CASE VOLUME DISPLACEMENT ? / Introduction

[SHOVELHEAD]

To measure the cc with a buret,
Level case.
Cut plexiglass to fit case, apply thin coat of grease to case to produce seal, place cutout in center for connecting rod and place plexiglass on case and fill till no air is trapped beneath plexiglass.
( may have to move case around as filling to release air bubbles)
I use a light weight fork oil it displaces air and is none corrosive

 

[SHOVELHEAD]

Build it on one, then switch it to the other and see what you like.

I do have both 2156 &2159 saws that I could build & do a comparison.
But I would need some help gathering small stuff to make them complete runners.
I also have 2 272xp cylinders that could be used.
@ mastermind 's hooking me up with OEM Stihl piston
I would need 1 more.
And funds are tight.

 

[lwhaples]

This is going to be fun to follow along. Glad you joined. Your mentor does good work.

 

[Marshy]

I do have both 2156 &2159 saws that I could build & do a comparison.
But I would need some help gathering small stuff to make them complete runners.
I also have 2 272xp cylinders that could be used.
@ mastermind 's hooking me up with OEM Stihl piston
I would need 1 more.
And funds are tight.

Make sure he sends a Hooski piston instead. Unless there is some other trickery you are pulling that you are not telling us.

 

[SHOVELHEAD]

This is going to be fun to follow along. Glad you joined. Your mentor does good work.

Thanks for hooking me up with the 272xp cylinder.
With the 2 I have now, it opens up the possibility for a 2156 & 2159 build.
Thanks

 

[drf256]

SH,

Thanks for taking the time to do this. I just read Jim’s thread again.

It’s my understanding that the tunnel volume counted in case displacement. Jim opened his tunnels to match the base, that had to help his case to displacement ratio.

I’d have to say, the only accurate way I could see measuring true case volume would be to cut the head off an old or cheap AM 272 head. Bring piston to BDC, tape off both uppers (leaving just enough space to fill/vent air), seal off intake port with skirt with some pressed in clay, and fill the uppers with a burret.

Alternatively, one can use an overflow beaker and a graduated cylinder for measuring or a scale if water is being used. 1cc of water weighs one gram.

With the overflow Beaker, you fill till spills, then you measure what flows out when you add mass. It’s failrly simple.

So measure case without crank or bearing installed.
Dump crank, pin and pin bearing in overflow, measure displacement
Drop 2 bearing in overflow, measure displacement
Mark where the crank sticks out of the seals. Dip each side to line, measure displacement.
Tape off both transfer tunnels, measure with Burette
Dump piston in overflow, measure.
Measure base of cylinder with piston at BDC from crown. Seal uppers, measure.

Do the math on what belongs in calculation and what doesn’t.

At least that’s how I see it. I could be wrong or over complicating it for sure.

(Case + tunnels/uppers + outer crank measures+ cylinder bore at BDC) - (crank/rod/bearing/pin/piston)

That’s how I see it.

 

[paragonbuilder]

SH,

Thanks for taking the time to do this. I just read Jim’s thread again.

It’s my understanding that the tunnel volume counted in case displacement. Jim opened his tunnels to match the base, that had to help his case to displacement ratio.

I’d have to say, the only accurate way I could see measuring true case volume would be to cut the head off an old or cheap AM 272 head. Bring piston to BDC, tape off both uppers (leaving just enough space to fill/vent air), seal off intake port with skirt with some pressed in clay, and fill the uppers with a burret.

Alternatively, one can use an overflow beaker and a graduated cylinder for measuring or a scale if water is being used. 1cc of water weighs one gram.

With the overflow Beaker, you fill till spills, then you measure what flows out when you add mass. It’s failrly simple.

So measure case without crank or bearing installed.
Dump crank, pin and pin bearing in overflow, measure displacement
Drop 2 bearing in overflow, measure displacement
Mark where the crank sticks out of the seals. Dip each side to line, measure displacement.
Tape off both transfer tunnels, measure with Burette
Dump piston in overflow, measure.
Measure base of cylinder with piston at BDC from crown. Seal uppers, measure.

Do the math on what belongs in calculation and what doesn’t.

At least that’s how I see it. I could be wrong or over complicating it for sure.

(Case + tunnels/uppers + outer crank measures+ cylinder bore at BDC) - (crank/rod/bearing/pin/piston)

That’s how I see it.

Wouldn’t you want to measure volume at intake closing??? That’s when the case seals and starts to compress and then move mix to the chamber.

 

[Mastermind]

Just build it and see how it runs.

 

[EvilRoySlade]

Just build it and see how it runs.

Well that seems productive, but where’s the fun in that!

 

[Mastermind]

Well that seems productive, but where’s the fun in that!

I enjoy the discussion, but am interested more in results. To really see if it's worth doing we need a 272 built the same to compare to. If the hybrid comes close, then it's a win because of weight savings.

 

[Red97]

Just build it and see how it runs.

I like this approach.

Put it together however you see fit. Test against a 272,or any other 70cc saw. See how it stacks up. Then make changes.

Yes it is possible to calculate every possible scenario. Where is the fun in That?

 

[Mastermind]

I like this approach.

Put it together however you see fit. Test against a 272,or any other 70cc saw. See how it stacks up. Then make changes.

Yes it is possible to calculate every possible scenario. Where is the fun in That?

It makes for good banter....but can lead to overcomplicating a fairly straightforward build.

 

[Sleeper]

Hmm... you're making me want a 2159 with a 272 top end...

That will go on the list as a project that I will undertake at a later date. First, the raffle saw...

 

[Terry Syd]

If the hybrid comes close, then it's a win because of weight savings.

And then it could be made even lighter because it has the Husky small mount, you could put one of the newer, stronger and lighter Narrow Kerf bars on it. It would be a very light saw that would need a 9-pin on it to try and keep a load on the engine. - Just the thing for an old fart like me with a bad back.

 

[XP_Slinger]

It makes for good banter....but can lead to overcomplicating a fairly straightforward build.

+1

The more we get into theory the less we build.

 

[paragonbuilder]

+1

The more we get into theory the less we build.

Yes, but understanding it is where it’s at for me. Doing it and having it be great is good, but knowing why is what drives me to do it. Otherwise I’d send them out...
Different strokes for different folks...


Sent from my iPhone using Tapatalk

 

[SHOVELHEAD]

I'm only going to cc the 3 cases with the appropriate cranks in them,
Then I can compare the 272xp case volume to the others 2156 / 2159

I just finished putting my latest 2156 back together today.
Had the EPA muffler so I placed a 288 deflector and screen on the right back half.
Had torn it down to clean and replace some missing & incorrect parts.

 

[XP_Slinger]

Yes, but understanding it is where it’s at for me. Doing it and having it be great is good, but knowing why is what drives me to do it. Otherwise I’d send them out...
Different strokes for different folks...


Sent from my iPhone using Tapatalk

Didn’t mean to come off like theory is never important, it certainly is and I enjoy learning too. Just meant that at some point we should build it and start collecting evidence of theory or all this discussion just fades away and leaves questions unanswered. I’d love to see this hybrid run head to head against a 272. If there are differences, then plunge into the what, where and why elimination process.

 

[SHOVELHEAD]

Didn’t mean to come off like theory is never important, it certainly is and I enjoy learning too. Just meant that at some point we should build it and start collecting evidence of theory or all this discussion just fades away and leaves questions unanswered. I’d love to see this hybrid run head to head against a 272. If there are differences, then plunge into the what, where and why elimination process.

The idea of running 272xp agains my build would be great.
Unfortunately the only one I have is almost stripped.
It's a complete crankcase from intake to muffler.
If I had a tank/ clutch & cover / starter and other smart parts ,
Then I would have something to compare too.

 

[Chainsaw Jim]

This hybrid build is every bit as strong if not stronger than a 272. But the downside is the oiler and clutch size. Ok for cant racing and gtg's, but maybe not as ideal for an every day work saw.