Chassis flex - LT40

[KWood255]

I have sawn a few thousand feet of 8' in the new LT40, but nothing longer until yesterday. Since day 1 when I set up the mill for its initial use, it has worked flawlessly and produced exceptionally uniform boards. Yesterday, I began cutting some 6x6x16's for my own timber frame (new house construction begins next month after losing our home in a fire last fall...) 

Anyway, I made the first cut, rolled 90* and made the second. When I rolled to 180* of the initial face, the cant was about 3/16-1/4" above the forward most bunk, and say an 1/8 above the second. The remaining bunks were touching the cant evenly. Through input from you folks, and my own experience I am aware that the stress in a log can (at times) cause similar issues. I made the cut, and flipped the cant 180* again, to square it off. To my surprise, both 1st and 2nd bunks were untouched again, just as before...concerning...as the 8' was perfect. 

Long story short, to my surprise the chassis flexes quite a bit. After some other troubleshooting, I cranked my forward Jack support downward, and watched the gap on the bunk completely close. I then measured my blade height vs every bunk, and they were perfect. I cut 6-7 more timbers with perfect dimensional results. 

What I believe happened, the mill has settled or thawing allowed the front Jack to sink a bit. On the 8' it was not noticeable but was significantly obvious on the 16's. 

Hopefully this helps someone else in the future. 

 

[John S]

I always crank the rearmost fine adjust outrigger a little extra.  I am told (by WM) that the rail has a slight crown, about the thickness of a dime.  I also check each FAO periodically during a job to check for settlement and or soil compaction.  I also rotate 180° after the first surface is milled to insure they are parallel.

[barbender]

This is a common issue. Your end jacks need to not have any slack in them, yet not be lifting the rail either or it will flex upward. Just firm bearing.

[Andries]

Sharing this small detail is what makes the Forum so good. 
I recall that @YellowHammer mentioned the dime sized crown at one of the Projects in Georgia. He also made a post about giving the FAOs a slight downward turn every so often to keep the frame evenly supported. Ground moisture and compaction, freeze thaw cycles or just the pounding that comes from loading and flipping a big cant will cause the legs to pack the soil under the mill. 
Makes me happy to have installed the fine adjust outriggers !

[KWood255]

I agree Andries. I will be ordering the FAO as an upgrade. 

[Larry]

If its made of steel its gonna flex, no matter what brand of mill.

The human eye is a very precise measuring instrument, capable of detecting a few thousandths of an inch if used correctly.  I occasionally sight down the bunks and rails of my mill to see if its aligned correctly.  Just takes a few seconds, and if something is out, another minute to align with a twist on the outrigger jack.

[YellowHammer]

It will definitely flex, and should be taken out using a long straight edge across all the hunks.  The frame is amazingly strong, as one day, years ago, in a fit of frustration, I hooked both ends of a log chain to where the loader arms connect to the frame, and dropped it on the hitch of my 100 up tractor, and drove off, slowly spinning all four tires.  

When I let up off the clutch, the frame flexed back in position pulling the tractor backwards, and nothing had moved or bent.  True story, the details only being given at Jake's Projects. 

So you may flex it, but it ain't gonna break.   

[Resonator]

Also unless a mill is permanently mounted to concrete, the feet will pack soft dirt down after a hard days sawing. Especially with big logs that rock the mill when turning them. Periodically I check overall level, and shim up any feet that have settled. Putting a crank style trailer jack on the front of my mill frame was one of the best mods I ever added, and makes it easy to fine tune level.

[Crossroads]

Mine has a pretty strong arch built in, I have a homemade FAO on the back and anytime I see a gap over the front bed rail, I go back and give it a few turns.