The torque's non existing influence on cutting speed.

[spike60]

Peter;

If I still had my Dodge Coronet 500 with the 440 Magnum and 4 Speed, I would extend an invitation for you to come over and drive it, whence you would understand torque to a depth far greater than your calculater can demonstrate. One of the torqueiest motors ever was the 455 Olds with it's 4.25" stroke. (not trying to start another argument here)

A formula 1 engine pulling heavy loads in a truck? That's an absurd suggestion. Without the twisting force of the torque, you couldn't get moving.

How this relates to saws rather than cars and trucks is of course a bit different, as some of us may confuse chain speed and power and therefore, how it relates to torque. I think that most of us would think that torque plays a role in a saws ability to continue cutting when you really lean on it, as opposed to a saw whose chain stops when you try to push it hard.

 

[peter399]

Now you are comparing apples and oranges....stick with chainsaws!

Harley doesnt make an 1100 cc right now 1000 and 1200 is the closest. And the Harley is an air cooled, 45 degree engine, made for.........wait for it.......................TORQUE!!!!!!

250cc Japanese engines are USUALLY 90 degree, liquid cooled, made for PEAK HP.

Harley will usually grab most of these bikes off the line for a VERY short distance because of their TQ.

Dont forget TQ gets you off the line HP carries you the rest of the way. If TQ isnt as important in saws than why do most of the saw builders build it into their engines? So that we can push down harder, which in turn makes the saw cut faster, and we dont have to worry about losing the max power as soon and thus bogging the saw down or even stalling it in the cut.

*I am no expert I just believe this guy doesnt have the whole story.....and you opened a huge can of worms!!* opcorn: opcorn: opcorn:

OK, I'll stick to chainsaws, although I'm very tempted to discuss the Harleys

2 reasons:

1. Marketing. There is a TQ hype right now. Earlier it was cool to own a 400hp car, today you should have TQ. Although it still is IMO cooler to have 400 hp and leave the TQ guy behind with a big smile on the face. How many aren't attracted to buy a saw if X-Torq is written on it? (personally if prefer for instance 346 and 372 over 353 and 575 "TQ saws".)

2. More user friendly as already discussed. Chainsaw is now a plastic thing that you put on and off, tool less chain tensioning, easy2start, softpulll bla bla bla. It's consumer now. Logging is done by harvsters or at least, there is no longer big money to make on the PROs still doing manual logging.

"So that we can push down harder, which in turn makes the saw cut faster, and we dont have to worry about loosing the max power ...."
Exactly. The thing is, one must be experienced enough to push just enough, to hear if the engine drops rpm and then loosen a little bit. One can wonder how hard that can be..... For the pro and his 346 it's done by feel and is not really an issue, for the consumers cutting firewood it might be.

 

[AJLOGGER]

Anytime you see torque on a Husky it is marketing. I'm sorry I had to do it, I just couldn't help myself.

 

[Ekka]

A longer stroke will give more torque.

Those F1 engines have short strokes so they rev out more, more hp coz hp is calculated from


HP=TORQUE * RPM / 5252

http://auto.howstuffworks.com/horsepower.htm

http://auto.howstuffworks.com/question622.htm

http://en.wikipedia.org/wiki/Horsepower#Mechanical_horsepower

So I agree that HP is king coz it is calculated from torque.

A low torque high RPM engine such as the F1 simply need gearing to multiply it's torque ... similar to switching to low range in a 4WD. Those low revving high torque truck engines still have big HP numbers in the real world.

Thanks, been interesting reading the google searches.

 

[PES+]

Horsepower if a function of torque

I drive a great example of a high torque low HP short stroke diesel

A Mereceds 240D 616 engine about 65 BHP rated moving an over two ton car and acceleration from a stop and passing are quite lazy but once up to speed it has no trouble climbing all but the steepest grades. The cruise control is rock solid as the high torque and low HP makes engine speed control a very precise thing.

 

[Woodie]

I just have to make a comment on this "torque issue" that I see in many many threads. Torque is a thing invented by car magazines that has totally overtaken peoples minds: Statements like: My car (or chainsaw like we discuss here ) performs so great because it has tons of torque... is totally BS IMO.

A Formula 1 engine with 601 HP and 400Nm of torque will hence pull a fully loaded truck up the hill quicker than would the truck engine with 600HP with 2500Nm torque. The reason trucks use 16liters diesel engines is because they will last a bit longer than the F1 engine..

- Peter

This rationale fails on so many levels. I'll just cover one, though.

You have completely ignored the RANGE of RPM that an engine must operate at. Do you honestly believe that an F1 engine could get a 75-ton truck MOVING? I suppose, perhaps it could...if the reduction gear on the transmission was the size of the truck itself, although it might need to be bigger. Oops, we just added another two tons to the truck weight due to that reduction gear...

If the F1 truck engine operated solely and only at the RPM level at which it produced its max HP, it would be possible. But it can't. So you have to have an engine with the proper torque curve. An engine which produces good power across its operating range. That way it has the ability to get a load MOVING in the first place, then keep it moving. An F1 car gets the luxury of operating on a track, where it can keep its revs sky high. It also gets the luxury of an engine rebuild after each and every race.

There's a reason you don't see F1 engines in drag races, and you don't see drag motors in F1 cars. And that reason is TORQUE CURVE!

 

[Jim Mesthene]

Horsepower is a calculation, an invented number derived by mutiplying torque by time. Lb/ft X minutes, or nm X minutes.
You can't have one without the other because horsepower is torque measured over time.

Long strokes have greater leverage on the crankshaft, Wide bores have more square inches exposed to the high psi generated by combustion. It's six of one, half dozen of the other. The only advantage of wide bore/short stroke engines is lower piston speed that allows higher rpm, because piston speed is limited (by materials) to about 4000 feet per minute.

The engineer decides what rpm he wants his engine to run at, and arranges for its torque peak to be at that rpm. That's 400 rpm for a two stroke ship's diesel or 13,000 rpm for a chain saw.

 

[begleytree]

Did somebody mention Formula 1???

As far as I know, sice the downgrade from v-10s and v-12s, the F1 v-8s are running @750 BHP at 19,500rpms, down form @950 BHP

imo, the assumption that the short stroke would be more powerful is wrong. visualize the crankshaft of a long stroke engine, and visualize the piston having more leverage to turn the crankshaft bacause the journals are set farther out from the centerline of the crankshaft. Its a function of a simple machine, the lever, the longer the lever, the more force applied to the load.
I'll back out now.
-Ralph

 

[PES+]

I need to look into the 575

I was yakking with a local logger who I do listen to and believe as he is a very reasoning type. He has both the 372s and the 575s and says that the torque on the 575s is far superior for felling though we both agree that the 575 weight wise feels rather piggish. I intend to go where he is cutting soon and see the difference for myself. I asked him about fuel consumption but he addmitted that he hadn't really checked and will try similar cutting on the landing to give me some idea. He seemed to think that the 575 was quite efficient

 

[Monkeyhanger]

Anyway, my point is that the torque itself doesn't have anything to do with performace or max cutting capacity.

Hi,

the way I see things is that torque has everything to do with performance and cutting ability - no torque, no work. Torque is the actual force that gets things done, power is a bit of a synthetic value calculated from torque.

bye

 

[PES+]

Greatly simplified but yes

Did somebody mention Formula 1???

As far as I know, sice the downgrade from v-10s and v-12s, the F1 v-8s are running @750 BHP at 19,500rpms, down form @950 BHP

imo, the assumption that the short stroke would be more powerful is wrong. visualize the crankshaft of a long stroke engine, and visualize the piston having more leverage to turn the crankshaft bacause the journals are set farther out from the centerline of the crankshaft. Its a function of a simple machine, the lever, the longer the lever, the more force applied to the load.
I'll back out now.
-Ralph

That is precisely why in general longer strokes make more torque but at the expense of top RPM. HP is based on time so more RPMs makes it easier to get higher HP numbers but torque falls

 

[Jim Mesthene]

Again:
Long strokes have greater leverage on the crankshaft, Wide bores have more square inches exposed to the high psi generated by combustion. It's six of one, half dozen of the other.

 

[timberwolf]

Now were bringing the torque of a diesel into a debate of saw torque.

If you have driven a diesel you know that toque is what it is about, forget RPM, torque goes to next to nothing as you push toward redline.

Building any work saw I would say the best stratigie is to focus on torque, for most people using stock chain, this will be the best runing setup.

Now if you start towards racing it is a differnt story. Question: two saws, one stock, one ported for high RPM and HP, put a stock chain on both saws the ported saw only shows 10-15% gain, put a race chain on both saws and the ported saw shows much higher gains.

It is complicated to explain, but I think it is importaint to look at availible power, ie power to the wheels, in this case power to the wood. What maters is how much power is left over to cut wood, once friction and chain acceleration losses are taken off the torque numbers.

Here is an example say fictitional lightly modified 100 cc saw, where from engine alone it shows a strong HP in the 13-14k RPM range. But when chain and drive losses are taken in the max output is found between 9-12k.

 

[PES+]

Personally

Personally I have never been one for stroker two strokes as the only way I can see them working efficiently is with rotary valve induction. I still laugh like heck when I read about a mountain sled builder taking a full square (or close) engine and making a new jug to make it failry high oversquare and then everyone marvels at how powerful it is. Over square is me......but I was a mac guy in a past life. (sigh)

 

[Woodie]

This is gonna get ugly, mark my words. I don't agree with you , but will wait 24hours before responding.....

Can I safely say this is like buying a gun...you need a 24-hr cooling off period??

Peter, I don't know how popular basketball is in your country, but to use a basketball analogy, Freak is about to go baseline on you, and you should avoid trying to draw the charge at all costs...

 

[timberwolf]

So then if we do some more engine mods to try to get mor HP and end up with this, just buy looking at the engine HP numbers, it looks like we have made good gains on the high RPM output. But once we look at the net we see realy nothing has been gained in reality, the saw will still cut roughly in the 12k range at roughly the same torque. Though a small gain will be had when the saw hits the wood in changeovers as it will have more torque at the higher RPM, at least until it comes down to the in the cut RPM.

All this to say that torque is just as critical as HP, they are interdependent and must be considdered as net in the wood. RPM can produce impressive HP numbers, but they mean nothing unless the system will opperate at that RPM.

 

[12guns]

This is why I love this site! The knowledge never ends. When talking about diesil trucks and tractors w/ ridiculous amounts of torque, it's all about gearing right? Like a 45 HP tractor that can pull a house down, but can't go over 30 mph. Or a 8 HP go cart that will run 20 mph. But the go cart doesn't have any torque to speak of...oh my...So it is about horse power!!

 

[PES+]

Just a thought

If your 8 HP kart only does 20 take your foot off the brake

 

[SRT-Tech]

I like the new Shimano saltwater reels that claim to have BOTH more torque (for more winching power) AND a higher gear ratio (for more inches of line retrieved per revolution of the heel handle) all in ONE!

That's a pretty good trick!

thats because they have a lever that switches from a high gear to a low gear.

normal mode = faster retrieve, low torque

low gear mode = slower retrieve, more torque


example: when in high speed mode on the reel, you can retrieve the line very quickly, but as soon as you have a big fish on, it bogs down and you have to fight hard to turn the reel. Switch it to low speed mode (lower gearing) and you can retrieve that big fish with little effort, but it takes forever (more cranks of the handle)

 

[ShoerFast]

thats because they have a lever that switches from a high gear to a low gear.

normal mode = faster retrieve, low torque

low gear mode = slower retrieve, more torque


example: when in high speed mode on the reel, you can retrieve the line very quickly, but as soon as you have a big fish on, it bogs down and you have to fight hard to turn the reel. Switch it to low speed mode (lower gearing) and you can retrieve that big fish with little effort, but it takes forever (more cranks of the handle)

The fish real makes a good example:

What would have more fish, a truck filled with a pan-fish caught with the real stuck in high-gear?

Or a truck full on lunkers, taken with the real stuck in low-gear?

Work is work, a conveyor running at 25mph with a bricks placed 1 foot apart, would pass bricks at the same rate as a conveyor running at 50mph with a brick every other foot, or 2 feet apart.