Biggest perpetuated Myths about Modded Saws.

[timberwolf]

The more I learn about, saws, motors, fuel and everything else that goes along with it the more I learn there is much more to know.

Anyone who says saws are dead simple really does not know saws. Sure anyone can do a little port work and get some gains, even a blind squirle finds a nut the odd time, but just as a blind squirle can find a nut but not know where he found it or be abe to use that info to gain insght to where the next nut might be, what someone doing "try and see" port work can understand about how the gains were made is pretty limited, and
how well this informaton can be extrapolated to other stuatons is dubious.

I think it was Rumsfeld who said, "there are things we know, there are things we don't know, and things we don't know we don't know.'

Absents of evidence is not evidence of absents.

 

[Mr.]

hang on Mr.

in post #8 you said "For saws without a custom combustion chamber, i.e. two piece heads........

the squish does not mean much."

then in post #13 you said "I said that it doesn't matter much for a stock 288 head. It comes into greater play with a custom combustion chamber"

now post 8 seems to contradict post 13????

what am i missing?

cheers, Serg

If you cannot understand this, I cannot help you.

I'm not a teacher, I am a do'er.

Fred

 

[Mr.]

Some of the main things I was looking for in your calculations were how you are how you are treating the air-fuel mixture. Polar/nonpolar? Wave characteristics? Density?

I find it much easier to treat the A/F as a wave and then you can use some fairly simple equations. BTW IT IS a wave so it is appropriate.

As far as people not understanding what I am saying..... it's just my cross to bear. I don't make things more complicated on purpose, things that seem obvious to me that are not obvious to others.

I do find it comical that I made a fairly benign statement, Brian complicates it with his math and I'm the guy that made it hard.

I have seen inside the FASTEST saws on earth and know for a fact that the guys that built them would laugh their arse off if they read this thread.

Fred

 

[husq2100]

If you cannot understand this, I cannot help you.

I'm not a teacher, I am a do'er.

Fred

Fred, you already responded to my first post with post #22

go read post # 37 and i explained where i was coming from.... maybe then you can teach me

more explainations, less statements please... not just for me but for all newbies.

cheers, Serg

 

[Crofter]

Some of the main things I was looking for in your calculations were how you are how you are treating the air-fuel mixture. Polar/nonpolar? Wave characteristics? Density?

I find it much easier to treat the A/F as a wave and then you can use some fairly simple equations. BTW IT IS a wave so it is appropriate.

As far as people not understanding what I am saying..... it's just my cross to bear. I don't make things more complicated on purpose, things that seem obvious to me that are not obvious to others.

I do find it comical that I made a fairly benign statement, Brian complicates it with his math and I'm the guy that made it hard.I have seen inside the FASTEST saws on earth and know for a fact that the guys that built them would laugh their arse off if they read this thread.

Fred

Fred you certainly are an interesting piece of work! You are complaining about TW making things complicated yet you ~ DR Miller are the ones asking peevishly for more and more detail; far more than would necessarily be used to do a ball park squish set up for a work saw. You keep trying to find a fatal flaw in the calculating process yet appear not to understand it very well at all.

" things that seem obvious to me that are not obvious to others."
"When did we ring your bell Sweetheart? We all know that math isn't your strongpoint.
"I'll go ahead and take the lumps. I assumed the charts were backing up TW's figures and didn't look at them close enough".

Rather than flattering yourself for discerning things that are not obvious to others, I suggest that your agenda has you seeing what is not there or distorting by inference what is!

As to the statement that you have seen the inside of the fastest saws on earth, that is rather a pathetic attempt to have it convey the idea that you are at that level of expertise yourself. I could rightly say that I have seen the insides of severa of the worlds Nuclear reactors. Though I actually worked in them it would be laughable to insinuate that I knew anything about one.

"And know for a fact that the guys that built them would laugh their arse off if they read this thread. "Hearsay Fred! I think you will find that the reasearch teams behind most top level racing that involves engines in general are exploring exactly the kind of parameters that TW is toying with. Much more sophisticated of course. If I am not mistaken Chauncey Varney and Marcel Vincent were not exactly technophobic luddites!


That type of manupulation of perception is quite prevalent in politics and lawyers use it to the point of getting their fingers slapped in the process of attempting to cast doubt on persons giving testimony. They too have an agenda and no shame whatsoever in pushing it. In some circles that skill is admired; it is not when it is used in everday personal relations.

 

[husq2100]

Fred,

could you please explain what you mean by "custom combustion chamber"

at the end of the day this thread is under the topic of modded WORK saws.
what percent of modded work saws would have a custom combustion chamber??(im serious here, i wouldn't know)

for me the novice, im happy to use/trust the general rule FOR A WORK SAW to set my squish around 0.02 and no smaller....

this being my first mod and a work saw i will shape/lighten the piston, set squish, then post pics and ask for more help.....

cheers, Serg

 

[timberwolf]

Very few work saws have modified combustion chambers, I have done a few, I know Dean and a handfull of others who have made some too, not easy machiening to set up, and very easy to screw it up if it's not done right.

If the goal is just a good work saw, they yes, set it at 0.020 and forget it. This will work just fine in about any standard saw.

If you interested in building custom heads and race type saws, then understanding squish is going to help make a little more power and save a few 10ths of a second.

 

[drmiller100]

i started a thread on saws 101 about squish. feel free to jump in.

the angle of the piston/head is the MOST critical issue there is. this and the distance are fundamentally the only two variables that are effectively controllable.

When the combustion chamber isn't centered, the math gets REALLY ugly. I can guess the squish velocity on the exhaust side (zero), but on the intake side it turns rapidly into a five dimensional equation which gives even the best of them headaches.

if you can solve for this, you are wasting your time here and should probably stick to something easy like general relativity and tensors.

doug

 

[timberwolf]

the angle of the piston/head is the MOST critical issue there is. this and the distance are fundamentally the only two variables that are effectively controllable.

When the combustion chamber isn't centered, the math gets REALLY ugly. I can guess the squish velocity on the exhaust side (zero), but on the intake side it turns rapidly into a five dimensional equation which gives even the best of them headaches.

if you can solve for this, you are wasting your time here and should probably stick to something easy like general relativity and tensors.

Squish angle is mainly a factor as it increases the squish height, esp at the inner most side of the squish band where it has the greatest effect on the velocity. Though a squish with .024 at the cyl wall and .032 at the dome will have a slightly higher squish velocity than one with .032 all the way accross. Even if a hemi combustion chamber was off centered to the cylinder wall on the exhaust side or a full hemi head was used squish would still not be zero, because the angled dome still acts like a steep angled squish band. Most applications were only talking a couple degrees angle. Things with can mufflers like saws often do best with zero squish angle.

I don't follow your 5 dimentional equation, I count only 4, seeing its a 3 dimentional space plus time.

But you may well be right about the waste of time part, this has certainly tuned into a recreational arguement.

Here is a simple squish calculator I found, It does not cover angled squish bands or off set heads, but maybe useful to someone. http://www.torqsoft.net/squish-velocity.html

Here also a link to piston position calculator http://www.torqsoft.net/piston-position.html

Don't know that these are 100% accurate, but its on the web, so it must be right???

 

[Danger Dan]

Knowledge is Power...oooOHWHAAAAHMMmmm, whether it's from the classrooom or the work bench. It's probably better to have both.

 

[RiverRat2]

The more I learn about, saws, motors, fuel and everything else that goes along with it the more I learn there is much more to know.
Anyone who says saws are dead simple really does not know saws. Sure anyone can do a little port work and get some gains, even a blind squirle finds a nut the odd time, but just as a blind squirle can find a nut but not know where he found it or be abe to use that info to gain insght to where the next nut might be, what someone doing "try and see" port work can understand about how the gains were made is pretty limited, and
how well this informaton can be extrapolated to other stuatons is dubious.

I think it was Rumsfeld who said, "there are things we know, there are things we don't know, and things we don't know we don't know.'

Absents of evidence is not evidence of absents.

I agree TW,,,, just when I think I really have a handle on it all,,,,, It slips!!!!

LOL!!!!!! Is that why those clusters of 3/5 rogue pecan and walnut trees keep popping up randomly in the yard cause that blind squirrel forgot where he hid them!!!!! Eh???? :monkey:

 

[RiverRat2]

Some Pix from the PNW GTG,,,,

Adam Clarkes piped saw From Montecito Ca and his buddy Gary had some really slick/trick saws,,, that definitely hauled the mail!!!!!

 

[RiverRat2]

More Pix

I apologize for not including your head in the photo Adam but your times were so quick and I dont move as well as I did when I was younger,,,, I was doing good to catch the rooster tails and they were wicked!!!!!
I think this one is a 7900 Dolmar

and I also apologize if they seem blurry cause my camera lens was smudged,,,

and this one in the next 2 photos is Garys 046, both saws in the last two post had two piece heads,,,, and the workmanship was neat what seemed funny is the difference in the size of the pipes!!!!!!! but I found out,,,(Learned) later, (Thank you Adam) that the one of them had a stroker crank so it had different displacement and the port timing also which is what governs the size/shape of the expansion chamber,,, I suppose I should have posted this on pipe saws now that I looked around!!!!! Sorry!!!!!

 

[drmiller100]

adam clarke and his buddy gary.

i sure learned a alot this weekend!!!

 

[weenieroaster]

Smudge or no smudge, cool photos!

 

[RiverRat2]

adam clarke and his buddy gary.

i sure learned a alot this weekend!!!

Thanks DR,,, + 1 on the learning!!! Was good meeting you,,

 

[Mr.]

Serg, you seem honestly confused so I will state it simply.

FOR A WORKSAW.......... it will not make VERY MUCH difference if you set the squish at 16 thousands or 25 thousandths.

IF WE TALK ABOUT ########...... that changes.

Good??

Fred

Go back, forget what you think was said, and read the first page of this thread. I started talking about worksaws and felt directed elsewhere.

 

[husq2100]

Fred wrote

"1. You should set your squish at 20 thousandths. Really? For every saw? Regardless of combustion chamber shape or size?"

ok well considering that you are writting this in MODDED WORK SAWS, and yes i am a novice, i was thinking along the lines of standard cylinders and WORKSAWS.

i see you take alot of people to task about exact english and grammer, well i tell you, you could pic holes through mine every day of the week. cant spell to save my life and dont even have much of a clue when it comes to grammer, but, you have a very clever way of spinning and turning, must be one helll of a dancer...

anyway could you please explain what YOU mean by custom combustion
chamber

oh and for your post to TW about the fact that he learnt math in class so he shold be just as apt at english.... pffft. you dont have much understanding about the human mind do you.

cheers, Serg

 

[Mr.]

Did you kick the dog today Serg.

I don't think you see me correct people's english often. The only time I do is when it is funny. Like a pun, ect.

TW is lucky to have a friend like you.

I do agree your english is horrible, but we don't expect much from Aussies. (See I added that just for you)


Fred

 

[Mr.]

I thought I would repost my first few posts for the senior members of this discussion. LOL

For saws without a custom combustion chamber, i.e. two piece heads........

the squish does not mean much. With good equipment it would be difficult to measure the difference in power or temperature between .014 and .025 inch.

The compression will vary a little, but that's about the size of it.

The rules change when the combustion chamber becomes a variable (changeable.)

Fred

If you can find a machine that is within 3% accurate on measuring the kW of a chainsaw, then..................

If not, a theoretical 3-5% gain does not really amount too much.

BTW what are you using as the coefficent for the efficency of a heat engine. (As described by Newton)

Fred

It has been my thought that such a small squish band, as in present in a stock 288, cannot be factored in the same manner as a relatively wide squishband.

There seems to be an inverse relationship between the two.

Fred

I said that it doesn't matter much for a stock 288 head. It comes into greater play with a custom combustion chamber.

Thermal efficency of a chainsaw is ~.25 and it decreases as we modify them in the conventional method we use. That is why I asked you about a coeffiecient.

It is obvious that you do not want actually discuss your theory and math with your response.

I have never accused anyone of cheating. I think most of that talk comes from further north of here. I really don't give a damn if people do cheat. It just means that they can't win any other way.

BTW

I think your quantified chart states otherwise.

Fred