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Ten Helpful Hints for Harvester Cutting Problems

Ten Helpful Hints for Harvester Cutting Problems_02.jpg

The following information highlights common problems harvester owners have with their cutting attachments. Hopefully the explanations of causes and suggestions on how these problems may be overcome is helpful. 

If you are having a problem and it is not listed here or if our suggestion doesn't help you, please contact us. If we aren't able to solve it, we communicate regularly with the engineers at Oregon Cutting Systems and we'll get them involved.  We can help you.

Problem #1

When I start my harvester in the morning, the sprocket nose sometimes fails right away. This occurs on bars that worked fine the previous day. Why do these tips fail?

Explanation/Cause: Chains are a little longer when they are hot. So, if you adjust the chain at the end of the day when it is warm, it may be too tight in the morning. Damage due to shrinkage occurs first thing because chain tension is extreme before the chain warms up again.

Suggestion: Do not set chain tension when the chain is hot. If the chain is warm, you may tension the chain, but be sure to run it at least a half an hour after tensioning it. Never tension a warm chain at the end of a work day or shift - otherwise expect damage. 

Problem #2

The nose of my harvester bar is split, bent, and broken. Why does this occur?

Explanation/Cause: If a tree sits back on the bar and chain, it may temporarily pinch the bar rails and close the groove on the drive links. The wood may pinch the chain, too. These binds may not be obvious because many hydraulic drive motors on harvesters have plenty of power, and may be able to pull a chain in spite of the binds. When the bind occurs in the upper part of the bar (before it is past the nose), a powerful hydraulic motor can pull the chain with a such a force, that separates the nose laminates. When this occurs, the chain is pulled into the nose causing the sprocket and bearing to fail.

Suggestion: Prepare for the cut by trying to avoid situations you know may result in accidental bar pinching. Also, make sure your hydraulics are set up correctly.

Problem #3

The sprocket nose on my harvester bar is jammed and broken. I know I didn't hit anything. Why does this happen?

Explanation/Cause: Sometimes when a bar and chain gets bound in the cut, it requires the operator to force it out of the tree. This force usually includes pulling it out with the boom. The force of pulling the bar and chain out is often carried on the bar tip. The power the boom can exert on the nose may be even greater than a hydraulic drive motor in the example above. When this occurs the chain exerts extreme pressure on the nose, the nose laminates separate, bearings fall out and are lost, and the sprocket may get crushed or broken.

Suggestion: When removing a pinched bar from a tree, try to relieve as much pressure as possible before resorting to pulling with the boom or other methods of extreme leverage. In general, avoid situations where the bar and chain have to be removed by brute force.

Problem #4

The bearings appear to have fallen out of the tip on my harvester bar and are lost. Why would they fail like this?

Explanation/Cause: Sometimes, when cutting a tree, the bar will actually be cutting another tree that is behind it or attached to it. Sometimes a butt will split and allow one part of the tree to fall when the other is still being cut. When this occurs, the tip will bend, and sometimes the laminates will separate.

Suggestion: Beware of trees that look like they might split. Never try to cut two trees at once. Initiate the cut so the bar is in only one tree at a time.

Problem #5

The tips on my harvester bars don't last very long. I know the bars are not pinched or damaged (as in the examples above). What can I do to increase the life expectancy?

Explanation/Cause: Running your bar and chain without sufficient lubrication will cause premature bearing failure. When the bearing fails, the tip will seize and may delaminate. The end result is failure that looks similar to the examples above.

Suggestion: Grease the bar nose twice a day (on 11BC bars only), and be sure the bar is receiving a sufficient supply of oil at all times during operation. 

Problem #6

I don't get good life out of my harvester bars. The rails seem to fail prematurely. I know of other harvesters running the same bars and they get good service life. Why doesn't mine last as well?

Explanation/Cause: Cutting with a dull chain will wear out bar rails very quickly. This occurs on all harvesters to some degree, because the hydraulic motors have so much power. Operators sometimes fail to recognize when the chain becomes dull, when it continues to cut. Some operators practice this theory: If you apply enough feed pressure with plenty of horsepower, a chain will cut no matter how dull it is. Some operators are guilty of this and don't even realize it. Forcing a dull chain to cut by applying extra hydraulic power will reduce the life of the entire cutting attachment. 

Suggestion: If you have recently changed from a solid-nose bar to a sprocket-nosed bar, sharpen just as often as you did when you ran the solid-nose bar. Better yet, with either type bar, watch the chip size to tell when it is time to re sharpen. You should always be making good chips. If you are not, stop and sharpen the chain. The sharper the chain - the easier the cutting attachment has to work - the longer your bar rails will last.

Problem #7

On my harvester bars, the bar rails chip out near the sprocket nose. What causes this?

Explanation/Cause: This usually means the chain is being run too loose. Here is why: When the chain goes around the nose of the bar, each link has to pivot to make the turn. When those links come around to the bottom of the bar, the tip rails have to straighten each pivot point so the chain heads back to the sprocket. When the chain is loose, each link slaps against the tip rails. This happens millions of times in one day. Increasing chain tension will help the chain pull itself straight after rounding the nose. This reduces the impact on the nose rails, and they will last much longer.

Suggestion: Chain must be tensioned more tightly on sprocket-nose bars than on solid-nose bars. On sprocket-nose bars, adjust the tension to meet this test: On the bottom of the bar, near mid span, pull the chain down by hand lightly. The gap between the bar rail and the chain's cutters should be 1/8th inch - not more. Also, remember to never tension warm chain at the end of work (see problem #1).

Problem #8

My bar seems to climb in the cut. What causes this?

Explanation/Cause: The cause is uneven bar rails and/or a partially dulled chain. The cutters on the side closest to the ground are most often damaged by rocks. When damaged bottom cutters quit cutting, the sharp cutters on the high-side will pull the bar up. This causes the high-side rails to wear faster, making them uneven.

Suggestion: Check for damaged cutters and uneven bar rails several times per day. If damage is moderate, dress the bar rails even and grind all cutters back until damage is removed. Remember, keep all the cutter teeth the same length. This means you may have to grind away good cutter material on the undamaged teeth for them to match the length on the side that was damaged. If damage on the chain or bar is severe, it's best to replace them.

Problem #9

Whenever I start a new operator, he bends and ruins a lot of bars learning how to run the machine. How can I reduce the cost of starting a new guy?

Explanation/Cause: The learning curve (no pun intended)

Suggestion: There are two types of harvester bars; solid and laminated. Solid bars will outperform laminated bars in nearly every case, even though they are usually more expensive. You will also find that the solid bars can often be straightened. Laminated bars are usually ruined when they are bent. 

Problem #10

It seems like I pay a lot for harvester bars and my supplier never has what I need!

Explanation/Cause: Your supplier is not Madsen's.

Suggestion: Buy your harvester cutting attachments at Madsen's. We are one of the largest dealers of harvester bars, harvester chain, and harvester accessories on the West Coast. We have a large inventory of harvester cutting attachments. We can help you.

Got more questions about the cutting attachment on your harvester? Call or stop in.

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