Twins will have a 10 percent weight advantage and force equals mass times acceleration, so it is a big difference.


Sixstroke Beare 900cc Vtwin MOTO GP

Bore 116.25 mm stroke 42.5 upper bore 82mm upper stroke 34mm
compression ratio 12.25 to 1
power 337HP @ 15000 RPM
torque 74.6Ft/Lbs x80% x2 = 118Ft /Lbs
piston speed at 18000 is 5019 Ft/min or 25.4965 Mtre / sec
XL engine file
Torque 101.2 NM or 74.6 Ft /Lbs discount by 20% and multiply by 2 for twin cylinder is 118 FT/ Lbs
6 port design with 3 exhaust ports leading to a rotary disk, 3 intake ports,One intake rotary disk and 2 reed valves with air assisted injectors. 2 or 4 10mm plugs per cylinder.
The port area is oprox 20% to 30% more than a 4 valve head
Results of XL file sixstroke touque calculator

Based on Dual Cycle
Total Torque
Fourstroke 62.00

Main Top
66.05 35.15 101.20

Increase in torque 63.23%


www.sixstroke.com/

Malbeare
Things are a little more complicated than you would expect
During the intake stroke the main piston is increasing the cylinder volume while the upper piston is decreasing the volume (half of its stroke) so the net change in volume is +722cc . During the compression stroke the upper piston is still reducing volume (half its stroke) while the main piston is also reducing volume, net change -1082cc.
During the expansion stroke the upper piston is increasing the volume (half of its stroke) while the main piston is increasing volume, also net change +1082cc.
During the exhaust stroke the upper piston is increasing volume (half of its stroke) while the main piston is decreasing volume, net change -722cc
if you add all the strokes together and average them you get 900cc
The story changes again when you phase the coordination of upper and main pistons but the average remains constant.
The combustion chamber is only aprox 75 mm in diameter maybe 2 plugs will be OK.
http://www.sixstroke.com/
malbeare





1 the piston speed of the upper piston is lower than the main piston so the wear rate is lower.
2 Mechanically the engine is silent as there is no tappet noise. The scotch yoke is a silent sliding action with no sudden changes in direction. The shape of the exhaust lip can be designed to give any desired effect to the exhaust note, from a sharp crack with a flat lip to a soft thump with a rounded lip.
3. The disk has no problems as carbon buildup is wiped off to the desired clearance. There is a protruding boss that the disk has minimal clearance to affect a low-pressure labyrinth seal. During the initial run in period the disk may rub this soft bronze to a clearance of 1 to 2 thousandth of an inch.
4. Alan Cathcart quote after testing the Ducati Beare sixstroke
"One thing he certainly doesn't need to worry about is torque, which together with the crisp responsive throttle pick-up and the reduced vibration - even compared to a smooth-action 90 degree V-twin - are three strong points of the six-stroke motor. The Beare engine is unbelievably muscular in terms of torque, and from very low revs, to"

The Beare head offers an array of advantages, but it specifically offers a compact combustion chamber with a 50 per cent squish. Thus, the combustion in the center of the piston is concentrated, increasing the flame speed and the speed of combustion. In doing so the thermal stress on the piston is actually reduced.
2. An added benefit of this configuration is that it allows a higher bore stroke ratio, due to a lesser expansion of the piston. As there are no cut outs for valves, the crown of the piston can be slightly domed for higher strength and less weight. The 50 per cent squish factor keeps the edges of the piston from being exposed to the flame. By doing so, it allows the use of a gapless L shaped compression ring to be implemented right to the top of the piston. Therefore ring flutter is reduced or even eliminated. The main source of hydrocardon emitions is also reduced as the
Crevices – these are narrow regions in the combustion chamber into which the flame cannot propagate because it is smaller than the quenching distance.
Crevices are located around the piston, head gasket, spark plug and valve seats and represent about 1 to 2% of the clearance volume.
The crevice around the piston is by far the largest, during compression the fuelair mixture is forced into the crevice (density higher than cylinder gas since gas is cooler near walls) and released during expansion.
The Beare head eliminates most of these Crevices.
head.gif


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. We know that we can do much better with our air assisted fuel injection.

FUEL CONSUMPTION TEST
ROAD SPEED MPH 4STROKE RUN TIME SECONDS 100cc FUEL 6STROKE RUN TIME SECONDS100cc FUEL LOADED RPMIn 5th GEAR % LONGER RUN TIME
30 159 216 2000 35.8%
35 138 184 2500 33%
40 107 134 3000 25.2%
45 89 101 3500 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
malbeareSixstroke
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Guest_PAULIE_D_*
post Apr 30 2005, 09:33 PM
Post #17





Guests






QUOTE(malbeare @ Apr 30 2005, 11:56 PM)
Sixstroke Beare 900cc Vtwin MOTO GP

Bore 116.25 mm stroke 42.5 upper bore 82mm upper stroke 34mm
compression ratio 12.25 to 1
power 337HP @ 15000 RPM
torque 74.6Ft/Lbs x80% x2 = 118Ft /Lbs

Wow! I must admit that I am not very knowledgeable about MOTO GP specs but the power output and torque of the Sixstroke Beare 900cc Vtwin MOTO GP engine are very impressive. I take it that this is considerably more powerful that conventional MOTO GP engines.

You think you could be kind enough to post some pics of the test bike?
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malbeare
post Jul 24 2007, 11:24 AM
Post #18


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Just some more blerb for you guys to contemplate. sixstroke"][www.sixstroke.com]sixstroke

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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Mitlov
post Jul 24 2007, 12:02 PM
Post #19


Halfabusa lover
*****

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I'm always suspicious of huge technological advances pushed by self-proclaimed geniuses. Especially when the results are too good to be true (improved fuel economy AND power AND reliability?). But that's just me.
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malbeare
post Jul 24 2007, 02:18 PM
Post #20


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Mitlov,
A fair enough oppinnion mate, but please note that the opening post by
PAULIE_D was not writen by me as the author is the noted motorcycle journalist Sir Alan Cathcart.
I we are not touting for investors or shareholders in fact it is the precise reason for me to withdraw and resign as a director from Jack Brabham Engines when I realised that shareholder funds were being used only to support the lifestyle of the managing director Mr Alan Casey. firedevil.gif

http://sixstroke.com/truth.htm
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