Well, not so much a question as it is a ponder.
Some of you may know about my Tree Sling'r ported 7900 and the Solo 681 which I purchased from Brad Snelling. Since I have received both saws they have seen quite a large amount of attention, with good reason (thanks to Brad and Jasha).
As previously stated in other threads, both saws have been built slightly different. Without any of the major details being given, the Snellerized 681 has been built for speed and it has an unlimited coil. The Sling'r Ported 7900 has been built for torque and the limited stock coil remains on the saw.
There has been some confusion from more than just myself about the results in cutting times with both saws. As stated, the 7900 has more torque - not an uber amount more. It's not the difference between an MS170 and an MS361, but the difference is there. When I say torque I mean the amount of power the saw has left when leaned or pushed upon. I cut some cookies earlier of 28" white pine and I could clearly lean / push on the 7900 harder before stopping the chain. The 681 has a buttload of torque - but it does take less pushing to slow/stop the chain.
The compression on the 681 reads 150psi, the compression on the 7900 reads 160psi (this is with the westspartan's AutoZone compression tester). When Brad sent me the 681 it was around 170psi with his compression tester. When the westspartan's 441 was in Ohio it was at about 170 with Brad's compression tester, but here it shows about 150psi - just like the 681. Brad believes that Dan's comp tester is not calibrated properly since both saws are consistently reading 20psi less. Either way, the fact is that the 7900 is about 10psi higher than the 681.
To my knowledge more compression = more torque. This would make sense because the 7900 feels to have a bit more torque than the 681. The 681 pulls in 14,500 at WOT, and the 7900 is showing 13,000 at WOT.
In recent experimentation with the westspartan, we found that with both the 7 pin and 8 pin rims the 681 is faster. Why is this? Shouldn't the saw with more torque cut faster, especially with the 8 pin rim??
And I guess to throw a real monkey wrench in the mix I guess I could use J. Walkers 372 as an example. In 25" wood, his 372 will definitely out cut my 7900 by a long shot. But if you so much as breathe down on the handle of that 372 the chain practically comes to a dead stop as the torque isn't there on his 372 like my 7900 (no offense Jack - your 372 kicks a$$).
That is where I get confused. The whole "torque = speed" (in big wood) does not apply there. J.Walker has the speed with the 372, but the logic behind "torque will help speed in big wood" does not seem to hold water. If that was the case, then my 7900 (in theory) would be faster than his, correct? His saw does not have the torque mine has but yet it is able to keep the RPMs up just fine without the torque.
I usually hear "torque = speed". But it then makes me think that "torque = RPMs", but then again one could also say that "RPMs = speed". Which comes first... RPMs, torque, or speed? Which one comes next, and which one is third? And do the orders switch? Or does it always stay the same??
My confusion here is this - wouldn't the 681 naturally be faster with an 8 pin rim since it is already faster with a 7 pin rim? I do know that with more torque you can push harder which gives an advantage as far as slowing the chain down - but the general consensus is "the torquiest saw is the fastest saw". That's what I generally see a lot of around here - more torque = more speed.
I have spent some time going back and forth with Brad and after lot's of detailed questioning from me, this is what he had to say:
"It's actually over my head as well. I believe torque and RPMs are independent, yet related. Take an old gear-drive saw for example. You cannot stop the chain on them, yet they are very slow. The 681 has more RPMs, but not as much torque. I would think that if you put a long enough bar, or large enough rim on the 7900, it would eventually catch up and pass the 681, since it has the torque to keep pulling longer. What's kind of confusing, is that the 681, although faster, has to have enough torque to maintain those RPMs. I don't know the topic well enough to understand or explain it any better."
I'm not able to comprehend the relation among torque, speed, and RPMs currently. There is a lot of talk of "in the cut RPMs" as if that is all that matters. Then once it's a discussion of large wood then torque gets mentioned. Speed more or less seems to be the result of the compilation of torque and RPMs but I can't seem to find the direct relation between the two in order to get an answer regarding all three.
Any opinions or light that could be shed on the matter would be much obliged.
Some of you may know about my Tree Sling'r ported 7900 and the Solo 681 which I purchased from Brad Snelling. Since I have received both saws they have seen quite a large amount of attention, with good reason (thanks to Brad and Jasha).
As previously stated in other threads, both saws have been built slightly different. Without any of the major details being given, the Snellerized 681 has been built for speed and it has an unlimited coil. The Sling'r Ported 7900 has been built for torque and the limited stock coil remains on the saw.
There has been some confusion from more than just myself about the results in cutting times with both saws. As stated, the 7900 has more torque - not an uber amount more. It's not the difference between an MS170 and an MS361, but the difference is there. When I say torque I mean the amount of power the saw has left when leaned or pushed upon. I cut some cookies earlier of 28" white pine and I could clearly lean / push on the 7900 harder before stopping the chain. The 681 has a buttload of torque - but it does take less pushing to slow/stop the chain.
The compression on the 681 reads 150psi, the compression on the 7900 reads 160psi (this is with the westspartan's AutoZone compression tester). When Brad sent me the 681 it was around 170psi with his compression tester. When the westspartan's 441 was in Ohio it was at about 170 with Brad's compression tester, but here it shows about 150psi - just like the 681. Brad believes that Dan's comp tester is not calibrated properly since both saws are consistently reading 20psi less. Either way, the fact is that the 7900 is about 10psi higher than the 681.
To my knowledge more compression = more torque. This would make sense because the 7900 feels to have a bit more torque than the 681. The 681 pulls in 14,500 at WOT, and the 7900 is showing 13,000 at WOT.
In recent experimentation with the westspartan, we found that with both the 7 pin and 8 pin rims the 681 is faster. Why is this? Shouldn't the saw with more torque cut faster, especially with the 8 pin rim??
And I guess to throw a real monkey wrench in the mix I guess I could use J. Walkers 372 as an example. In 25" wood, his 372 will definitely out cut my 7900 by a long shot. But if you so much as breathe down on the handle of that 372 the chain practically comes to a dead stop as the torque isn't there on his 372 like my 7900 (no offense Jack - your 372 kicks a$$).
That is where I get confused. The whole "torque = speed" (in big wood) does not apply there. J.Walker has the speed with the 372, but the logic behind "torque will help speed in big wood" does not seem to hold water. If that was the case, then my 7900 (in theory) would be faster than his, correct? His saw does not have the torque mine has but yet it is able to keep the RPMs up just fine without the torque.
I usually hear "torque = speed". But it then makes me think that "torque = RPMs", but then again one could also say that "RPMs = speed". Which comes first... RPMs, torque, or speed? Which one comes next, and which one is third? And do the orders switch? Or does it always stay the same??
My confusion here is this - wouldn't the 681 naturally be faster with an 8 pin rim since it is already faster with a 7 pin rim? I do know that with more torque you can push harder which gives an advantage as far as slowing the chain down - but the general consensus is "the torquiest saw is the fastest saw". That's what I generally see a lot of around here - more torque = more speed.
I have spent some time going back and forth with Brad and after lot's of detailed questioning from me, this is what he had to say:
"It's actually over my head as well. I believe torque and RPMs are independent, yet related. Take an old gear-drive saw for example. You cannot stop the chain on them, yet they are very slow. The 681 has more RPMs, but not as much torque. I would think that if you put a long enough bar, or large enough rim on the 7900, it would eventually catch up and pass the 681, since it has the torque to keep pulling longer. What's kind of confusing, is that the 681, although faster, has to have enough torque to maintain those RPMs. I don't know the topic well enough to understand or explain it any better."
I'm not able to comprehend the relation among torque, speed, and RPMs currently. There is a lot of talk of "in the cut RPMs" as if that is all that matters. Then once it's a discussion of large wood then torque gets mentioned. Speed more or less seems to be the result of the compilation of torque and RPMs but I can't seem to find the direct relation between the two in order to get an answer regarding all three.
Any opinions or light that could be shed on the matter would be much obliged.
