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DRAG BACK ... who makes the best, fastest, most effecient and why.

Started by woodbowl, November 30, 2005, 10:31:03 PM

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woodbowl

All the drag backs that I've seen on band mills work pretty good, or at least they seem to. Since I don't have a standard to compare with, I've been comparing them to each other. What can you do to a drag back that will make it better? It's just a drag back! ......... At Moultrie this year I noticed a few hang ups. That caused the operator to have to stop and untangle the matter. Wood that is already comming apart seems to give the most problems. This may not be a big problem to some but it does have it's moments as a time killer. Any one got any first hand problems and solutions?
Full time custom sawing at the customers site since 1995.  WoodMizer LT40 Super Hyd.

Tom

There is only one catastrophic thing that happens when a dragback fails and that is the destruction of the blade.  The blades aren't supported to withstand pressure from the back.  If the dragback "fingers" or blade misses the board, there is nothing between the board and the blade. The resolution is to be careful.

Dragbacks will miss the board if there isn't enough board for them to catch.  This happens on a slab cut of a crowned log where the exit of the blade leaves a board/slab end with no thickness.

You can miss the board if you return without allowing the dragbacks to clear the end of the board.  Operator error!

You can lose a blade if the end of the log wasn't cut square or clean.  Protruding fibers may reach past the dragbacks and hit the back of the blade.

You can lose a blade if the end of the log is rotten and the dragback goes through the board.

Lessor problems are caused as the miscut butt of the board, off level of the mill, or other problems causes the board to fall to the side of the cant and off of the mill rather than being returned to the off-bearer.  There are devices manufactured to stop this occurrance.

Any of them can fail.  The onlyl true way to operate dragbacks is to pay close attention during the entire retrieval.  Haphazard operation is conducive to equipment or personal injury.

The one thing to be concerned about with any board retrieval system is the number of "pinch points" along the board travel path.  Instructions should be given to anyone working around the mill to be aware of the danger.   Boards should be handled from their edges not their ends.  An off-bearer who handles a board from the end is apt to lose fingers or a hand.  Hydraulics or electrics have no compassion and the mill operator may not see the danger or be able to stop the mill quickly enough.   A board moving to the rear which comes into contact with a bed rail or other structural member may sever a human body part that is caught between.

It's not so much that you should be looking for a better dragback but that you learn to operate the one that your have.  :)

Brad_S.

I'm not a fan of drag backs and in fact had them delete them from my mill when I ordered it. I've seen more operators fussing around with them than I care to and often see them tied back with bungee cords to get them out of the way. I think the fingers that hang down like anti-kickback fingers are the worst.
I don't know what the standard WM drag backs are, but I did see one WM that had a paddle like drag back that could be engaged with a switch, otherwise it was up and out of the way. I liked that idea.
"Life is what happens to you while you're busy making other plans." J. Lennon

DanG

I agree with everything Tom said, except that last statement.  Firstly, I know that you don't have a dragback. ;D :D  Secondly, I know that you want to build one that really WORKS the way it should.  I think the key is precision.  The blade is at a constant level in respect to the structure to which it is mounted, so there is no reason not to place the dragback in very close proximity to that plane.  I would think it should be a solid bar with teeth on the back to catch those tapered bits that would want to slide under it.  It should be well behind the blade, at least six inches, to keep those protruding splinters from fouling the blade.  Six inches more of forward travel isn't going to bother your production that much.

My dragback is held down by gravity only, and it will jump over a thin slab in nothing flat.  If it were held down mechanically, it would be a lot more effective.  It needs to be controllable from the operators station, imho, so that it won't lock down when sawing through "uneven terrain" on that first slab.

Come over to the house soon, and we'll invent one for ya. ;D 8) 8)
"I don't feel like an old man.  I feel like a young man who has something wrong with him."  Dick Cavett
"Beat not thy sword into a plowshare, rather beat the sword of thine enemy into a plowshare."

woodbowl

I've been thinking about adding a drag back onto my WM LT40 for several years now. I would like to boost my production but there seem to be more problems created by adding a drag back. I don't really have enough electric power to bring a board back without adding a bigger feed motor, then it needs a beefier chain drive. Gona' need a bigger alternator. Got to make a different alternator mount. My hydraulic controls are right in the way so I need to move all that. Need to splice 12 hoses for the reroute. Gona' need a ............ I'm not sure I want to do it any more. It may be cheaper and quicker to get another mill.
Full time custom sawing at the customers site since 1995.  WoodMizer LT40 Super Hyd.

Tom

I've found that a woodmizer's design lends itself to off-bearing without a drag-back.   Where Drag-backs are really nice is unloading the big cants/timbers.   12 x 12's are a bear by hand.   I drag them off of the mill onto a set of forks on a tractor and hardly miss a lick.  :)

Bibbyman

Everything Tom said.

Plus....

We have the Command Control station on our LT40 and have the dragback that is raised and lowered by a switch.  I probably use the dragback at least once a log – depending on what we're sawing. 

I'll use it when grade sawing when Mary's not there to pull the board and I need to turn to a new face.  I'll use it when we're down to the heart saw and sawing thru and thru.  I'll saw all the way to the bed and then drag all the boards (except the clamped one) off after the last cut.  Mary can offbear these as I'm pulling the last board and loading the next log.

We will use it most when we're sawing alone.  We will use it when we're "squaring down" a cant.  We will drag the board or flitch back about half way and then step from behind the Command Control and pull it the rest of the way onto the return table.  Once we have the cant squared out, we'll saw it all the way down and then unclamp the stack and move the head forward out of the way.  Then we'll shut off the mill and edge the flitches on the edger and offbear the lumber that's on the mill.

Even when there are two of us running the mill, we'll often use the dragback to bring the board back about half way.  This saves the offbearer the effort of "breaking loose" the board from the cant and a few steps.  It's just easier to grab the board that's kind of handed to you. 

The dragback on our mill seems to work better when there is more of a load.  If we cut all the flitches or boards from one face and leave them stacked on the cant and then drag back two or more at one time, it just seems to work better.  Also, for some reason, it does a better job on the last few boards than the first few.

The shortcoming of the LT40 dragback design is that there are no guide system.  Guys with the "walk along" or "ride along" setups can rest a hand on the slab or board and give guidance but with Command Control, there is no control.  You got to be REAL careful.

The LT70 style guide system appears to work really well. The only thing missing is being able to raise and lower it from the control panel.

Wscott posted some pictures and info on the guide system he built for his LT40 under the thread "Useful Sawmill Mods". 



Link to wscott's post




Wood-Mizer LT40HDE25 Super 25hp 3ph with Command Control and Accuset.
Sawing since '94

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