DWELL Sixstroke

[malbeare]

ivymike (Mechanical) Sep 15, 2004
TDC dwell time

define "TDC dwell time" as the amount of time that the piston spends within 1% of the stroke of TDC (so within 1.2mm of TDC for a 120mm stroke)

pick a "short" rod / stroke ratio of 1.5:1
TDC dwell is 19.98deg for a conventional configuration
TDC dwell is 22.94deg for a yoke configuration

pick a "long" rod/stroke of 2:1
TDC dwell is 20.54deg for a conventional configuration
TDC dwell is 22.94deg for a yoke configuration





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GraviMan (Automotive) Sep 16, 2004
OK, so are you saying that a long crank is better than yoke? Granted it is simpler...

Mart

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ivymike (Mechanical) Sep 16, 2004
who was that question addressed to?

I'm saying that the maximum additional "tdc dwell time" is about 13%, depending on how you define dwell.


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patprimmer (Automotive) Sep 17, 2004
I must say for 1% of the stroke, that is more time than I thought and could generate worthwhile pressure build up gains, providing the extra strength necessary to accommodate it does not more than offset it.
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pat pprimmer@acay.com.au
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GraviMan (Automotive) Sep 17, 2004
"I'm saying that the maximum additional "tdc dwell time" is about 13%, depending on how you define dwell."

Well worth having for high rpm engine then. Admitedly it will have a reduced efficiency benefit in a detonation engine, since combustion time is "small".

Does anyone have any info on detonation times, or even a P-V curve? I'm curious how it compares with S.I. and C.I.

Mart

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malbeare (Automotive) Sep 17, 2004
ivymike there is another way to express dwell ; rate of change in combustion chamber volume.

B/S 74.5 x 68 B/S 74.5x 68 upper B/S 54x22
TDC 4 stroke TDC 6 cycle Beare
30.4cc 30.4cc combustion chamber volume


3.04E-05 3.04E-05 360 TDC
3.07E-05 3.06E-05
3.10E-05 3.09E-05
3.14E-05 3.12E-05
3.18E-05 3.16E-05
3.23E-05 3.21E-05
3.28E-05 3.26E-05
3.34E-05 3.32E-05
3.40E-05 3.38E-05
3.47E-05 3.45E-05
3.55E-05 3.52E-05
3.63E-05 3.60E-05
3.71E-05 3.68E-05
3.80E-05 3.77E-05
3.90E-05 3.87E-05
4.00E-05 3.97E-05
4.11E-05 4.08E-05
4.22E-05 4.19E-05
4.34E-05 4.31E-05
4.46E-05 4.43E-05
4.58E-05 4.56E-05
4.72E-05 4.69E-05
4.85E-05 4.83E-05
4.99E-05 4.97E-05
5.14E-05 5.11E-05
5.29E-05 5.27E-05
5.44E-05 5.42E-05
5.60E-05 5.59E-05
5.77E-05 5.75E-05
5.94E-05 5.92E-05
6.11E-05 6.10E-05
6.29E-05 6.28E-05
6.47E-05 6.46E-05
6.65E-05 6.65E-05 393 degrees ATDC

The rate of change in volume of the combustion chamber of the beare head is less than the rate of change of the fourstroke. with the upper piston retarded in its relationship by 20 degrees.
malbeare

http://www.jack-brabham-engines.com/

A tidy mind not intelligent as it ignors the random opportunities of total chaos. Thats my excuse anyway
Malbeare



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GraviMan (Automotive) Sep 20, 2004
I'm puzzled about the Beare head. Basically it is a 4-stroke, but with a different valve mechanism. I presume the main advantage is that using the reed valve, and piston head, you get very high volumetric efficiency with very low pumping losses. How do these compare with a poppet valve design? Does the Beare head offer better working fluid replacement across rpm range, without the complexity of VVT?

Mart

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malbeare (Automotive) Sep 22, 2004
GraviMan (Automotive)
you are right in that you get very high volumetric efficiency with very low pumping losses especially at low rpm low throttle settings. we setup a good stratification with the ignitable mixture swirling towards the outside close to the spark plugs in the combustion chamber side wall.
The head actually produces power this is fundimental to a gain in mechanical efficiency aprox 8 to 10%.
The rate of change in combustion chamber volume is less than a fourstroke during combustion so that it is closer to the ideal of constant volume during combustion. but the rate of change in volume during the rest of the expansion stroke is faster and larger than a fourstroke. so there is a gain similar to the atkins or miller cycle.
Coupled with our air assisted fuel injector that produces dropplet sizes of 5 micron and the ability to induce a premix of 20% intake volume thruogh the injector. we efectivly have all the advantages of direct injection without the nozzle being in the combustion chamber and subject to cylinder temps and pressure.
It is still very much work in progress so I cannot diclose all . But I hope this gives you an overview of the advantages

http://www.jack-brabham-engines.com/

A tidy mind not intelligent as it ignors the random opportunities of total chaos. Thats my excuse anyway
Malbeare



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GraviMan (Automotive) Sep 23, 2004
"...good stratification with the ignitable mixture swirling towards the outside close to the spark plugs in the combustion chamber side wall."

OK, so the flame starts from outside in? Does this produce any flame quenching?

"The rate of change in combustion chamber volume is less than a fourstroke during combustion so that it is closer to the ideal of constant volume during combustion."

And you avoid cams and valves...

"Coupled with our air assisted fuel injector that produces dropplet sizes of 5 micron and the ability to induce a premix of 20% intake volume thruogh the injector."

This alone is a nice line of endeavor. Can this be fitted to other engines, or is it part of the Beare package?

Mart

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btrueblood (Mechanical) Sep 23, 2004
Ok, I've resisted this post twice now, but once again we have a claim of "a gain in mechanical efficiency aprox 8 to 10%." We've seen similar statements that the Bourke engine and others have very high efficiency/low BSFC. So far, I've not seen anything that substantiates these claims.

Can anybody measure the fuel consumption of their engine, under a load (say, a generator operating a bank of light bulbs) and report it?

If there is some confusion about how to rig such a test, post your query here and we can all kick some ideas around.


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NickE (Materials) Sep 23, 2004
btrueblood- read SBBlue's first post, click on his last link, that gives a good method for measuring torque. (Of course you have to remember your engineering mechanics)

nick

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btrueblood (Mechanical) Sep 23, 2004
NickE - that's exactly what I'm talking about. There are claims made on various websites and various postings; none of these are substantiated with test data (including descriptions of the test rig). I could care less HOW the output power is measured (tie a rope to a weight and measure velocity, pump liquid, generate electricity, do whatever, but just MEASURE IT!). And then report it. If your claims match test data, then we can talk. Until then, this whole thread is just so much exhaust.

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malbeare (Automotive) Sep 23, 2004
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.
The sixstroke head was designed to as closely match the fourstroke as possible compression ratio , valve timing , port sizes.
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.I think that the maximum horsepower is in the region of 18 HP for the sixstroke and 22HP for the fourstroke
Same gearing same carburetor.
Fuel was gravity fed to the carb from a long clear tube with two level marks to indicate 100cc

A tidy mind not intelligent as it ignors the random opportunities of total chaos. Thats my excuse anyway
Malbeare



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btrueblood (Mechanical) Sep 23, 2004
Malbeare,

THANK YOU! That's a nice, brief, concise test report. It's nice to see somebody making the effort, taking the time, measuring some data, and having the guts to report it.

Now - I'm impressed by the numbers, but I'm not sure if we aren't looking at two different engine "sizes"... i.e. I wonder what happens when each engine is run at near-stall conditions. I'd expect the 4-banger is actually giving more peak h.p. and probably has a higher top end. Having a way to modulate and measure the output power, to run the motor up against its stall limit, would allow a better comparison than just the run time at a fixed power setting. What I'm saying is that the BSFC of the 6-stroke motor may or may not be better than the 4-banger at reduced throttle settings, without measuring power we just don't know (but your numbers certainly look good, and make me curious to find out!) Could you not couple the motor's output shaft to a generator, or a brake, and vary the load to map the power-specific fuel consumption?



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patprimmer (Automotive) Sep 23, 2004
Malbeare

Would you like to start a new thread on this as it is technically off subject, not being a Bourke engine, but more to the point, this thread has become VERY long and it takes quite a time for the page to load and allow me to scroll to the end.
Regards
pat pprimmer@acay.com.au
eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.



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malbeare (Automotive) Sep 23, 2004
btrueblood (Mechanical)
The laod or power output is the same for each engine at the designated speed because the fan is absorbing the same X horspower or requires the same torque to turn it at the same speed . only the throttle settings must have been different.
It would be a good debating point whether the reed valves alone accounted for the superior performance by not allowing any spittback and therefore making carburation cleaner and more precise. Or how much the mechanical construction added to the gain in fuel efficiency. I suspect a little of both.
I have come to the conclusion that to obtain good gas flow at higher RPM the a combination of reed and rotary disk is needed on the intake. Reeds tend to fall over above 6000 and flutter.
If you look at the change in volumes for each engine then the 4 stroke is 500cc for each stroke , but the sixstroke is smaller on the intake and larger on the compression and expansion but smaller again on the exhaust. This varies depending on the phasing relationship between the upper and lower main crankshaft.
At 2000 rpm the 4 banger is at its stall limit in 5 gear
The practical result is that on the road the sixstroke would save fuel.

http://www.jack-brabham-engines.com/

A tidy mind not intelligent as it ignors the random opportunities of total chaos. Thats my excuse anyway
Malbeare




A tidy mind not intelligent as it ignors the random opportunities of total chaos. Thats my excuse anyway
Malbeare

 

[malbeare]

GraviMan (Automotive) Sep 23, 2004
"Coupled with our air assisted fuel injector that produces dropplet sizes of 5 micron and the ability to induce a premix of 20% intake volume thruogh the injector."

This alone is a nice line of endeavor. Can this be fitted to other engines, or is it part of the Beare package?"

what we have found is that when using the injector on port injection on a standard 4 stroke is that the spray hits the standing wave and gets thrown against the port walls and the dropplets recombine, drip off the back of the valve and end up as 20 micron in the cylinder.
So that is not much better than a standard injector. though you do get better cold starting.
We would much prefer a total package as we place the injector in front of the reed valve and get a good clear shot at the cylinder and avoid the standing wave and back of the popett valve.

A tidy mind not intelligent as it ignors the random opportunities of total chaos. Thats my excuse anyway
Malbeare

 

[tbuelna]

malbeare:

Good luck with your project.

I've tried selling something similar to the OEMs here in the states. What I've learned is that there is only one thing that matters to them: How will your device improve my bottom line? If it is not going to increase my profit margin on my existing product line, I'm not interested.

Regards,
Terry

 

[GregLocock]

That'd be because the OEMs are owned by the shareholders, and it would be illegal, or at least immoral, for them to behave otherwise without shareholder approval.

If your idea is not cost-effective then why would you expect any interest in it?

Sorry Mal, I didn't mean to hijack your thread, good luck with your project.

Cheers

Greg Locock

 

[malbeare]

GregLocock (Automotive)
I think that the argument will be for older established companies, If you wish to maintain your market share then you cannot afford to allow the newer aisian companies to steel the march on you and outsell you with cheeper prices as well as an inovative product that meets customer expectations with fuel economy and drivability.
The only way that you can maintain your market share with your current pricing ( PROFIT) is to invest now and and offer me a good return for my expensis in return for a 5 year period of exclusivity, or onlicencing at your discretion.


A tidy mind not intelligent as it ignors the random opportunities of total chaos. Thats my excuse anyway
Malbeare

 

[GraviMan]

Sorry guys, workload etc...

"It would be a good debating point whether the reed valves alone accounted for the superior performance..."

I must admit to wondering whether to modify a standard head along the same lines. A single cam could actuate inlet and exhaust valves, at the same time, between BDC during pumping phase. The inlet and exhaust reed valves would allow all the timing adjustment throughout the whole rpm range. This is much neater than either BMW Vanos, Rover VVC, or the Honda actuation system. The injector/spark could also be left at cylinder top.

My 2-stroke Yamaha used a reed valve, and happilly got to 9000 rpm - some get to 12000 rpm. To avoid choking losses, cam/valve closing delay could allow inlet gas bypass, before compression began - good for partload (vanos advantage).

"...the injector on port injection on a standard 4 stroke is that the spray hits the standing wave and gets thrown against the port walls"

Interesting - I hadn't realised. I would imagine diesel direct inject would fair much better, since the primary motion is a vortex swirl. In fairness, as long as the fuel is resonably mixed before valve shuts, I can't imagine a petrol suffering too much from fuel collection since the swirl becomes turbulent anyway (to improve flamespread).

"...place the injector in front of the reed valve and get a good clear shot at the cylinder"

I'm not very familiar with the Ford Orbital 2-stroke, but was this also infront of the valve? I imagined it to be like a diesel DI.

"The only way that you can maintain your market share... offer me a good return for my expensis..."

I would imagine that the best way forwards is to approach the OEM as a development/research project. That way the concept can be taylored to suit the OEM. It seems to be a good business model.

Mart