Just wondering what determines the top rpm's of a motor . Particularly chainsaws . I know some are limited by the coil...but what about ones that have an unlimited coil ? Just a curiousity...as I'm digging the 42/242/242xp/246 lately...and all 4 have different peak recommended rpms. Here's a pic of my 242...always ready to cut..fast ! Boy..what a saw
Wow that is not an easy question to answer. Almost everything on the saw will affect RPM. Ignition timing, port timing, port size and shape, squish band, compression ratio, the carburetor size and tuning. The muffler or tuned pipe. Some things are going to affect the RPM's more then others. You can mod a saw for just torque but one of the by products will be RPM's even if you did not intend to.
Excluding physical strength of the engine components and lubrication? Air flow, fuel delivery, ignition circuitry. In that order.
Actually, I think the question HoneyFuzz meant to ask is what determines the manufacturer's high rpm limit. And that is indeed a complicated answer. I'm sure it involves a few dyno runs to determine the power characteristics of the engine, and once the peak rpm limit is determined, a slew of durability testing to ensure the engine doesn't develop problems with those settings.
Machining tolerance and balance of rotating parts is probably the biggest influence on max RPMs, lest the engine vibrate itself to death at the top of the range.
Yes I would agree. Especially when it comes to tuning the carb. Everybody knows you can run these things lean and make them scream, but how long would that last until the seize.
Poor, Gary.. No fish. Too busy printing inserts for black Friday.. So they can spill all out over everyone's floor on Thanksgiving.. You all can thank me later.. I like this smiley too..
how quickly an engine can reach its top rpm should also be mentioned, heavier flywheels and clutches slow the process down.......don't forget about short stroke vrs long stroke......and the weight of the crankshaft, piston assembly and conn rod, also small and big end bearing.....
Are you looking for a top RPM recommendation for that 242? Or just the general question on how they come about it?
Nice stumps, but there's two more chunks of firewood in each one. Left tall to push over with a dozer? As far as unlimited saws and the top rpm. That's the rpm the saw is designed to be tuned to without being too lean.
Any saw really . What got me thinking was the 242. 242...242xp..42...42 special all have different top rpm ratings. Figured some had to do with open port/closed port and such.
I found it easier to use the weight of the tree to bring them down than trying to grub the stumps out.
Thanks !!! I pushed and uprooted all I could with the skid steer . The rest wouldn't budge......so when my dad's excavator comes home....I'll clip the roots and pop em out ! It's alot of b.s lol....but the machines are free to use....as long as they don't break lol Lets just say...its been the year of the hydro hose lol ! I tell ya...someday I'll have a dozer ! Man...the things I could do lol !
That's true .... But this time...the timing wasn't right. The firewood was needed...and the mini excavator wasn't around to clip the roots so the skid could push em over. Someday...I'd love to have an old JD450 dozer !!
