Pop ups and windows. Your thoughts.

[ECsaws]

"MY" findings... pop-ups do indeed make gains in a chainsaw motor .. Now "I" find a lot depends on how the pop-up is done if you cut a square edge gains are not so much but a nice gradual rounded edge seem to work better for "ME".
In some cases I have seen saws go in reverse from to much compreshion... then again to much depends on what saw your working on, seems everyone likes something a little differnt.
My take on windows . In "theory" they should "help" cool the piston crown. also cutting windows dose reduced piston weight, witch dose lighten the rotating mass witch "should" result in a quicker spool up but possible lose in tourque. negatives to windows is of course the obvious increasing the case volume, depending on what you do to the transfers how much affect windowing dose. One other thing on windowing I've always wondered when the windows pass the upper transfers what happens? is the pressure causing a reverse pressure affect on how the transfer feed ? I havent found any measurable gains (in a GAS saw) in windowing a non windowed piston, I honistly thing those engineers who designed that piston/ cly... know a heck of a lot more than I do......
Without CCing the case volume and doing all the math, doing any off this is like shooting in the dark unless your willing to do all the testing witch trust me get real pricey real quick...

 

[wigglesworth]

Probably about 3*. That's a by product anytime you do a popup.

No, not everytime

 

[blsnelling]

No, not everytime.

039?

 

[wigglesworth]

039?

Actually, that one is the first one I did, a partner 5000 slug. The 039 will be done today though

 

[sps3172]

Hi Guys....

Does anyone actually have and use a steady state (not inertial) load type, dyno(water break, eddy current, etc)? It seems that there are lots of great ideas floating around the forums.....but no real way to test for the small gains.

I found some OOOOLLLLLDDD threads where it seems that Walker's Saw Shop was testing with a Land and Sea water brake.....but I don't hear anyone talking about that sort of testing these days.

 

[Terry Syd]

A Works Connection tach can be installed on the saw for less than $40. You can monitor the tach when you make a change to the saw. It is hard to pick up a couple of hundred rpm with your ears or by subjective feel, but the tach is an objective indicator that can tell you if you are making progress or just fooling yourself.

 

[sps3172]

A Works Connection tach can be installed on the saw for less than $40. You can monitor the tach when you make a change to the saw. It is hard to pick up a couple of hundred rpm with your ears or by subjective feel, but the tach is an objective indicator that can tell you if you are making progress or just fooling yourself.

Terry,

Was this in response to my question about using steady state dynamometers?

- Steve

 

[Terry Syd]

Yep, I haven't heard of any dynos available for saws. The tach is something everybody can have access to.

 

[sps3172]

Yep, I haven't heard of any dynos available for saws. The tach is something everybody can have access to.

I agree that there don't seem to be any 'bolt on' solutions for chain saw dynamometers. That being said, there are many small engine brakes available....and the software to 'watch' them. It's down to a matter of making the fixtures to interface the saw engine with the brake. As mentioned in my first post, it seems that at one time, Walker's Saw Shop was using a land and sea water brake for testing. I found this info searching old posts. At some point ('03-'04??) all discussion of this dyno and their testing stopped. I'm just wondering how/why that sort of testing fell out of favor.

I suppose the tach is better than nothing....but logic suggests that it's not better by much. Using a saw is a 'subjective' activity. Cutter pushes harder one time....softer the next. One time the chain has 'x' sharpness.....next time it's 'x+ or - y'. One time the wood is 'x' hardness.....next time it's 'x+ or - y'. Etc.

If the outcome of the cut (time, typically) can be impacted/skewed by all the variables above (operator, chain, wood), then the 'data' provided by the tach can be skewed in the same way.

 

[spacemule]

I agree that there don't seem to be any 'bolt on' solutions for chain saw dynamometers. That being said, there are many small engine brakes available....and the software to 'watch' them. It's down to a matter of making the fixtures to interface the saw engine with the brake. As mentioned in my first post, it seems that at one time, Walker's Saw Shop was using a land and sea water brake for testing. I found this info searching old posts. At some point ('03-'04??) all discussion of this dyno and their testing stopped. I'm just wondering how/why that sort of testing fell out of favor.

I suppose the tach is better than nothing....but logic suggests that it's not better by much. Using a saw is a 'subjective' activity. Cutter pushes harder one time....softer the next. One time the chain has 'x' sharpness.....next time it's 'x+ or - y'. One time the wood is 'x' hardness.....next time it's 'x+ or - y'. Etc.

If the outcome of the cut (time, typically) can be impacted/skewed by all the variables above (operator, chain, wood), then the 'data' provided by the tach can be skewed in the same way.

You make too much sense. Ask these guys--all they need is a decibel meter to tell how fast their saw is. :hmm3grin2orange:

 

[Log Hogger]

Could use a water pump. Pipe the water up vertically and into a barrel, then measure gallons/minute. By adjusting the height of the head you could find the right load range. Then it's down to the matter of determining which mods give the best head.

 

[sps3172]

Then it's down to the matter of determining which mods give the best head.

Thoughts like this display the whole 'engine mod' thing in a whole new light.


Sorry....I grew up on Beavis and Butthead.

 

[showrguy]

Then it's down to the matter of determining which mods give the best head.

i'm not sure, but some of the site moderators might get pissed at you for that statement !!!

 

[parrisw]

So far there are allot of opinions floating around here. The OP started this, so lets hear what he thinks!

 

[parrisw]

"MY" findings... pop-ups do indeed make gains in a chainsaw motor .. Now "I" find a lot depends on how the pop-up is done if you cut a square edge gains are not so much but a nice gradual rounded edge seem to work better for "ME".
In some cases I have seen saws go in reverse from to much compreshion... then again to much depends on what saw your working on, seems everyone likes something a little differnt.
My take on windows . In "theory" they should "help" cool the piston crown. also cutting windows dose reduced piston weight, witch dose lighten the rotating mass witch "should" result in a quicker spool up but possible lose in tourque. negatives to windows is of course the obvious increasing the case volume, depending on what you do to the transfers how much affect windowing dose. One other thing on windowing I've always wondered when the windows pass the upper transfers what happens? is the pressure causing a reverse pressure affect on how the transfer feed ? I havent found any measurable gains (in a GAS saw) in windowing a non windowed piston, I honistly thing those engineers who designed that piston/ cly... know a heck of a lot more than I do......
Without CCing the case volume and doing all the math, doing any off this is like shooting in the dark unless your willing to do all the testing witch trust me get real pricey real quick...

I've seen some pics of popups as well that had a harsh uprise to them, or square! Don't know why they'd do that.

Here is a 460 piston that I did, this is how much I "chamfer" them.

I've heard the disruption of flow theory many times. Has anyone actually tested it to see if its true? I mean the only way you'd know is with a high speed camera and see how air flows across the top of the piston.

 

[Dennis Cahoon]

I've heard the disruption of flow theory many times. Has anyone actually tested it to see if its true? I mean the only way you'd know is with a high speed camera and see how air flows across the top of the piston.

Isn't all about disruption in the right direction???????......Hahahahahahaha!

 

[Dennis Cahoon]

Imagin that piston originally having a dome......them gradually cutting in your pop-up.

 

[parrisw]

Isn't all about disruption in the right direction???????......Hahahahahahaha!

??????? not sure what you mean.

 

[parrisw]

Imagin that piston originally having a dome......them gradually cutting in your pop-up.

So what would that leave? A domed pop-up?


Anyone seen a 2stroke outboard piston? Some of them have huge ramps facing the intake.

 

[parrisw]

Here is a 2 stroke piston, what say you on flow across the piston with this.