Stihl saws

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HUSKYMAN

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Just curious, but why doesnt Stihl advertise the rpm ranges of their saws. I have never used one but judging from other people it sounds like they do not turn as high as Husqvarna and the Japanese sawmakers. What kind of rpms do they run and do they make more torque in the cut? I know a lot about two strokes and I know they like rpms. Thanks
 
Im not a expert on rpms, but Stih uses bph, I have sold them for yrs. still dont know what that is. I guess that what read & read & just eat the books means.
 
As I recall, BHP stands for British Horsepower, which equals 550 foot-lbs per second, or 745.7 watts. Really, it is a measurement of "work."

In my experience, horsepower is less a component of the ability of a saw to make a cut as displacement, which roughly translates into torque, and the rpms, which directly translate into how many cutters are going to contact the wood directly below the kerf.

As for why Stihl does not publish their rpms, that remains a mystery to me.
 
BPH stands for Base Horsepower
Stihl dealers can tell you what the rpm for a particular saw is if you ask
They range anywhere from about 11.000 to 14,500 rpm depending on model
Horsepower is a more reliable way to rate a saw than is c.c's or cubic inches. Stihl makes some saws that are smaller cubes and put out more horsepower. This is especially true if you look at their string trimmers.
Stihl #1
 
You have two horsepower figures for any given engine.

ihp(indicated horsepower):this is the theoretical horsepower of an engine. It can be calculated using advanced math calculations and is the hp an engine could produce if there were no frictional losses inside the engine.

bhp(brake horsepower):this is the actual usable hp. It comes from the first dyno's where a band brake would be used to put a load on an engine to figure out the actual usable hp. Here is the formula to calculate bhp.

BHP=(torque x rpm)/5250
 
In reality the manufacturer should post both RPM and HP(both at the crank and applied) However what seems to be missing which in all actuality isnt hard to figure out is HP/inch and or torque/inch. Because really the power is translated through the chain to the wood there. So thinking about your power per inch of chain bar has more to do with how strong a saw is verses RPM or HP alone.

No expert but computer/mechanical engineering major though.
 
Yes, Deere John, 12 in/lb equals 1 ft/lb of torque. Rubicon's answer about BHP is right on. BHP or usable horse power is the main number to use to compare a saw's power.

But because chain saws don't have variable ratio transmissions like trucks, horsepower isn't the only factor affecting cutting speed. This makes Huskyman's point about RPM listing is very important.

Husqvarna model 55 and 346XP are both rated at 3.4 HP. Many chain saws are designed to make maximum horse power at 9000 RPM. So, while cutting a large log at near 9000 RPM, the 55 and 346XP will cut at the same speed.

The rated maximum RPM for the 55 is 12,500 RPM. However, the rated maximum RPM for the 346XP is 14,700 RPM. This means that on a small log that requires less than maximum torque, the 346XP will have a higher chain speed and thus cut faster than the 55 even though they have the same HP.

For this reason, it doesn't make sense to put a long bar on a high speed saw: - either you are trying to cut smaller wood faster, or you are making a compromise, trying to do two things at once.

Different chains sizes, (91, .325, 3/8) require different amounts of torque to cut at the same speed and also effect how fast a saw can cut at its rated RPM.
 
So I take you would be better off with .325 on the 346 because it can turn it faster and it will probably outcut 3/8 ON THAT SAW. You hit the nail on the head, that is why I was curious about Stihl rpms because that is very important to me in the decision making process both with which saw to buy and when selecting the right bar/chain combo for a particular saw. I have .325 on my 55 with a 20" bar. I dont think i would want to switch to 3/8 because, even though the saw can handle it, I think it would lower my rpms and actually cut slower then the .325. As long as it is sharp she flies right now.
 
Huskyman, you are right on it! Most users don't need more than a 20 inch bar. Not only does a longer bar take more power to turn, greater weight in front of the saw makes the operator tire more quickly.

If a user really needs a longer bar, he probably also needs at least a Husquvarna 372XP or Stihl 044 or LARGER saw to make large cuts in a reasonable amount of time.

Most really long chains are skip sequence so that they don't overly slow the saw's RPM in the cut. Oregon's 200 page "Application Guide" is the bible of chain and bar selection. You can get it for free by calling 800 547-7800 or emailing [email protected]
 
Hi Huskyman,
I know you from the other forum but don't remember your username there, Oh well that goes with age (they say). You have a good point about Stihl not making this info more available to the public, Although they do provide this in the service literature it should be more made more readilly available.

John Deere.
Yes 12in/lbs =1 ft/lb of torque, example 120 in/lbs= 10 ft/lbs and this is handy also when applying torque to fastners as you can switch torque wrench's for varying reasons.

Rubicon,
You are right on with the Brake Horse Power thing good post.

Chaingang,
Good point about the bar length, the only thing better than a 16" bar is a 14" bar. But try to convince people of that is like pulling teeth.

Confused,
I have a double Engineering Degree From the University of Alabama and Dam if you haven't Confused me also, ha ha just ribbing you a little don't worked up.
 
Huskyman,
Here's some rpm info, taken right out of the shop manuals, for some Stihls I own.

Stihl 044, 70.7cc, max RPM 14000 (w/ bar & chain), 5.2bhp @ 9500rpm, 3.2lb.ft torque @ 6500rpm.

Stihl 028 Super, 51.5cc, max RPM 13000 (w/ bar & chain), 3.4bhp @ 9000rpm, 2.14lb.ft @ 6500rpm.

The 044 has a 20" bar (3/8 pitch). It cuts very well. I mean, VERY WELL. The 028 Super used to have a 16" bar (.325 pitch). That cut fairly well. I've recently switched it to a 16" (3/8 pitch). It cuts faster & seems to stay sharp longer, but vibrates a bit more.

Hope this info helps,

Larry
 
Yeah, Husky does rev their saws higher for publicity reasons,
which is why you see more burnt up Huskies and Jonsereds, than
Stihls on any given Saw Shop's floor. But I may be digressing!
 
huskyman,ive pretty much come to the same conclusion.
question, why are some small saws
coming with 3/8.
question,at what point is the breakover point ,when 3/8 is better.
i own an 036 thats 3/8. cant imagine a saw cutting better.
i own 2 saws, partner 500 and this 295poulan pro,
that are greased lightening w sharp chain . these run 325.
would the 036 not cut stronger with
325 for the same reason a 346 xp does.
not making statements here . just looking for input.
on a race car the higher gear gets more speed ,but a chainsaw aint a race car ,
and the drag on the engine would not decrease as u get into full throttle cut,in the same way 180mph would change[reduce] the force required to keep the car at that speed
 
Mr Lambert, Is that Alice Cooper with the chain saw? Yes it would be nice to have a tach on the saw. Maybe it would help in diagnosing problems?
 
Max torque

Here's a related question about RPM and torque when milling.

On my Solo 90cc saw with 24" 3/8" bar purchased to mill wood the max running RPM is something like 12,000 rpm and the max torque created at around 9,000 rpm.

Since milling is like cruising on the highway (long long cuts), I would think that I would want lower rpm to maximize engine life. True?

But wouldn't I want max rpm so the cutting goes faster?

Seems like it could go either way....

Another question I have is this: Under what cutting conditions would max torque be more useful than max rpm?

My milling will be done in green red pine using a Lumber Maker with a guide board.
 
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