blades keep jumping off

ncsawyer · August 15, 2017, 12:19:28 AM

I ran into a problem this afternoon that I have never had. I couldn't keep the blade on my mill. I just had it at Woodmizer Carolina's for a routine alignment (it has about 380 hours on it) a few weeks ago and they made a few minor adjustments and put on a new B57 on the drive side. The only adjustment made to anything blade related was to the guide rollers. The front of the blade was tilted up slightly, and we corrected that.

I have sawed 4 red oak logs since the alignment and that is it. This afternoon I tried to saw two large pine logs that had been down a year. The outside was soft, but the heart wood was fat lightard. I got it worked down to a 6 inch cant with no problems, but when I flipped the cant up to cut 1x6's the fun began. I cut a few boards off of the cant (I disengage at the end of each cut). About the 4th board, I engaged the blade (I have auto clutch) and it popped off as it engaged. The blade came off the front of the drive wheel and off the back of the idle side.

I took that blade off, inspected my B57 Belts, wiped the sawdust off of them and put on a "new" resparp blade. When I engaged the blade to cut the second board with that blade, it popped off. I was slightly irritated by now.

So I pulled both B57 belts off made sure there was no sawdust behind them, cleaned them off best I could and put them back on. I re-installed the same blade even though it was damaged to see if I had fixed the problem. I engaged the blade and it popped off immediately. The blade did have some pitch build up, but not excessive. I have sawed much worse stuff than this before with no problems.

The next thing I tried was one of my spare B57 belts that was used but still had some life. I installed it and another resharp and decided to stop running water on the blade to see if that might help keep the blade on.

It didn't come off again and I was able to finish that log, but I did notice, when I got done with that log, that the gullet is about 10 millimeters (way too far) away from the band wheel on the drive side and about 5 millimeters (still a bit too far according to the manual) on the idle side. I have never noticed the blade running this far off the front of the band wheel before. And Woodmizer checked the tracking less than 4 mill hours ago and everything was OK. They also checked my blade guides to make sure the back flange was not contacting the blade. I double checked that again this afternoon and it was fine.

My last mill had 2,000 hours and I never had to adjust the blade tracking. From what I understand this is something that should rarely need adjusting.

Has anyone else had a similar problem, and how did you solve it?

ladylake · August 15, 2017, 05:28:18 AM

Check the bearings in both the drive wheel and idle wheel, also for loose or broken bolts. It doesn't take much play to change the tracking and make the blade come off. Also some batches of blades track different and need to be adjusted. Steve

terrifictimbersllc · August 15, 2017, 05:48:03 AM

Yes, grab each guide roller assembly by the roller end and see if it moves at all, those vertical bolts that hold the shaft esp. the drive side one can break. Also see if you can move anything else (guide arm, band wheels) while blade is under tension.

East ky logging · August 15, 2017, 07:49:07 AM

My lt-15 started throwing blades off suddenly right after I broke a blade. My problem was that one of the two bearings that allows the idle side to pivot when you tension the blade had busted. I don't know if you're mill is the same setup but might be something to look at.

Dave Shepard · August 15, 2017, 12:11:23 PM

The only time I've thrown bands is when I got pitch clumps under the band wheel belt sawing larch, which has a crazy amount of pitch. I scraped the grooves and the problem went away.

ncsawyer · August 16, 2017, 12:41:02 AM

I sawed the other large heart pine tree tonight and have come up with a theory about why the mill kept popping the blades off when trying to engage.

I took you guys advice and checked everything good this afternoon, and no play at all, nothing loose, everything looked great. I even called Tyler at Woodmizer Carolina's and he suggested that the band wheel belts were sticking to the band wheel allowing the "slack bubble" in the belt to become ridged and popping the blade off.

I started off this afternoon pulling the B-57 belts off and cleaning any sawdust out of the band wheel grooves (there were some hard clumps stuck in the drive side groove) and I got the wire brush to the B-57 belts and cleaned them until there was absolutely nothing stuck to them.

I placed the newest B-57 (maybe 5 hours run time) on the drive side and put on a new blade, tightened it down and engaged the blade. When I disengaged the blade I double checked to see where it was tracking on the band wheels, and it looked good. So I put a couple flitches on the mill and engaged the blade. It popped off immediately, before I could even make the first cut.

I installed a spare B-57 on the drive side. This particular B-57 was used yesterday to finishing sawing the first heart pine log. The first time I tried to engage the blade, it popped the blade off as well.

I happened to have two more spare B-57s that had some chunks missing from them. I grabbed one and put it on the drive side and everything worked like a charm, until half way through the log. Then it popped the blade off when trying to engage. I replaced the drive side B-57 with my last spare and a resharp blade and finished cutting the log with no issues.

Over the past two evening's sawing those two logs, I saw a distinct pattern, each one of my B-57 belts was able to cut about 1/2 of one of those large heart pine logs, before it allowed the blade to pop off. Once the blade did pop off with that particular B-57 belt, there was nothing I could do to get the blade to stay on, except to swap the drive side belt to one that have never been used on one of those heart pine logs.

My theory is that the turpentine from that particular tree, changed the physical properties of the B-57 belts, much like distilled turpentine, mineral spirits, or alcohol would do to a racing tire. Here is a picture of my newest B-57 after half a log and it would no longer keep the blade on.

The belt does not have build up on it and does not look worn. It has about 5 hours on it, but after about half a log with that turpentine, the belt would become soft and "sticky". Normally the B-57 belts would allow the blade to move or "track" to the correct position on the band wheel when the blade was engaged. I suspect as the turpentine reacted with the rubber in the belt and it became tacky, it would not allow the blade to track to the correct position as it was engaged, forcing the blade to "walk off" the band wheel.

The only reason I believe this is what was happening, is because a fresh B-57 would always "fix" the problem until it had cut about half the log. Even extensively cleaning a "used" B-57 would not fix the problem, it had to be a fresh one that had not cut one of those heart pine logs.

Here is a picture of some of the wood.

I have cut heart pine before and had to run diesel on the blade the keep it from gumming up so it would cut, but never had the kind of trouble I had out of these two logs.

I know it was a lightning strike tree. Don't know if that had anything to do with it, but I guess it is possible that a lightning strike could change the chemical structure of the turpentine in the tree to make it more likely to react with the rubber band wheel belts.

Anyhow that is my theory, and its just a theory.

Ianab · August 16, 2017, 02:51:50 AM

Certainly looks like a lot of resin in that log. Not familiar with how rubber belts react to it, but if you can see and feel a difference in the belt, then "something" is going on.

A tree may produce more resin if it's "stressed" for some reason, and being hit by lighting sounds pretty stressful. :D

Kbeitz · August 16, 2017, 05:04:44 AM

Just me but I would take a bar of caning wax and rub all side of the belt.

ladylake · August 16, 2017, 05:23:14 AM

Time to try a set of B56 belts. Steve

Ga Mtn Man · August 16, 2017, 08:14:36 AM

Cut something else and see how it does.

ncsawyer · August 16, 2017, 11:39:10 AM

Quote from: ladylake on August 16, 2017, 05:23:14 AM
Time to try a set of B56 belts. Steve

I have heard of others running the B56 belts. What is the difference between the B57 and B56?

Quote from: Ga Mtn Man on August 16, 2017, 08:14:36 AM
Cut something else and see how it does.

I intend to do just that and see where it leads!

terrifictimbersllc · August 16, 2017, 11:48:31 AM

I don't use diesel, just cascade in water. Pitchiest stuff I've ever cut is old syp beams. Sometimes the cascade/water isn't enough but that's rare. I've cut larch and been OK. What I'm wondering is if you were using a lot of water and soap would that possibly counteract some of the effect of sap on your belts, if that's what the problem is.

Ga Mtn Man · August 16, 2017, 12:14:40 PM

Quote from: ncsawyer on August 16, 2017, 11:39:10 AM
... What is the difference between the B57 and B56?

One inch. ;D

ncsawyer · August 16, 2017, 12:21:34 PM

Quote from: terrifictimbersllc on August 16, 2017, 11:48:31 AM
I don't use diesel, just cascade in water. Pitchiest stuff I've ever cut is old syp beams. Sometimes the cascade/water isn't enough but that's rare. I've cut larch and been OK. What I'm wondering is if you were using a lot of water and soap would that possibly counteract some of the effect of sap on your belts, if that's what the problem is.

I used a ton of water and soap, and didn't have much problem with pitch build up, just had a problem keeping the blade on the mill. I plan on picking up a new set of belts and cutting some "normal" pine and some poplar and see what happens.

Quote from: Ga Mtn Man on August 16, 2017, 12:14:40 PM
Quote from: ncsawyer on August 16, 2017, 11:39:10 AM
... What is the difference between the B57 and B56?

One inch. ;D

Thanks! That makes perfect sense! ;D

ladylake · August 16, 2017, 12:52:51 PM

B56 fit tight and you wont get any sawdust under them, at first they are a pain to get on but now it takes me about 5 to 10 minutes to get a new one on. Steve

ncsawyer · August 19, 2017, 10:02:43 PM

After cutting that pine and having the problem with the blade coming off, I ordered a fresh set of band wheel belts and installed them after cleaning everything good. Sawed a bunch of hickory, red oak and two hemlock logs today with no issues whatsoever! 8)

So the blade issues were indeed tied to what I was sawing and not a problem with the mill.

Magicman · August 19, 2017, 10:10:48 PM

Thank You for the report. I have been following this closely because I have never had a blade to come off while sawing. That plus I have sawn much pitchy SYP such as you pictured.

Anyway, I am glad that you isolated the problem and did not resort to "adjusting".