LT40 drive belt tension?

[KWood255]

I have a new LT40, now with 70 hours on it. Yesterday while cutting spruce, I began getting waves. 
I began with a new 4* WM blade, then swapped it out for a new 747WM blade...no noticeable improvement. I checked the belt tension, which is about 16lbs at 7/16". I find the belt tension gauge to be a bit frustrating, as I get a slightly different reading each time. 

Should I increase the belt tension slightly? When the auto clutch engages, it seems to squeal a hair more then it did initially. I realize too much belt tension can cause crankshaft bearing failures over time, but what is too much? Is it safe to go to say 20lbs for troubleshooting? 

I will go to another new blade this morning. I have options of 4, 747, 9, or 10's. All WM double hards. 

I understand many folks have issues with spruce. I've cut somewhere around 20mbf of spruce on my LT35 and did not have this significant of issues. Up until yesterday, the LT40 performed great. Any ideas are appreciated. Thanks.  

[KWood255]

I should of added...2022 LT40 with the 38hp Kohler. 

[Dave Shepard]

Is that a triple V belt? My 51 CAT is 18#@7/16". If your belt is properly tensioned, then your problem is somewhere else. 

[KWood255]

Is that a triple V belt? My 51 CAT is 18#@7/16". If your belt is properly tensioned, then your problem is somewhere else.

Yes, triple V belt. 

[GAB]

What blade tension are you running at?

If you are sawing Colorado Blue Spruce yard trees - GOOD LUCK.
Those are the worst logs I have had on my mill.
Could not saw a flat board, and I tried everything I could think of.
GAB

[John S]

18 lbs at 7/16 inch deflection?

[Crossroads]

I agree, if your belt tension is correct, then the issue is somewhere else. Did you check the guide wheels for level?

[trimguy]

Try a different blade. You may have gotten waves with the 4* degree because it was dull. I didn't have any luck with the 7/47 cutting straight thru knots in pine.

[KWood255]

Thanks for the replies. I've tried a few blades so far. 4/747/10. All new. I increased belt tension to 18lbs at 7/16 and there's an improvement, but not perfect. I will keep troubleshooting tomorrow if the rain holds off 

[caveman]

We were having problems at one time and Yellowhammer suggested checking the blade guide arm for tightness.  I seem to recall that it needed to be "monkey tight".  That got us to sawing flatter lumber.

There are many who saw a lot more than we do but when the cuts begin to wave, we check
 Blade alignment
 Blade
  Blade guide for play
 Drive belt tension (the drive belt is a little bit of a pita, but it does not have to be adjusted often)
  Try another log

[YellowHammer]

There is tremendous amount of load on the blade guide alignment arm and roller assembly when sawing, especially when sawing problematic logs.  As a quick check, tension the band about normal, extend the blade guide arm fully, as far as it will go to the drive wheel, and grab the roller assembly with your hand and twist it hard, while you are looking at the glint of the blade.  Then tub it up and down, hard, then up and down, hard.  It should feel like is welded to the idle drive side.  There should be zero play and zero rotation.  If the rollers or blocks rotate at all, you will see a change in the glint of the blade.  If everything is right, you will see almost zero glint change.  If not, you will notice it clearly, and start twisting and tugging everything to find out what is moving or flexing.  Then move the arm to your normal sawing position, and do it again.  Sometimes there will be little wear at that position, and you will see some slack.

The squeal when engaging the band is due to the settings of there timing of the when the head rotates to tension the belt and when the motor throttles up.  If the motor is accelerating when the belt begins to tighten, it will slip and squeal until it is tight.  If the head rotates and tightens the drive belt before the engine throttles up and is still near idle, then there is no slippage and so very little or no squeal.  The timing can be adjusted by fiddling with the throttle and head rotation mechanisms.  The less squeal, the less slippage, and so the less drive belt wear over time.  

Of course, all the normal alignment and stuff but be spot on while troubleshooting.  

 

[OlJarhead]

Check band alignment as well.  If the band is pointing up or down it will want to follow that path so make sure it is within spec as well as the head while you are at it.  The WM manual will explain how and most of those things are checked around 50hrs I think

[Brad_bb]

Other factors...spruce knots are a lot harder than the wood.  Could you be deflecting at the knots?  Sharp band helps.  Slowing down a little might?

Build up of sawdust on one side of the band can also be a factor.  What are you using for lube, and it is keeping the band clean on both sides?

[KWood255]

There is tremendous amount of load on the blade guide alignment arm and roller assembly when sawing, especially when sawing problematic logs.  As a quick check, tension the band about normal, extend the blade guide arm fully, as far as it will go to the drive wheel, and grab the roller assembly with your hand and twist it hard, while you are looking at the glint of the blade.  Then tub it up and down, hard, then up and down, hard.  It should feel like is welded to the idle drive side.  There should be zero play and zero rotation.  If the rollers or blocks rotate at all, you will see a change in the glint of the blade.  If everything is right, you will see almost zero glint change.  If not, you will notice it clearly, and start twisting and tugging everything to find out what is moving or flexing.  Then move the arm to your normal sawing position, and do it again.  Sometimes there will be little wear at that position, and you will see some slack.

The squeal when engaging the band is due to the settings of there timing of the when the head rotates to tension the belt and when the motor throttles up.  If the motor is accelerating when the belt begins to tighten, it will slip and squeal until it is tight.  If the head rotates and tightens the drive belt before the engine throttles up and is still near idle, then there is no slippage and so very little or no squeal.  The timing can be adjusted by fiddling with the throttle and head rotation mechanisms.  The less squeal, the less slippage, and so the less drive belt wear over time.  

Of course, all the normal alignment and stuff but be spot on while troubleshooting.  

This is great information YellowHammer. Thanks very much. I will check this today. 

[KWood255]

Check band alignment as well.  If the band is pointing up or down it will want to follow that path so make sure it is within spec as well as the head while you are at it.  The WM manual will explain how and most of those things are checked around 50hrs I think

I will do. Thank you. 

[KWood255]

Other factors...spruce knots are a lot harder than the wood.  Could you be deflecting at the knots?  Sharp band helps.  Slowing down a little might?

Build up of sawdust on one side of the band can also be a factor.  What are you using for lube, and it is keeping the band clean on both sides?

Yes the spruce knots are problematic. I feel I may of been going too slow at times, if that's possible. When cutting spruce I rarely get any pitch buildup on the blade, unlike when cutting pine. My blade lube right now is windshield washer fluid, with a couple oz of pinesol. I keep a spray bottle of diesel to give the blade a thorough cleaning every so often. I would like to go to 100% diesel lube in the near future.