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Author Topic: Stihl 075 sprocket size  (Read 6012 times)

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Offline oldsaw-addict

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Stihl 075 sprocket size
« on: April 19, 2004, 08:23:52 pm »
I was just looking at the Oregon webpage matching up a bar and chain for an 075, it says that the 075 uses an 8 tooth sprocket, I would think that this saw would be optimized with a 7 not an 8 tooth on it, unless an 8 is standard for this saw and a 9 is optional or was at one point in time. Kevin, perhaps you know which sprocket is right for this saw.  I am only talking about a STOCK 075AV running regular fuel for sawmilling not racing, just to make sure that there are no misunderstandings there. I dont have a clue which one is the right one, I think a 7 tooth would be best, but an 8 is the one listed for an 075 by Oregon cutting systems.  TIA.
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Offline iain

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Re: Stihl 075 sprocket size
« Reply #1 on: April 20, 2004, 09:33:50 am »
calm down icalm down i've not sent it yet


missed the 075 on ebay uk by 10
got stuck in traffic taking linda to work

but have found parts in germany so we'll  see what happens now
do you think i could put the 84 on the pulling side with the other 75 pushing (so to speak) to finish a job or would that be to unbalanced?

Offline Kevin

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Re: Stihl 075 sprocket size
« Reply #2 on: April 20, 2004, 10:20:08 am »
I'll go out on a limb without my rope and say 8 tooth for 3/8 and 7 with .404.

Offline oldsaw-addict

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Re: Stihl 075 sprocket size
« Reply #3 on: April 20, 2004, 02:07:31 pm »
Would a 7 3/8 bo too much torque? Just wondering.
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Offline Kevin

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Re: Stihl 075 sprocket size
« Reply #4 on: April 20, 2004, 03:25:26 pm »
Likely be more chain speed and less torque.
You''ll be driving a smaller chain faster with the 7.
If you are cutting big wood you would likely be better off with the 8 and 3/8 pitch.

Offline oldsaw-addict

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Re: Stihl 075 sprocket size
« Reply #5 on: April 20, 2004, 03:53:54 pm »
Kevin, I have no idea what I'd do without your expertise on this sort of thing. I'm confused though, you say the 7 tooth will give more speed with a smaller chain, while an 8 will work better in bigger logs. Are you sure that you didnt make a mistake there? It just didnt sound quite right to me as I have been taught that a 7 tooth will give lower chain speeds, but more torque while an 8 will give more chain speed with slightly less torque. This is what I learned if I'm wrong then please correct me. Thanks for the help guys, I appreciate your assistance.
Let there be saws for all mankind!

Offline Kevin

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Re: Stihl 075 sprocket size
« Reply #6 on: April 20, 2004, 04:02:18 pm »
If I'm wrong it won't be long before someone corrects me.  :D

Try to think of it like a 10 speed bike.
Small sprocket at the back for more speed on the flats and a large sprocket at the back for the hills while the horsepower(you) remains the same.

Offline oldsaw-addict

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Re: Stihl 075 sprocket size
« Reply #7 on: April 20, 2004, 04:08:07 pm »
Ok it all seems to be coming together now, thanks for clearing that up for me. I have a slight issue understanding how that can be that I get more torque with an 8 tooth and more chain speed with the 7, but since you explained it to me, I understand it better. Thanks kevin, you are an asset to us all.
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glens

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Re: Stihl 075 sprocket size
« Reply #8 on: April 20, 2004, 05:42:03 pm »
Quote
If I'm wrong it won't be long before someone corrects me.  :D

Try to think of it like a 10 speed bike.
Small sprocket at the back for more speed on the flats and a large sprocket at the back for the hills while the horsepower(you) remains the same.


Your wish is my command.  Your analogy would be correct if you were driving the chain from the rear axle on the bike for some reason.

For each drive sprocket revolution, a 3/87 will pull 5.25 inches of chain, a .4047 will pull 5.66 inches, and a 3/88 will pull 6.0 inches.


Offline Kevin

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Re: Stihl 075 sprocket size
« Reply #9 on: April 20, 2004, 05:43:15 pm »
Yabut the drive sprocket on the chainsaw is at the rear.

glens

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Re: Stihl 075 sprocket size
« Reply #10 on: April 20, 2004, 05:50:51 pm »
The drive sprocket on the chainsaw is the equivalent of the front sprocket on your bike.

I'm not going to argue with you; you wanted to be corrected and I had to register just to do so.  Do the math and you'll come up with the figures I provided.

This board software sucks harder than any I've ever seen.  Got to enable javascript just to use the stupid stuff and the quoted portions are black text on a black background.

Offline etat

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Re: Stihl 075 sprocket size
« Reply #11 on: April 20, 2004, 06:14:31 pm »
Kevin, me thinks he's got ya on the sproket thing. I think you're looking at it backwards.

BUT, I have NO idee what he's talking about on the rest.  I never had no problem with any software ??? ??? ???
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Offline Kevin

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Re: Stihl 075 sprocket size
« Reply #12 on: April 20, 2004, 06:21:15 pm »
There's no argument from me, it's been awhile since I did any sprocket changing and I'm too tired to look into it tonight .
If you're right that's good with me.
Thanks for your input.

Offline etat

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Re: Stihl 075 sprocket size
« Reply #13 on: April 20, 2004, 06:24:02 pm »
Turn the bike upside down.  Put it on the big gear.  Spin the rear wheel.  With the big gear the pedal will be going really really fast.  Put the rear end on a small gear.  Turn the wheel.  The pedal won't be moving as fast. There will be more torque at the pedal with the small gear, and more speed with the big gear.  

I made a mistake one time too, just hard to remember when ;D 8) 8) 8)
Old Age and Treachery will outperform Youth and Inexperence. The thing is, getting older is starting to be painful.

glens

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Re: Stihl 075 sprocket size
« Reply #14 on: April 20, 2004, 06:27:15 pm »
oldsaw, in the manner that you compile data and parrot it I'm surprised you had to ask this question; well, not really, but that's another topic for another time maybe.

The Oregon site suggests 3/88 if you want to use the lighter chain with more cutters per given loop.  That saw should be able to pull that all day every day.  If for some odd reason you wanted to both use the lighter chain and an effectively higher "gear ratio" (lower gear in typical terminology) you could get Oregon's Standard 7 Spline 3/87 rim.  Would not be a smart move in my opinion.

If you must go with 3/8 chain stick with the 8-pin driver.

If you want slightly less chain speed as well as pulling fewer, heavier cutters per loop revolution and with more authority then stick with the .4047 setup, as Oregon also recommends.  That saw might could pull the .4048 quite satisfactorily.

Glen

Offline Kevin

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Re: Stihl 075 sprocket size
« Reply #15 on: April 20, 2004, 06:30:57 pm »
I had it backwards, here's a bit from Madsens ...
Information on Rim Sprocket Size & Gearing
http://www.madsens1.com/sprktsaw.htm

Offline Jeff

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Re: Stihl 075 sprocket size
« Reply #16 on: April 20, 2004, 06:46:06 pm »
glens, you are getting a poor start here. This is not a public commercial site this is MY website.You had to register for that reason.  I would appreciate it if you keep you negative thoughts to your self and the language appropriate for a family site, which this is. Is is listed as a resource by several educational organizations . Save tha attitude for where ever it is you came from and we will get along fine. Your comments put you in a very poor light in front of THOUSANDS of guests and also our members that appreciate what we have here.
I don't need to know everything, I just need to know where to find it, when I need it - Albert Einstein
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Offline Kevin

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Re: Stihl 075 sprocket size
« Reply #17 on: April 20, 2004, 06:53:12 pm »
That's what I like about this site, you can always get the right answer by putting out the wrong one first.  :D

glens

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Re: Stihl 075 sprocket size
« Reply #18 on: April 20, 2004, 07:29:12 pm »
Jeff,

There's no good reason to /require/ javascript be enabled to do anything being done here, and you have to admit that black text on a black background is pretty questionable in terms of usability design (and I should be able to insert simple HTML directives to do things like make the word "require" above be presented in an italic font face).  I appreciate you wanting a friendly atmosphere.  Perhaps you did not realize you were being unfriendly via the site setup.  This is one of the problems which arise when testing/evaluating software configurations without considering some of the simpler, fully standard ways it might be used by others.

Kevin,

That Madsens link is generally good but contains a couple of errors.  They say

"The eight tooth sprocket has the same effect as a high gear ratio rear end has in a truck - the speed is great, but you better have plenty of horsepower when you come to a hill."

which is exactly backwards.  A high gear *ratio* means the input (in this case) is a higher multiple of the output while a low gear *ratio* is what they're describing.  It's a common mistake, much like saying current flows from positive to negative in a DC circuit when in reality the current flow is a result of the electrons migrating toward the positive.  

The second mistake is much the same, where they say

"the 3/8 X 7 sprocket is the smallest diameter of all sprockets.  This gives these small pro saws low "gearing" and enables them to run fairly long bars"

when it should maybe say ``gives these small pro saws a lower "gear"...'' (or more correctly ``higher "gearing"...'').  The result of what they're trying to say is the crank throw has a greater leverage against the pitch diameter of the drive sprocket as the sprockets decreases in pitch diameter (the pitch diameter is the circle through which the link rivets travel).

The mistakes should not be perpetuated merely because "sixty million Frenchmen can't be wrong".


I've read through many of the threads in this forum over the last week or so and finally felt like I had to address something.  My apologies for the manner in which I've done it.

Glen

Offline Jeff

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Re: Stihl 075 sprocket size
« Reply #19 on: April 20, 2004, 07:34:11 pm »
Glen, as to the problems you are having with the forum. THey are your problems due to configuration of your computer. Either you have an old, devective, or incompatable browser. You are the ONLY one seeing the forum in that manner. You should not be so quick to point when the problem is your own. In most cases I make every effort to help a member with a computer glitch. I promise you, this is your defect.  
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