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LT40 Head Drove Down While Cutting

Started by forksdad, February 15, 2018, 12:44:33 PM

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forksdad

While cutting a hemlock log, the head started driving down , stalled the engine and bent the blade guide assemblies, drive and idle.  The blade guide arm weldment twisted and the upper drive and lower idle blade guide roller arm bolts bent.  The frame plate the upper drive side bolt goes through also bent.  The blade did not break or come off.  Blade was in good condition, speeds were slow and steady, the cut was 3/4 the way down the log and three 1" thick boards were previously cut on a 16 foot log - 18" diameter.  This mill has 35 hours, a lube system and had never shown signs of operating incorrectly.  I was following along and tried to raise the head with the lever or stop it but not fast enough to stop the damage.  The down force pegged the tension pressure gauge and broke it.  Best choice would have been to turn the key off to prevent all these bent parts and stop the up/down servo.
After getting the head free and out of the way, the key was turned on and the head started going down.  Turned the key off.  Turned back on and flipped the lever to see if I could get it to go back up.
Later I tried the same thing and the head went down about an inch and stopped.  Did this several times before it went down and would continue until the head bottomed out - tripped the breaker. 
Contact with Woodmizer was great.  Jason A. walked me through several checks and all appeared to be fine.  Simple Set settings were correct.  They supplied me with a new arm and the shaft weldment drive side.  Looks like I'm going to need new cam bolts too as I can't get the weldment arm to travel true. 
I'm most concerned that the head will travel again out of control and bend or break more items.  I need to be able to resolve this and have confidence in the up/down servo again.
I've been reading many of the posts on this and there is a ton of talent and experience on here.  Appreciate all the posts I've read so far.
Any and all help greatly appreciated - Scott

Percy

Wow!! That's a new one. Just a thought but if you aren't sure the head dropping thing is resolved, I'd get that log off there and with no blade on, I'd run it back and forth a few times trying to replicate the same situation/conditions when it messed things up. I had problems similar to yours back in 2003 when my LT70 was new and still had the original accuset. I was lucky as my mishap occurred when I was out of the log. Good luck with repairs hope all goes well, gets resolved.
GOLDEN RULE : The guy with the gold, makes the rules.

forksdad

Thanks - as soon as I get the blade tracking again, I'll certainly run it through some dry runs....

Stuart Caruk

Could be simply the result of inadvertently tapping the down lever mid cut with simple set engaged. When the blade starts to dive, the best option is to stop traveling by pulling back the travel lever or turning the feed pot to zero.

You should play with simple set with the blade clear of a log. You'll find that if you inadvertently tap the down lever and it's heading down to the next set value, you can tap the lever up and it will stop. It's important to know exactly how the feed will respond before you try and figure it out in a time of urgent need.
Stuart Caruk
Wood-Mizer LX450 Diesel w/ debarker and home brewed extension, live log deck and outfeed rolls. Woodmizer twin blade edger, Barko 450 log loader, Clark 666 Grapple Skidder w/ 200' of mainline. Bobcats and forklifts.

MartyParsons

Hello,
   I would guess the cam bolts are not bent but the metal that holds the bolts would be. I have no information on why the saw head would drift down.
Marty



 



 
"A pessimist sees difficulty in every opportunity; an optimist sees opportunity in every difficulty." -Winston Churchill

PAmizerman

I had this happen to me a couple times after I installed accuset II last year. I was lucky and it didn't happen in the cut and I turned the key off before it bottomed out. I took and put dielectric grease on the fittings that go from the control panel to the transducer. It has not happened since.
Woodmizer lt40 super remote 42hp Kubota diesel. Accuset II
Hydraulics everywhere
Woodmizer edger 26hp cat diesel
Traverse 6035 telehandler
Case 95xt skidloader
http://byrnemillwork.com/
WM bms250 sharpener
WM bmt250 setter
and a lot of back breaking work!!

forksdad

Thanks Marty - I did have to flatten that mounting plate - appreciate your pictures.  This forum does such a great job with training and repair tools.  My thanks to you and all who have built this knowledge base...

I'm going to have to look at what it takes to change from SimpleSet to Accuset II. 

Scott (new to posting today)

Chuck White

Welcome to the Forestry Forum, forksdad/Scott!
~Chuck~  Cooks Cat Claw sharpener and single tooth setter.  2018 Chevy Silverado and 2021 Subaru Ascent.
With basic mechanical skills and the ability to read you can maintain a Woodmizer  LT40!

Sixacresand

Hitting a nail, hard knot or a sudden build up of resin will cause a blade to dive.  In pitchy pine, a slow drip of diesel helps.  When the blade has took a dive, I stop forward moment and disengage blade, adjust the height of the saw head to match the current cut height and slowly finish the cut.
"Sometimes you can make more hay with less equipment if you just use your head."  Tom, Forestry Forum.  Tenth year with a LT40 Woodmizer,

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