One ring vs Two rings on 2 stroke chainsaws

[CentaurG2]

The NE 346XP has one ring.

One ring to rule them all, One ring to find them, One ring to bring them all and in the darkeness bind them.


Wait.... what are we talking about again???

 

[2000ssm6]

A good thread for a few of these>:notrolls2: :notrolls2: :deadhorse: :deadhorse:

If you like 2 rings, run 2. If you like 1, run 1.

 

[04ultra]

My Ryobi trimmers have one ring, I think it is primarly because they are cheap.

Mark

How many rings do old Mc's and Homies have ???

 

[Evan]

i bet most of us wear one ring. hmmmmm maybe we should get another on the side

i just looked up the new kawasaki kx65 it has 2 rings. couldnt find the hp spec for it. im sure its leaps and bounds above and 60cc saw that was designed as saw motor.

 

[edisto]

The ring debate brings out something that has been in the back of my mind...sorry if it is too tangental. I mentioned earlier that an advantage to having 1 ring would be the ability to use a longer connecting rod. It doesn't seem to be what is done though...I attached a picture with 3 50mm pistons, a Stihl on the left, a 2-ring Husky in the middle, and a 1-ring Husky on the right.

Bottom line, there is plenty of room for the second ring on the Husky, which means there would be room for a longer rod on the single-ring piston. All of the aftermarket pistons I have seen have the location of the pin bore cast...does anyone know of a source that bores them instead of casting them? How hard would it be to find a rod with the same (or smaller) crank and pin dimensions but longer?

Looks like there is room to move the ring land up too. Probably be stupid expensive (and a pain in the butt) for the gains, but it is fun to think about. Well, fun for me anyways...

 

[Evan]

what about powervalves. the powervalves on hightech 2 strokes raised and lower depdning on rpm. this changes volume in the cylinder almost like change port timeing with stone.

makes it so they produce optimum power across the board rather being a fixed port that comes on at 3/4 throttle.

are there saw motors like this. ado the big saws have power vavles.

i think strokeing a saw would be cool. turn a 359 int 365 with nothing more than longer rod. would probly make crazy tourge compared to a stock saw.

kinda like turning 350 chevy into a 383. thats done in the crank only with factory bore diameter

 

[edisto]

i think strokeing a saw would be cool. turn a 359 int 365 with nothing more than longer rod. would probly make crazy tourge compared to a stock saw.

kinda like turning 350 chevy into a 383. thats done in the crank only with factory bore diameter

The longer rod wouldn't change the stroke...that is determined by the crankshaft. That's why the pin bore needs to be raised to use a longer rod. A loner rod just allows better transfer to the crank (and from the crank on the upstroke) because the rod is more vertical.

 

[FATGUY]

what about powervalves. the powervalves on hightech 2 strokes raised and lower depdning on rpm. this changes volume in the cylinder almost like change port timeing with stone.

makes it so they produce optimum power across the board rather being a fixed port that comes on at 3/4 throttle.

are there saw motors like this. ado the big saws have power vavles.

i think strokeing a saw would be cool. turn a 359 int 365 with nothing more than longer rod. would probly make crazy tourge compared to a stock saw.

kinda like turning 350 chevy into a 383. thats done in the crank only with factory bore diameter

that's incorrect... A chevy 383 is a 350 bored 0.03" over, with a 3.75" crank (from a 400).

Anyway too bad this whole thread turned into a Stihl vs. the world match.

Here's what confuses me, and maybe Andy can explain. I thought the most wear would occur during the power/exhaust stroke (as this is the most violent) and I would think the bottom portion of the bottom ring would wear first. This appears not to be the case, I wonder why?

 

[J.W Younger]

wondering if lower ring helps with crankcase pressures? I sure as hell don't know beans about 2-strokes

 

[bigjake]

A longer rod would just change rod ratio .This is a big factor in engine
torque and rpm as it changes with stroke and rod length . moving the pin hieght
and rod length will change a lot of things in the genaral rpm range.and
there is no piston slap in drag motors.I have run pistons that have buttons
in because the ring goes thru the pin.

Bottom line it was explained the difference. i think its just going on for trolling
purposes.

 

[J.W Younger]

A longer rod would just change rod ratio .This is a big factor in engine
torque and rpm as it changes with stroke and rod length . moving the pin hieght
and rod length will change a lot of things in the genaral rpm range.and
there is no piston slap in drag motors.I have run pistons that have buttons
in because the ring goes thru the pin.

Bottom line it was explained the difference. i think its just going on for trolling
purposes.

does that mean they don't slap or you just can;t hear em slap. I can't hear the planetary gears whine in my bracket car but i'm thinkin they prob do, since its a power glide trans

 

[brinkwolf]

A longer rod would just change rod ratio .This is a big factor in engine
torque and rpm as it changes with stroke and rod length . moving the pin hieght
and rod length will change a lot of things in the genaral rpm range.and
there is no piston slap in drag motors.I have run pistons that have buttons
in because the ring goes thru the pin.

Bottom line it was explained the difference. i think its just going on for trolling
purposes.

I could rebutle but I'm done with this.

 

[Crofter]

I imagine if there was a boatload of merit on way or the other the number of rings question would have been all buttoned up a long time ago. Same with rod length/ stroke ratio and pin placement. Theoretical benefits get thrown on the scale along with dependability, cost to produce and a lot of other issues.

Piston stability and wear is a real issue in a close coupled piston ported engine. What applies performance wise in a four stroke might have little to do with some claimed advantages when applied to a 2 stroke. Dwell times around exhaust and intake events is about 90 degrees different in the two designs.

No question rod angularity puts side pressure on the piston and bore and would be affected by rod length. The loading is straight down while the force is off to the side. Twice each revolutions the forces move the piston from one side of the bore to the other. It would be nice to have the centre of force around the middle of the available wear surface but drag on on the piston from cylinder contact is variable so that is not an easy spot to put your finger on. Rocking movements are induced by drag and if forces arent reasonably in balance you get rapid wear or skirt breaking. If you think the rings can supply the amount of force necessary to absorb unbalanced loads you will not be in agreement with a lot of designers. Going one ring merely so you could place the pin up closer to the top of a saw piston might not be all good for piston stability.

 

[bigjake]

does that mean they don't slap or you just can;t hear em slap. I can't hear the planetary gears whine in my bracket car but i'm thinkin they prob do, since its a power glide trans

Ok now in YOUR bracket motor how much piston to wall clearance do you run
My point is if the bore is tight why would the piston make noise in any motor
and i run mufflers on my dragster to run national events .And i dont here a thing . were and what do you race . i might have run into you we race all
division 3 and a lot of the big money bracket races .

And brinkwolf if i am wrong in anything i said point it out .I am not perfect
but i have been racing a long time .Like 25 years.Good luck to all om done.

 

[bigjake]

Ok now in YOUR bracket motor how much piston to wall clearance do you run
My point is if the bore is tight why would the piston make noise in any motor
and i run mufflers on my dragster to run national events .And i dont here a thing . were and what do you race . i might have run into you we race all
division 3 and a lot of the big money bracket races .

And brinkwolf if i am wrong in anything i said point it out .I am not perfect
but i have been racing a long time .Like 25 years.Good luck to all om done.

And i know nothing about 2 strokes.but we were talking rod length and piston
slap .Were the hell that term ever came from i dont know .

 

[J.W Younger]

I run a srp. piston with about .004 piston to wall clearance. small block4.030 bore,3.75 stroke, 6in rod.pin is in the oil ring groove.

 

[brinkwolf]

Hey Jake, don't know if we have met or not but I run mostly in the Houston,TX area. The car we use to run which we won classes with and all the money with was a green 74 Pontiac Ventura running a small block Chevy. Our new car is an Orange Chevy Nova also SBC(working on a motor for it now). We haven't had much chance lately to do anything with it(my partners boy races bmx bikes and they're always gone lately). I don't have as much time as you racing but I have been in the Automotive business going on 30 years now.

 

[Lakeside53]

Here's what confuses me, and maybe Andy can explain. I thought the most wear would occur during the power/exhaust stroke (as this is the most violent) and I would think the bottom portion of the bottom ring would wear first. This appears not to be the case, I wonder why?

The combustion pressure mainly affects the exposed top ring, and forces it out into contact with the bore. More pressure, more wear.

 

[FATGUY]

The combustion pressure mainly affects the exposed top ring, and forces it out into contact with the core. More pressure, more wear.

I think I'm begining to see the light.... so it's the combustion "charge" that wears the ring(s) and not the contact with the cylinder wall. Ok I'll buy that.

 

[Tzed250]

This cr@p is hilarious...