Howdy,
If you guys get to wondering why some saws of smaller displacement out cut larger units, you may be on the edge of discovering some important truths. One of which is most saws these days develope their torgue peak at too high of RPM, for the sawchain to be able to take advantage of it!
This is why some of those old reed valve dogs of yesteryear outcut the new racehorses, rather profoundly. The reedvalve engine developed it's torgue peak in the same band as the peak effeciency of the sawchain with which they were equipped.
This torgue peak thing is tricky with piston ported engines. Some will have considerably better useable output than others, and the results you get can be quite surprising.
The figures for sawchain are: The lowest chain speed practical is 1,700 sq.Ft/sec. The highest is 3,500 sq.Ft/sec. Outside of this band things all work against total effeciency. You can push the envelop by throwing more hp. at it, which is what the contest guys do. Incidently the low end is the speed of a slow ratio geardrive chainsaw, and the upper end usually works out to be around 8,000RPM depending on sprocket size (pitch and tooth count) for direct drive.
Reed valve engines used to prefer to cut around 6,500 RPM, which was just fine with the sawchain.
This is a might slow for modern saws, and if pulled down this much, they really fall off their torgue curve.
Every unit has it's prefered cutting speed, and this does not follow the dyno data. You just learn it by trial and error, and it is amazing how consistant you cut after that.
The complex situation with the sawchain is caused by the necessity for the cutters to work in and out of the wood, very unlike the teeth on a bandsaw or circular saw. Too high of speed, and this cutting action gets increasingly ineffecient, with sawchain, where-as the high speed can be beneficial for the mill saw. That's a whole different world of cutting theory.
Many of the Harvester machines (especially the ones from Sweden) use chain speeds above 4,000 sq.Ft/sec. This results in some amazing chain failure scenarios, but very fast cuts due to the massive hp. available. This is an example of throwing power at the problem and ???? the consequences.
Regards,
Walt Galer
maybe i will some day get one stihl or another, but i will only ever be an illegitemate bas***d in your "stihl family". and i will buy that stihl whenever im buying a type of saw that stihl makes a better version of - and it has not happened yet. i like the viking saws cos they pillage the wood better!!
