chain saw bar question

[big bubba]

starting to cut wood for the season. have a question re: increasing bar length & chain saw performance. have a Stihl 460 that i increased the bar length from 18" to 25" (saw is easily capable of handling extra length). new bar & chain cuts great. got to thinking...because of the added bar length with a sharp chain, will the saw cut through material at a better rate because of the increased cutting surface feet per minute, or will it not preform as well because of the drag of added bar length? (at the same rpm for both lengths)

know it seems academic, but will it cut more efficiently because of the added surface cutting feet? yes, i have too much time on my hands, but the day's chore is done & now just thinking. i think about these things as a retired machinist. thanks in advance

 

[ruffdog]

Unless you change the size of the drive sprocket, chain speed won't change. A skip tooth chain has less teeth and will cut slower....but, it will help a saw pull a long bar if it is struggling. I have a MS460 with the dual port muffler and jetted to match and it is wicked with a 20" bar. I sharpen chains with a file so they are very sharp.

 

[ericm979]

I'm a member of the 460 club too.

The longer bar will have slightly more friction. So the chain speed may be a bit slower if you did not tune the carb. If you did, it will be the same but there will be still be a little less power to do the cutting so the saw will bog a little easier. I have not seen measurements but I feel the added friction would be small.

The chain speed won't change between bars (assuming you tuned the carb). If both bars are sticking out the other side of the log, then the same number of teeth are cutting at the same speed. Both bars are removing the same volume of wood (assuming not on the edge of bogging).

If the log is smaller than the 18" bar so both bars can cut in one pass, the speed will be the same between the bars.

If the log is bigger than the 18" bar then you'll have to cut twice, once from each side. If the log is smaller than the 24" bar then the 24 will do the cut faster because you did not have to reposition.

 

[oldballs]

Youze guys sound like the academinans of chain saws.

Cheers,
Mike

 

[dodge man]

If your cutting a bigger piece of wood, say using the entire 25” bar it will obviously take more power. If your cutting say a 12” log, like somebody said, a little more friction but otherwise the same amount of saw in the cut. In my mind the reason to switch to a longer bar is because you’re cutting larger logs.

 

[milkman636]

I have an ms460 that came equipped with a 25” bar when it was brand new. To me, it seems perfectly matched for the 25” bar and I never even considered a shorter bar for it. I like a smaller power head like my 340 with an 18” bar. To me it seems that you’re exactly right that my 460 is way faster and makes more chips while cutting because it has more teeth simultaneously engaged in cutting the kerf.

 

[ruffdog]

^^Agree, the 460 is well balanced with a 25" and I use the shorter 20" with the 361.

 

[big bubba]

thank you for the well informed replies, makes sense. agree the 25" is a perfect match for the 460, & have a MS260 w/16" as a back up. for safety reasons, i am very aware of the extra length/ increased exposed chain... but always wear chaps & helmet.
thx again, & always keep an eye out for your safety. & try to avoid cutting alone as i do most of the time, we do as we can, cheers

 

[bullbreaker]

more good learning on chainsaw bars .........

 

[Egon]

Only an Empiracal test will answer your questions.