Post by tommyhnavix on Nov 14, 2012 17:19:30 GMT -5
This is interesting math. Engine RPM rules in similar horsepower saws
Figuring surface speed in feet per minute.
www.sawmillchainsaws.com/sawfacts.htm
Chain pitch x 2 3/8=.750 .404=.808 Take this x teeth on drive sprocket. Then that number x engine RPM. Take that number divided by 12 for surface feet per minute.
Chain Speed ______SFPM @ _______RPM
Drive
Teeth _________11,500 RPM , _____8000 RPM , _____6000 RPM
7 tooth STD ____3/8 ____5031sfpm, ____ 3500sfpm, ____2625sfpm
.404 ____ 5424sfpm, _____3773sfpm, _____2830sfpm
8 th ____3/8 ______5750sfpm, ____ 4000sfpm, _____ 3000sfpm
.404 _______ 6191sfpm, ____ 4307sfpm, _____ 3230sfpm
9 th ___3/8 _____6469sfpm, _____4500sfpm, _____3375sfpm
.404 _______ 6967sfpm, ______4847sfpm, _____3635sfpm
10 th ___3/8 _______ 7188sfpm, _____ 5000sfpm, _____3750sfpm
.404 _________ 7743sfpm, ______5387sfpm, ______4040sfpm
11 th ____3/8 ________7906fspm, _______5500sfpm, ______4125sfpm
.404____________ 8520sfpm, _______ 5927sfpm, _______ 4445sfpm
12 th___ 3/8 ______ 8625sfpm, ________ 6000sfpm, ________ 4500sfpm
.404____________ 9296sfpm, _________ 6467sfpm, _________ 4850sfpm
13 th___ 3/8 ________ 9344sfpm, _________ 6500sfpm, _________ 4875sfpm
.404 _________10,063sfpm, _________ 7000sfpm, _________ 5250sfpm
14 th___ 3/8 __________10,063sfpm, __________ 7000sfpm _________ 5250sfpm
.404 __________10,839sfpm, __________ 7540sfpm, __________ 5655sfpm
WOW!!! Just a few more drive teeth really jumps the speed!!
I have a saw I put an 8 tooth sprocket on with shorter bar and had trouble with the sprocket on the end of the bar smoking in heavy cutting. Started putting a little synthetic oil in the bar oil and it works fine now and cuts like wildfire.
More teeth eats up horsepower in a hurry!!
Shortening the bar length helps up to a point. I checked my engine RPM in a cut with a 24 inch bar on and jumped 1 tooth from a 7 to an 8 and lost RPM. Put an 18 in bar on and engine RPM the came back in the cut but could see much faster cutting. Tried a 9 tooth and saw RPM was very low and power was poor. WOW!! Amazing how much difference 1 tooth can make!!
This guy has many different size available.
www.ebay.com/itm/Chain-Saw-Racing....Y-/360398399396
Figuring surface speed in feet per minute.
www.sawmillchainsaws.com/sawfacts.htm
Chain pitch x 2 3/8=.750 .404=.808 Take this x teeth on drive sprocket. Then that number x engine RPM. Take that number divided by 12 for surface feet per minute.
Chain Speed ______SFPM @ _______RPM
Drive
Teeth _________11,500 RPM , _____8000 RPM , _____6000 RPM
7 tooth STD ____3/8 ____5031sfpm, ____ 3500sfpm, ____2625sfpm
.404 ____ 5424sfpm, _____3773sfpm, _____2830sfpm
8 th ____3/8 ______5750sfpm, ____ 4000sfpm, _____ 3000sfpm
.404 _______ 6191sfpm, ____ 4307sfpm, _____ 3230sfpm
9 th ___3/8 _____6469sfpm, _____4500sfpm, _____3375sfpm
.404 _______ 6967sfpm, ______4847sfpm, _____3635sfpm
10 th ___3/8 _______ 7188sfpm, _____ 5000sfpm, _____3750sfpm
.404 _________ 7743sfpm, ______5387sfpm, ______4040sfpm
11 th ____3/8 ________7906fspm, _______5500sfpm, ______4125sfpm
.404____________ 8520sfpm, _______ 5927sfpm, _______ 4445sfpm
12 th___ 3/8 ______ 8625sfpm, ________ 6000sfpm, ________ 4500sfpm
.404____________ 9296sfpm, _________ 6467sfpm, _________ 4850sfpm
13 th___ 3/8 ________ 9344sfpm, _________ 6500sfpm, _________ 4875sfpm
.404 _________10,063sfpm, _________ 7000sfpm, _________ 5250sfpm
14 th___ 3/8 __________10,063sfpm, __________ 7000sfpm _________ 5250sfpm
.404 __________10,839sfpm, __________ 7540sfpm, __________ 5655sfpm
WOW!!! Just a few more drive teeth really jumps the speed!!
I have a saw I put an 8 tooth sprocket on with shorter bar and had trouble with the sprocket on the end of the bar smoking in heavy cutting. Started putting a little synthetic oil in the bar oil and it works fine now and cuts like wildfire.
More teeth eats up horsepower in a hurry!!
Shortening the bar length helps up to a point. I checked my engine RPM in a cut with a 24 inch bar on and jumped 1 tooth from a 7 to an 8 and lost RPM. Put an 18 in bar on and engine RPM the came back in the cut but could see much faster cutting. Tried a 9 tooth and saw RPM was very low and power was poor. WOW!! Amazing how much difference 1 tooth can make!!
This guy has many different size available.
www.ebay.com/itm/Chain-Saw-Racing....Y-/360398399396