The torque's non existing influence on cutting speed.

[Canyon Angler]

Want to know an EASY way to increase your torque??? put a smaller drive wheel on.

Actually the "torque" at the shaft and at the sprocket (regardless of whether it's a 7-tooth or 9-tooth or 111-tooth sprocket) will remain the same number of foot-pounds or Newton-meters or whatever.

The only thing you change by changing the size of the drive sprocket is your mechanical advantage. The torque remains the same.

Think about the ring gears and sprockets on your 10-speed bike. Your weight, your leg strength and the length of the lever arm on the pedal all remain the same no matter what gear you're in, so the torque you apply remains the same, too. Only the gear ratios (and mechanical advantage and output shaft torque) change when you change the sizes of the driving and driven gears.

 

[Beweller]

I quote from "Laddle Rat Rotten Hut":

"Yonder nor sorgum stenches shut laddle gulls stopper torque wet strainers!"

 

[Beweller]

Maybe a bit off the subject, but still relevant.

Some years back, before the Eastern block broke up, the Russians operated an aircraft shuttle flight between Moscow and Warsaw. The Russians and Pollocks didn't get along very well, so to keep the peace on the flight it was ruled that the Russians would sit on the right side of the plane and the Pollocks on the left. One day, leaving Warsaw, there were many Pollocks on the flight but only a few Russians. In fact there was one more Pollock than seats on the left half of the plane, and one Pollock was left standing, holding on to a seat back amid the turbulance. He eyed all those empty seats on the Russian side, and deciding that no one was watching, eased himeself into one of the Russian seats.

The aircraft immediately nosed over, began to spin and crashed to the ground killing all aboard. The Russians began an investigation to determine the cause of the crash. After careful study, they concluded that the aircraft had become unstable as there had been a pole in the right half plane.

Hey, you guys who laughed, mums the word. Lets see what the others make of the incident.

 

[drmiller100]

\

The only thing you change by changing the size of the drive sprocket is your mechanical advantage. The torque remains the same.

funnny stuff. by definition, the mechanical advantage changes teh "torque" the chain sees.

we all cut with chains right? no one cuts with the sprocket or shaft???

 

[ShoerFast]

funnny stuff. by definition, the mechanical advantage changes teh "torque" the chain sees.

we all cut with chains right? no one cuts with the sprocket or shaft???

Changing the DG (depth gauges) from sprocket - sprocket , or sprocket - bar length would cut near the same speed, the nature this thread took as it is the view of many.

Not a math question, but just for a think, what would cut faster, a 7-pin sprocket with .035 DG's or .025 DG's with an 8-pin sprocket?

 

[timberwolf]

Just like changing tire size on a car. Biger tires only work to give higher top end as long as there is enough engine torque to overcome rolling and air resistance. Price is paid on acceleration.

 

[drmiller100]

Changing the DG (depth gauges) from sprocket - sprocket , or sprocket - bar length would cut near the same speed, the nature this thread took as it is the view of many.

Not a math question, but just for a think, what would cut faster, a 7-pin sprocket with .035 DG's or .025 DG's with an 8-pin sprocket?

Well, it depends if you have enough HORSEPOWER to turn the bigger sprocket.

I know for a FACT that on a 28 inch bar, on 36 inch logs, 7900 home opened up, the 8 tooth driver with .030 will outcut a 7 tooth driver with .100 DG.

It doesn't run out of horsepowr in either case, but with no rakers, It beats you up pretty bad after a couple of hours.

 

[ShoerFast]

Well, it depends if you have enough HORSEPOWER to turn the bigger sprocket.

I know for a FACT that on a 28 inch bar, on 36 inch logs, 7900 home opened up, the 8 tooth driver with .030 will outcut a 7 tooth driver with .100 DG.

It doesn't run out of horsepowr in either case, but with no rakers, It beats you up pretty bad after a couple of hours.

You mean if it had enough HORSEPOWER to turn the smaller sprocket?

This is were I think your loosing it,,,,, please allow me to explain.

The saw with a 7-pin sprocket and .035 DG's , would see more wood in a minute then the 8-pin with .025 DG's

If we apply simple math, the 7-pin @ for a say, say 10K would flip 70000 DL's a minute, or 35000 cutters digging .035 a cutter, that's 1225" of wood

The 8-pin sprocket would flip 80000 DL's a minute, or 40000 cutters digging .025 a cutter that's 1000" of wood.

I shoveled a lot of snow today, and would not launch a rocket by my math, but I hope this helps you understand were the properties of pure old fashion TQ come into play?

 

[drmiller100]

I know for a FACT that on a 28 inch bar, on 36 inch logs, 7900 home opened up, the 8 tooth driver with .030 will outcut a 7 tooth driver with .100 DG.

You have different real world experience???? Please share it.

 

[Stihl 041S]

drmiller100;
Real world, as in getting work done.
In Germany when the car would't start, I'd tow the car to the top of the hill with the Superglide, with a shift to second. High horsepower? No. Did the bikes of the time (mid 70's) with much smaller displacment have have higher HP rating? Yup. Both went thru a trans, with the HD having a much wider range. We could get into a lot of talk about other optional data, but it got the job done. All the logic and reasoning in the world wouldn't have gotten that car to the top if the hill, unless you used the HP of the smaller bike to take parts of the car to the top of the hill faster.

 

[Woodie]

Here's a perfect example of torque curve:

Husky 372: Max HP: 5.4 Max RPM: 13,500
Husky 575: Max HP: 5.4 Max RPM: 13,600

For all practical purposes, those engines perform identically, right? Same peak horsepower, thus same cutting speed, right?

Wrong. Here's some real-world testimonial from a dealer/sponsor posted earlier tonight in a different thread:

A little info on the 575XP's, I have been selling these and in our area we have had good results. Most of the loggers and tree services that have bought these all claim they like the powerband better on the 575's versus the 372's. We have had some problems with the mufflers on these saws that the loggers are using but they still come in and buy new 575's. They all rave about the power.

And here's another from a dealer posted a few days ago:

I know this has been visited before a few times, but another customer whose opinion I have a lot of respect for stopped in yesterday, and I asked him how he likes his 575 compared to his 372's. (he has owned it for 7 or 8 months)

His answer: The 575 has way more power and will out cut the 372 day in and day out. Much broader power curve. Lot's of compression, and a little harder to start in cold weather for guys who aren't familiar with it. Wouldn't think of buying another 372. (And I have 4 left in stock)

And this has pretty much been the norm for nearly all of my customers. We did have the one early failure, and I know that Ben Walker has seen a few of them in his area. We have only had that one problem with that one saw. But by and large my customers are very happy with them and aren't looking back. In fact, as we wind down the year here, the 575 has outsold the 372 this year, and I have had both in stock since march when I loaded up on 372's when Husky had that "last chance" opportunity.

Funny thing is that I am the type of guy who doesn't like change, and would normally be one of the guys hanging on to the 372 myself. But my customers have spoken, and they prefer the new 575 hands down.

The fact of the matter is that the 575 appears to have a.....

...wait for it....

...coming right up...

that's right...you guessed it...

BROADER TORQUE CURVE!!!!!

It's engine produces higher torque over a .......

...wait for it...

greater range of engine speed.

Now, anything else is casting pearls before swine, so I'm outta here.

 

[RiverRat2]

So are you saying Peter is full of chid???
and torque in a chainsaw is a desirable thing????????

 

[ol'homey]

wood newbie, I like your previous posts but just want to point out that the RPM at which max HP is measured has nothing to do with the max RPM spec. IOW max HP might occur at 9500 and max torque at 9000 on a powerhead with a max RPM spec. of 13,500. You can call Stihl tech support at 800-GOSTIHL and have them look in the service manual for your powerhead and give you the RPM for max torque and max HP. I asked one of the techs why they don't publish this data in the owner's manual and he said "sir most folks can't even understand what the max. RPM spec is for and now you want us to give them 2 more RPM numbers and confuse them even more?""For folks like you that put a tach on their saw and want to dial in the bar/chain/sprocket combo so that the RPM runs close to the max HP spec. we have that info and are glad to help.""BTW if you look at our recommended bar/chain/sprocket combo for any given powerhead, that selection is the result of our putting a tach on the powerhead and finding the combo that allows the powerhead to run as close as possible to it's max HP RPM under "average" cutting conditions.

So if you own a stock saw and you want it to cut as fast as possible all you have to do is find out at what RPM max HP is at from the factory and then set it up to run as close as possible to that RPM in the type of wood you cut. You want it set up so if you lean on it or hit a knot the RPM stays above the max torque RPM so it doesn't bog. Once you modify a saw the factory max. HP RPM number is no longer valid and you're on your own to find the RPM where max. HP occurs.

 

[Woodie]

wood newbie, I like your previous posts but just want to point out that the RPM at which max HP is measured has nothing to do with the max RPM spec. IOW max HP might occur at 9500 and max torque at 9000 on a powerhead with a max RPM spec. of 13,500.

NOT THAT I'M HERE, mind you... ...but I agree with you completely. I was just trying to point out how silly it was for the original poster to look at peak HP numbers only, and with no knowledge of the engine's torque curve, extrapolate which saw was "fastest." I wish I had the peak torque RPM for those saws, I agree they're far more relevant.

I will now go back to not being here...

 

[ol'homey]

Cool, I agree with you even if you aren't really here anymore!
Looking at 2 saws both having the same advertised HP doesn't tell you much about how fast either of them is going to cut. Most people think a powerhead rated at 5 HP is making 5 HP period. They don't have a clue that there is a power curve and that the powerhead is only making the rated HP at one point on the RPM curve and LESS than rated power everywhere else. So if one saw is set up so that it is running at the peak HP RPM in the cut and the other one is running a few hundred RPM above or below it's peak HP RPM, the first saw will cut faster because it is able to deliver it's rated HP to the wood while the second one is not. Heck, if you've got a really wacked out bar/chain/sprocket combo, really low rakers etc., you might have a powerhead rated at 5 HP actually making only 3.5 HP in the cut because your set up is forcing the saw to operate at an off peak RPM on the power curve where your 5HP powerhead actually makes only 3.5 HP.
Any power not delivered to the wood (due to a dull chain etc.) will be dissipated as heat from the chain and bar.
I bet somebody on this forum is smart enough and has enough time on their hands to:
1. weigh the bar and chain
2. measure the bar/chain temp. with an infrared thermometer before and after a timed cut at several points to come up with an average before and after temp.
3. calculate the HP required to heat the mass of the bar and chain up X deg F in T sec. Somebody here should know the alloy of the chain and bar so you can look up the specific heat of the materials.
This would give you a rough idea of the HP lost as heat. A race chain would show a small temp rise over a small time in the cut. A dull chain would show a large temp rise over a long time in the cut. IOW whatever HP the powerhead makes either goes into making wood chips or into the chain/bar as heat.

 

[Sprig]

Just like changing tire size on a car. Biger tires only work to give higher top end as long as there is enough engine torque to overcome rolling and air resistance. Price is paid on acceleration.

Yupo, and you have to take into account the drivetrain's strength too, no point in tons of torque if the transfer system (ie. gears, driveshaft, clutch) can't take the beating. And speaking of beating, me thinks some of the posters here haven't taken the time to read through the first few pages of this flogged ta death thread imho and miss the point of it. Seems to me, by thread title, there was a question whether torque really has any influence on cutting faster. I have little doubt this has proved to be a huge dilemma for some to understand but the principals are very simple. You can have power +speed+physical strength=torque and cutting speed, but, it all rolls down to the weakest link, the point at which failure occurs. In this case it really seems to be the inability for some of us to look at the big over-all picture, higher the torque the tougher the machine has to be (in most/all aspects) to actually apply that power to get work done. Someone started a post here dangling Mandarin oranges and it keeps getting turned into mashed bananas. Fer Dogs sake please read the references here (including my unbiased much earlier post) on what torque really is! Everyone (well some anyhow) is thrashing about trying to redefine a known physical entity with comparisons of machines and ignoring the understandable principles.
A short hairy guy with a wee thing and a good back may be applying the same 'torque' to the ex as I do one handed exercising imagining her best friend groping my testicles, but the difference is rpm's and the fact I can come to grips with this with more psi See what I mean, apples and limes, but the same stuff applies.............

GAH!!! Just shoot me now! Oh oh, not yet, I have another fantasy coming up................:help:
or is sucking a bit more each day :monkey:

And a GREAT new year All!!

 

[drmiller100]

So if you own a stock saw and you want it to cut as fast as possible all you have to do is find out at what RPM max HP is at from the factory and then set it up to run as close as possible to that RPM in the type of wood you cut. You want it set up so if you lean on it or hit a knot the RPM stays above the max torque RPM so it doesn't bog. Once you modify a saw the factory max. HP RPM number is no longer valid and you're on your own to find the RPM where max. HP occurs.

I'll go with all that. The goal is a WIDE horsepower range for real world conditions. Most people call this "wide torque range", but technically according to the physics definition this isn't really the case.

 

[drmiller100]

IOW whatever HP the powerhead makes either goes into making wood chips or into the chain/bar as heat.

I think you missed a few things. The air gets heated up because the chain is fanning the air. Not a big deal for saws I'll agree.
And the chain heats the wood chips. As an example, a dull chain will beat on the wood more then a sharp one.

 

[Woodie]

I think you missed a few things. The air gets heated up because the chain is fanning the air. Not a big deal for saws I'll agree.
And the chain heats the wood chips. As an example, a dull chain will beat on the wood more then a sharp one.

And I believe YOU missed something...what about the bar oil getting slung off? That's heated too, isn't it? Yikes-a-hootie.

I believe it was ShoerFast who said, "Splitting frog-hairs is down the hall, to your left."