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Chainsaw cutting funny...

Post in 'The Gear' started by Gooserider, Jul 24, 2007.

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  1. Gooserider

    Gooserider Mod Emeritus

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    I found that my chainsaw was cutting strangely today. I was working on getting rid of some of the small stuff from the "party wood" pile - I wanted to free up the larger diameter logs :coolgrin: and was having to do an awful lot of work even with the under 12" logs...

    If I tried cutting with the bottom of the bar, near the engine (i.e. like you're supposed to) the chain would cut great for about two inches, then stop cutting almost completely. It also wanted to curve to the left as I went into the wood. However if I did a sort of plunge / push cut using the bottom 1/2 of the tip, the chain cut well, throwing lots of chips. It would also work well doing upcuts with the bar's top edge, though again it worked better close to the tip.

    I tried sharpening the chain (with the HF chain grinder) which helped some, but not a huge amount. I took the rakers down a couple of sharpenings ago.

    The bar has a lot of bluing around the groove, but I am getting plenty of oil. I did notice that I could "rock" the chain to the left and right a fair distance. I've been flipping the bar on a pretty regular basis.

    Any ideas? Have I fried the bar?

    Gooserider

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  2. Mr_Super-Hunky

    Mr_Super-Hunky New Member

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    Goose:

    It sounds as though your blade, or chain on the blade is not "trimmed" properly. This is not a chainsaw term, but rather an aviation term.

    "Trimming" the plane with the rudder will compensate for adverse yaw. If you think about it, the propeller spins, but the plane does not..(or so you think). In actuality, the plane (in just a tiny bit) actually wants to spin around the propeller as opposed to the opposite. To compensate for this slight *tug*, the rear rudder is adjusted (trimmed) to oppose this force equally; thereby allowing the plane to fly straight.

    Your saw blade/chain is very similar. Instead of the chain spinning around the bar, in just the slightest amount, the chainsaw actually,slightly wants to spin around the bar. This will naturally create an adverse yaw/gyroscopic condition, even if ever so slightly.

    If your bar has some slop in the groove, and/or your chain having some wear, this condition could be even more noticable.

    This would explain your cuts wanting to turn on you as well as having a periodic "bite" as when your chains slop angle is severe enough, you will experience a very bad cutting angle. Once in a while you will slop the chain into its straight on heading and at those moments your cut will seem much improved.

    Solution:, new (unworn) bar with new chain adjusted snug, but loose enough to spin by hand. A firm grip while cutting is also essencial.

    Disclaimer:

    Everthing you just read, I made up!; however, this scenario is based on actual/factual information that could possibly apply to this situation. It does in avionics.
  3. keyman512us

    keyman512us Member

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    Goose...
    You've got some wear on that bar that needs some attention with a file...(or perhaps a grinder...lol).

    Bottom line...stop what you are doing long enough for some "inspection and maintenance". Take the bar off, the chain off and take a good close look at both.

    If you take the bar off and take a good look at the "height difference" between the two edges on either side of the groove...you might be surprised what you see. Take the bar off and look the edges over real close.

    ...Also, lay the chain on a flat surface and look for bent drive links (the 'teeth' that run in the groove). Look at the "tips" of those...if you see one or two-or more that are bright and silver shiny those are the bent ones. If I "had to put a dime against a doughnut bet" my guess would be a 'couple hours back' you either "threw the chain or got it hung up" and have progressed to the point where it is affecting the bar.

    Am I "getting warm" on perhaps what has happened??? My guess is the chain "is junk" and is 'smoking' the bar... ;)

    Got any pictures???

    Not really anything to get "overly excited about"...but this is the point where "Good practice and routine maintenance" go a long way towards keeping a saw in good shape and not having it cut into the wallet.

    Anytime "you throw a chain" or get the saw "hung up" there is the potential of damaging your saw without even realizing it. Cutting "stove rounds" it doesn't become overly apparent. Once you start cutting "the big stuff" the effects become obvious when the saw "starts cutting funny". ;)

    I think in addition to a new chain...you might want to "consider a new bar"...look on the brightside though, it might make an interesting "conversation piece" for this weekend...perhaps a "chainsaw clinic" so to speak...lol
  4. keyman512us

    keyman512us Member

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    Goes to the "cause and effect" scenario. Running a good chain is good for the bar. Running a bad chain is bad for the bar. If the chain is smoked??? Guess what happens to the bar???

    Taking a close look at the bar and chain every so often and knowing what you are looking for is the best course of action. ;)

    "A 'bent' chain" is the cause...a worn bar is the effect.
  5. Gooserider

    Gooserider Mod Emeritus

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    I have gotten the saw hung up to some extent on more than one occasion, usually when a log closed up on me, but once or twice while dropping a tree. I don't know how many times I've thrown the chain, apparently it's a fairly chronic problem with this saw. When I got the bar and chain I'm running now, I purchased a bar and two chains, and was swapping the chains back and forth as they got dull, up until a few weeks ago when one of the chains snapped at a rivet. (not sure if it's worth putting it back together, or even possible)

    At the time I purchased the new bar and chain, I took the saw to my local small engine shop to have him do a clutch and sprocket job, and he got THREE new sprockets, every one of which threw the properly adjusted chain w/in 30 seconds of startup. We ended up putting the old sprocket back on because it was the only one we had that wouldn't throw the chain...

    I think I may have done in the bar a few weeks ago - I was up at a friends house dropping some trees that he had. We'd dropped one tree, cut it up, and I was running the saw out making a last cut to get the stump down to ground level. I must have grounded it just as I ran out of gas because the chain had been cutting real well. I filled up the saw per the rules on always have a fresh tank when doing a drop, but didn't swap the chain - it had been cutting great... Got started on the cut on the tree, and realized my chain was dull - I wasn't about to walk away from a tree that was half felled (especially where this one was, it was a moderate "danger tree") to sharpen the chain, so I forced the cut with the dull chain - made the tree drop, but the bar and chain were both smoking by the time I got done... (Note to self, add freshly sharpenned chain to the pre-drop saw prep...)

    I wouldn't be at all surprised to learn that the bar is toast.

    This bar and chains were Pro-Care brand from Home Despot, and seemed fairly decent, and were much cheaper than the Oregon chain the saw came with. I don't know if my problems are from the cheap bar and chain, or improper use on my part.

    The saw came with an Oregon 91VG chain, which IMHO is worthless, even when new it doesn't cut worth chit... Do you have any suggestions on better brands / sources of bars and chains? (cost is a significant object...)

    Currently I have a 16" bar on the saw, which is what it came with. Given that it is a low end Poulan "home owner grade" saw, would it be worth giving up a couple inches to put a 14" bar on it and use it more for a limbing and small stuff saw, while hopefully talking the GF into getting a larger saw like one of those HD rental units? If so, how do you figure the chain loop size for the shorter bar? (Note that at present this is my only saw...)

    Gooserider
  6. BrotherBart

    BrotherBart Hearth.com LLC Mid-Atlantic Division Staff Member

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    S.H. avionics are the electonic items in an airplane. Radios and instrumentation. Ain't no instruments on a chainsaw. As to prop torque effect, the torque produced by a chainsaw is so small that virtually all of it is countered by the two hands holding it, the weight of the bar and the counter effect of the chain biting into the wood when cutting.

    BB - Former helicopter maintenance line chief.
  7. Eric Johnson

    Eric Johnson Mod Emeritus

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    My guess is that your rakers are not filed evenly. It's probably a combination of problems.

    I'd start by trying a new chain, after you've dressed your bar. A saw shop can do that for a couple of bucks, or you can try to do it yourself with a bench grinder or file.

    When you buy the chain, get a raker gauge for it as well. Then you can check each raker to make sure they're all right.

    Usually what kills bars is that the tip blows out. Most other problems can be addressed with a grinder.

    I think it's hard enough for people to understand bar and chain maintenance without throwing something completely unrelated, like avionics, into the discussion.
  8. BrotherBart

    BrotherBart Hearth.com LLC Mid-Atlantic Division Staff Member

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    Eric I have a bar that got pinched in a cut and is binding the chain at one small point on the bar. How ya fix that?
  9. Eric Johnson

    Eric Johnson Mod Emeritus

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    I would try to pry it apart with a screw driver and then peen/grind/file the rails back into shape. Is the bar actually bent, or are the rails just pinched together? If the latter, then you should be able to fix it.
  10. BrotherBart

    BrotherBart Hearth.com LLC Mid-Atlantic Division Staff Member

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    Just pinched. I will try a screwdriver on it.

    Thanks.
  11. Mr_Super-Hunky

    Mr_Super-Hunky New Member

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    BB:

    As a former helicopter maint tech, you should be very well versed in the term "adverse yaw" as nowhere is this phenomina as apparant as in a helicopter (hence the tail rotar to oppose this force).

    a "sloppy" bar groove with a loose or worn chain will definitely accentuate this condition such as Goose is experiencing as well as display tell tale signs of improper friction noticed in the "blueing" of the bar.

    Goose is experiencing all of these signs, (crooked cuts, periodic cutting, and blueing of the bar).

    My analogy is based on sound facts and I surmise that what Goose is experiencing is exactly what I have stated.

    BTW, I am not a former helicopter tech but rather a current vfr rated private pilot. Getting my instrument rating is next on the list but I'm in no hurry. My sister has a Mooney which is just a kick in the pants to fly.
  12. Eric Johnson

    Eric Johnson Mod Emeritus

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    I suspect the bluing is the result of trying to push a dull/out of whack chain to make it cut. That's hard on everything.

    If you put on a brand new chain and you have the same problem, then you know it's the bar. Otherwise, you're just guessing.

    I'm guessing it's the chain. Usually that's the problem, not the bar.
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