Milling wide - chain slabber versus band

[scsmith42]

About 7 years ago I built a chain slabber on a spare Peterson carriage.  




 

The build is detailed in this thread (Response 4)

https://forestryforum.com/board/index.php?topic=76301.msg1158070#msg1158070

My slabber allows me to cut through a 6' wide log.  It's seen a lot of use over the years and it's getting a little tired and ready for a rebuild / refresh.

I'm also to the point where I would like to mill logs/crotches that are wider than 6', and also to increase my speed / yield.  

Last year I attended the Paul Bunyon show and looked at the Tru-cut 8' wide mill.  Although it's well constructed, it does not have the speed that I'd like, and also the wheels will not provide the depth of cut that I need for quartering large logs.  One of the motivations that I had for building my own slabber back in 2013 was that Peterson and Lucas did not offer anything with a 20" depth of cut back then (today they do).

So I've been kicking around the idea of either building a wide band mill, or building a new slabber that will provide me with an 8' cut.  I have a couple of spare 40hp 1075 rpm electric motors, and I'm thinking of dedicating one to the project if it's a chain slabber.  For a band slabber, I think that I'd like to step up to 75hp or so in order to yield the best cutting speed.

In seeking some advice from Richard (Cutting Edge), he indicated that he thought that a chain slabber would be a better option for ultra-wide cuts.  He pointed out that a chain slabber is less likely to deflect when cutting through a limb pith, as opposed to a band, and that the milling speeds from wide band mills do not appear to be any faster than wide chain slabbers.

In terms of production band mills, the Woodmizer 1000 does not have the width that I'm looking for, and the others are lacking either power, durability or width.  A Lucas super-slabber is slow and underpowered (IMO) for a 7' range cut with the yield speed that I'm looking for, and I think that I can modify my existing setup for a lot less than the price of a new one.  I can make up to an 8' wide pass with my existing Peterson WPF tracks, so one thought is to rebuild my existing setup into a more HP, wider bar version.

If I go the chain slabber route, one thing that I'll incorporate into it is a support structure that allows me to put the bar in tension so as to keep it flatter / straighter during the cuts. I already have some ideas about how to do this.

What say y'all?  There is a wealth of knowledge on this forum so I thought that I'd reach out for advice before going too far down this rabbit hole.  Thanks.

Scott

[longtime lurker]

I've tossed similar ideas around in my head a few times, but never got to the build stage. Heres where I got to, so far as the mental loop:

I think a thin band is out.... too much width and too much wander.
Wide bands maybe but you've got the same gravity/ sag effect as a bar.
I've managed to dial a Lucas slabber in to the point where I've got them quite flat over the full 5' width, but there is a little crown... maybe 1/8" over 5 foot. You've got to have some preload to stop sag as you know, and wider is going to make that worse.
The other thing I found was for best results I would wind up taking about a quarter to a third off the log slabbing, then roll it and come back from the other side: takes any movement out of the log when you're dragging big slabs off and stress relief as well.

So what I'd figured on doing was mounting my bar vertically. That way sag/ preload isn't an issue.
From there I decided I'd need a big lump of a steel beam  (at least 14" I beam with the top cut back to 3" or so width) on the floor for the log to sit on, maybe spikes that engage the log like a sharp chain would, and end dogs to stop it rolling as well. It's not that hard to set up, really.
Then a big lump of a bar, electric motor & drive sprocket mounted on top, bar nose positioned forward of vertical at the bottom, chain spinning so it cuts from nose back to sprocket. I wanted that bar setup so
(1) I was cutting at an angle which is always better going,
(2) I wanted the sawdust to clear "down" and "back" past the bar as much as possible so it wasn't carried up the chain to the drive any more than necessary. I figure that would save a lot of the recutting of sawdust that happens in a wide slabber which robs efficiency, and help the whole thing run cooler.
(3) I wanted the bar nose to be in an oil bath of some sort so there was plenty of lubrication + oil on the drive end for the back of the bar as well. Those big bars are serious $ and you need oil both sides to help keep wear costs down.

I figured to put the drive end onto a setup like a Westford Rail Mill done ultra heavy, and permanently mounted above the centre rail the log sits on, probably running between a big post either end of the beam. The westford setup the rail stays stationary and the saw head moves in and out of the traveller on a graduated beam.
http://www.westfordmills.com.au/rail%20mill.htm

then run an adjustable gauge roll kind of setup down to carry the nose support, kinda like a big alaskan mill runs off the cut face. That part I hadn't quite figured out: but at the dollars involved in real wide slabs I dislike the idea of not having the bar nose guided as well... to me thats as futile as mounting the bar horizontally and cutting a crown into each one.

Probably a friction drive to feed it, I got better things to do than push a supersize chainsaw along a log all day.

I figured I needed to be able to vertically adjust that rail/traveller/drive unit, so if I was doing smaller logs I could change out to a shorter bar and chain, which would greatly reduce operating cost.

I figured I needed to be able to reverse or turn that drive unit, so I could slab both sides of the log without shifting it, both for stress relief and to keep it weight balanced on the beam/dogging setup. Or have two motors and bars one each side and cut two slabs at once.

In use I was thinking bring the log up with forklift or loader, center it over the beam and lower onto the beam spikes, then crowd the log to align the top and end dog it into place. Then drop the railmill style beam down to hold the top of the log as well.

One thing with vertical slabs is with open sides gravity is your friend getting them away, but it would be probably necessary to whack a couple straps around them behind the slabber to help hold them in place until the cut was finished.... some form of bottom support anyway.

Then I thought on it some more, looked at the price of that 10' bar, plus the headaches of build from scratch. And decided that fundamentally it would be cheaper in the long run to find a 72" band headrig secondhand and put it in, because it will do the same thing at about 30 times the speed and be up and sawing straight away. Big bands aren't that expensive really - which is to say they are expensive but theres a lot of bang in that buck if you were using it as an intermittent use slabber not all day every day as a headsaw. ( It took me under 5 minutes to find a 72" Salem for sale within 500 mile of you for $8k, bet theres one in a scrap yard you can get for $100 a ton in the same radius .... nobody wants 'em)

My current mindset is no more slabs. But maybe there's something in that lot might be useful to you.

[terrifictimbersllc]

Have you talked to Steve Cross? A number of years ago he was considering building a very wide chain bar mill. But haven't heard if he went down that road.  Looks from his website that he is still going with the very wide band.  https://crosssawmill.com

[Hilltop366]

I like the vertical bar idea, solves a few problems but causes some others, perhaps a compromise of not quite vertical maybe tilted back a bit would be better. With the motor and drive on top and the nose on bottom sounds like it would be pushing the chain? The little 30" bar (horizontal)  16 hp CSM I had made years ago ended up pushing the chain one problem was that the bit of slack in the chain would "pile up" at the log just before the cut and eventually chip or wear out the bar in that spot. Moving the drive to the bottom would fix this, put a length of shaft on bearings and flex coupler on the motor to move it back from the cutting and some dust shielding would help keep the motor cleaner.

The mill structure itself and log holding would have to be considerably heaver than the Peterson style slobber mill.

Another problem I had with the bar was the nose sprocket/bearing wore out long before the bar, I was wondering if it would make sense to put bar oil directly in the bearing hole to provide continuous bearing oiling and much better cooling or perhaps a separate nose sprocket with its own regular bearings.

Another question would be how much Hp/torque can a saw chain take? I'm guessing you are looking to use at least .404 chain.