Recorded Some Cuts

[svk]

Just messing around while cutting wood yesterday. Propped my phone up with my gloves and ran all three saws.

This isn't posted to give one saw bragging rights but simply to see how these cut in the real world as I have them set up. In full disclosure I haven't even timed these yet. I warmed up the saws right before I started to video to make sure they weren't going off a cold start.

First saw 550xp with 16" bar and freshly sharpened (by grinder) Oregon LGX.

Second saw 562xp with 20" bar and new loop of Rotary brand chisel chain.

Third saw 2186 with 20" bar and a lightly used loop of Rotary brand chisel chain.

This is the first time I've recorded saws in action. I guess I should have moved the camera back a bit so you can actually see the saw.

The quarry was frozen aspen. It was water stained on the side opposite of the saw but was still pretty solid.

I have some real nice square ground chain that I'll run next time and swap it across all three saws for a true apples to apples comparison.

 

[blsnelling]

As great as they all run, you could definitely see the progression of power. Nice technique.

 

[svk]

So just running the stopwatch on my phone I'm seeing a best of 6.46 for the 550, 6.08 on the 562, and 4.65 on the 2186.

Of course the two larger saws are slinging 20 percent more chain so I'd expect times to improve commensurately if this was a true scientific test.

 

[wde_1978]

Nice clip @svk !

I'd skip the "small" saws and use just the 2186!

I downed another dead spruce yesterday, the last one standing in front of my house, maybe 6" at the base and some 8 meters tall.
I used my little Sachs-Dolmar 108 (40cc, 14" bar) to get it down because of the control while placing the felling cut, but I used my Dolmar PS-7900 for limbing and bucking just for the fun of it.

Call me nuts, I don't care.

 

[295 tramp]

+1 on the 2186.
All saws will make a fun and productive day cutting.
Is that standvic bar a John 12 12?

 

[svk]

+1 on the 2186.
All saws will make a fun and productive day cutting.
Is that standvic bar a John 12 12?

That Sandvik bar came from @A10egress. Nice guy to deal with!

 

[lone wolf]

So just running the stopwatch on my phone I'm seeing a best of 6.46 for the 550, 6.08 on the 562, and 4.65 on the 2186.

Of course the two larger saws are slinging 20 percent more chain so I'd expect times to improve commensurately if this was a true scientific test.

A lot depends on what diameter and hardness the logs also. A small saw rips through small stuff as fast or close to a big saw where a big saw beats a small saw in heavy large stuff.

 

[svk]

I was surprised that the first two saws were as close as they were in speed as the 562 feels a lot faster.

 

[svk]

A lot depends on what diameter and hardness the logs also. A small saw rips through small stuff as fast or close to a big saw where a big saw beats a small saw in heavy large stuff.

If I had been thinking I would have used the big birch I cut later in the day (the one that the 562 was temporarily pinned under, thread over in firewood forum) but I wanted to make sure all chains were sharp.

 

[lone wolf]

If I had been thinking I would have used the big birch I cut later in the day (the one that the 562 was temporarily pinned under, thread over in firewood forum) but I wanted to make sure all chains were sharp.

Now race the biggest against the smallest saw in small diameter pine!

 

[Chris-PA]

This was an interesting video to me, as it gives an opportunity to compare Autotune to conventional carbs in a relatively constant setting. The 2186 just sounds different to me even when I cannot hear obvious 4-stroking, so I wondered if I could see anything in the spectrum plots.

Here is a section from the first cut on the 2186 - it a pretty short sample so I had to reduce the number of points on the transform. The peaks are wide and not well defined, and you can see a smaller peak down at about half speed, which is 4-stroking:



Cutting the sample down still further, I looked at the first half. Now you can see the 4-stroking fully - it is firing every other revolution at about 6000rpm (100Hz), and there are harmonics of that at multiples of 100Hz:



Now the second half - it's mostly firing every revolution now, but there is still a hint of a half frequency spike there, so it misfired a few times over the length of the sample:



And here is the 562. The plot is clean a whistle and there is no hint of misfire at all. Autotune doing what it was supposed to:



The thing is that when I listen to that section of the 2186 cut I cannot hear the 4-stroking, but it is still misfiring.

 

[blsnelling]

I don't know what the software is picking up, but the 2186 is definitely not 4-stroking in the cut. It's either 4-stroking or hitting the rev limiter before it goes in the wood, but not in the cut.

 

[svk]

This was an interesting video to me, as it gives an opportunity to compare Autotune to conventional carbs in a relatively constant setting. The 2186 just sounds different to me even when I cannot hear obvious 4-stroking, so I wondered if I could see anything in the spectrum plots.

Here is a section from the first cut on the 2186 - it a pretty short sample so I had to reduce the number of points on the transform. The peaks are wide and not well defined, and you can see a smaller peak down at about half speed, which is 4-stroking:

View attachment 493203

Cutting the sample down still further, I looked at the first half. Now you can see the 4-stroking fully - it is firing every other revolution at about 6000rpm (100Hz), and there are harmonics of that at multiples of 100Hz:

View attachment 493204

Now the second half - it's mostly firing every revolution now, but there is still a hint of a half frequency spike there, so it misfired a few times over the length of the sample:

View attachment 493205

And here is the 562. The plot is clean a whistle and there is no hint of misfire at all. Autotune doing what it was supposed to:

View attachment 493206

The thing is that when I listen to that section of the 2186 cut I cannot hear the 4-stroking, but it is still misfiring.

Very interesting Chris. On the 2186 do you think this is a fuel delivery or ignition issue?

Did you analyze the 550 clips? Curious how that one sounds.

 

[blsnelling]

I was surprised that the first two saws were as close as they were in speed as the 562 feels a lot faster.

The cut times aren't that much different, but the 550 is working MUCH harder to do the same work. Try pushing on the 562 as much as you were the 550 and see what happens.

 

[Chris-PA]

I don't know what the software is picking up, but the 2186 is definitely not 4-stroking in the cut. It's either 4-stroking or hitting the rev limiter before it goes in the wood, but not in the cut.

This is a screen capture of the part of the video I was analyzing:



It's definitely in the wood here, but it's still early in the cut at the narrow end of the log, coming off higher rpm. Hitting the rev limiter is a interesting possibility, but I don't know what rpm it limits at. If we assume that it's cutting out every other firing then the shaft rpm would be at twice the firing rpm, or 200Hz, which is 12krpm. I don't think it limits that low, but I'm not really sure those are valid assumptions anyway. Still, 1/2 second later it's at 10,2000rpm (170Hz), so it seems to be rather far away from the rev limiter.

I have to go back outside and keep working - I'll look at it more later.

One of the things that has long bothered me about the way these carbs work is that way before it gets to the point where it's completely misfiring and 4-stroking is obvious to the ears, it is still way too rich for optimal running. I think that is what this is showing - you can't hear it 4-stroking, but it's still misfiring. I'll try to see if there is any more support for that view later - maybe there is another explanation.

 

[Chris-PA]

Very interesting Chris. On the 2186 do you think this is a fuel delivery or ignition issue?

Did you analyze the 550 clips? Curious how that one sounds.

I'll post some more later, but I was surprised how low the rpm was on the 550. It's mostly around 8200rpm, sometimes up to 9200rpm. It really does sound like it's working too though, so perhaps that shouldn't be surprising. It doesn't seem to be cutting all that slow, so rpm isn't everything for sure.

What chain is on it?

 

[svk]

Oregon LGX on the 550.

 

[Chris-PA]

This is kind of interesting - I selected 1/2sec intervals of the 2nd cut on the 2186, and plotted the rpm at each point:



From what I could find it looks like the 2186 limiter will kick in at 13,000 to 13,500rpm, and so it's quite likely it was hitting the limiter. The 1st second into the cut (first 2 data points on the graph) look like this:



There is a peak at 70Hz (4200rpm), which just happens to be 1/3 of the larger peak at 210Hz. I have no idea what scheme they use to limit rpm - I assume they cut out ignition pulses, but I don't know what pattern is used. But I'd guess rev limiting is what is happening here. Then in the next 1/2sec, the rpms have come down to 11,500rpm, which should be well below rev limiting range, and the plot looks very different:


Here there are two peaks, one at exactly half the main rpm spike 96Hz (5760rpm) - I think this is 4-stroking. The rpms are not high enough for rev limiting, but at 11,500rpm they're well above the rest of the cut, which is around 10,000rpm and shows no sign of 4-stroking.

 

[Chris-PA]

Oregon LGX on the 550.

That's full 3/8? So that would be consistent with a 50cc saw that's working hard I guess?

 

[svk]

That's full 3/8? So that would be consistent with a 50cc saw that's working hard I guess?

Yes full 3/8. And the guy who does my chains usually has them pretty aggressive/rakers down. As I cut mostly softwood they seem to work very well.