One big log, a 96" bar and my observations

[Can8ianTimber]

I wanted to share my milling project this last weekend.
The log is a insence cedar about 14' long and between 70" and 82" wide
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As you can see from this next picture it log split off into several limbs. Unfortunatly because the log was dropped with about 20' of each of the limbs on it, there was some cracking that almost split the log in half. I had a crane come in at rotate the log about 90 deg so the crack did not ruin every single slab.
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I ordered the 96" bar, which gives me about 84" of cutting capacity specificly for this project. I really did not know how bad the bar would sag at that width. I did a project with a 84" bar made by the same company 3 years ago and experianced very little to no sag but the 96" bar had about 3/4" of sag. From my experiance the power head can act like a counterballance and help reduce sag but there was no helping this long bar.
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For the second cut we put the bar right up to where the cut starts and then manually pushed the bar up and screwed a 2x4 in place. I remember Bob talking about if you enter the cut straight it will help it stay straight in the cut. That did not seem to help it by the time it got to the end. It is hard to see by this picture but the cut is probably sagging by 3/4" at the end. I really only needed 72" of clearance so I wish I would have moved the bar support further from the power head to reduce the total width but I did not really think about it at the time. This picture shows the 2x4 block screwed into the log where we started the cut. I think this helped but it was not enough to keep it straight.
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Here is the log before the last slab was cut. You can see the bark inclusion and some cracking becoming prevelent in the slab. The rest of the log is cracked and messed up so it will probably be firewood.
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The 3120 ran great. I started with 2 brand new 404 skip tooth, semi chisle chains and they cut great. I sharpend every 2 slabs and I could deffinitly tell that it needed sharpening in the second half of the second slab. As far as the bar is conserned I have cut slabs with great results using a 60" and 84" bar but I was not happy with this 96". Both my 84" and 96" bars are made by the company that makes bars for Granberg. If anyone out there has any ideas of how to minimize sag in a bar that size let me know.

All things considered the day went OK. We ended up with 5 good slabs at 4" thick each and about 66" - 72" wide.

 

[kpantherpro]

The 3120 ran great. I started with 2 brand new 404 skip tooth, semi chisle chains and they cut great. I sharpend every 2 slabs and I could deffinitly tell that it needed sharpening in the second half of the second slab. As far as the bar is conserned I have cut slabs with great results using a 60" and 84" bar but I was not happy with this 96". Both my 84" and 96" bars are made by the company that makes bars for Granberg. If anyone out there has any ideas of how to minimize sag in a bar that size let me know.

All things considered the day went OK. We ended up with 5 good slabs at 4" thick each and about 66" - 72" wide.[/QUOTE]

a stouter csm might help, also if you adjust the top push bar so that it has a positve bow in it rather than the sag it might help, it works with the panthermill 2's but they are also steel and a bit stouter, not sure if it would work or hold with the granberg's but you can try.

 

[srcarr52]

Use the mill to put the bar in tension, to do this leave the rail bolts and the push bar loose and clamp the bar on. Then push the mill to rail connections out a little way and tighten, then put a ratchet strap across the top and pull the tops in before tightening the push bar. Repeat with different preload until you get the verticals vertical or slightly smaller on the bar side than the rail side, a little angle there helps keep the sag out as well.

Love the way cedar smells when milling, your yard is going to smell great all year.

 

[DaltonPaull]

I've never tried a bar that long but with my 56" it helps to make sure the bar is straight when setting the adjustments on the mill. I use a straight edge to check it. Nice log.

 

[john taliaferro]

How did you handle the slabs? THAT was a big a$$ hunk of wood .

 

[Can8ianTimber]

We had a 40 HP kabota with forks on the bucket. It was all it could do to pick up the slabs. One time it started to tip to tractor so we put the slab down and put the backhoe attachment on the back to give it more counterweight.

Thanks for the idea of tensioning the milling attachment. If I do this size of log again I a going to have to fab up a more heavy duty rig so I can get adequate tension on it. The power head didn't struggle to keep up with that size of bar but it sure wanted a razor sharp chain. The best cut was one tank of fuel, and the worst cut was 2 tanks per slab.

 

[jimdad07]

I am very impressed, that is incredible work!

 

[Jim Timber]

Depending what you want the slabs for, you could fill the cracked sections with epoxy and do the whole surface in epoxy which leaves a nice gloss surface. Extra character like that would make nice tables or bar tops.

Nice looking wood!

 

[rwoods]

I can smell that cedar from here. Nice work. I can see one heck of a table from one of those slabs. Ron

 

[Nato]

wow very cool can8! i bet that bar and saw setup wasn't all that light also. i have a 880 and a 72 inch cannon. whenever i get to run that setup it always puts a smile on my face... and makes me sleep good too! i just wish i could find some wood in ohio to bury a 96 inch in! big envy here man!

 

[BobL]

Use the mill to put the bar in tension, to do this leave the rail bolts and the push bar loose and clamp the bar on. Then push the mill to rail connections out a little way and tighten, then put a ratchet strap across the top and pull the tops in before tightening the push bar. Repeat with different preload until you get the verticals vertical or slightly smaller on the bar side than the rail side, a little angle there helps keep the sag out as well.

Relying on tension alone will remove some of the sag but to remove it down to an acceptable level using tension requires so much force (many tons) that it will bend the uprights and even tear the mill apart.

I have had some success with using tension in combination with a antisag support mechanism to at least start the cut straight. After that, a small amount of tension and the fact that bar supports itself on a bed of saw dust will keep the bar straight for a while. How far along the slab it keeps straight depends on a lot of factors. If the mill is not jerked around and let run smoothly it lasts all the way through the cut, other times it lasts about 1/2 to 2/3rd of the cut and then it begins to sag.

Some pics of my anti sag devices are here. CSM millers like Aggiewoddbutcher uses a thick plastic hook to get started.

 

[mortenh]

I ordered the 96" bar, which gives me about 84" of cutting capacity specificly for this project. I really did not know how bad the bar would sag at that width. I did a project with a 84" bar made by the same company 3 years ago and experianced very little to no sag but the 96" bar had about 3/4" of sag.
...
I remember Bob talking about if you enter the cut straight it will help it stay straight in the cut. That did not seem to help it by the time it got to the end. It is hard to see by this picture but the cut is probably sagging by 3/4" at the end. I really only needed 72" of clearance so I wish I would have moved the bar support further from the power head to reduce the total width but I did not really think about it at the time.

Rather than milling with the bar horizontally, you could cut the labs at a 45 degree angle (with the power head at the top). This would reduce the downward forces on the bar considerably.

Also, I really don't understand why a 96" bar would sag much more than an 84" bar, all else being equal. Are you sure the two bars are of the same quality. Quite possibly, the 96" bar may be much softer, regardsless of it being the same brand.

 

[Can8ianTimber]

The two bars are made by the same company, same power head, same milling attachement, same chain. After reading some of the posts I am wondering if the tension in the milling attachement may have messed me up. I will tinker with this more next time I have a giant log. For now I am going to go back to my bandsawmills and hope I am not sucking 2 stroke fumes again for a while.

 

[BobL]

Rather than milling with the bar horizontally, you could cut the labs at a 45 degree angle (with the power head at the top). This would reduce the downward forces on the bar considerably.

Unfortunately this is not the case. At 45º the bar will still sag 70% of the horizontal amount. Even at 60º the bar will sag by 50%

Also, I really don't understand why a 96" bar would sag much more than an 84" bar, all else being equal. Are you sure the two bars are of the same quality. Quite possibly, the 96" bar may be much softer, regardsless of it being the same brand.

Same applies to a 44" and 60" bar. 44" bar shows 0.01" sag, 60" has 0.09"

 

[mortenh]

Unfortunately this is not the case. At 45º the bar will still sag 70% of the horizontal amount. Even at 60º the bar will sag by 50%

I did not claim that it would eliminate sagging, but that sagging would be reduced. A 30-50% reduction is worth going for, right?

 

[devonhubb]

I wander if it would be worthwhile to mount one of those super magnets mid-point on the mill.

Those things come in various sizes & strengths. I am just curious to know if a good strong magnet would provide enough pull to offset gravity. And just how strong of a magnet that it would take......

 

[BobL]

I wander if it would be worthwhile to mount one of those super magnets mid-point on the mill.

Those things come in various sizes & strengths. I am just curious to know if a good strong magnet would provide enough pull to offset gravity. And just how strong of a magnet that it would take......

I have two of these magnets that are 1" thick, 6" wide and about 14" long and weigh about 10 lbs.
To give you an idea over how short a range the magnetism acts over, the magnet is wrapped in a 0.03" thick non magnetic stainless steel jacket.
When I remove the jacket and place a nut on it I cannot move it by hand (I have to screw a bolt into the nut and lever it off).
With the jacket on it is still a struggle but I can slide the nut to a corner and then get my fingers around it and lift it off.
This is typical of these magnets that they can generate a lot of force on contact but much less force when even just 1/8" away.

There is no doubt a magnet that would lift the bar from a distance of a few of inches but it would probably weigh a couple of hundred pounds.

 

[BobL]

I did not claim that it would eliminate sagging, but that sagging would be reduced. A 30-50% reduction is worth going for, right?

Sure but it would also mean a lot of drag on the mill as a substantial part of its weight plus the extra pull of the chain would drag the saw into the log. Wheels on the inboard side of the mill would be needed. A 96" bar on a 60º slope would put the power head 10ft off the ground so a platform to stand on would be required.

 

[Jim Timber]

The question is will the rare earth magnet have enough field to pull through the wood? I don't know, but an electromagnet might be the better option here. One can be made quite easily with a bar of steel and a roll of magnet wire. You might even find directions online for how to calculate what kind of force to expect and how much current you'll need to power it.

The other benefit of electromagnets is that if it does pick up crud, it will fall off when the field is removed (no more current through the coil) - they're also substantially lighter for the same relative strength. Cost of the wire can add up, but it's often available surplus for little more than the raw price of copper. So if it doesn't work out, you're not out much money when you scrap it.

 

[glennschumann]

Thoughts...

Try mounting the bar the other way... there may be some inherent stresses or flex in the bar that may be lessened if it is flipped over in your mill. Also check to see if it is straight to begin with.

You may also look at the mounting clamps... if they are dirty, bent etc, this may have an impact on how it holds your bar. You may try shimming here and there to make the clamps hold the bar at a bit of an angle (opposite of the current sag) to see if you can eliminate a 1/4" of sag or so. The shims should not be thick, just a few thousanths, to start with... it may help. Your clamps / verticals may have been bumped out of plumb / level over time, so if you can check their alignment, that may be helpful to know too.

Yes, moving the clamping mechanisms closer together when you can may help the sag issue with a shorter clamped area, and more cantilevered weight, at least on the powerhead end. I don't know that you actually want to add weight to the sprocket end, but it may help.

If you clamp directly onto the sprocket nose, the "wiggle room" between the sprocket nose and bar may contribute to the sag... you may wish to make sure to clamp direclty onto the bar at that end if you can.

A double ended bar would have the advantage of ballancing counterweights that would reduce the flex of your bar too, but that would require another 3120xp... Whoo Hoo! : )

You may also try resetting the bar clamps after the bar has warmed up... a hot bar, and cool mill, may force the bar to sag if it is trying to expand, especially over that enviable length.


P.S. That is way cool!!!