Cc or hp

[Eddy_t]

How do you see a power curve eddy?

 

 

Usually dyno testing, kwf does some on their website, but they only show current models, and in the case of previous saws, only fitted with standard mufflers, not jungle or magnum mufflers.

[Eddy_t]

The point is this. There could be two different saws with exactly the same cc and hp. But the one with the greater torque delivery will be the best.

 

The max torque will come in beneath max revs, but it is at the point where the revs are held onto best.

 

Torque is what gets work done.

 

High speed equals low torque, and vice versa. Peak torque is where the max power is generated.

 

 

Peak torque and max power are usually at opposite ends of the scale, max torque is usually around 5-7k rpm, whereas max power is usually 8-12k rpm. A longer stroke and lower exhaust (longer blow-down) usually produces higher torque, at the expense of rpm. This is why the old behemoth saws would have much lower depth gauges (0.35 and lower, instead of 0.2-0.25 of modern equivalent). They relied on brute force to rip the tree down rather than the speed to chase it down.

 

The 070 (106cc) has marginally less (0.1lbf) torque than an Ms880 (121cc), but the 880 has marginally more power (0.1kW) than an 090 (137cc).

 

So that shows nothing, as the 090 is faster through the largest timber, despite running much slower (4k rpm less).

 

The op needs to try out saws to find out the saw best suited to his technique. The correct saw in the right hands will beat a larger, faster saw in the wrong hands.

[wyk]

How do you see a power curve eddy?

 

[GardenKit]

If the chain is blunt, torque struggles, there is many variables in this argument. Infact, too any to Come up with a sensible answer.

Torque is only developed in response to load. A blunt chain imposes no load as it merely spins. Just like a Landy with bald tyres.

It just spins, developing high speed but no torque.

[Stubby]

The point is this. There could be two different saws with exactly the same cc and hp. But the one with the greater torque delivery will be the best.

The max torque will come in beneath max revs, but it is at the point where the revs are held onto best.

Torque is what gets work done.

High speed equals low torque, and vice versa. Peak torque is where the max power is generated.

 

Easy example of the above ...200HP tractor pulls multi sheer plough through soil at a constant speed of 10mph. ( torque ) 200HP sports car drives in a strait line at 186mph ( horse power ) Same power different torque out put for different jobs .

[mowandgo]

I found low reving engines like 4 strokes work best on lawnmowers and rotorvators where speed is steady and torque is in demand. Strimming, Hedge Cutting and Timber Cutting is all about speed & high revs which is where 2 strokes win. I might be wrong but I thought 2 strokes have higher torque than a 4 stroke the difference being 4 stroke torque peaks at low revs and a 2 stroke peaks at high and has little to give low to mid range revs.

[peatff]

so its a heavy bugger with x amount of power, then another model lighter with the same power or more would have a better power to weight ratio

 

What difference does power to weight ratio make in a saw ? I can understand it in a car or bike as it is propelling the vehicle so it is an advantage but in a saw it is only driving the chain through the wood so the weight of the saw is only a factor due to the operator having to lift it.

[wrsni]

As the Americans like to put it, "there's no replacement for displacement".

 

Too much emphasis on horsepower considering that it's a totally theoretical value, it can't even be measured in real terms, it's only ever either calculated or estimated.

 

But of-course it suits manufacturers of everything mechanical really well as it allows them to make all sorts of claims that can never be properly disproven.

[Stubby]

What difference does power to weight ratio make in a saw ? I can understand it in a car or bike as it is propelling the vehicle so it is an advantage but in a saw it is only driving the chain through the wood so the weight of the saw is only a factor due to the operator having to lift it.

 

So if you were on piece work felling in a wood all day and you had 4.5hp saw weighing 5kg and a 4.5hp saw weighing 10kg you would not care which one you use ?

[peatff]

So if you were on piece work felling in a wood all day and you had 4.5hp saw weighing 5kg and a 4.5hp saw weighing 10kg you would not care which one you use ?

 

There's no mention of what the saw is doing in the original question. It could be fastened to a sawbench cutting firewood for all I know. If I was a 20 stone giant with hands like shovels I might prefer a larger saw. If we are going to move the goalposts the question is pointless. All I asked was how does the weight affect the power ? Obviously the lighter saw is the better option for anyone using it as you say.