PistonHeads.com Forum

RE: 4 Stroke Redesigned

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John_S4x4

1,260 posts

176 months

Tuesday 22nd February 2005
quotequote all
There is also the Beare Six-stroke engine which can be found here :
www.jack-brabham-engines.com/articles.htm



Ducati V-Twin 6 stroke




Very simular to Andrew Feliks 'New 4stroke' engine at the begining of this thread. The Beare Six-stroke uses a piston in the head too, but the piston in the head uses a 2 stroke type of design. Revs quite well, with lot of torque apparently, claiming a 23% increase in torque.

For those interested in obscure piston designs, have a look at the DYNACAM engine




www.dynacam.com/Product/Design_Overview/design_overview.html

Another interesting engines and can be found here www.siscom.net/~louisekramer/
and here www.ballpistonengine.com/simplified/index.html
and here www.geocities.com/CapeCanaveral/2542/oper.htm

And another one
www.quasiturbine.com/



If you want a real suprise, check this engine out
www.geocities.com/ljaya6390/cycle1.htm

Regards John S

>> Edited by John_S4x4 on Tuesday 22 February 03:06

phase90

85 posts

193 months

Tuesday 22nd February 2005
quotequote all
Interesting that the first prototype dates back to 1979. Twenty-six years in the making...

I run across another engine maker that is doing something similar (pistons as valves). [url]www.sixstroke.com/ [/url]

dinkel

24,250 posts

177 months

Tuesday 22nd February 2005
quotequote all
Jack Brabham Engines Limited / Utilising Beare Technology

"The Beare engine is unbelievably muscular in terms of torque, and from very low revs, too."

"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 2-3,000rpm or so (there's no rev counter fitted, but having ridden the odd Ducati V-twin down the years, I may claim to have a rev sensitive seat of the pants). There's also no transmission snatch at very low revs, indicating a responsive, torquey motor, while the way it pulls hard from way down low bears all the hallmarks of a long-stroke engine, whereas the opposite is in fact the case; the lower crankshaft assembly has 86 by 57mm dimensions, while the upper 'two-stroke' one measures 60 by 25mm. Yet the inherent nature of the Beare motor is one of a torquey slugger, belying these measurements. And allied with the so-responsive pick-up and a wide spread usable power that seems to be the same at high rpm as it is way down low, this makes the bike ridiculously easy to ride - you hardly ever need to use the gearbox at all, just park it in top gear and ride it like an automatic. Even backing off the throttle in the middle of a turn to let the chassis straighten up and fly right doesn't require you to hook down a gear - just open when you're ready, feel the front wheel start to aviate on you, and drive."

What happened to this six-stroke concept? I asked.

chickensoup

374 posts

174 months

Tuesday 22nd February 2005
quotequote all
Dont see how this is efficient, unless you can draw power from the top crank also, as these are being driven by the power stroke also. Watching the flash animation on his web, as the valve pistons are going 2 stroke at half the speed, they are going in the wrong direction some of the time (exhaust is compressing during induction). Would need two overhead cranks to give a more interesting combustion chamber shape, but at the end of the day - Why bother. Fixes so many things on engine breathing, has a very old valve design and adds weight & complication. Fancy fixing a HGF on one?

malbeare

4 posts

149 months

Tuesday 22nd February 2005
quotequote all
Power is indeed drawn from the Head

(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.
(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



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.
Malbeare
www.sixstroke.com/




Edited by malbeare on Thursday 15th March 19:40
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dinkel

24,250 posts

177 months

Wednesday 23rd February 2005
quotequote all
Malcolm, what will happen to this design other than used on the racetrack?

cjrv8

62 posts

175 months

Wednesday 23rd February 2005
quotequote all
I haven't had time to look through the web-site completely but in general isn't this how top-flight bike engines work? don't they push & pull the 'valves' & therefore are permenantly connected to the cam?

gary_tholl

1,013 posts

189 months

Wednesday 23rd February 2005
quotequote all
cjrv8 said:
I haven't had time to look through the web-site completely but in general isn't this how top-flight bike engines work? don't they push & pull the 'valves' & therefore are permenantly connected to the cam?


As far as I know, Ducati is the only manufacturer to be currently running a desmodromic cam setup. There have been countless variations of it over the years. Mercedes toyed with it in the 50's IIRC.

Gary

malbeare

4 posts

149 months

Thursday 24th February 2005
quotequote all
dinkel said:
Malcolm, what will happen to this design other than used on the racetrack?


We are negotiating with various Aisian companies for 150cc motorbike production.
Here is some more guff to ponder

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%





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.
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.
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




Edited by malbeare on Thursday 15th March 19:42

alextgreen

12,753 posts

161 months

Thursday 24th February 2005
quotequote all
Re. original topic: is that what a real 'pistonhead' looks like?

malbeare

4 posts

149 months

Friday 25th February 2005
quotequote all
Yes there is one piston in the head
Malbeare

dinkel

24,250 posts

177 months

Friday 25th February 2005
quotequote all
Impressive figures! Thanx for that info.

Feliks

569 posts

148 months

Monday 21st March 2005
quotequote all
malbeare said:
Yes there is one piston in the head
Malbeare


Qne important question:In my heads are two piston.
The arm crank of the exhaust piston is 70-120 deg after the T.D.C , while the greatest combustion forces take place - it may cause a strange effect - the maximum torque can be taken from the smallest piston (!!).

>> Edited by Feliks on Monday 21st March 09:29

gadgeroonie

5,361 posts

155 months

Monday 21st March 2005
quotequote all
Has anybody heard of the engine design where vales are removed and repaced by hollow cams with slots cut in them

they rotate and allow the gasses in and out.

Another Design i have heard of is electronic poppet vales

the valves are operated electrically like an injector and can be mapped using electronics !!!!!

Annodomini2

5,447 posts

170 months

Monday 21st March 2005
quotequote all
name said:
www.ptfnasty.com/ptfDeltic.html


Looks like a modified merlin!

anonymous user

7,609 posts

154 months

Tuesday 22nd March 2005
quotequote all
This is an impressive thread.

I believe that Felix Wankel came up with literally thousands of pump designs, quite a few of which could be used as engines. IIRC, the Wankel rotary engine was an air compressor first.

Pigeon

18,535 posts

165 months

Tuesday 22nd March 2005
quotequote all
gadgeroonie said:
Has anybody heard of the engine design where vales are removed and repaced by hollow cams with slots cut in them

they rotate and allow the gasses in and out.

Yes. Like most alternatives to poppet valves, they tend to be a bugger to lubricate, especially if you want to avoid chucking oil out of the exhaust, and have problems with expansion due to heat.
gadgeroonie said:
Another Design i have heard of is electronic poppet vales

the valves are operated electrically like an injector and can be mapped using electronics !!!!!

You need some bloody big solenoids to do that, which is why most variable valve timing methods use some other means of varying the timing.

Feliks

569 posts

148 months

Wednesday 23rd March 2005
quotequote all


Yes. Torque are large, because arm crank on main piston are too
large. See ,what change deg. minimum volume in my prototype.(exactly no electronics )




>> Edited by Feliks on Wednesday 23 March 11:03

>> Edited by Feliks on Wednesday 23 March 11:12

>> Edited by Feliks on Wednesday 23 March 11:14

>> Edited by Feliks on Wednesday 23 March 11:16

andytk

1,542 posts

185 months

Wednesday 23rd March 2005
quotequote all
[quote=gadgeroonie]Has anybody heard of the engine design where vales are removed and repaced by hollow cams with slots cut in them

they rotate and allow the gasses in and out.
/[quote]

Someone has solved all the problems associated with these valves.

www.coatesengine.com/

Thats the website. Looks like an interesting development.

Andy

dilbert

7,740 posts

150 months

Sunday 3rd April 2005
quotequote all
Annodomini2 said:


name said:
<a href="http://www.ptfnasty.com/ptfDeltic.html">www.ptfnasty.com/ptfDeltic.html</a>


Looks like a modified merlin!



Strangely I think it was designed around the same sort of time, by Napier, with the same sort of war winning goal in mind. It was used on the fast patrol boats for defending the east coast, I believe.

When we came out of the war, there was high demand from the ministry of transport for rapidly available heavy haulage on the railways. GEC dropped the deltic into/onto a hydraulic chassis/bogie, tuned the heck out of it and the rest is history.

They weren't all that reliable compared to a railway steam engine. I believe the big/little ends failed often unless the engines were rebuilt regularly. I think that this was due to the high stresses associated with high temperatures and pressures in the combustion chamber.

Forget that.... I'd not realised that information was in the link.



>> Edited by dilbert on Sunday 3rd April 01:31