Well Bwalker, yes the scenario you describe would be correct. But it nevertheless has little to do with a design teams initial decision on weather or not to equip a new design with 1 or 2 rings.
And Motorhead, thanks for the kind words. As far as the 250 honda and weisco and such. Yes you too are correct that a larger bore usually has a need for a larger skirt/wall clearance. But it is because of the greater expansion of a bigger piston. And weisco is one of the best at creating pistons of lower mass so the expansion is smaller, and clearance can be less, so rpms can be higher. several advantages to their stuff. But alos keep in mind, that they can produce pistons that will be "hand fit" to each bore that they will be installed in. and a manufacturer cannot.
Bwalker, you called it a QC issue, well kind of, but 15 to 20 years ago it was very hard for us to get in Jugs from italy, and pistons from mahle, and hold a less than .oo5 tolerance. In sweden we decided to make our own pistons to each run of jugs we recieved from Italy for the then 2101xp saws to hold a closer tolerance and get better life at the Demanded rpm level that the market required. Consider this the old way, you might say. As manufacturing capability became better from vendors, this need was precluded. Im pretty sure other companies were trying the same methods.
Aslo you know that as a closer tolerance is required from a vendor, the price usually goes up, if they have the capability at all.
But as time and volume go up, these prices decrease. today you have a very large range of choices based on the need for tolerances from vendors, with the lowest quality and largest tolerence, but lower prices coming from guess where???...yup..the good ole USA
Ever wonder why the cheap saws in anyones lines are made in america?...and the good ones come from abroad?
Now, also I must address the engineered life of a design, it is ALWAYS one of the 1st criteria when a design team sets to work on a new product. this will give us parameters to hold as to the quality and tolerance levels or each component designed.
There are many Saws in the market today, and the Lifetime duty goes from an low of 30 hours, to a high of 2500 hours. These are industry standards men. and they all equate to predicted use by the owner to the warranty period issued by the manufacturer.
to say it another way..A consumer saw with a 2 year warranty directed at a market where the users operate the saw an average of 15 hours a year!...
that saw runs about 20 to 30 minutes on a tank of gas, and the owner will not run more than 30 to 40 tANKS FULL A YEAR.
This saw has 2 rings and a .006 to .008 new skirt clearance, and the 2 rings afre there to keep the short skirted , hogh rpm devil from pistonslappin itself to death for about 30 hours,,,then...we dont care!
so in summary, the original question had to do with determining the quality of a design by how many rings it has. I only hope I have been able to explain that that will not be an accurate measure. And that if anything, a single ring will usually represent a higher quality design made to a closer tolerance......Usually!
