20" Oregon 72LG vs. 28" Oregon 72LG chains

[kodiakfisher]

I decided I was curious enough to put some money into an experiment. Someone please tell me how I should have my wife time the two runs. I would suspect that she should start when the chips start and stop when the chips stop.

Anyways I will be running two tests on Hemlock about 25"-26".

I will do one test with a 20" bar full comp Oregon chain rakers set to .025, this test will take two cuts and the changeover time will be included in total time. I actually only get about 18" to cut with including the dawgs. The log is just big enough where cutting over the top doesn't quite get it done. I am not a racer just a guy in the woods cutting firewood so I will be running my saw for safety as I would be in the woods not for the fastest time.

The second test will be with a 28" bar full skip Oregon chain rakers set to .025 this will be done in one cut. The saw is totally stock and broke in.

I will then do the same test once I get my Walkers muffler and reset the jets on the carb. Same logs, bars and chains and check times again. The test with the Walkers probably will not get done until after Thanksgiving but the stock test I will do this weekend.

Doug

 

[Billy_Bob]

Might be interesting to also do the test with both bars, but with a say 16" log.

 

[kodiakfisher]

Billy_Bob

It is well documented that a log that can be cut in one pass with a bar running full comp chain will be faster than a longer bar running full skip all other things being equal. Second there is absolutely no point in using such a long 28" bar to cut a log that can be cut with a 20" bar.

Kodiakfisher

 

[16gauge]

Kodiak, I definitely get it...I think I know the outcome but I will be watching for confirmation...Phil

 

[Diesel JD]

They told me that the .325" pitch on the long bar would have the opposite effect I was looking for. I had a 28" bar on my 390, which it couldn't quite handle with full comp chain...had I used skip it might have worked... .325" will make you need more drive links which means more cutters plus you'll have to make sure your sprockets match in pitch and your bar and chain are the same gauge.

 

[kodiakfisher]

Diesel JD,

I had not thought about the .325 having smaller drive links causing the use of more cutters, makes perfect sense.

I have the 28" bar and skip tooth chain, there is actually one less cutter on the bottom of the bar with 28" vs. the 20" with full comp.

16 Guage,

I have no idea how this will turn out, I would just like to know how well does it work in soft wood and which is more efficient. I know that out here in the West many times cutting with a long bar is the only option due to how steep the country. I also never want to be on the down hill side of any log. You never know when a limb may decide to give way and that log moves down hill right on top of you. I will take a slower cut from the uphill side. I only expect to want to use this larger set-up 15% of the time.

Kodiakfisher

 

[twistedtree]

Assuming you are cutting a log that is smaller than both bars, and using the same chain (other than length) the bar length should have no impact on the cut time. As others have stated, the friction on the longer bar will be negligible.

If you change to skip chain, the skip chain will cut slower. You could put skip chain on the 20" bar and get the same results as the 28" skip chain. Similarly, if you put full comp chain on both bars, they will cut the same speed.

The reason for full skip on long bars is to lighten the load so you can cut bigger logs. The size of the log creates the load, not the bar length (assuming the bar is longer than the log)

 

[kodiakfisher]

twistedtree,

Your moniker twisted tree how ironic, the log doesn't create the load the number of cutters, size of the kerf, depth of cut all create a load. The log is static and remains static throughout the test. It is the variables that can be changed that can increase or decrease the load on the saw. I.E. filing the rakers down creates more load, cutter a larger kerf creates a more load, full comp chain creates more load than a skip chain on the same length bar.

Granted there is no load on the saw until it touches the wood but what we are doing is comparing the load by changing a few variables i.e. full comp 20" bar or full skip 28" bar. I will be comparing the load/cut times between the two set-ups the log is not a variable that is going to change and therefore is not considered as part of the equation into total load on the saw.

Kodiakfisher

 

[TimberPig]

The reason for full skip on long bars is to lighten the load so you can cut bigger logs. The size of the log creates the load, not the bar length (assuming the bar is longer than the log)

Actually, skip chain is normally for chip clearance when buried, not specifically to reduce the load. It is to allow the chips to be cleared, so that the cutters can take a fresh bite out of the log instead of jamming up and re cutting the chips.

The added bar length doesn't really add to the load on the saw through friction, it is the extra weight of the longer chain that adds to the load placed on the saw.

 

[twistedtree]

twistedtree,

Your moniker twisted tree how ironic, the log doesn't create the load the number of cutters, size of the kerf, depth of cut all create a load. The log is static and remains static throughout the test. It is the variables that can be changed that can increase or decrease the load on the saw. I.E. filing the rakers down creates more load, cutter a larger kerf creates a more load, full comp chain creates more load than a skip chain on the same length bar.

Granted there is no load on the saw until it touches the wood but what we are doing is comparing the load by changing a few variables i.e. full comp 20" bar or full skip 28" bar. I will be comparing the load/cut times between the two set-ups the log is not a variable that is going to change and therefore is not considered as part of the equation into total load on the saw.

Kodiakfisher

I think we are saying the same thing. My point is that if you have the same chain, and just change the bar length, it's going to cut exactly the same, (assuming the log is smaller than both bars). It's the chain that matters, not bar length.

If you change the chain, it will make a difference, and it will make the same difference on both bar lengths.

 

[twistedtree]

Actually, skip chain is normally for chip clearance when buried, not specifically to reduce the load. It is to allow the chips to be cleared, so that the cutters can take a fresh bite out of the log instead of jamming up and re cutting the chips.

The added bar length doesn't really add to the load on the saw through friction, it is the extra weight of the longer chain that adds to the load placed on the saw.

True, but isn't the net result that a skip chain cuts less for every foot of chain that passes over the wood?

 

[kodiakfisher]

I received the 28" small mount Oregon bar with 72lg (full skip) Oregon chain. The diameter of the log I used was a 24" tapering to 26" Hemlock. The length of the wood was 19" so you can get an idea of the taper. I made a total of five cuts (last one was just because I couldn't believe the difference). The saw used is a 357xp with about 9 tanks of gas through it completely stock. The timing was done by taping a stop watch to the handle and starting the cut at the 10 second mark and marking the time as soon as the cut finished and I could read the time, not perfect but it is what I had to work with.

The first cut with the 20" bar full comp Oregon chain:
57 seconds (leaned on it a bit too hard towards the end of the second cut)
The second cut moving towards the bigger end of log
52 seconds (pretty smooth cut)

The first cut with the 28" bar full skip Oregon chain
32 seconds
The second cut log is now close to 26"
35 seconds

I could not believe these times so I went and put the 20" bar and chain back on and made one last cut on the log, (log is now 26") the last time was
71 seconds!

I will stipulate that the 20" Oregon loop was not out of the box sharp like the 28" loop was, although due to being sharpened a few times the gullet on the 20" was a little bigger. Rakers on both loops set to .025. My feeling was that the chain going around the nose of the bar was creating much of the load/drag because once I moved around for the second cut on the log it was noticeably quicker also probably less wood. I think some of the difference was the chain not being able to clear any last bits of wood chips off the nose of the bar. I notice the saw will throw a small amount of chips off the nose with a 20" bar and smaller wood. I would have to believe the difference in times is more than just the sharpness of the chain + changeover time but it really doesn't matter to me. In larger soft wood I will be using the 28" bar with full skip. These times should drop even more when I get my walkers muffler in a few days making the changeover time a larger percentage of the total cut time due to saw making more power. John sent me a picture of the mufller I requested two deflectors be welded on one on each side along with screens so the modification is less obvious. I work for the U.S. Forest Service and don't want to be caught with spark screens.

I would guess many of you would get different results, the only reason I attempted this was to see how the saw would do in some of the larger SOFT wood in the PNW with ME cutting. Sometimes cutting can be much safer and convenient to cut in one pass. This set-up for hardwood I'm certain would not work at all and probably the 20" bar with full comp wouldn't be the best set-up either.

Kodiakfisher

 

[jokers]

Hi Kodiakfisher,

I`d like to offer that any time that you overbuck as in cutting a 24" to 26" log with a 20" bar, you double cut and it will slow you down.

Unfortunately I can`t accept your results as scientific but do accept that the skip chain cuts larger wood faster with your 357. I don`t think that if all were equal with the exception of cutter sequence that you would find such disparity in the cut times.

Russ

 

[Crofter]

Kodiakfisher;

Cutting with the tip partially or totally burried is a big handicap in timed cuts compaared to a bar that is nose out, plus the possible difference in chain sharpness hurts a good comparison. Try a loop of of full comp on the 28 inch bar, both equally sharp. That size of wood with that fairly small saw should favour the full skip for cutting speed but I think the difference would be less than those times indicate. Interesting test though. Wouldnt it be interesting to test both a 20 and a 28 inch bar on say 16 inch wood to see the difference bar length makes and try skip and comp chain on both small and large wood to see if the advantage shifts.

Frank

 

[Crofter]

Russ, you got there first! I like to see trials to compare things but it is very easy to have things creep into the deal that skews the results even if you are not trying to. Now when it comes to politics and other games of persuasion when the intent is deliberate; forget it! Kodiak, keep it coming!

Frank

 

[kodiakfisher]

Russ,

I agree with you totally after reading your post of muffler mods I figured you would be all tuned up and really let me have it . If someone sends me a new loop of 72lp I will run the test again.

The only reason for this test was to see if I could cut larger wood faster with a longer bar and full skip. Even with the difference in chain I think we can agree that the long bar with full skip is faster. I think with equally sharp chains the times would be closer as Russ indicated, (holy $%$ I just remembered I have a loop of RS for when my buddy decides he wants to race me with is 290) I will break this loop out and try it again unfortunately there isn't much of the log left I will see how much below the 70 seconds I get and use that as an estimate by taking a percentage of the decrease in time and apply it to the other times. Yes I know not very scientific, give me break Russ I'm not a scientist. I think someone else mentioned that when you are putting up firewood for the winter the cutting time turns out to be a small percentage of the total time so in the big picture a couple of seconds of cut time doesn't make much of a difference in the long run.

Kodiakfisher

 

[kodiakfisher]

Crofter,

I think we know in small wood the full comp is faster, I read somewhere on this board that this is what all the racers run. Take that information for what it's worth. I just recurgitated what someone else said without qualification of any observation or knowledge of my own (there that should keep Russ off my arse) .

So two bars of different length same sharpness, both full comp the shorter bar will always win due to less friction and weight of chain. It would be interesting to know how full skip would do on the 20" bar compared to the 28" bar in the larger wood. I do have a brand new loop of Windsor full skip that I could try it with.

Doug

 

[Billy_Bob]

To be more "scientific", try to make everything pretty much the same except for one thing (like the length of bar).

So maybe use a square block which is the same exact size for each cut.

And even more scientific would be to use a weight for pressing down on the saw while cutting, perhaps a weight attached to your left arm like one of those "wrap around attach with Velcro leg weights". Then don't put any muscle into the cutting, just let the weight on your arm do the pressing down.

 

[kodiakfisher]

I tend to notice on this board lots of ideas being offered when someone else is doing the work but very few volunteers to run tests. I don't think you have gotten the point of the test, but now that I have done the test I'm pretty sure that the 28" bar with full comp would also be slightly faster due to the nose of the bar sticking out. The point was to compare full comp short bar to long bar full skip. If the wood is not large enough to warrant a long bar there is no point in using the long bar, using the short bar makes more sense.

I don't care enough about the results to try and make this scientific enough to pass anyones litmus test. I collected enough data to be happy with my decision and shared the information. I do have a neighbor that has a bandsaw mill and could make a perfect block but then it would just be something else that wasn't perfecty controlled and would become suspect.

If I inadvertantly asked for input on how to make this more scientific please disregard. This was never intended to be scientific only some casual observation passed on for those that may be interested.

Kodiakfisher