Fred ....Can you name the spy ??
Biggest perpetuated Myths about Modded Saws.
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husq2100
Addicted to ArboristSite
what the hell? now theres spies????
anyway i re read (re custom combustion chamber and stock type head) and finally it sunk into my thick scull, well i did say that english wasnt my strong point.
BUT FRED, you never answered my question after i asked it more than once. now i know you have the answer and chose not to answer it.... but thats just part of the reason you come across they way you do.....
it just looks like you stir the pot to get it to turn.....
i think one of the biggest perpetuated myths about modded saws is the common use of 2 peice heads on WORK SAWS
Serg
anyway i re read (re custom combustion chamber and stock type head) and finally it sunk into my thick scull, well i did say that english wasnt my strong point.
BUT FRED, you never answered my question after i asked it more than once. now i know you have the answer and chose not to answer it.... but thats just part of the reason you come across they way you do.....
it just looks like you stir the pot to get it to turn.....
i think one of the biggest perpetuated myths about modded saws is the common use of 2 peice heads on WORK SAWS
Serg
timberwolf
Addicted to ArboristSite
One more time around.
Take a saw, something like an 80cc saw with 7mm wide squish band.
Example 1
Stock
8.5 cc combustion chamber, squish at .043
159 PSI compression
1.08 cc lost in endgas = 13.5% of the total charge
MSV ~22 m/s
Eample 2
Base gasket taken out with transfers and exhaust back to stock numbers
7.3 cc combustion chamber, squish at 0.25
177 psi compression
0.63 cc lost in endgas = 8.3% of the total charge
MSV ~32 m/s
Example 3
Base gasket taken out and base turned down 0.09 with transfers and exhaust back to stock numbers
7.05 cc combustion chamber
188 psi compression
.40 cc lost in end gas = 5.6%
MSV ~41 m/s
So yes, no big deal 2.7% more charge availible for combustion, and maybe about 2% gain from compression and related improved thermal efficiency. Then a bit more with the extra turbulance. So again 5% plus.
Here is the kicker though the 5% is compounded by other gains, say the other porting measures including opening up the intake and muffler gain an easy 50% then the 5% gain becomes 7.5%, add a pipe and more radical porting the 5% becomes 10% or more.
Maybe I just pay attention to details, but to me 7.5% is significant, even for a work saw, and 10% is crutial if it's a r@cesaw.
.016 is likely a little tight on an 80 cc saw, but can likley get away with it on a little 50cc saw.
Take a saw, something like an 80cc saw with 7mm wide squish band.
Example 1
Stock
8.5 cc combustion chamber, squish at .043
159 PSI compression
1.08 cc lost in endgas = 13.5% of the total charge
MSV ~22 m/s
Eample 2
Base gasket taken out with transfers and exhaust back to stock numbers
7.3 cc combustion chamber, squish at 0.25
177 psi compression
0.63 cc lost in endgas = 8.3% of the total charge
MSV ~32 m/s
Example 3
Base gasket taken out and base turned down 0.09 with transfers and exhaust back to stock numbers
7.05 cc combustion chamber
188 psi compression
.40 cc lost in end gas = 5.6%
MSV ~41 m/s
So yes, no big deal 2.7% more charge availible for combustion, and maybe about 2% gain from compression and related improved thermal efficiency. Then a bit more with the extra turbulance. So again 5% plus.
Here is the kicker though the 5% is compounded by other gains, say the other porting measures including opening up the intake and muffler gain an easy 50% then the 5% gain becomes 7.5%, add a pipe and more radical porting the 5% becomes 10% or more.
Maybe I just pay attention to details, but to me 7.5% is significant, even for a work saw, and 10% is crutial if it's a r@cesaw.
.016 is likely a little tight on an 80 cc saw, but can likley get away with it on a little 50cc saw.
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drmiller100
ArboristSite Guru
why do you think the "endgas" is not combusted and burned?????
Crofter
Addicted to ArboristSite
It is not a matter of "thinking" whether it will or not!
Flashback arrestors work on the principle of flame not propagating into a space under certain dimensions. The surface area to volume ratio dissipates the heat and extinguishes combustion. That is for normal flame front travel. Detonation of the same mixture, which is deflagration at 10 times higher rate will travel through much tighter spaces. I have installed such devices in refinery piping and remember some of the theory involved.
Flashback arrestors work on the principle of flame not propagating into a space under certain dimensions. The surface area to volume ratio dissipates the heat and extinguishes combustion. That is for normal flame front travel. Detonation of the same mixture, which is deflagration at 10 times higher rate will travel through much tighter spaces. I have installed such devices in refinery piping and remember some of the theory involved.
drmiller100
ArboristSite Guru
wow.
them thar is some big ole words you no!!!!
so when the flames are still going at 15 degrees atdc, do you suppose them "endgasses" remember they ain't sposed to cook off????
them thar is some big ole words you no!!!!
so when the flames are still going at 15 degrees atdc, do you suppose them "endgasses" remember they ain't sposed to cook off????
timberwolf
Addicted to ArboristSite
Yup, in a nut shell, gases located within .010 to.020 of an inch of a cooler solid will not burn normally if at all, so in that way a normal flame will not be able to pass through a .040 screen. Try it with a Bic lighter an a piece of fine metal screen. Though if the screen is heated over the autoignition temperature then it can light a flame on the other side. Proof of this very basic boundry layer effectis is the very fact that an alluminium piston can resist being melted by flame temperatures inside the engine well over two times the pistons melting temperature.
So as far as the squish band, if it is less than .040 in height, flame simply won't enter into this area, then by the time the squish opens up after TDC say about 20 deg after TDC and factor in some time for the end gas to get going were already passing the point where much combustion energy can be transfered to the crank. By 45 deg or so after TDC cylinder pressures have dropped way off so residual remnant combustion will be lazy and the piston is moving away from the expanding charge nearly as fast as the charge is expanding so relativly little energy can be transfered into it. this is esp so in a high RPM over square engine, where the distance the flame must travel is greater and time less.
Here are a couple tech articles, text books are also saying the same thing.
http://www.nkn.com/articles/squish.pdf
Page 2 top right
http://www.motorcycle.com/how-to/wrenching-with-robchemical-soup-the-mystery-of-detonation-3420.html?page=2
http://www.ozebook.com/compendium/t500_files/morgan/head.htm
http://www.supercoolprops.com/articles/stuntsquish.php
So as far as the squish band, if it is less than .040 in height, flame simply won't enter into this area, then by the time the squish opens up after TDC say about 20 deg after TDC and factor in some time for the end gas to get going were already passing the point where much combustion energy can be transfered to the crank. By 45 deg or so after TDC cylinder pressures have dropped way off so residual remnant combustion will be lazy and the piston is moving away from the expanding charge nearly as fast as the charge is expanding so relativly little energy can be transfered into it. this is esp so in a high RPM over square engine, where the distance the flame must travel is greater and time less.
Here are a couple tech articles, text books are also saying the same thing.
http://www.nkn.com/articles/squish.pdf
Page 2 top right
http://www.motorcycle.com/how-to/wrenching-with-robchemical-soup-the-mystery-of-detonation-3420.html?page=2
http://www.ozebook.com/compendium/t500_files/morgan/head.htm
http://www.supercoolprops.com/articles/stuntsquish.php
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Crofter
Addicted to ArboristSite
Hey Doug, just off the top of my head I can think of a few more biggies for you, like "bulldozer" and "miscellaneous"
You jumped in so cock sure with an assumption that the other person is wrong and now you want to smart off. You either seem to think you know everything you need to know or you have a strange method of acquiring any further information.
Crofter
Addicted to ArboristSite
I get the issue now. You guys take info off the net (THAT IS NOT PEER REVIEWED) and think it is Fact.
That's been our problem all along. Now I understand you guys.
Aren't we all glad M.D.'s don't do the same.
Fred
You do have to be selective for sure; my, that is a nice strawman you throw up, but it is no proof whatsoever that there is any error!
How about pointing out any fallacy in those links instead of merely trying to suggest that there might be some? I think there is lots of peer reviewed work in regards to unburned hydro carbons in exhaust to support it as a fact that all of the charge does not burn or if it does burn, too late to be very effective.
I think the statement has been made that squish volume and clearance (excepting for its affect on compression) makes no difference in performance, and someone is trying to wiggle out of it or cast doubts on TW's allegation to the contrary.
Not too long ago the statements were made about how simple this should all be, now you are comparing it to the work of doctors. You definitely have the tendency to make the story suit the thrust of the moment. I think it does not take much critical thinking here, to see exactly who is trying to fly unsupported or unsupportable statements.
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You do have to be selective for sure; my, that is a nice strawman you throw up, but it is no proof whatsoever that there is any error!
How about pointing out any fallacy in those links instead of merely trying to suggest that there might be some? I think there is lots of peer reviewed work in regards to unburned hydro carbons in exhaust to support it as a fact that all of the charge does not burn or if it does burn, too late to be very effective.
I think the statement has been made that squish volume and clearance (excepting for its affect on compression) makes no difference in performance, and someone is trying to wiggle out of it or cast doubts on TW's allegation to the contrary.
Not too long ago the statements were made about how simple this should all be, now you are comparing it to the work of doctors. You definitely have the tendency to make the story suit the thrust of the moment. I think it does not take much critical thinking here, to see exactly who is trying to fly unsupported or unsupportable statements.
Let's get this straight.
1. Serge is upset because I stated that it doesn't matter much and excluded custom work.
2. Crofter is upset because I said it doesn't make much difference on home built worksaws.
Where should I go from here saw fans?
Maybe we should make this a voting thread. eh
Fred
weenieroaster
ArboristSite Operative
Crofter
Addicted to ArboristSite
Crofter is not upset at all,
just noting how some stories change and the attempts are made to cast doubt on information that someone else posts, while being very careful not to discuss it point by point on a technical level ;just attempts by far fetched scenarios to cast doubt. It really is rather useless except as a study of human nature. It is just a bunch of slippery talking agenda with very little demonstration of technical ability or depth of knowledge of the points being discussed.
You are probably correct in a way about your statement earlier about "people reading this thread and laughing their arses off", but I doubt you are correct in your assumption of who is the target of their mirth!
just noting how some stories change and the attempts are made to cast doubt on information that someone else posts, while being very careful not to discuss it point by point on a technical level ;just attempts by far fetched scenarios to cast doubt. It really is rather useless except as a study of human nature. It is just a bunch of slippery talking agenda with very little demonstration of technical ability or depth of knowledge of the points being discussed.
You are probably correct in a way about your statement earlier about "people reading this thread and laughing their arses off", but I doubt you are correct in your assumption of who is the target of their mirth!
My claim was that on a 288 that there is not much difference between a squish of 15 thousandths and at 25 thousandths.
What kind of evidence do you want. Allusions to 100,000,s of Excel calculations? You guys are dazlled by BS. If I posted a link to a website and quoted a number, then I am legitimate???????
How about we just test it in the wood? Isn't that better than home-grown equations?
You tell me.
Fred
BTW I have earned my attitude and reserve the right to displace it at whim.
Fred
Why don't we divide this into the 3 or 4 arguements going on anyways?
If you want to argue with me, make a new thread and BE SPECIFIC.
It is so easy to pick and choose which part of the arguement to argue with it isn't entertaining anymore.
And Frank, you do seem a little peevish.
Fred
If you want to argue with me, make a new thread and BE SPECIFIC.
It is so easy to pick and choose which part of the arguement to argue with it isn't entertaining anymore.
And Frank, you do seem a little peevish.
Fred
drmiller100
ArboristSite Guru
i started a thread.
i bet if i claim that rain falls from clouds tw and crofter will correct me.
i bet if i claim that rain falls from clouds tw and crofter will correct me.
husq2100
Addicted to ArboristSite
Fred you are so full of ####!
read your first post #1/sweeping statement, then tell me what it has to do with modded worksaws, AFTER YOU TELL US THAT 0.02 IS OK.... you use custom combustion chambers as an out, nothing to do with work saws...
well evey time someone explains somthing you move 1 step to the left and change your angle, forever running.... dont run fred, you are a smart guy. but your ego is clouding your judgement...
and im not upset with you, just the evolution of the human race....
cheers, Serg
read your first post #1/sweeping statement, then tell me what it has to do with modded worksaws, AFTER YOU TELL US THAT 0.02 IS OK.... you use custom combustion chambers as an out, nothing to do with work saws...
well evey time someone explains somthing you move 1 step to the left and change your angle, forever running.... dont run fred, you are a smart guy. but your ego is clouding your judgement...
and im not upset with you, just the evolution of the human race....
cheers, Serg
timberwolf
Addicted to ArboristSite
No, Fred/Doug if you said something inline with generally accepted principals there would be no arguement. But ya, go out on a limb and make claims without backing them up with even the weekest of references, calculations or any sort of scientific reasoning, and yes, you might meet a little resistance when it come to claiming stuff like you and Fred have been.
I would be the first to admit that any sort of conceptual or mathimatical model is not going to be perfect, and science is an ever changing study. Civilization, once thought the world was flat and everything revolved arround it, and humans could never take flight, then when they did, they could never pass the speed of sound... But as we gain more indepth understanding of things, we develop a more accurate preception of them, and things that we thought to be impossible become possible.
Don't take it all personal, but you have been offering nothing of substance to support your position. I have offered several tech articals, quotes from text books written by experts in the field, some mathmatical modeling right down to the whole process, even a couple videos... I guess you are still are convinced the earth is flat and everything revolves around you too.
Oh well, I have no interest in changing your mind, or teaching cats to sing, and anyone with the slightest twinkle of scientific reasoning or critical thinking would quickly see your pumping junk science at best.
If the law is on your side argue the law, if the facts are on your side argue the facts, if absolutly nothing is on your side, just argue.
I suspect you guys are working from the later.
I have said my bit, put more than enough substance on the table to back up my reasoning, and have much better things to do than continue with this recreational arguement simply to pleasure you.
I would be the first to admit that any sort of conceptual or mathimatical model is not going to be perfect, and science is an ever changing study. Civilization, once thought the world was flat and everything revolved arround it, and humans could never take flight, then when they did, they could never pass the speed of sound... But as we gain more indepth understanding of things, we develop a more accurate preception of them, and things that we thought to be impossible become possible.
Don't take it all personal, but you have been offering nothing of substance to support your position. I have offered several tech articals, quotes from text books written by experts in the field, some mathmatical modeling right down to the whole process, even a couple videos... I guess you are still are convinced the earth is flat and everything revolves around you too.
Oh well, I have no interest in changing your mind, or teaching cats to sing, and anyone with the slightest twinkle of scientific reasoning or critical thinking would quickly see your pumping junk science at best.
If the law is on your side argue the law, if the facts are on your side argue the facts, if absolutly nothing is on your side, just argue.
I suspect you guys are working from the later.
I have said my bit, put more than enough substance on the table to back up my reasoning, and have much better things to do than continue with this recreational arguement simply to pleasure you.
