Rim Sprocket ?'s

[qbilder]

I have a 3/8-8 rim sprocket on my 084. I want it to have the most torque for milling. Would a 7 tooth be better? And will any Stihl or sub. 7 tooth sprocket fit or is there a certain size I need? The only thing stamped on the sprocket is 3/8-7 Stihl. If anybody could simplify this for me, i'd sure appreciate it. I suppose it's about like bicycles?

 

[showrguy]

yes the 3/8 7 pin will work and give you more torque.
just make sure it's the large spline (i think it's 7/8" inside diameter)

 

[Philbert]

It's a lot like bicycle gearing. Just waiting for some A.S. member to come up with a derailleur to allow you to shift in the cut!

The rim sprocket has to match your chain pitch and the spline on your clutch drum. Oregon and STIHL have a lot of choices, but not every possible combination. There are other companies that offer rims in some sizes that these guys don't offer. Check with some of the site sponsors to look for non-standard sizes.

http://www.oregonproducts.com/pdf/sprockets/RimSproxFB0601.pdf

Philbert

 

[qbilder]

According to Philbert's link, it looks like I have the SD7, 7/8" ID. That makes things easy as they are readily available on ebay for cheap. Couldn't find anything at Baileys. Now gotta find a bar & chain to go with the sprocket. Saw came with a 36" hard nose & 8 tooth sprocket. Gotsta change that. Thank you gentlemen :msp_thumbup:

 

[Philbert]

Couldn't find anything at Baileys.

Bailey's - Oregon Power Mate Rim Sprocket .3/8" x 7 Tooth

Philbert

 

[qbilder]

Cool thanks! I couldn't find it when I was looking. Cheap enough & the measurements are pretty much spot on.

 

[BobL]

I use an 8 pin sprocket on my 880 in Aussie hardwoods up to 30" wide cuts and only then do I switch to a 7 pin.

It's not all cookies and cream with lower pin counts. Although they provide more torque, unless you drop your rakers so the cutters cat take a bigger bite the resulting slower chain speed may actually mean slower cutting.

Somewhere I have some 9, 10 and 11 pin sprockets I should drag out and have a crack with.
View attachment 282912

 

[qbilder]

I use an 8 pin sprocket on my 880 in Aussie hardwoods up to 30" wide cuts and only then do I switch to a 7 pin.

It's not all cookies and cream with lower pin counts. Although they provide more torque, unless you drop your rakers so the cutters cat take a bigger bite the resulting slower chain speed may actually mean slower cutting.

Somewhere I have some 9, 10 and 11 pin sprockets I should drag out and have a crack with.
View attachment 282912

You just answered my question about bar size Seeing how large those sprockets can be in comparison to the end of the bar, a 7 or 8 tooth sprocket on the 084 should be just fine on the smaller bar once I swap the studs.

 

[BlueRider]

There is more to consider then just the number of pins on your rim sprocket. Your saw was originaly equiped with .404 pitch chain, not sure what number of pins on the sprocket but probably 7 or 8. If you swap out to 3/8 pitch with the same number of pins you will end up with a slower chain speed (chain pitch x 2, multiplied by the number of pins on the rim sprcket x RPM = speed in inches/ minute)

So with your set up you have dropped chain speed but if you are useing standard milling chain with standard depth rakers you are wasting the power of your saw. It is like driving down the freeway in first gear. to optimize the power of your saw you need to set the rakers substantialy deeper which would not be the direction I would go with 3/8 pitch chain, .404 sure, but why swap out to lighter chain and then ask it to take more stress. I would opt to crank the chain speed up and take the same depth of cut that the chain was designed to take.

Another thing to consider is that your saw has a large bore & short stroke compared to the older torque monsters like the 075 & 090. that means your saws power band is in the upper rpms. If you can match the pin size so that you can keep the rpm up you will always out cut an 075 or 090.

 

[john taliaferro]

It's a lot like bicycle gearing. Just waiting for some A.S. member to come up with a derailleur to allow you to shift in the cut!

The rim sprocket has to match your chain pitch and the spline on your clutch drum. Oregon and STIHL have a lot of choices, but not every possible combination. There are other companies that offer rims in some sizes that these guys don't offer. Check with some of the site sponsors to look for non-standard sizes.

http://www.oregonproducts.com/pdf/sprockets/RimSproxFB0601.pdf

Philbert

your derailleur idea gave me a headache :msp_thumbup:

 

[qbilder]

There is more to consider then just the number of pins on your rim sprocket. Your saw was originaly equiped with .404 pitch chain, not sure what number of pins on the sprocket but probably 7 or 8. If you swap out to 3/8 pitch with the same number of pins you will end up with a slower chain speed (chain pitch x 2, multiplied by the number of pins on the rim sprcket x RPM = speed in inches/ minute)

So with your set up you have dropped chain speed but if you are useing standard milling chain with standard depth rakers you are wasting the power of your saw. It is like driving down the freeway in first gear. to optimize the power of your saw you need to set the rakers substantialy deeper which would not be the direction I would go with 3/8 pitch chain, .404 sure, but why swap out to lighter chain and then ask it to take more stress. I would opt to crank the chain speed up and take the same depth of cut that the chain was designed to take.

Another thing to consider is that your saw has a large bore & short stroke compared to the older torque monsters like the 075 & 090. that means your saws power band is in the upper rpms. If you can match the pin size so that you can keep the rpm up you will always out cut an 075 or 090.

Makes perfect sense to me. Thanks

 

[mtngun]

So with your set up you have dropped chain speed but if you are useing standard milling chain with standard depth rakers you are wasting the power of your saw. It is like driving down the freeway in first gear. to optimize the power of your saw you need to set the rakers substantialy deeper which would not be the direction I would go with 3/8 pitch chain, .404 sure, but why swap out to lighter chain and then ask it to take more stress.

I tried both a 7 pin and and 8 pin on my 084 and the saw preferred the 7 pin, even on small (12") logs. The 7 pin cut faster and the rpm's stayed in the powerband, whereas the 8 pin dropped the rpm's down and made the saw work harder. Your mileage may vary.

Those who mill with a temperature gage have reported that their engine runs cooler if they keep the rpms up rather than lug it.

3/8 chain has no problem milling on a 120cc saw even with aggressive rakers, and one guy even runs .325. Chain breakage is rare. Bear in mind that milling takes smaller bites than crosscutting.

 

[BlueRider]

....3/8 chain has no problem milling on a 120cc saw even with aggressive rakers, and one guy even runs .325. Chain breakage is rare. Bear in mind that milling takes smaller bites than crosscutting.

I have no doubt that this is true for others here but it has not been my experiance. I was milling with .404 and hit a massive steel bar which ripped 5 cutters off the chain. I then was using another saw with 3/8 chain to cut around the inclusion and miss judged and snpped the chain on the same piece of steel that mearly ripped the teeth off the .404 chain.

Milling takes the same size bite per tooth as cross sutting and for those of us that lower our rakers, milling takes and even larger bite than cross cutting. Milling produces smaller bits of sawdust but the tooth is still bitting as much wood either way the fibers are oriented.

The different angles used in milling chain vs standard chain don't effect the size of the chip but rather the smoothness of the cut as well as the making the chain more prone to kickbacks. The shallow angle of milling chain also requires more work to pull through the wood, not because of the amount of wood being removed, but due to the way the cutting edge of each individual tooth is entering to wood at a more oblique angle or put another way all at once instead of gradually. more work also implies greater restance on the chain.

The biggest reason for switching to 3/8 from .404 is not a smaller kerf but less weight, less weight requires less work.

 

[BobL]

I have no doubt that this is true for others here but it has not been my experiance. I was milling with .404 and hit a massive steel bar which ripped 5 cutters off the chain. I then was using another saw with 3/8 chain to cut around the inclusion and miss judged and snpped the chain on the same piece of steel that mearly ripped the teeth off the .404 chain.

Milling takes the same size bite per tooth as cross sutting and for those of us that lower our rakers, milling takes and even larger bite than cross cutting. Milling produces smaller bits of sawdust but the tooth is still bitting as much wood either way the fibers are oriented.

Maybe it does in softer woods but it definitely does not do this in Aussie hardwoods. It's not just the raker depth that determines the size of the chip but the hardness of the wood. The reason for this is the hardness determines the amount of penetration of the raker into the wood during the cutting and end grain is usually harder for the raker to penetrate than side grain. The cutters don't shave like a hand plane or a circular saw but instead rock their way into the wood - rocking between cutter tip and raker - creating a chip size that is as much wood hardness dependent as it is raker depth dependent.

A good test of this is to time cross and rip cuts. The only test I have done of this in in Aussie hardwood where the time difference was about 30%.