Is compression king?

[Red97]

While we talking about compression.

What you guys like in a squish band???

Large? small? Offset?

Beginning to think the band can have a good amount of influence on how a saw responds. Mostly form a tuning standpoint...

 

[drf256]

I like it being squishy

 

[mdavlee]

While we talking about compression.

What you guys like in a squish band???

Large? small? Offset?

Beginning to think the band can have a good amount of influence on how a saw responds. Mostly form a tuning standpoint...

We don't get much choice in them unless we want to machine a different band in the cylinder or build a head.

 

[Terry Syd]

In a few weeks I'll have a 6100 of my own to play with Terry. Then we will try new and different stuff. I promise.

I'm looking forward to that build. The 6100 is a very impressive design, it wouldn't surprise me if the Stihl and Husky engineers are working overtime to try and figure out something that will compete with it. - Good luck guys!

 

[Red97]

We don't get much choice in them unless we want to machine a different band in the cylinder or build a head.

That is exactly what I am talking about. Wouldn't be hard to do especially with a mandrel.



I think 20-35% is a good range to shoot for. Some bands get wide in a hurry. Might be something to try in a really high comp saw that you already have the ports set in.

 

[Red97]

I like it being squishy

But how much squishy is "just right"

 

[mdavlee]

That is exactly what I am talking about. Wouldn't be hard to do especially with a mandrel.



I think 20-35% is a good range to shoot for. Some bands get wide in a hurry. Might be something to try in a really high comp saw that you already have the ports set in.

25-35% is real narrow. 50% is about ideal. It's total area of the chamber if it was flat.

 

[MustangMike]

Have not read all the posts, don't have the time, but there was some discussion about fuel octane. Stihl recommends higher octane because it runs cooler, so I always run high test (93 octane around here).

Ethanol free is not available here, but I always mix my gas soon after I get it, and never leave a saw not run for too long, and I have not had any problems. Even my weed wacker, which goes for many months in the winter w/o use, is doing fine.

 

[RI Chevy]

Same for me Mike.

 

[Red97]

25-35% is real narrow. 50% is about ideal. It's total area of the chamber if it was flat.

ex 50mm bore 25mm chamber 12.5 mm band width. 50% correct?

Just wonder if we are fighting ourselves sometimes.. seems like a band with in the 50%+ would be better suited for "low end" as it takes time and builds heat to get the gasses from the end to the "burn chamber" with a larger band. If you are looking for more top end.?

I believe the smaller band could achieve the same squish velocity in less time at high rpm.

Don't know any of this to be fact. Just another variable I have been thinking about in the black magic of saw porting.

Is the band with related to why some saws seem to turn up more than others of similar build durations?

 

[jmssaws]

I've ran vp 93 or 91 for years without any problems,both efree

I also ran 87 10% for years without any problems.
I run the higher octane gas because it's generally better if the station sells much of it but around here they mostly sell 87
So the higher octane gas could be much older.

 

[Red97]

Sometimes I run 110 just for the smell

 

[jmssaws]

Sometimes I run 110 just for the smell

Saws seem a little sluggish on it?

 

[Nitehawk55]

Sometimes I run 110 just for the smell

Another oil sniffer !!

 

[Red97]

Saws seem a little sluggish on it?

Honestly that was before I knew anything bout saws and running 60's homies. Only e free fuel I could get at the time.

Never noticed an increase/decrease, but wasn't looking for one.

 

[mdavlee]

ex 50mm bore 25mm chamber 12.5 mm band width. 50% correct?

Just wonder if we are fighting ourselves sometimes.. seems like a band with in the 50%+ would be better suited for "low end" as it takes time and builds heat to get the gasses from the end to the "burn chamber" with a larger band. If you are looking for more top end.?

I believe the smaller band could achieve the same squish velocity in less time at high rpm.

Don't know any of this to be fact. Just another variable I have been thinking about in the black magic of saw porting.

Is the band with related to why some saws seem to turn up more than others of similar build durations?

This is around 55-60% of the area. It's area so it's not measured just by the number. R squaredxpie

 

[Red97]

This is around 55-60% of the area. It's area so it's not measured just by the number. R squaredxpie

I gots to go touch up on my maths...

Google here I come.

Thank you sir.

 

[mdavlee]

I gots to go touch up on my maths...

Google here I come.

Thank you sir.

I figured that on 12mm. I think it's more like 10mm wide. Need to open the chamber more for gas.

 

[Red97]

Ok, I just mathed the heck outta this stuff. Smell the smoke...

I believe I found a simple solution (calculator's) for figuring area on concentric circles, centered chamber in a bore.

50mm bore, radius 25mm.

3.14x25x25= 1962 (area)
1962×.5= 981. That is the area I need for 50% squish band.

Now using a online annulus calculator. Aka ring or in our case "squish band"

With a known bore size I can adjust the area of the band to determine the correct diameter for the chamber.

Which happens to be a 7.3 mm band or 35.3 mm chamber for a 50mm bore to get a 50% squish band area.

Only reason I bothers to show the work is so I can come back to remember what the eff I was talking bout.

 

[Mastermind]

Maths hurt my heads.