Do shorter bars cut faster?

[pinemartin]

Here is a jonsered 920 with a 20" and 36" bar in the same wood being used by the same guy. Who ever has a stopwatch can (not me) can tell the time difference if any.

 

[bitzer]

Teach me not to pay attention. I assumed it was the same saw, different bars, on the same log...

It looks like the same saw, just different bars and different wood.

 

[timberwolf]

A wise man uses no more bar than needed to get the job done. Some still feel the need to try to impress the girls though...

Every inch of extra bar and chain is more weight the engine must accelerate and more friction it must overcome. Not to think of the poor sap at the handle that must lug it about the woods.

The smaller stock saws will notice bigger losses with extra bar than bigger higher output saws. I calculated out losses on chain once and depending on the chain, gearing and RPM it was easy to loose between 0.5 and 1hp or a little more on a work saw just spinning the chain. to a 40-50 cc saw thats a big percentage of the output, but not so much for a ported 100cc saw.

 

[scotclayshooter]

The second log is much larger.

Nah its just the camera angle:greenchainsaw:

 

[bitzer]

A wise man uses no more bar than needed to get the job done. Some still feel the need to try to impress the girls though...

Every inch of extra bar and chain is more weight the engine must accelerate and more friction it must overcome. Not to think of the poor sap at the handle that must lug it about the woods.

The smaller stock saws will notice bigger losses with extra bar than bigger higher output saws. I calculated out losses on chain once and depending on the chain, gearing and RPM it was easy to loose between 0.5 and 1hp or a little more on a work saw just spinning the chain. to a 40-50 cc saw thats a big percentage of the output, but not so much for a ported 100cc saw.

I usually try to impress the trees!

I knew you had to stop in and set us straight with numbers. Ruining all of the speculation again. Ha! Ha!

 

[timberwolf]

Here is a jonsered 920 with a 20" and 36" bar in the same wood being used by the same guy. Who ever has a stopwatch can (not me) can tell the time difference if any.

Nope, different cutting style, and who knows what chain difference was either.

 

[Paul001]

Ok, this isn't "in the cut" but I'm to damn old and lazy to go further.

I just finished up 10 200T's for a customer. Grabbed the first one and recorded tach speeds with new bars/chains.

Set with 16" 14,040 RPM
with 14" 14,160 RPM
with 12" 14,600 RPM
with 12" 14,600 RPM (12" .43ga) Firgured why not give it a try.
with no B/C 15,120 RPM

So yes at full throttle, no load, the bar/chain combo is providing a load, how much this will effect cutting speed I couldn't answer without looking at torque curves. Even then it would depend on the size of wood you are cutting.

In the extreme's 16" vs 36" of course it'll make a difference. To those min/max'ers it'll make a difference. To those timing their cuts within .001, it'll make a difference. To those in the woods, not so much. I think the weight factor of carrying the extra poundage over an 8 hour day would be a bigger factor there.

 

[scotclayshooter]

A wise man uses no more bar than needed to get the job done. Some still feel the need to try to impress the girls though...

Every inch of extra bar and chain is more weight the engine must accelerate and more friction it must overcome. Not to think of the poor sap at the handle that must lug it about the woods.

The smaller stock saws will notice bigger losses with extra bar than bigger higher output saws. I calculated out losses on chain once and depending on the chain, gearing and RPM it was easy to loose between 0.5 and 1hp or a little more on a work saw just spinning the chain. to a 40-50 cc saw thats a big percentage of the output, but not so much for a ported 100cc saw.

You did a thread about the amount of tons of chain the saw threw around in a given time, Thats what sold me on shorter bars.

 

[2dogs]

A wise man uses no more bar than needed to get the job done. Some still feel the need to try to impress the girls though...

Every inch of extra bar and chain is more weight the engine must accelerate and more friction it must overcome. Not to think of the poor sap at the handle that must lug it about the woods.

The smaller stock saws will notice bigger losses with extra bar than bigger higher output saws. I calculated out losses on chain once and depending on the chain, gearing and RPM it was easy to loose between 0.5 and 1hp or a little more on a work saw just spinning the chain. to a 40-50 cc saw thats a big percentage of the output, but not so much for a ported 100cc saw.

I run a 36" bar on an MS660. I don't always cut 3' diameter wood but I can stand back from wood under tension. How does this apply? I have other saws BTW.

 

[Analyst Man]

You did a thread about the amount of tons of chain the saw threw around in a given time, Thats what sold me on shorter bars.

Weight!!! Weight = inertia = energy. Ok, I’ll buy that thought. But again it can’t make a noticeable difference just adding or subtracting 2 inches.

 

[Analyst Man]

Here is a jonsered 920 with a 20" and 36" bar in the same wood being used by the same guy. Who ever has a stopwatch can (not me) can tell the time difference if any.

Too much virus protection at work, I’ll have to check the videos when I get home.

 

[rms61moparman]

I think that video answers the question rather pointedly

That video proves that race chain is faster than work chain!!!

There will be a difference in the time if you cut a 14" log with a 16" bar and a 20" bar.
But all else being equal, you will have to have a stopwatch to see it.


Mike

 

[SawTroll]

Short answer.....YES! Less surface area=less drag, resistance, friction = less power needed to maintain chain speed, which allows more down pressure to be applied= more cut speed. And less chain weight helps as well.

:agree2:

You will not notice it probably too much if your power head has power to spare during the work, but when its nominal power is consumed by the sawing department, the additional friction will slow it down, no doubt about it.
You don't see many hard tip bars on smaller saws, there's a reason probably.

:agree2:

A wise man uses no more bar than needed to get the job done. Some still feel the need to try to impress the girls though...

Every inch of extra bar and chain is more weight the engine must accelerate and more friction it must overcome. Not to think of the poor sap at the handle that must lug it about the woods.

The smaller stock saws will notice bigger losses with extra bar than bigger higher output saws. I calculated out losses on chain once and depending on the chain, gearing and RPM it was easy to loose between 0.5 and 1hp or a little more on a work saw just spinning the chain. to a 40-50 cc saw thats a big percentage of the output, but not so much for a ported 100cc saw.

:agree2:

 

[timberwolf]

But again it can’t make a noticeable difference just adding or subtracting 2 inches.

In a single cut it likely won't, but at the end of the day it will. If you are in doubt take a new 16 inch 3/8 chisel chain on 16 inch bar with stock 50 cc saw and run it, then switch to a 20 inch bar and new chain of same brand and the difference will be noticed easily. A good part of it just in spool up and chain speed, as pointed out above it can be seen on a tach.

If the bar you run clears the tip it will be more efficient and have more availible power to put into the wood than a longer bar will.

Some tall guy slike long bars for reach so they don't need to bend over as much, thats a different story again

 

[Analyst Man]

Ok, this isn't "in the cut" but I'm to damn old and lazy to go further.

I just finished up 10 200T's for a customer. Grabbed the first one and recorded tach speeds with new bars/chains.

Set with 16" 14,040 RPM
with 14" 14,160 RPM
with 12" 14,600 RPM
with 12" 14,600 RPM (12" .43ga) Firgured why not give it a try.
with no B/C 15,120 RPM

So yes at full throttle, no load, the bar/chain combo is providing a load, how much this will effect cutting speed I couldn't answer without looking at torque curves. Even then it would depend on the size of wood you are cutting.

In the extreme's 16" vs 36" of course it'll make a difference. To those min/max'ers it'll make a difference. To those timing their cuts within .001, it'll make a difference. To those in the woods, not so much. I think the weight factor of carrying the extra poundage over an 8 hour day would be a bigger factor there.

Looks like your comparison data proves my point. Only 120 rpm difference at 14,000 rpm between a 12 in bar and a 14 inch bar. And I agree with your thought “In the extreme's 16" vs 36" of course it'll make a difference.”

 

[bitzer]

In a single cut it likely won't, but at the end of the day it will. If you are in doubt take a new 16 inch 3/8 chisel chain on 16 inch bar with stock 50 cc saw and run it, then switch to a 20 inch bar and new chain of same brand and the difference will be noticed easily. A good part of it just in spool up and chain speed, as pointed out above it can be seen on a tach.

If the bar you run clears the tip it will be more efficient and have more availible power to put into the wood than a longer bar will.

Some tall guy slike long bars for reach so they don't need to bend over as much, thats a different story again

"A wise man uses no more bar than needed to get the job done.," goes both ways. Too short a bar is foolish and making 6 fast cuts can take longer than 3 slower ones on a tree.

Safety is also an issue. It all depends on situation. Its also tougher to pack a 16" barred saw on your shoulder than it is a 25+" barred saw. Obviously the +" is within reason.


Basic physics of friction, circular motion, distance, and acceleration point to the fact that a short bar will run faster off load and the longer the distance the longer the time and the greater loss of power, but real world situations may toss that all to the wind when it comes to safety and expediancy.

Again it all depends on situation, that is why there are different sized bars, saws, etc...

 

[cjnspecial]

With longer bars you have more cutters in the wood at the same time, this is the main drag in the saws hp. The fewer the # of cutter in the wood at the same time= higher possible chain speed.

Ever try a 440 with a 20 inch bar and 8 pin sprocket?

 

[rarefish383]

Analyst Man, I didn't notice if you had a particular saw in question or just saws in general. If your talking about swapping an 18" for a 16" on a Wild Thing, I don't think you will see or feel any difference. On my old Homelite 1050 with the 24" bar, I can carry it around by the handle and it is balanced, it's comfortable to use, and is so loud that it impresses the girls and scares the trees. The same saw with the 36" bar, and it is very nose heavy. Just to walk around with it you have to use both hands and the weight pulls on your back noticabley. It's still so loud that it impresses the girls and scares the trees, but it beats my poor 53 year old body to a pulp. It might cut just as fast but it feels like every cut is never ending. When I had to make a living with that saw, I actually have 2 of them, I had a long bar on one, short bar on the other. I would use the long bar only as needed and grab the shorty. I feel that every extra ounce of weight I have to control is worth 10 seconds in a cut. Thoughts of an old fat guy, Joe.

 

[J.Walker]

But what about the added drag of the sprocket tip of a bar?

Are roller tip bars faster?




.

 

[Analyst Man]

With longer bars you have more cutters in the wood at the same time, this is the main drag in the saws hp. The fewer the # of cutter in the wood at the same time= higher possible chain speed.

Not sure I understand that? With a 6 inch diameter log you could theoretically run a 200 (that’s two hundred not twenty) inch bar and a 14 inch bar and they would both have exactly the same amount of teeth in the wood at any given moment.